status-go/vendor/github.com/anacrolix/go-libutp/utp_internal.cpp

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/*
* Copyright (c) 2010-2013 BitTorrent, Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include <stdio.h>
#include <assert.h>
#include <string.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <limits.h> // for UINT_MAX
#include <time.h>
#include "utp_types.h"
#include "utp_packedsockaddr.h"
#include "utp_internal.h"
#include "utp_hash.h"
#define TIMEOUT_CHECK_INTERVAL 500
// number of bytes to increase max window size by, per RTT. This is
// scaled down linearly proportional to off_target. i.e. if all packets
// in one window have 0 delay, window size will increase by this number.
// Typically it's less. TCP increases one MSS per RTT, which is 1500
#define MAX_CWND_INCREASE_BYTES_PER_RTT 3000
#define CUR_DELAY_SIZE 3
// experiments suggest that a clock skew of 10 ms per 325 seconds
// is not impossible. Reset delay_base every 13 minutes. The clock
// skew is dealt with by observing the delay base in the other
// direction, and adjusting our own upwards if the opposite direction
// delay base keeps going down
#define DELAY_BASE_HISTORY 13
#define MAX_WINDOW_DECAY 100 // ms
#define REORDER_BUFFER_SIZE 32
#define REORDER_BUFFER_MAX_SIZE 1024
#define OUTGOING_BUFFER_MAX_SIZE 1024
#define PACKET_SIZE 1435
// this is the minimum max_window value. It can never drop below this
#define MIN_WINDOW_SIZE 10
// if we receive 4 or more duplicate acks, we resend the packet
// that hasn't been acked yet
#define DUPLICATE_ACKS_BEFORE_RESEND 3
// Allow a reception window of at least 3 ack_nrs behind seq_nr
// A non-SYN packet with an ack_nr difference greater than this is
// considered suspicious and ignored
#define ACK_NR_ALLOWED_WINDOW DUPLICATE_ACKS_BEFORE_RESEND
#define RST_INFO_TIMEOUT 10000
#define RST_INFO_LIMIT 1000
// 29 seconds determined from measuring many home NAT devices
#define KEEPALIVE_INTERVAL 29000
#define SEQ_NR_MASK 0xFFFF
#define ACK_NR_MASK 0xFFFF
#define TIMESTAMP_MASK 0xFFFFFFFF
#define DIV_ROUND_UP(num, denom) ((num + denom - 1) / denom)
// The totals are derived from the following data:
// 45: IPv6 address including embedded IPv4 address
// 11: Scope Id
// 2: Brackets around IPv6 address when port is present
// 6: Port (including colon)
// 1: Terminating null byte
char addrbuf[65];
#define addrfmt(x, s) x.fmt(s, sizeof(s))
#if (defined(__SVR4) && defined(__sun))
#pragma pack(1)
#else
#pragma pack(push,1)
#endif
// these packet sizes are including the uTP header wich
// is either 20 or 23 bytes depending on version
#define PACKET_SIZE_EMPTY_BUCKET 0
#define PACKET_SIZE_EMPTY 23
#define PACKET_SIZE_SMALL_BUCKET 1
#define PACKET_SIZE_SMALL 373
#define PACKET_SIZE_MID_BUCKET 2
#define PACKET_SIZE_MID 723
#define PACKET_SIZE_BIG_BUCKET 3
#define PACKET_SIZE_BIG 1400
#define PACKET_SIZE_HUGE_BUCKET 4
struct PACKED_ATTRIBUTE PacketFormatV1 {
// packet_type (4 high bits)
// protocol version (4 low bits)
byte ver_type;
byte version() const { return ver_type & 0xf; }
byte type() const { return ver_type >> 4; }
void set_version(byte v) { ver_type = (ver_type & 0xf0) | (v & 0xf); }
void set_type(byte t) { ver_type = (ver_type & 0xf) | (t << 4); }
// Type of the first extension header
byte ext;
// connection ID
uint16_big connid;
uint32_big tv_usec;
uint32_big reply_micro;
// receive window size in bytes
uint32_big windowsize;
// Sequence number
uint16_big seq_nr;
// Acknowledgment number
uint16_big ack_nr;
};
struct PACKED_ATTRIBUTE PacketFormatAckV1 {
PacketFormatV1 pf;
byte ext_next;
byte ext_len;
byte acks[4];
};
#if (defined(__SVR4) && defined(__sun))
#pragma pack(0)
#else
#pragma pack(pop)
#endif
enum {
ST_DATA = 0, // Data packet.
ST_FIN = 1, // Finalize the connection. This is the last packet.
ST_STATE = 2, // State packet. Used to transmit an ACK with no data.
ST_RESET = 3, // Terminate connection forcefully.
ST_SYN = 4, // Connect SYN
ST_NUM_STATES, // used for bounds checking
};
static const cstr flagnames[] = {
"ST_DATA","ST_FIN","ST_STATE","ST_RESET","ST_SYN"
};
enum CONN_STATE {
CS_UNINITIALIZED = 0,
CS_IDLE,
CS_SYN_SENT,
CS_SYN_RECV,
CS_CONNECTED,
CS_CONNECTED_FULL,
CS_RESET,
CS_DESTROY
};
static const cstr statenames[] = {
"UNINITIALIZED", "IDLE","SYN_SENT", "SYN_RECV", "CONNECTED","CONNECTED_FULL","DESTROY_DELAY","RESET","DESTROY"
};
struct OutgoingPacket {
size_t length;
size_t payload;
uint64 time_sent; // microseconds
uint transmissions:31;
bool need_resend:1;
byte data[1];
};
struct SizableCircularBuffer {
// This is the mask. Since it's always a power of 2, adding 1 to this value will return the size.
size_t mask;
// This is the elements that the circular buffer points to
void **elements;
void *get(size_t i) const { assert(elements); return elements ? elements[i & mask] : NULL; }
void put(size_t i, void *data) { assert(elements); elements[i&mask] = data; }
void grow(size_t item, size_t index);
void ensure_size(size_t item, size_t index) { if (index > mask) grow(item, index); }
size_t size() { return mask + 1; }
};
// Item contains the element we want to make space for
// index is the index in the list.
void SizableCircularBuffer::grow(size_t item, size_t index)
{
// Figure out the new size.
size_t size = mask + 1;
do size *= 2; while (index >= size);
// Allocate the new buffer
void **buf = (void**)calloc(size, sizeof(void*));
size--;
// Copy elements from the old buffer to the new buffer
for (size_t i = 0; i <= mask; i++) {
buf[(item - index + i) & size] = get(item - index + i);
}
// Swap to the newly allocated buffer
mask = size;
free(elements);
elements = buf;
}
// compare if lhs is less than rhs, taking wrapping
// into account. if lhs is close to UINT_MAX and rhs
// is close to 0, lhs is assumed to have wrapped and
// considered smaller
bool wrapping_compare_less(uint32 lhs, uint32 rhs, uint32 mask)
{
// distance walking from lhs to rhs, downwards
const uint32 dist_down = (lhs - rhs) & mask;
// distance walking from lhs to rhs, upwards
const uint32 dist_up = (rhs - lhs) & mask;
// if the distance walking up is shorter, lhs
// is less than rhs. If the distance walking down
// is shorter, then rhs is less than lhs
return dist_up < dist_down;
}
struct DelayHist {
uint32 delay_base;
// this is the history of delay samples,
// normalized by using the delay_base. These
// values are always greater than 0 and measures
// the queuing delay in microseconds
uint32 cur_delay_hist[CUR_DELAY_SIZE];
size_t cur_delay_idx;
// this is the history of delay_base. It's
// a number that doesn't have an absolute meaning
// only relative. It doesn't make sense to initialize
// it to anything other than values relative to
// what's been seen in the real world.
uint32 delay_base_hist[DELAY_BASE_HISTORY];
size_t delay_base_idx;
// the time when we last stepped the delay_base_idx
uint64 delay_base_time;
bool delay_base_initialized;
void clear(uint64 current_ms)
{
delay_base_initialized = false;
delay_base = 0;
cur_delay_idx = 0;
delay_base_idx = 0;
delay_base_time = current_ms;
for (size_t i = 0; i < CUR_DELAY_SIZE; i++) {
cur_delay_hist[i] = 0;
}
for (size_t i = 0; i < DELAY_BASE_HISTORY; i++) {
delay_base_hist[i] = 0;
}
}
void shift(const uint32 offset)
{
// the offset should never be "negative"
// assert(offset < 0x10000000);
// increase all of our base delays by this amount
// this is used to take clock skew into account
// by observing the other side's changes in its base_delay
for (size_t i = 0; i < DELAY_BASE_HISTORY; i++) {
delay_base_hist[i] += offset;
}
delay_base += offset;
}
void add_sample(const uint32 sample, uint64 current_ms)
{
// The two clocks (in the two peers) are assumed not to
// progress at the exact same rate. They are assumed to be
// drifting, which causes the delay samples to contain
// a systematic error, either they are under-
// estimated or over-estimated. This is why we update the
// delay_base every two minutes, to adjust for this.
// This means the values will keep drifting and eventually wrap.
// We can cross the wrapping boundry in two directions, either
// going up, crossing the highest value, or going down, crossing 0.
// if the delay_base is close to the max value and sample actually
// wrapped on the other end we would see something like this:
// delay_base = 0xffffff00, sample = 0x00000400
// sample - delay_base = 0x500 which is the correct difference
// if the delay_base is instead close to 0, and we got an even lower
// sample (that will eventually update the delay_base), we may see
// something like this:
// delay_base = 0x00000400, sample = 0xffffff00
// sample - delay_base = 0xfffffb00
// this needs to be interpreted as a negative number and the actual
// recorded delay should be 0.
// It is important that all arithmetic that assume wrapping
// is done with unsigned intergers. Signed integers are not guaranteed
// to wrap the way unsigned integers do. At least GCC takes advantage
// of this relaxed rule and won't necessarily wrap signed ints.
// remove the clock offset and propagation delay.
// delay base is min of the sample and the current
// delay base. This min-operation is subject to wrapping
// and care needs to be taken to correctly choose the
// true minimum.
// specifically the problem case is when delay_base is very small
// and sample is very large (because it wrapped past zero), sample
// needs to be considered the smaller
if (!delay_base_initialized) {
// delay_base being 0 suggests that we haven't initialized
// it or its history with any real measurements yet. Initialize
// everything with this sample.
for (size_t i = 0; i < DELAY_BASE_HISTORY; i++) {
// if we don't have a value, set it to the current sample
delay_base_hist[i] = sample;
continue;
}
delay_base = sample;
delay_base_initialized = true;
}
if (wrapping_compare_less(sample, delay_base_hist[delay_base_idx], TIMESTAMP_MASK)) {
// sample is smaller than the current delay_base_hist entry
// update it
delay_base_hist[delay_base_idx] = sample;
}
// is sample lower than delay_base? If so, update delay_base
if (wrapping_compare_less(sample, delay_base, TIMESTAMP_MASK)) {
// sample is smaller than the current delay_base
// update it
delay_base = sample;
}
// this operation may wrap, and is supposed to
const uint32 delay = sample - delay_base;
// sanity check. If this is triggered, something fishy is going on
// it means the measured sample was greater than 32 seconds!
//assert(delay < 0x2000000);
cur_delay_hist[cur_delay_idx] = delay;
cur_delay_idx = (cur_delay_idx + 1) % CUR_DELAY_SIZE;
// once every minute
if (current_ms - delay_base_time > 60 * 1000) {
delay_base_time = current_ms;
delay_base_idx = (delay_base_idx + 1) % DELAY_BASE_HISTORY;
// clear up the new delay base history spot by initializing
// it to the current sample, then update it
delay_base_hist[delay_base_idx] = sample;
delay_base = delay_base_hist[0];
// Assign the lowest delay in the last 2 minutes to delay_base
for (size_t i = 0; i < DELAY_BASE_HISTORY; i++) {
if (wrapping_compare_less(delay_base_hist[i], delay_base, TIMESTAMP_MASK))
delay_base = delay_base_hist[i];
}
}
}
uint32 get_value()
{
uint32 value = UINT_MAX;
for (size_t i = 0; i < CUR_DELAY_SIZE; i++) {
value = min<uint32>(cur_delay_hist[i], value);
}
// value could be UINT_MAX if we have no samples yet...
return value;
}
};
struct UTPSocket {
~UTPSocket();
PackedSockAddr addr;
utp_context *ctx;
int ida; //for ack socket list
uint16 retransmit_count;
uint16 reorder_count;
byte duplicate_ack;
// the number of packets in the send queue. Packets that haven't
// yet been sent count as well as packets marked as needing resend
// the oldest un-acked packet in the send queue is seq_nr - cur_window_packets
uint16 cur_window_packets;
// how much of the window is used, number of bytes in-flight
// packets that have not yet been sent do not count, packets
// that are marked as needing to be re-sent (due to a timeout)
// don't count either
size_t cur_window;
// maximum window size, in bytes
size_t max_window;
// UTP_SNDBUF setting, in bytes
size_t opt_sndbuf;
// UTP_RCVBUF setting, in bytes
size_t opt_rcvbuf;
// this is the target delay, in microseconds
// for this socket. defaults to 100000.
size_t target_delay;
// Is a FIN packet in the reassembly buffer?
bool got_fin:1;
// Have we reached the FIN?
bool got_fin_reached:1;
// Have we sent our FIN?
bool fin_sent:1;
// Has our fin been ACKed?
bool fin_sent_acked:1;
// Reading is disabled
bool read_shutdown:1;
// User called utp_close()
bool close_requested:1;
// Timeout procedure
bool fast_timeout:1;
// max receive window for other end, in bytes
size_t max_window_user;
CONN_STATE state;
// TickCount when we last decayed window (wraps)
int64 last_rwin_decay;
// the sequence number of the FIN packet. This field is only set
// when we have received a FIN, and the flag field has the FIN flag set.
// it is used to know when it is safe to destroy the socket, we must have
// received all packets up to this sequence number first.
uint16 eof_pkt;
// All sequence numbers up to including this have been properly received
// by us
uint16 ack_nr;
// This is the sequence number for the next packet to be sent.
uint16 seq_nr;
uint16 timeout_seq_nr;
// This is the sequence number of the next packet we're allowed to
// do a fast resend with. This makes sure we only do a fast-resend
// once per packet. We can resend the packet with this sequence number
// or any later packet (with a higher sequence number).
uint16 fast_resend_seq_nr;
uint32 reply_micro;
uint64 last_got_packet;
uint64 last_sent_packet;
uint64 last_measured_delay;
// timestamp of the last time the cwnd was full
// this is used to prevent the congestion window
// from growing when we're not sending at capacity
mutable uint64 last_maxed_out_window;
void *userdata;
// Round trip time
uint rtt;
// Round trip time variance
uint rtt_var;
// Round trip timeout
uint rto;
DelayHist rtt_hist;
uint retransmit_timeout;
// The RTO timer will timeout here.
uint64 rto_timeout;
// When the window size is set to zero, start this timer. It will send a new packet every 30secs.
uint64 zerowindow_time;
uint32 conn_seed;
// Connection ID for packets I receive
uint32 conn_id_recv;
// Connection ID for packets I send
uint32 conn_id_send;
// Last rcv window we advertised, in bytes
size_t last_rcv_win;
DelayHist our_hist;
DelayHist their_hist;
// extension bytes from SYN packet
byte extensions[8];
// MTU Discovery
// time when we should restart the MTU discovery
uint64 mtu_discover_time;
// ceiling and floor of binary search. last is the mtu size
// we're currently using
uint32 mtu_ceiling, mtu_floor, mtu_last;
// we only ever have a single probe in flight at any given time.
// this is the sequence number of that probe, and the size of
// that packet
uint32 mtu_probe_seq, mtu_probe_size;
// this is the average delay samples, as compared to the initial
// sample. It's averaged over 5 seconds
int32 average_delay;
// this is the sum of all the delay samples
// we've made recently. The important distinction
// of these samples is that they are all made compared
// to the initial sample, this is to deal with
// wrapping in a simple way.
int64 current_delay_sum;
// number of sample ins current_delay_sum
int current_delay_samples;
// initialized to 0, set to the first raw delay sample
// each sample that's added to current_delay_sum
// is subtracted from the value first, to make it
// a delay relative to this sample
uint32 average_delay_base;
// the next time we should add an average delay
// sample into average_delay_hist
uint64 average_sample_time;
// the estimated clock drift between our computer
// and the endpoint computer. The unit is microseconds
// per 5 seconds
int32 clock_drift;
// just used for logging
int32 clock_drift_raw;
SizableCircularBuffer inbuf, outbuf;
#ifdef _DEBUG
// Public per-socket statistics, returned by utp_get_stats()
utp_socket_stats _stats;
#endif
// true if we're in slow-start (exponential growth) phase
bool slow_start;
// the slow-start threshold, in bytes
size_t ssthresh;
void log(int level, char const *fmt, ...)
{
va_list va;
char buf[4096], buf2[4096];
// don't bother with vsnprintf() etc calls if we're not going to log.
if (!ctx->would_log(level)) {
return;
}
va_start(va, fmt);
vsnprintf(buf, 4096, fmt, va);
va_end(va);
buf[4095] = '\0';
snprintf(buf2, 4096, "%p %s %06u %s", this, addrfmt(addr, addrbuf), conn_id_recv, buf);
buf2[4095] = '\0';
ctx->log_unchecked(this, buf2);
}
void schedule_ack();
// called every time mtu_floor or mtu_ceiling are adjusted
void mtu_search_update();
void mtu_reset();
// Calculates the current receive window
size_t get_rcv_window()
{
// Trim window down according to what's already in buffer.
const size_t numbuf = utp_call_get_read_buffer_size(this->ctx, this);
assert((int)numbuf >= 0);
return opt_rcvbuf > numbuf ? opt_rcvbuf - numbuf : 0;
}
// Test if we're ready to decay max_window
// XXX this breaks when spaced by > INT_MAX/2, which is 49
// days; the failure mode in that case is we do an extra decay
// or fail to do one when we really shouldn't.
bool can_decay_win(int64 msec) const
{
return (msec - last_rwin_decay) >= MAX_WINDOW_DECAY;
}
// If we can, decay max window, returns true if we actually did so
void maybe_decay_win(uint64 current_ms)
{
if (can_decay_win(current_ms)) {
// TCP uses 0.5
max_window = (size_t)(max_window * .5);
last_rwin_decay = current_ms;
if (max_window < MIN_WINDOW_SIZE)
max_window = MIN_WINDOW_SIZE;
slow_start = false;
ssthresh = max_window;
}
}
size_t get_header_size() const
{
return sizeof(PacketFormatV1);
}
size_t get_udp_mtu()
{
socklen_t len;
SOCKADDR_STORAGE sa = addr.get_sockaddr_storage(&len);
return utp_call_get_udp_mtu(this->ctx, this, (const struct sockaddr *)&sa, len);
}
size_t get_udp_overhead()
{
socklen_t len;
SOCKADDR_STORAGE sa = addr.get_sockaddr_storage(&len);
return utp_call_get_udp_overhead(this->ctx, this, (const struct sockaddr *)&sa, len);
}
size_t get_overhead()
{
return get_udp_overhead() + get_header_size();
}
void send_data(byte* b, size_t length, bandwidth_type_t type, uint32 flags = 0);
void send_ack(bool synack = false);
void send_keep_alive();
static void send_rst(utp_context *ctx,
const PackedSockAddr &addr, uint32 conn_id_send,
uint16 ack_nr, uint16 seq_nr);
void send_packet(OutgoingPacket *pkt);
bool is_full(int bytes = -1);
bool flush_packets();
void write_outgoing_packet(size_t payload, uint flags, struct utp_iovec *iovec, size_t num_iovecs);
#ifdef _DEBUG
void check_invariant();
#endif
void check_timeouts();
int ack_packet(uint16 seq);
size_t selective_ack_bytes(uint base, const byte* mask, byte len, int64& min_rtt);
void selective_ack(uint base, const byte *mask, byte len);
void apply_ccontrol(size_t bytes_acked, uint32 actual_delay, int64 min_rtt);
size_t get_packet_size() const;
};
void removeSocketFromAckList(UTPSocket *conn)
{
if (conn->ida >= 0)
{
UTPSocket *last = conn->ctx->ack_sockets[conn->ctx->ack_sockets.GetCount() - 1];
assert(last->ida < (int)(conn->ctx->ack_sockets.GetCount()));
assert(conn->ctx->ack_sockets[last->ida] == last);
last->ida = conn->ida;
conn->ctx->ack_sockets[conn->ida] = last;
conn->ida = -1;
// Decrease the count
conn->ctx->ack_sockets.SetCount(conn->ctx->ack_sockets.GetCount() - 1);
}
}
static void utp_register_sent_packet(utp_context *ctx, size_t length)
{
if (length <= PACKET_SIZE_MID) {
if (length <= PACKET_SIZE_EMPTY) {
ctx->context_stats._nraw_send[PACKET_SIZE_EMPTY_BUCKET]++;
} else if (length <= PACKET_SIZE_SMALL) {
ctx->context_stats._nraw_send[PACKET_SIZE_SMALL_BUCKET]++;
} else
ctx->context_stats._nraw_send[PACKET_SIZE_MID_BUCKET]++;
} else {
if (length <= PACKET_SIZE_BIG) {
ctx->context_stats._nraw_send[PACKET_SIZE_BIG_BUCKET]++;
} else
ctx->context_stats._nraw_send[PACKET_SIZE_HUGE_BUCKET]++;
}
}
void send_to_addr(utp_context *ctx, utp_socket *socket, const byte *p, size_t len, const PackedSockAddr &addr, int flags = 0)
{
socklen_t tolen;
SOCKADDR_STORAGE to = addr.get_sockaddr_storage(&tolen);
utp_register_sent_packet(ctx, len);
utp_call_sendto(ctx, socket, p, len, (const struct sockaddr *)&to, tolen, flags);
}
void UTPSocket::schedule_ack()
{
if (ida == -1){
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "schedule_ack");
#endif
ida = ctx->ack_sockets.Append(this);
} else {
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "schedule_ack: already in list");
#endif
}
}
void UTPSocket::send_data(byte* b, size_t length, bandwidth_type_t type, uint32 flags)
{
// time stamp this packet with local time, the stamp goes into
// the header of every packet at the 8th byte for 8 bytes :
// two integers, check packet.h for more
uint64 time = utp_call_get_microseconds(ctx, this);
PacketFormatV1* b1 = (PacketFormatV1*)b;
b1->tv_usec = (uint32)time;
b1->reply_micro = reply_micro;
last_sent_packet = ctx->current_ms;
#ifdef _DEBUG
_stats.nbytes_xmit += length;
++_stats.nxmit;
#endif
if (ctx->callbacks[UTP_ON_OVERHEAD_STATISTICS]) {
size_t n;
if (type == payload_bandwidth) {
// if this packet carries payload, just
// count the header as overhead
type = header_overhead;
n = get_overhead();
} else {
n = length + get_udp_overhead();
}
utp_call_on_overhead_statistics(ctx, this, true, n, type);
}
#if UTP_DEBUG_LOGGING
int flags2 = b1->type();
uint16 seq_nr = b1->seq_nr;
uint16 ack_nr = b1->ack_nr;
log(UTP_LOG_DEBUG, "send %s len:%u id:%u timestamp:" I64u " reply_micro:%u flags:%s seq_nr:%u ack_nr:%u",
addrfmt(addr, addrbuf), (uint)length, conn_id_send, time, reply_micro, flagnames[flags2],
seq_nr, ack_nr);
#endif
send_to_addr(ctx, this, b, length, addr, flags);
removeSocketFromAckList(this);
}
void UTPSocket::send_ack(bool synack)
{
PacketFormatAckV1 pfa;
zeromem(&pfa);
size_t len;
last_rcv_win = get_rcv_window();
pfa.pf.set_version(1);
pfa.pf.set_type(ST_STATE);
pfa.pf.ext = 0;
pfa.pf.connid = conn_id_send;
pfa.pf.ack_nr = ack_nr;
pfa.pf.seq_nr = seq_nr;
pfa.pf.windowsize = (uint32)last_rcv_win;
len = sizeof(PacketFormatV1);
// we never need to send EACK for connections
// that are shutting down
if (reorder_count != 0 && !got_fin_reached) {
// if reorder count > 0, send an EACK.
// reorder count should always be 0
// for synacks, so this should not be
// as synack
assert(!synack);
pfa.pf.ext = 1;
pfa.ext_next = 0;
pfa.ext_len = 4;
uint m = 0;
// reorder count should only be non-zero
// if the packet ack_nr + 1 has not yet
// been received
assert(inbuf.get(ack_nr + 1) == NULL);
size_t window = min<size_t>(14+16, inbuf.size());
// Generate bit mask of segments received.
for (size_t i = 0; i < window; i++) {
if (inbuf.get(ack_nr + i + 2) != NULL) {
m |= 1 << i;
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "EACK packet [%u]", ack_nr + i + 2);
#endif
}
}
pfa.acks[0] = (byte)m;
pfa.acks[1] = (byte)(m >> 8);
pfa.acks[2] = (byte)(m >> 16);
pfa.acks[3] = (byte)(m >> 24);
len += 4 + 2;
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "Sending EACK %u [%u] bits:[%032b]", ack_nr, conn_id_send, m);
#endif
} else {
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "Sending ACK %u [%u]", ack_nr, conn_id_send);
#endif
}
send_data((byte*)&pfa, len, ack_overhead);
removeSocketFromAckList(this);
}
void UTPSocket::send_keep_alive()
{
ack_nr--;
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "Sending KeepAlive ACK %u [%u]", ack_nr, conn_id_send);
#endif
send_ack();
ack_nr++;
}
void UTPSocket::send_rst(utp_context *ctx,
const PackedSockAddr &addr, uint32 conn_id_send, uint16 ack_nr, uint16 seq_nr)
{
PacketFormatV1 pf1;
zeromem(&pf1);
size_t len;
pf1.set_version(1);
pf1.set_type(ST_RESET);
pf1.ext = 0;
pf1.connid = conn_id_send;
pf1.ack_nr = ack_nr;
pf1.seq_nr = seq_nr;
pf1.windowsize = 0;
len = sizeof(PacketFormatV1);
// LOG_DEBUG("%s: Sending RST id:%u seq_nr:%u ack_nr:%u", addrfmt(addr, addrbuf), conn_id_send, seq_nr, ack_nr);
// LOG_DEBUG("send %s len:%u id:%u", addrfmt(addr, addrbuf), (uint)len, conn_id_send);
send_to_addr(ctx, NULL, (const byte*)&pf1, len, addr);
}
void UTPSocket::send_packet(OutgoingPacket *pkt)
{
// only count against the quota the first time we
// send the packet. Don't enforce quota when closing
// a socket. Only enforce the quota when we're sending
// at slow rates (max window < packet size)
//size_t max_send = min(max_window, opt_sndbuf, max_window_user);
time_t cur_time = utp_call_get_milliseconds(this->ctx, this);
if (pkt->transmissions == 0 || pkt->need_resend) {
cur_window += pkt->payload;
}
pkt->need_resend = false;
PacketFormatV1* p1 = (PacketFormatV1*)pkt->data;
p1->ack_nr = ack_nr;
pkt->time_sent = utp_call_get_microseconds(this->ctx, this);
//socklen_t salen;
//SOCKADDR_STORAGE sa = addr.get_sockaddr_storage(&salen);
bool use_as_mtu_probe = false;
// TODO: this is subject to nasty wrapping issues! Below as well
if (mtu_discover_time < (uint64)cur_time) {
// it's time to reset our MTU assupmtions
// and trigger a new search
mtu_reset();
}
// don't use packets that are larger then mtu_ceiling
// as probes, since they were probably used as probes
// already and failed, now we need it to fragment
// just to get it through
// if seq_nr == 1, the probe would end up being 0
// which is a magic number representing no-probe
// that why we don't send a probe for a packet with
// sequence number 0
if (mtu_floor < mtu_ceiling
&& pkt->length > mtu_floor
&& pkt->length <= mtu_ceiling
&& mtu_probe_seq == 0
&& seq_nr != 1
&& pkt->transmissions == 0) {
// we've already incremented seq_nr
// for this packet
mtu_probe_seq = (seq_nr - 1) & ACK_NR_MASK;
mtu_probe_size = pkt->length;
assert(pkt->length >= mtu_floor);
assert(pkt->length <= mtu_ceiling);
use_as_mtu_probe = true;
log(UTP_LOG_MTU, "MTU [PROBE] floor:%d ceiling:%d current:%d"
, mtu_floor, mtu_ceiling, mtu_probe_size);
}
pkt->transmissions++;
send_data((byte*)pkt->data, pkt->length,
(state == CS_SYN_SENT) ? connect_overhead
: (pkt->transmissions == 1) ? payload_bandwidth
: retransmit_overhead, use_as_mtu_probe ? UTP_UDP_DONTFRAG : 0);
}
bool UTPSocket::is_full(int bytes)
{
size_t packet_size = get_packet_size();
if (bytes < 0) bytes = packet_size;
else if (bytes > (int)packet_size) bytes = (int)packet_size;
size_t max_send = min(max_window, opt_sndbuf, max_window_user);
// subtract one to save space for the FIN packet
if (cur_window_packets >= OUTGOING_BUFFER_MAX_SIZE - 1) {
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "is_full:false cur_window_packets:%d MAX:%d", cur_window_packets, OUTGOING_BUFFER_MAX_SIZE - 1);
#endif
last_maxed_out_window = ctx->current_ms;
return true;
}
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "is_full:%s. cur_window:%u pkt:%u max:%u cur_window_packets:%u max_window:%u"
, (cur_window + bytes > max_send) ? "true" : "false"
, cur_window, bytes, max_send, cur_window_packets
, max_window);
#endif
if (cur_window + bytes > max_send) {
last_maxed_out_window = ctx->current_ms;
return true;
}
return false;
}
bool UTPSocket::flush_packets()
{
size_t packet_size = get_packet_size();
// send packets that are waiting on the pacer to be sent
// i has to be an unsigned 16 bit counter to wrap correctly
// signed types are not guaranteed to wrap the way you expect
for (uint16 i = seq_nr - cur_window_packets; i != seq_nr; ++i) {
OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(i);
if (pkt == 0 || (pkt->transmissions > 0 && pkt->need_resend == false)) continue;
// have we run out of quota?
if (is_full()) return true;
// Nagle check
// don't send the last packet if we have one packet in-flight
// and the current packet is still smaller than packet_size.
if (i != ((seq_nr - 1) & ACK_NR_MASK) ||
cur_window_packets == 1 ||
pkt->payload >= packet_size) {
send_packet(pkt);
}
}
return false;
}
// @payload: number of bytes to send
// @flags: either ST_DATA, or ST_FIN
// @iovec: base address of iovec array
// @num_iovecs: number of iovecs in array
void UTPSocket::write_outgoing_packet(size_t payload, uint flags, struct utp_iovec *iovec, size_t num_iovecs)
{
// Setup initial timeout timer
if (cur_window_packets == 0) {
retransmit_timeout = rto;
rto_timeout = ctx->current_ms + retransmit_timeout;
assert(cur_window == 0);
}
size_t packet_size = get_packet_size();
do {
assert(cur_window_packets < OUTGOING_BUFFER_MAX_SIZE);
assert(flags == ST_DATA || flags == ST_FIN);
size_t added = 0;
OutgoingPacket *pkt = NULL;
if (cur_window_packets > 0) {
pkt = (OutgoingPacket*)outbuf.get(seq_nr - 1);
}
const size_t header_size = get_header_size();
bool append = true;
// if there's any room left in the last packet in the window
// and it hasn't been sent yet, fill that frame first
if (payload && pkt && !pkt->transmissions && pkt->payload < packet_size) {
// Use the previous unsent packet
added = min(payload + pkt->payload, max<size_t>(packet_size, pkt->payload)) - pkt->payload;
pkt = (OutgoingPacket*)realloc(pkt,
(sizeof(OutgoingPacket) - 1) +
header_size +
pkt->payload + added);
outbuf.put(seq_nr - 1, pkt);
append = false;
assert(!pkt->need_resend);
} else {
// Create the packet to send.
added = payload;
pkt = (OutgoingPacket*)malloc((sizeof(OutgoingPacket) - 1) +
header_size +
added);
pkt->payload = 0;
pkt->transmissions = 0;
pkt->need_resend = false;
}
if (added) {
assert(flags == ST_DATA);
// Fill it with data from the upper layer.
unsigned char *p = pkt->data + header_size + pkt->payload;
size_t needed = added;
/*
while (needed) {
*p = *(char*)iovec[0].iov_base;
p++;
iovec[0].iov_base = (char *)iovec[0].iov_base + 1;
needed--;
}
*/
for (size_t i = 0; i < num_iovecs && needed; i++) {
if (iovec[i].iov_len == 0)
continue;
size_t num = min<size_t>(needed, iovec[i].iov_len);
memcpy(p, iovec[i].iov_base, num);
p += num;
iovec[i].iov_len -= num;
iovec[i].iov_base = (byte*)iovec[i].iov_base + num; // iovec[i].iov_base += num, but without void* pointers
needed -= num;
}
assert(needed == 0);
}
pkt->payload += added;
pkt->length = header_size + pkt->payload;
last_rcv_win = get_rcv_window();
PacketFormatV1* p1 = (PacketFormatV1*)pkt->data;
p1->set_version(1);
p1->set_type(flags);
p1->ext = 0;
p1->connid = conn_id_send;
p1->windowsize = (uint32)last_rcv_win;
p1->ack_nr = ack_nr;
if (append) {
// Remember the message in the outgoing queue.
outbuf.ensure_size(seq_nr, cur_window_packets);
outbuf.put(seq_nr, pkt);
p1->seq_nr = seq_nr;
seq_nr++;
cur_window_packets++;
}
payload -= added;
} while (payload);
flush_packets();
}
#ifdef _DEBUG
void UTPSocket::check_invariant()
{
if (reorder_count > 0) {
assert(inbuf.get(ack_nr + 1) == NULL);
}
size_t outstanding_bytes = 0;
for (int i = 0; i < cur_window_packets; ++i) {
OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(seq_nr - i - 1);
if (pkt == 0 || pkt->transmissions == 0 || pkt->need_resend) continue;
outstanding_bytes += pkt->payload;
}
assert(outstanding_bytes == cur_window);
}
#endif
void UTPSocket::check_timeouts()
{
#ifdef _DEBUG
check_invariant();
#endif
// this invariant should always be true
assert(cur_window_packets == 0 || outbuf.get(seq_nr - cur_window_packets));
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "CheckTimeouts timeout:%d max_window:%u cur_window:%u "
"state:%s cur_window_packets:%u",
(int)(rto_timeout - ctx->current_ms), (uint)max_window, (uint)cur_window,
statenames[state], cur_window_packets);
#endif
if (state != CS_DESTROY) flush_packets();
switch (state) {
case CS_SYN_SENT:
case CS_SYN_RECV:
case CS_CONNECTED_FULL:
case CS_CONNECTED: {
// Reset max window...
if ((int)(ctx->current_ms - zerowindow_time) >= 0 && max_window_user == 0) {
max_window_user = PACKET_SIZE;
}
if ((int)(ctx->current_ms - rto_timeout) >= 0
&& rto_timeout > 0) {
bool ignore_loss = false;
if (cur_window_packets == 1
&& ((seq_nr - 1) & ACK_NR_MASK) == mtu_probe_seq
&& mtu_probe_seq != 0) {
// we only had a single outstanding packet that timed out, and it was the probe
mtu_ceiling = mtu_probe_size - 1;
mtu_search_update();
// this packet was most likely dropped because the packet size being
// too big and not because congestion. To accelerate the binary search for
// the MTU, resend immediately and don't reset the window size
ignore_loss = true;
log(UTP_LOG_MTU, "MTU [PROBE-TIMEOUT] floor:%d ceiling:%d current:%d"
, mtu_floor, mtu_ceiling, mtu_last);
}
// we dropepd the probe, clear these fields to
// allow us to send a new one
mtu_probe_seq = mtu_probe_size = 0;
log(UTP_LOG_MTU, "MTU [TIMEOUT]");
/*
OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(seq_nr - cur_window_packets);
// If there were a lot of retransmissions, force recomputation of round trip time
if (pkt->transmissions >= 4)
rtt = 0;
*/
// Increase RTO
const uint new_timeout = ignore_loss ? retransmit_timeout : retransmit_timeout * 2;
// They initiated the connection but failed to respond before the rto.
// A malicious client can also spoof the destination address of a ST_SYN bringing us to this state.
// Kill the connection and do not notify the upper layer
if (state == CS_SYN_RECV) {
state = CS_DESTROY;
utp_call_on_error(ctx, this, UTP_ETIMEDOUT);
return;
}
// We initiated the connection but the other side failed to respond before the rto
if (retransmit_count >= 4 || (state == CS_SYN_SENT && retransmit_count >= 2)) {
// 4 consecutive transmissions have timed out. Kill it. If we
// haven't even connected yet, give up after only 2 consecutive
// failed transmissions.
if (close_requested)
state = CS_DESTROY;
else
state = CS_RESET;
utp_call_on_error(ctx, this, UTP_ETIMEDOUT);
return;
}
retransmit_timeout = new_timeout;
rto_timeout = ctx->current_ms + new_timeout;
if (!ignore_loss) {
// On Timeout
duplicate_ack = 0;
int packet_size = get_packet_size();
if ((cur_window_packets == 0) && ((int)max_window > packet_size)) {
// we don't have any packets in-flight, even though
// we could. This implies that the connection is just
// idling. No need to be aggressive about resetting the
// congestion window. Just let it decay by a 3:rd.
// don't set it any lower than the packet size though
max_window = max(max_window * 2 / 3, size_t(packet_size));
} else {
// our delay was so high that our congestion window
// was shrunk below one packet, preventing us from
// sending anything for one time-out period. Now, reset
// the congestion window to fit one packet, to start over
// again
max_window = packet_size;
slow_start = true;
}
}
// every packet should be considered lost
for (int i = 0; i < cur_window_packets; ++i) {
OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(seq_nr - i - 1);
if (pkt == 0 || pkt->transmissions == 0 || pkt->need_resend) continue;
pkt->need_resend = true;
assert(cur_window >= pkt->payload);
cur_window -= pkt->payload;
}
if (cur_window_packets > 0) {
retransmit_count++;
// used in parse_log.py
log(UTP_LOG_NORMAL, "Packet timeout. Resend. seq_nr:%u. timeout:%u "
"max_window:%u cur_window_packets:%d"
, seq_nr - cur_window_packets, retransmit_timeout
, (uint)max_window, int(cur_window_packets));
fast_timeout = true;
timeout_seq_nr = seq_nr;
OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(seq_nr - cur_window_packets);
assert(pkt);
// Re-send the packet.
send_packet(pkt);
}
}
// Mark the socket as writable. If the cwnd has grown, or if the number of
// bytes in-flight is lower than cwnd, we need to make the socket writable again
// in case it isn't
if (state == CS_CONNECTED_FULL && !is_full()) {
state = CS_CONNECTED;
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "Socket writable. max_window:%u cur_window:%u packet_size:%u",
(uint)max_window, (uint)cur_window, (uint)get_packet_size());
#endif
utp_call_on_state_change(this->ctx, this, UTP_STATE_WRITABLE);
}
if (state >= CS_CONNECTED && !fin_sent) {
if ((int)(ctx->current_ms - last_sent_packet) >= KEEPALIVE_INTERVAL) {
send_keep_alive();
}
}
break;
}
// prevent warning
case CS_UNINITIALIZED:
case CS_IDLE:
case CS_RESET:
case CS_DESTROY:
break;
}
}
// this should be called every time we change mtu_floor or mtu_ceiling
void UTPSocket::mtu_search_update()
{
assert(mtu_floor <= mtu_ceiling);
// binary search
mtu_last = (mtu_floor + mtu_ceiling) / 2;
// enable a new probe to be sent
mtu_probe_seq = mtu_probe_size = 0;
// if the floor and ceiling are close enough, consider the
// MTU binary search complete. We set the current value
// to floor since that's the only size we know can go through
// also set the ceiling to floor to terminate the searching
if (mtu_ceiling - mtu_floor <= 16) {
mtu_last = mtu_floor;
log(UTP_LOG_MTU, "MTU [DONE] floor:%d ceiling:%d current:%d"
, mtu_floor, mtu_ceiling, mtu_last);
mtu_ceiling = mtu_floor;
assert(mtu_floor <= mtu_ceiling);
// Do another search in 30 minutes
mtu_discover_time = utp_call_get_milliseconds(this->ctx, this) + 30 * 60 * 1000;
}
}
void UTPSocket::mtu_reset()
{
mtu_ceiling = get_udp_mtu();
// Less would not pass TCP...
mtu_floor = 576;
log(UTP_LOG_MTU, "MTU [RESET] floor:%d ceiling:%d current:%d"
, mtu_floor, mtu_ceiling, mtu_last);
assert(mtu_floor <= mtu_ceiling);
mtu_discover_time = utp_call_get_milliseconds(this->ctx, this) + 30 * 60 * 1000;
}
// returns:
// 0: the packet was acked.
// 1: it means that the packet had already been acked
// 2: the packet has not been sent yet
int UTPSocket::ack_packet(uint16 seq)
{
OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(seq);
// the packet has already been acked (or not sent)
if (pkt == NULL) {
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "got ack for:%u (already acked, or never sent)", seq);
#endif
return 1;
}
// can't ack packets that haven't been sent yet!
if (pkt->transmissions == 0) {
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "got ack for:%u (never sent, pkt_size:%u need_resend:%u)",
seq, (uint)pkt->payload, pkt->need_resend);
#endif
return 2;
}
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "got ack for:%u (pkt_size:%u need_resend:%u)",
seq, (uint)pkt->payload, pkt->need_resend);
#endif
outbuf.put(seq, NULL);
// if we never re-sent the packet, update the RTT estimate
if (pkt->transmissions == 1) {
// Estimate the round trip time.
const uint32 ertt = (uint32)((utp_call_get_microseconds(this->ctx, this) - pkt->time_sent) / 1000);
if (rtt == 0) {
// First round trip time sample
rtt = ertt;
rtt_var = ertt / 2;
// sanity check. rtt should never be more than 6 seconds
// assert(rtt < 6000);
} else {
// Compute new round trip times
const int delta = (int)rtt - ertt;
rtt_var = rtt_var + (int)(abs(delta) - rtt_var) / 4;
rtt = rtt - rtt/8 + ertt/8;
// sanity check. rtt should never be more than 6 seconds
// assert(rtt < 6000);
rtt_hist.add_sample(ertt, ctx->current_ms);
}
rto = max<uint>(rtt + rtt_var * 4, 1000);
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "rtt:%u avg:%u var:%u rto:%u",
ertt, rtt, rtt_var, rto);
#endif
}
retransmit_timeout = rto;
rto_timeout = ctx->current_ms + rto;
// if need_resend is set, this packet has already
// been considered timed-out, and is not included in
// the cur_window anymore
if (!pkt->need_resend) {
assert(cur_window >= pkt->payload);
cur_window -= pkt->payload;
}
free(pkt);
retransmit_count = 0;
return 0;
}
// count the number of bytes that were acked by the EACK header
size_t UTPSocket::selective_ack_bytes(uint base, const byte* mask, byte len, int64& min_rtt)
{
if (cur_window_packets == 0) return 0;
size_t acked_bytes = 0;
int bits = len * 8;
uint64 now = utp_call_get_microseconds(this->ctx, this);
do {
uint v = base + bits;
// ignore bits that haven't been sent yet
// see comment in UTPSocket::selective_ack
if (((seq_nr - v - 1) & ACK_NR_MASK) >= (uint16)(cur_window_packets - 1))
continue;
// ignore bits that represents packets we haven't sent yet
// or packets that have already been acked
OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(v);
if (!pkt || pkt->transmissions == 0)
continue;
// Count the number of segments that were successfully received past it.
if (bits >= 0 && mask[bits>>3] & (1 << (bits & 7))) {
assert((int)(pkt->payload) >= 0);
acked_bytes += pkt->payload;
if (pkt->time_sent < now)
min_rtt = min<int64>(min_rtt, now - pkt->time_sent);
else
min_rtt = min<int64>(min_rtt, 50000);
continue;
}
} while (--bits >= -1);
return acked_bytes;
}
enum { MAX_EACK = 128 };
void UTPSocket::selective_ack(uint base, const byte *mask, byte len)
{
if (cur_window_packets == 0) return;
// the range is inclusive [0, 31] bits
int bits = len * 8 - 1;
int count = 0;
// resends is a stack of sequence numbers we need to resend. Since we
// iterate in reverse over the acked packets, at the end, the top packets
// are the ones we want to resend
int resends[MAX_EACK];
int nr = 0;
#if UTP_DEBUG_LOGGING
char bitmask[1024] = {0};
int counter = bits;
for (int i = 0; i <= bits; ++i) {
bool bit_set = counter >= 0 && mask[counter>>3] & (1 << (counter & 7));
bitmask[i] = bit_set ? '1' : '0';
--counter;
}
log(UTP_LOG_DEBUG, "Got EACK [%s] base:%u", bitmask, base);
#endif
do {
// we're iterating over the bits from higher sequence numbers
// to lower (kind of in reverse order, wich might not be very
// intuitive)
uint v = base + bits;
// ignore bits that haven't been sent yet
// and bits that fall below the ACKed sequence number
// this can happen if an EACK message gets
// reordered and arrives after a packet that ACKs up past
// the base for thie EACK message
// this is essentially the same as:
// if v >= seq_nr || v <= seq_nr - cur_window_packets
// but it takes wrapping into account
// if v == seq_nr the -1 will make it wrap. if v > seq_nr
// it will also wrap (since it will fall further below 0)
// and be > cur_window_packets.
// if v == seq_nr - cur_window_packets, the result will be
// seq_nr - (seq_nr - cur_window_packets) - 1
// == seq_nr - seq_nr + cur_window_packets - 1
// == cur_window_packets - 1 which will be caught by the
// test. If v < seq_nr - cur_window_packets the result will grow
// fall furhter outside of the cur_window_packets range.
// sequence number space:
//
// rejected < accepted > rejected
// <============+--------------+============>
// ^ ^
// | |
// (seq_nr-wnd) seq_nr
if (((seq_nr - v - 1) & ACK_NR_MASK) >= (uint16)(cur_window_packets - 1))
continue;
// this counts as a duplicate ack, even though we might have
// received an ack for this packet previously (in another EACK
// message for instance)
bool bit_set = bits >= 0 && mask[bits>>3] & (1 << (bits & 7));
// if this packet is acked, it counts towards the duplicate ack counter
if (bit_set) count++;
// ignore bits that represents packets we haven't sent yet
// or packets that have already been acked
OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(v);
if (!pkt || pkt->transmissions == 0) {
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "skipping %u. pkt:%08x transmissions:%u %s",
v, pkt, pkt?pkt->transmissions:0, pkt?"(not sent yet?)":"(already acked?)");
#endif
continue;
}
// Count the number of segments that were successfully received past it.
if (bit_set) {
// the selective ack should never ACK the packet we're waiting for to decrement cur_window_packets
assert((v & outbuf.mask) != ((seq_nr - cur_window_packets) & outbuf.mask));
ack_packet(v);
continue;
}
// Resend segments
// if count is less than our re-send limit, we haven't seen enough
// acked packets in front of this one to warrant a re-send.
// if count == 0, we're still going through the tail of zeroes
if (((v - fast_resend_seq_nr) & ACK_NR_MASK) <= OUTGOING_BUFFER_MAX_SIZE &&
count >= DUPLICATE_ACKS_BEFORE_RESEND) {
// resends is a stack, and we're mostly interested in the top of it
// if we're full, just throw away the lower half
if (nr >= MAX_EACK - 2) {
memmove(resends, &resends[MAX_EACK/2], MAX_EACK/2 * sizeof(resends[0]));
nr -= MAX_EACK / 2;
}
resends[nr++] = v;
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "no ack for %u", v);
#endif
} else {
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "not resending %u count:%d dup_ack:%u fast_resend_seq_nr:%u",
v, count, duplicate_ack, fast_resend_seq_nr);
#endif
}
} while (--bits >= -1);
if (((base - 1 - fast_resend_seq_nr) & ACK_NR_MASK) <= OUTGOING_BUFFER_MAX_SIZE &&
count >= DUPLICATE_ACKS_BEFORE_RESEND) {
// if we get enough duplicate acks to start
// resending, the first packet we should resend
// is base-1
resends[nr++] = (base - 1) & ACK_NR_MASK;
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "no ack for %u", (base - 1) & ACK_NR_MASK);
#endif
} else {
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "not resending %u count:%d dup_ack:%u fast_resend_seq_nr:%u",
base - 1, count, duplicate_ack, fast_resend_seq_nr);
#endif
}
bool back_off = false;
int i = 0;
while (nr > 0) {
uint v = resends[--nr];
// don't consider the tail of 0:es to be lost packets
// only unacked packets with acked packets after should
// be considered lost
OutgoingPacket *pkt = (OutgoingPacket*)outbuf.get(v);
// this may be an old (re-ordered) packet, and some of the
// packets in here may have been acked already. In which
// case they will not be in the send queue anymore
if (!pkt) continue;
// used in parse_log.py
log(UTP_LOG_NORMAL, "Packet %u lost. Resending", v);
// On Loss
back_off = true;
#ifdef _DEBUG
++_stats.rexmit;
#endif
send_packet(pkt);
fast_resend_seq_nr = (v + 1) & ACK_NR_MASK;
// Re-send max 4 packets.
if (++i >= 4) break;
}
if (back_off)
maybe_decay_win(ctx->current_ms);
duplicate_ack = count;
}
void UTPSocket::apply_ccontrol(size_t bytes_acked, uint32 actual_delay, int64 min_rtt)
{
// the delay can never be greater than the rtt. The min_rtt
// variable is the RTT in microseconds
assert(min_rtt >= 0);
int32 our_delay = min<uint32>(our_hist.get_value(), uint32(min_rtt));
assert(our_delay != INT_MAX);
assert(our_delay >= 0);
utp_call_on_delay_sample(this->ctx, this, our_delay / 1000);
// This test the connection under heavy load from foreground
// traffic. Pretend that our delays are very high to force the
// connection to use sub-packet size window sizes
//our_delay *= 4;
// target is microseconds
int target = target_delay;
if (target <= 0) target = 100000;
// this is here to compensate for very large clock drift that affects
// the congestion controller into giving certain endpoints an unfair
// share of the bandwidth. We have an estimate of the clock drift
// (clock_drift). The unit of this is microseconds per 5 seconds.
// empirically, a reasonable cut-off appears to be about 200000
// (which is pretty high). The main purpose is to compensate for
// people trying to "cheat" uTP by making their clock run slower,
// and this definitely catches that without any risk of false positives
// if clock_drift < -200000 start applying a penalty delay proportional
// to how far beoynd -200000 the clock drift is
int32 penalty = 0;
if (clock_drift < -200000) {
penalty = (-clock_drift - 200000) / 7;
our_delay += penalty;
}
double off_target = target - our_delay;
// this is the same as:
//
// (min(off_target, target) / target) * (bytes_acked / max_window) * MAX_CWND_INCREASE_BYTES_PER_RTT
//
// so, it's scaling the max increase by the fraction of the window this ack represents, and the fraction
// of the target delay the current delay represents.
// The min() around off_target protects against crazy values of our_delay, which may happen when th
// timestamps wraps, or by just having a malicious peer sending garbage. This caps the increase
// of the window size to MAX_CWND_INCREASE_BYTES_PER_RTT per rtt.
// as for large negative numbers, this direction is already capped at the min packet size further down
// the min around the bytes_acked protects against the case where the window size was recently
// shrunk and the number of acked bytes exceeds that. This is considered no more than one full
// window, in order to keep the gain within sane boundries.
assert(bytes_acked > 0);
double window_factor = (double)min(bytes_acked, max_window) / (double)max(max_window, bytes_acked);
double delay_factor = off_target / target;
double scaled_gain = MAX_CWND_INCREASE_BYTES_PER_RTT * window_factor * delay_factor;
// since MAX_CWND_INCREASE_BYTES_PER_RTT is a cap on how much the window size (max_window)
// may increase per RTT, we may not increase the window size more than that proportional
// to the number of bytes that were acked, so that once one window has been acked (one rtt)
// the increase limit is not exceeded
// the +1. is to allow for floating point imprecision
assert(scaled_gain <= 1. + MAX_CWND_INCREASE_BYTES_PER_RTT * (double)min(bytes_acked, max_window) / (double)max(max_window, bytes_acked));
if (scaled_gain > 0 && ctx->current_ms - last_maxed_out_window > 1000) {
// if it was more than 1 second since we tried to send a packet
// and stopped because we hit the max window, we're most likely rate
// limited (which prevents us from ever hitting the window size)
// if this is the case, we cannot let the max_window grow indefinitely
scaled_gain = 0;
}
size_t ledbat_cwnd = (max_window + scaled_gain < MIN_WINDOW_SIZE) ? MIN_WINDOW_SIZE : (size_t)(max_window + scaled_gain);
if (slow_start) {
size_t ss_cwnd = (size_t)(max_window + window_factor*get_packet_size());
if (ss_cwnd > ssthresh) {
slow_start = false;
} else if (our_delay > target*0.9) {
// even if we're a little under the target delay, we conservatively
// discontinue the slow start phase
slow_start = false;
ssthresh = max_window;
} else {
max_window = max(ss_cwnd, ledbat_cwnd);
}
} else {
max_window = ledbat_cwnd;
}
// make sure that the congestion window is below max
// make sure that we don't shrink our window too small
max_window = clamp<size_t>(max_window, MIN_WINDOW_SIZE, opt_sndbuf);
// used in parse_log.py
log(UTP_LOG_NORMAL, "actual_delay:%u our_delay:%d their_delay:%u off_target:%d max_window:%u "
"delay_base:%u delay_sum:%d target_delay:%d acked_bytes:%u cur_window:%u "
"scaled_gain:%f rtt:%u rate:%u wnduser:%u rto:%u timeout:%d get_microseconds:" I64u " "
"cur_window_packets:%u packet_size:%u their_delay_base:%u their_actual_delay:%u "
"average_delay:%d clock_drift:%d clock_drift_raw:%d delay_penalty:%d current_delay_sum:" I64u
"current_delay_samples:%d average_delay_base:%d last_maxed_out_window:" I64u " opt_sndbuf:%d "
"current_ms:" I64u "",
actual_delay, our_delay / 1000, their_hist.get_value() / 1000,
int(off_target / 1000), uint(max_window), uint32(our_hist.delay_base),
int((our_delay + their_hist.get_value()) / 1000), int(target / 1000), uint(bytes_acked),
(uint)(cur_window - bytes_acked), (float)(scaled_gain), rtt,
(uint)(max_window * 1000 / (rtt_hist.delay_base?rtt_hist.delay_base:50)),
(uint)max_window_user, rto, (int)(rto_timeout - ctx->current_ms),
utp_call_get_microseconds(this->ctx, this), cur_window_packets, (uint)get_packet_size(),
their_hist.delay_base, their_hist.delay_base + their_hist.get_value(),
average_delay, clock_drift, clock_drift_raw, penalty / 1000,
current_delay_sum, current_delay_samples, average_delay_base,
uint64(last_maxed_out_window), int(opt_sndbuf), uint64(ctx->current_ms));
}
static void utp_register_recv_packet(UTPSocket *conn, size_t len)
{
#ifdef _DEBUG
++conn->_stats.nrecv;
conn->_stats.nbytes_recv += len;
#endif
if (len <= PACKET_SIZE_MID) {
if (len <= PACKET_SIZE_EMPTY) {
conn->ctx->context_stats._nraw_recv[PACKET_SIZE_EMPTY_BUCKET]++;
} else if (len <= PACKET_SIZE_SMALL) {
conn->ctx->context_stats._nraw_recv[PACKET_SIZE_SMALL_BUCKET]++;
} else
conn->ctx->context_stats._nraw_recv[PACKET_SIZE_MID_BUCKET]++;
} else {
if (len <= PACKET_SIZE_BIG) {
conn->ctx->context_stats._nraw_recv[PACKET_SIZE_BIG_BUCKET]++;
} else
conn->ctx->context_stats._nraw_recv[PACKET_SIZE_HUGE_BUCKET]++;
}
}
// returns the max number of bytes of payload the uTP
// connection is allowed to send
size_t UTPSocket::get_packet_size() const
{
int header_size = sizeof(PacketFormatV1);
size_t mtu = mtu_last ? mtu_last : mtu_ceiling;
return mtu - header_size;
}
// Process an incoming packet
// syn is true if this is the first packet received. It will cut off parsing
// as soon as the header is done
size_t utp_process_incoming(UTPSocket *conn, const byte *packet, size_t len, bool syn = false)
{
utp_register_recv_packet(conn, len);
conn->ctx->current_ms = utp_call_get_milliseconds(conn->ctx, conn);
const PacketFormatV1 *pf1 = (PacketFormatV1*)packet;
const byte *packet_end = packet + len;
uint16 pk_seq_nr = pf1->seq_nr;
uint16 pk_ack_nr = pf1->ack_nr;
uint8 pk_flags = pf1->type();
if (pk_flags >= ST_NUM_STATES) return 0;
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "Got %s. seq_nr:%u ack_nr:%u state:%s timestamp:" I64u " reply_micro:%u"
, flagnames[pk_flags], pk_seq_nr, pk_ack_nr, statenames[conn->state]
, uint64(pf1->tv_usec), (uint32)(pf1->reply_micro));
#endif
// mark receipt time
uint64 time = utp_call_get_microseconds(conn->ctx, conn);
// window packets size is used to calculate a minimum
// permissible range for received acks. connections with acks falling
// out of this range are dropped
const uint16 curr_window = max<uint16>(conn->cur_window_packets + ACK_NR_ALLOWED_WINDOW, ACK_NR_ALLOWED_WINDOW);
// ignore packets whose ack_nr is invalid. This would imply a spoofed address
// or a malicious attempt to attach the uTP implementation.
// acking a packet that hasn't been sent yet!
// SYN packets have an exception, since there are no previous packets
if ((pk_flags != ST_SYN || conn->state != CS_SYN_RECV) &&
(wrapping_compare_less(conn->seq_nr - 1, pk_ack_nr, ACK_NR_MASK)
|| wrapping_compare_less(pk_ack_nr, conn->seq_nr - 1 - curr_window, ACK_NR_MASK))) {
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "Invalid ack_nr: %u. our seq_nr: %u last unacked: %u"
, pk_ack_nr, conn->seq_nr, (conn->seq_nr - conn->cur_window_packets) & ACK_NR_MASK);
#endif
return 0;
}
// RSTs are handled earlier, since the connid matches the send id not the recv id
assert(pk_flags != ST_RESET);
// TODO: maybe send a ST_RESET if we're in CS_RESET?
const byte *selack_ptr = NULL;
// Unpack UTP packet options
// Data pointer
const byte *data = (const byte*)pf1 + conn->get_header_size();
if (conn->get_header_size() > len) {
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "Invalid packet size (less than header size)");
#endif
return 0;
}
// Skip the extension headers
uint extension = pf1->ext;
if (extension != 0) {
do {
// Verify that the packet is valid.
data += 2;
if ((int)(packet_end - data) < 0 || (int)(packet_end - data) < data[-1]) {
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "Invalid len of extensions");
#endif
return 0;
}
switch(extension) {
case 1: // Selective Acknowledgment
selack_ptr = data;
break;
case 2: // extension bits
if (data[-1] != 8) {
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "Invalid len of extension bits header");
#endif
return 0;
}
memcpy(conn->extensions, data, 8);
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "got extension bits:%02x%02x%02x%02x%02x%02x%02x%02x",
conn->extensions[0], conn->extensions[1], conn->extensions[2], conn->extensions[3],
conn->extensions[4], conn->extensions[5], conn->extensions[6], conn->extensions[7]);
#endif
}
extension = data[-2];
data += data[-1];
} while (extension);
}
if (conn->state == CS_SYN_SENT) {
// if this is a syn-ack, initialize our ack_nr
// to match the sequence number we got from
// the other end
conn->ack_nr = (pk_seq_nr - 1) & SEQ_NR_MASK;
}
conn->last_got_packet = conn->ctx->current_ms;
if (syn) {
return 0;
}
// seqnr is the number of packets past the expected
// packet this is. ack_nr is the last acked, seq_nr is the
// current. Subtracring 1 makes 0 mean "this is the next
// expected packet".
const uint seqnr = (pk_seq_nr - conn->ack_nr - 1) & SEQ_NR_MASK;
// Getting an invalid sequence number?
if (seqnr >= REORDER_BUFFER_MAX_SIZE) {
if (seqnr >= (SEQ_NR_MASK + 1) - REORDER_BUFFER_MAX_SIZE && pk_flags != ST_STATE) {
conn->schedule_ack();
}
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, " Got old Packet/Ack (%u/%u)=%u"
, pk_seq_nr, conn->ack_nr, seqnr);
#endif
return 0;
}
// Process acknowledgment
// acks is the number of packets that was acked
int acks = (pk_ack_nr - (conn->seq_nr - 1 - conn->cur_window_packets)) & ACK_NR_MASK;
// this happens when we receive an old ack nr
if (acks > conn->cur_window_packets) acks = 0;
// if we get the same ack_nr as in the last packet
// increase the duplicate_ack counter, otherwise reset
// it to 0.
// It's important to only count ACKs in ST_STATE packets. Any other
// packet (primarily ST_DATA) is likely to have been sent because of the
// other end having new outgoing data, not in response to incoming data.
// For instance, if we're receiving a steady stream of payload with no
// outgoing data, and we suddently have a few bytes of payload to send (say,
// a bittorrent HAVE message), we're very likely to see 3 duplicate ACKs
// immediately after sending our payload packet. This effectively disables
// the fast-resend on duplicate-ack logic for bi-directional connections
// (except in the case of a selective ACK). This is in line with BSD4.4 TCP
// implementation.
if (conn->cur_window_packets > 0) {
if (pk_ack_nr == ((conn->seq_nr - conn->cur_window_packets - 1) & ACK_NR_MASK)
&& conn->cur_window_packets > 0
&& pk_flags == ST_STATE) {
++conn->duplicate_ack;
if (conn->duplicate_ack == DUPLICATE_ACKS_BEFORE_RESEND && conn->mtu_probe_seq) {
// It's likely that the probe was rejected due to its size, but we haven't got an
// ICMP report back yet
if (pk_ack_nr == ((conn->mtu_probe_seq - 1) & ACK_NR_MASK)) {
conn->mtu_ceiling = conn->mtu_probe_size - 1;
conn->mtu_search_update();
conn->log(UTP_LOG_MTU, "MTU [DUPACK] floor:%d ceiling:%d current:%d"
, conn->mtu_floor, conn->mtu_ceiling, conn->mtu_last);
} else {
// A non-probe was blocked before our probe.
// Can't conclude much, send a new probe
conn->mtu_probe_seq = conn->mtu_probe_size = 0;
}
}
} else {
conn->duplicate_ack = 0;
}
// TODO: if duplicate_ack == DUPLICATE_ACK_BEFORE_RESEND
// and fast_resend_seq_nr <= ack_nr + 1
// resend ack_nr + 1
// also call maybe_decay_win()
}
// figure out how many bytes were acked
size_t acked_bytes = 0;
// the minimum rtt of all acks
// this is the upper limit on the delay we get back
// from the other peer. Our delay cannot exceed
// the rtt of the packet. If it does, clamp it.
// this is done in apply_ledbat_ccontrol()
int64 min_rtt = INT64_MAX;
uint64 now = utp_call_get_microseconds(conn->ctx, conn);
for (int i = 0; i < acks; ++i) {
int seq = (conn->seq_nr - conn->cur_window_packets + i) & ACK_NR_MASK;
OutgoingPacket *pkt = (OutgoingPacket*)conn->outbuf.get(seq);
if (pkt == 0 || pkt->transmissions == 0) continue;
assert((int)(pkt->payload) >= 0);
acked_bytes += pkt->payload;
if (conn->mtu_probe_seq && seq == conn->mtu_probe_seq) {
conn->mtu_floor = conn->mtu_probe_size;
conn->mtu_search_update();
conn->log(UTP_LOG_MTU, "MTU [ACK] floor:%d ceiling:%d current:%d"
, conn->mtu_floor, conn->mtu_ceiling, conn->mtu_last);
}
// in case our clock is not monotonic
if (pkt->time_sent < now)
min_rtt = min<int64>(min_rtt, now - pkt->time_sent);
else
min_rtt = min<int64>(min_rtt, 50000);
}
// count bytes acked by EACK
if (selack_ptr != NULL) {
acked_bytes += conn->selective_ack_bytes((pk_ack_nr + 2) & ACK_NR_MASK,
selack_ptr, selack_ptr[-1], min_rtt);
}
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "acks:%d acked_bytes:%u seq_nr:%d cur_window:%u cur_window_packets:%u relative_seqnr:%u max_window:%u min_rtt:%u rtt:%u",
acks, (uint)acked_bytes, conn->seq_nr, (uint)conn->cur_window, conn->cur_window_packets,
seqnr, (uint)conn->max_window, (uint)(min_rtt / 1000), conn->rtt);
#endif
uint64 p = pf1->tv_usec;
conn->last_measured_delay = conn->ctx->current_ms;
// get delay in both directions
// record the delay to report back
const uint32 their_delay = (uint32)(p == 0 ? 0 : time - p);
conn->reply_micro = their_delay;
uint32 prev_delay_base = conn->their_hist.delay_base;
if (their_delay != 0) conn->their_hist.add_sample(their_delay, conn->ctx->current_ms);
// if their new delay base is less than their previous one
// we should shift our delay base in the other direction in order
// to take the clock skew into account
if (prev_delay_base != 0 &&
wrapping_compare_less(conn->their_hist.delay_base, prev_delay_base, TIMESTAMP_MASK)) {
// never adjust more than 10 milliseconds
if (prev_delay_base - conn->their_hist.delay_base <= 10000) {
conn->our_hist.shift(prev_delay_base - conn->their_hist.delay_base);
}
}
const uint32 actual_delay = (uint32(pf1->reply_micro)==INT_MAX?0:uint32(pf1->reply_micro));
// if the actual delay is 0, it means the other end
// hasn't received a sample from us yet, and doesn't
// know what it is. We can't update out history unless
// we have a true measured sample
if (actual_delay != 0) {
conn->our_hist.add_sample(actual_delay, conn->ctx->current_ms);
// this is keeping an average of the delay samples
// we've recevied within the last 5 seconds. We sum
// all the samples and increase the count in order to
// calculate the average every 5 seconds. The samples
// are based off of the average_delay_base to deal with
// wrapping counters.
if (conn->average_delay_base == 0) conn->average_delay_base = actual_delay;
int64 average_delay_sample = 0;
// distance walking from lhs to rhs, downwards
const uint32 dist_down = conn->average_delay_base - actual_delay;
// distance walking from lhs to rhs, upwards
const uint32 dist_up = actual_delay - conn->average_delay_base;
if (dist_down > dist_up) {
// assert(dist_up < INT_MAX / 4);
// average_delay_base < actual_delay, we should end up
// with a positive sample
average_delay_sample = dist_up;
} else {
// assert(-int64(dist_down) < INT_MAX / 4);
// average_delay_base >= actual_delay, we should end up
// with a negative sample
average_delay_sample = -int64(dist_down);
}
conn->current_delay_sum += average_delay_sample;
++conn->current_delay_samples;
if (conn->ctx->current_ms > conn->average_sample_time) {
int32 prev_average_delay = conn->average_delay;
assert(conn->current_delay_sum / conn->current_delay_samples < INT_MAX);
assert(conn->current_delay_sum / conn->current_delay_samples > -INT_MAX);
// write the new average
conn->average_delay = (int32)(conn->current_delay_sum / conn->current_delay_samples);
// each slot represents 5 seconds
conn->average_sample_time += 5000;
conn->current_delay_sum = 0;
conn->current_delay_samples = 0;
// this makes things very confusing when logging the average delay
//#if !g_log_utp
// normalize the average samples
// since we're only interested in the slope
// of the curve formed by the average delay samples,
// we can cancel out the actual offset to make sure
// we won't have problems with wrapping.
int min_sample = min(prev_average_delay, conn->average_delay);
int max_sample = max(prev_average_delay, conn->average_delay);
// normalize around zero. Try to keep the min <= 0 and max >= 0
int adjust = 0;
if (min_sample > 0) {
// adjust all samples (and the baseline) down by min_sample
adjust = -min_sample;
} else if (max_sample < 0) {
// adjust all samples (and the baseline) up by -max_sample
adjust = -max_sample;
}
if (adjust) {
conn->average_delay_base -= adjust;
conn->average_delay += adjust;
prev_average_delay += adjust;
}
//#endif
// update the clock drift estimate
// the unit is microseconds per 5 seconds
// what we're doing is just calculating the average of the
// difference between each slot. Since each slot is 5 seconds
// and the timestamps unit are microseconds, we'll end up with
// the average slope across our history. If there is a consistent
// trend, it will show up in this value
//int64 slope = 0;
int32 drift = conn->average_delay - prev_average_delay;
// clock_drift is a rolling average
conn->clock_drift = (int64(conn->clock_drift) * 7 + drift) / 8;
conn->clock_drift_raw = drift;
}
}
// if our new delay base is less than our previous one
// we should shift the other end's delay base in the other
// direction in order to take the clock skew into account
// This is commented out because it creates bad interactions
// with our adjustment in the other direction. We don't really
// need our estimates of the other peer to be very accurate
// anyway. The problem with shifting here is that we're more
// likely shift it back later because of a low latency. This
// second shift back would cause us to shift our delay base
// which then get's into a death spiral of shifting delay bases
/* if (prev_delay_base != 0 &&
wrapping_compare_less(conn->our_hist.delay_base, prev_delay_base)) {
// never adjust more than 10 milliseconds
if (prev_delay_base - conn->our_hist.delay_base <= 10000) {
conn->their_hist.Shift(prev_delay_base - conn->our_hist.delay_base);
}
}
*/
// if the delay estimate exceeds the RTT, adjust the base_delay to
// compensate
assert(min_rtt >= 0);
if (int64(conn->our_hist.get_value()) > min_rtt) {
conn->our_hist.shift((uint32)(conn->our_hist.get_value() - min_rtt));
}
// only apply the congestion controller on acks
// if we don't have a delay measurement, there's
// no point in invoking the congestion control
if (actual_delay != 0 && acked_bytes >= 1)
conn->apply_ccontrol(acked_bytes, actual_delay, min_rtt);
// sanity check, the other end should never ack packets
// past the point we've sent
if (acks <= conn->cur_window_packets) {
conn->max_window_user = pf1->windowsize;
// If max user window is set to 0, then we startup a timer
// That will reset it to 1 after 15 seconds.
if (conn->max_window_user == 0)
// Reset max_window_user to 1 every 15 seconds.
conn->zerowindow_time = conn->ctx->current_ms + 15000;
// Respond to connect message
// Switch to CONNECTED state.
// If this is an ack and we're in still handshaking
// transition over to the connected state.
// Incoming connection completion
if (pk_flags == ST_DATA && conn->state == CS_SYN_RECV) {
conn->state = CS_CONNECTED;
}
// Outgoing connection completion
if (pk_flags == ST_STATE && conn->state == CS_SYN_SENT) {
conn->state = CS_CONNECTED;
// If the user has defined the ON_CONNECT callback, use that to
// notify the user that the socket is now connected. If ON_CONNECT
// has not been defined, notify the user via ON_STATE_CHANGE.
if (conn->ctx->callbacks[UTP_ON_CONNECT])
utp_call_on_connect(conn->ctx, conn);
else
utp_call_on_state_change(conn->ctx, conn, UTP_STATE_CONNECT);
// We've sent a fin, and everything was ACKed (including the FIN).
// cur_window_packets == acks means that this packet acked all
// the remaining packets that were in-flight.
} else if (conn->fin_sent && conn->cur_window_packets == acks) {
conn->fin_sent_acked = true;
if (conn->close_requested) {
conn->state = CS_DESTROY;
}
}
// Update fast resend counter
if (wrapping_compare_less(conn->fast_resend_seq_nr
, (pk_ack_nr + 1) & ACK_NR_MASK, ACK_NR_MASK))
conn->fast_resend_seq_nr = (pk_ack_nr + 1) & ACK_NR_MASK;
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "fast_resend_seq_nr:%u", conn->fast_resend_seq_nr);
#endif
for (int i = 0; i < acks; ++i) {
int ack_status = conn->ack_packet(conn->seq_nr - conn->cur_window_packets);
// if ack_status is 0, the packet was acked.
// if acl_stauts is 1, it means that the packet had already been acked
// if it's 2, the packet has not been sent yet
// We need to break this loop in the latter case. This could potentially
// happen if we get an ack_nr that does not exceed what we have stuffed
// into the outgoing buffer, but does exceed what we have sent
if (ack_status == 2) {
#ifdef _DEBUG
OutgoingPacket* pkt = (OutgoingPacket*)conn->outbuf.get(conn->seq_nr - conn->cur_window_packets);
assert(pkt->transmissions == 0);
#endif
break;
}
conn->cur_window_packets--;
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "decementing cur_window_packets:%u", conn->cur_window_packets);
#endif
}
#ifdef _DEBUG
if (conn->cur_window_packets == 0)
assert(conn->cur_window == 0);
#endif
// packets in front of this may have been acked by a
// selective ack (EACK). Keep decreasing the window packet size
// until we hit a packet that is still waiting to be acked
// in the send queue
// this is especially likely to happen when the other end
// has the EACK send bug older versions of uTP had
while (conn->cur_window_packets > 0 && !conn->outbuf.get(conn->seq_nr - conn->cur_window_packets)) {
conn->cur_window_packets--;
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "decementing cur_window_packets:%u", conn->cur_window_packets);
#endif
}
#ifdef _DEBUG
if (conn->cur_window_packets == 0)
assert(conn->cur_window == 0);
#endif
// this invariant should always be true
assert(conn->cur_window_packets == 0 || conn->outbuf.get(conn->seq_nr - conn->cur_window_packets));
// flush Nagle
if (conn->cur_window_packets == 1) {
OutgoingPacket *pkt = (OutgoingPacket*)conn->outbuf.get(conn->seq_nr - 1);
// do we still have quota?
if (pkt->transmissions == 0) {
conn->send_packet(pkt);
}
}
// Fast timeout-retry
if (conn->fast_timeout) {
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "Fast timeout %u,%u,%u?", (uint)conn->cur_window, conn->seq_nr - conn->timeout_seq_nr, conn->timeout_seq_nr);
#endif
// if the fast_resend_seq_nr is not pointing to the oldest outstanding packet, it suggests that we've already
// resent the packet that timed out, and we should leave the fast-timeout mode.
if (((conn->seq_nr - conn->cur_window_packets) & ACK_NR_MASK) != conn->fast_resend_seq_nr) {
conn->fast_timeout = false;
} else {
// resend the oldest packet and increment fast_resend_seq_nr
// to not allow another fast resend on it again
OutgoingPacket *pkt = (OutgoingPacket*)conn->outbuf.get(conn->seq_nr - conn->cur_window_packets);
if (pkt && pkt->transmissions > 0) {
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "Packet %u fast timeout-retry.", conn->seq_nr - conn->cur_window_packets);
#endif
#ifdef _DEBUG
++conn->_stats.fastrexmit;
#endif
conn->fast_resend_seq_nr++;
conn->send_packet(pkt);
}
}
}
}
// Process selective acknowledgent
if (selack_ptr != NULL) {
conn->selective_ack(pk_ack_nr + 2, selack_ptr, selack_ptr[-1]);
}
// this invariant should always be true
assert(conn->cur_window_packets == 0 || conn->outbuf.get(conn->seq_nr - conn->cur_window_packets));
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "acks:%d acked_bytes:%u seq_nr:%u cur_window:%u cur_window_packets:%u ",
acks, (uint)acked_bytes, conn->seq_nr, (uint)conn->cur_window, conn->cur_window_packets);
#endif
// In case the ack dropped the current window below
// the max_window size, Mark the socket as writable
if (conn->state == CS_CONNECTED_FULL && !conn->is_full()) {
conn->state = CS_CONNECTED;
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "Socket writable. max_window:%u cur_window:%u packet_size:%u",
(uint)conn->max_window, (uint)conn->cur_window, (uint)conn->get_packet_size());
#endif
utp_call_on_state_change(conn->ctx, conn, UTP_STATE_WRITABLE);
}
if (pk_flags == ST_STATE) {
// This is a state packet only.
return 0;
}
// The connection is not in a state that can accept data?
if (conn->state != CS_CONNECTED &&
conn->state != CS_CONNECTED_FULL) {
return 0;
}
// Is this a finalize packet?
if (pk_flags == ST_FIN && !conn->got_fin) {
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "Got FIN eof_pkt:%u", pk_seq_nr);
#endif
conn->got_fin = true;
conn->eof_pkt = pk_seq_nr;
// at this point, it is possible for the
// other end to have sent packets with
// sequence numbers higher than seq_nr.
// if this is the case, our reorder_count
// is out of sync. This case is dealt with
// when we re-order and hit the eof_pkt.
// we'll just ignore any packets with
// sequence numbers past this
}
// Getting an in-order packet?
if (seqnr == 0) {
size_t count = packet_end - data;
if (count > 0 && !conn->read_shutdown) {
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "Got Data len:%u (rb:%u)", (uint)count, (uint)utp_call_get_read_buffer_size(conn->ctx, conn));
#endif
// Post bytes to the upper layer
utp_call_on_read(conn->ctx, conn, data, count);
}
conn->ack_nr++;
// Check if the next packet has been received too, but waiting
// in the reorder buffer.
for (;;) {
if (!conn->got_fin_reached && conn->got_fin && conn->eof_pkt == conn->ack_nr) {
conn->got_fin_reached = true;
conn->rto_timeout = conn->ctx->current_ms + min<uint>(conn->rto * 3, 60);
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "Posting EOF");
#endif
utp_call_on_state_change(conn->ctx, conn, UTP_STATE_EOF);
// if the other end wants to close, ack
conn->send_ack();
// reorder_count is not necessarily 0 at this point.
// even though it is most of the time, the other end
// may have sent packets with higher sequence numbers
// than what later end up being eof_pkt
// since we have received all packets up to eof_pkt
// just ignore the ones after it.
conn->reorder_count = 0;
}
// Quick get-out in case there is nothing to reorder
if (conn->reorder_count == 0)
break;
// Check if there are additional buffers in the reorder buffers
// that need delivery.
byte *p = (byte*)conn->inbuf.get(conn->ack_nr+1);
if (p == NULL)
break;
conn->inbuf.put(conn->ack_nr+1, NULL);
count = *(uint*)p;
if (count > 0 && !conn->read_shutdown) {
// Pass the bytes to the upper layer
utp_call_on_read(conn->ctx, conn, p + sizeof(uint), count);
}
conn->ack_nr++;
// Free the element from the reorder buffer
free(p);
assert(conn->reorder_count > 0);
conn->reorder_count--;
}
conn->schedule_ack();
} else {
// Getting an out of order packet.
// The packet needs to be remembered and rearranged later.
// if we have received a FIN packet, and the EOF-sequence number
// is lower than the sequence number of the packet we just received
// something is wrong.
if (conn->got_fin && pk_seq_nr > conn->eof_pkt) {
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "Got an invalid packet sequence number, past EOF "
"reorder_count:%u len:%u (rb:%u)",
conn->reorder_count, (uint)(packet_end - data), (uint)utp_call_get_read_buffer_size(conn->ctx, conn));
#endif
return 0;
}
// if the sequence number is entirely off the expected
// one, just drop it. We can't allocate buffer space in
// the inbuf entirely based on untrusted input
if (seqnr > 0x3ff) {
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "0x%08x: Got an invalid packet sequence number, too far off "
"reorder_count:%u len:%u (rb:%u)",
conn->reorder_count, (uint)(packet_end - data), (uint)utp_call_get_read_buffer_size(conn->ctx, conn));
#endif
return 0;
}
// we need to grow the circle buffer before we
// check if the packet is already in here, so that
// we don't end up looking at an older packet (since
// the indices wraps around).
conn->inbuf.ensure_size(pk_seq_nr + 1, seqnr + 1);
// Has this packet already been received? (i.e. a duplicate)
// If that is the case, just discard it.
if (conn->inbuf.get(pk_seq_nr) != NULL) {
#ifdef _DEBUG
++conn->_stats.nduprecv;
#endif
return 0;
}
// Allocate memory to fit the packet that needs to re-ordered
byte *mem = (byte*)malloc((packet_end - data) + sizeof(uint));
*(uint*)mem = (uint)(packet_end - data);
memcpy(mem + sizeof(uint), data, packet_end - data);
// Insert into reorder buffer and increment the count
// of # of packets to be reordered.
// we add one to seqnr in order to leave the last
// entry empty, that way the assert in send_ack
// is valid. we have to add one to seqnr too, in order
// to make the circular buffer grow around the correct
// point (which is conn->ack_nr + 1).
assert(conn->inbuf.get(pk_seq_nr) == NULL);
assert((pk_seq_nr & conn->inbuf.mask) != ((conn->ack_nr+1) & conn->inbuf.mask));
conn->inbuf.put(pk_seq_nr, mem);
conn->reorder_count++;
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "0x%08x: Got out of order data reorder_count:%u len:%u (rb:%u)",
conn->reorder_count, (uint)(packet_end - data), (uint)utp_call_get_read_buffer_size(conn->ctx, conn));
#endif
conn->schedule_ack();
}
return (size_t)(packet_end - data);
}
inline byte UTP_Version(PacketFormatV1 const* pf)
{
return (pf->type() < ST_NUM_STATES && pf->ext < 3 ? pf->version() : 0);
}
UTPSocket::~UTPSocket()
{
#if UTP_DEBUG_LOGGING
log(UTP_LOG_DEBUG, "Killing socket");
#endif
utp_call_on_state_change(ctx, this, UTP_STATE_DESTROYING);
if (ctx->last_utp_socket == this) {
ctx->last_utp_socket = NULL;
}
// Remove object from the global hash table
UTPSocketKeyData* kd = ctx->utp_sockets->Delete(UTPSocketKey(addr, conn_id_recv));
assert(kd);
// remove the socket from ack_sockets if it was there also
removeSocketFromAckList(this);
// Free all memory occupied by the socket object.
for (size_t i = 0; i <= inbuf.mask; i++) {
free(inbuf.elements[i]);
}
for (size_t i = 0; i <= outbuf.mask; i++) {
free(outbuf.elements[i]);
}
// TODO: The circular buffer should have a destructor
free(inbuf.elements);
free(outbuf.elements);
}
void UTP_FreeAll(struct UTPSocketHT *utp_sockets) {
utp_hash_iterator_t it;
UTPSocketKeyData* keyData;
while ((keyData = utp_sockets->Iterate(it))) {
delete keyData->socket;
}
}
void utp_initialize_socket( utp_socket *conn,
const struct sockaddr *addr,
socklen_t addrlen,
bool need_seed_gen,
uint32 conn_seed,
uint32 conn_id_recv,
uint32 conn_id_send)
{
PackedSockAddr psaddr = PackedSockAddr((const SOCKADDR_STORAGE*)addr, addrlen);
if (need_seed_gen) {
do {
conn_seed = utp_call_get_random(conn->ctx, conn);
// we identify v1 and higher by setting the first two bytes to 0x0001
conn_seed &= 0xffff;
} while (conn->ctx->utp_sockets->Lookup(UTPSocketKey(psaddr, conn_seed)));
conn_id_recv += conn_seed;
conn_id_send += conn_seed;
}
conn->state = CS_IDLE;
conn->conn_seed = conn_seed;
conn->conn_id_recv = conn_id_recv;
conn->conn_id_send = conn_id_send;
conn->addr = psaddr;
conn->ctx->current_ms = utp_call_get_milliseconds(conn->ctx, NULL);
conn->last_got_packet = conn->ctx->current_ms;
conn->last_sent_packet = conn->ctx->current_ms;
conn->last_measured_delay = conn->ctx->current_ms + 0x70000000;
conn->average_sample_time = conn->ctx->current_ms + 5000;
conn->last_rwin_decay = conn->ctx->current_ms - MAX_WINDOW_DECAY;
conn->our_hist.clear(conn->ctx->current_ms);
conn->their_hist.clear(conn->ctx->current_ms);
conn->rtt_hist.clear(conn->ctx->current_ms);
// initialize MTU floor and ceiling
conn->mtu_reset();
conn->mtu_last = conn->mtu_ceiling;
conn->ctx->utp_sockets->Add(UTPSocketKey(conn->addr, conn->conn_id_recv))->socket = conn;
// we need to fit one packet in the window when we start the connection
conn->max_window = conn->get_packet_size();
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "UTP socket initialized");
#endif
}
utp_socket* utp_create_socket(utp_context *ctx)
{
assert(ctx);
if (!ctx) return NULL;
UTPSocket *conn = new UTPSocket; // TODO: UTPSocket should have a constructor
conn->state = CS_UNINITIALIZED;
conn->ctx = ctx;
conn->userdata = NULL;
conn->reorder_count = 0;
conn->duplicate_ack = 0;
conn->timeout_seq_nr = 0;
conn->last_rcv_win = 0;
conn->got_fin = false;
conn->got_fin_reached = false;
conn->fin_sent = false;
conn->fin_sent_acked = false;
conn->read_shutdown = false;
conn->close_requested = false;
conn->fast_timeout = false;
conn->rtt = 0;
conn->retransmit_timeout = 0;
conn->rto_timeout = 0;
conn->zerowindow_time = 0;
conn->average_delay = 0;
conn->current_delay_samples = 0;
conn->cur_window = 0;
conn->eof_pkt = 0;
conn->last_maxed_out_window = 0;
conn->mtu_probe_seq = 0;
conn->mtu_probe_size = 0;
conn->current_delay_sum = 0;
conn->average_delay_base = 0;
conn->retransmit_count = 0;
conn->rto = 3000;
conn->rtt_var = 800;
conn->seq_nr = 1;
conn->ack_nr = 0;
conn->max_window_user = 255 * PACKET_SIZE;
conn->cur_window_packets = 0;
conn->fast_resend_seq_nr = conn->seq_nr;
conn->target_delay = ctx->target_delay;
conn->reply_micro = 0;
conn->opt_sndbuf = ctx->opt_sndbuf;
conn->opt_rcvbuf = ctx->opt_rcvbuf;
conn->slow_start = true;
conn->ssthresh = conn->opt_sndbuf;
conn->clock_drift = 0;
conn->clock_drift_raw = 0;
conn->outbuf.mask = 15;
conn->inbuf.mask = 15;
conn->outbuf.elements = (void**)calloc(16, sizeof(void*));
conn->inbuf.elements = (void**)calloc(16, sizeof(void*));
conn->ida = -1; // set the index of every new socket in ack_sockets to
// -1, which also means it is not in ack_sockets yet
memset(conn->extensions, 0, sizeof(conn->extensions));
#ifdef _DEBUG
memset(&conn->_stats, 0, sizeof(utp_socket_stats));
#endif
return conn;
}
int utp_context_set_option(utp_context *ctx, int opt, int val)
{
assert(ctx);
if (!ctx) return -1;
switch (opt) {
case UTP_LOG_NORMAL:
ctx->log_normal = val ? true : false;
return 0;
case UTP_LOG_MTU:
ctx->log_mtu = val ? true : false;
return 0;
case UTP_LOG_DEBUG:
ctx->log_debug = val ? true : false;
return 0;
case UTP_TARGET_DELAY:
ctx->target_delay = val;
return 0;
case UTP_SNDBUF:
assert(val >= 1);
ctx->opt_sndbuf = val;
return 0;
case UTP_RCVBUF:
assert(val >= 1);
ctx->opt_rcvbuf = val;
return 0;
}
return -1;
}
int utp_context_get_option(utp_context *ctx, int opt)
{
assert(ctx);
if (!ctx) return -1;
switch (opt) {
case UTP_LOG_NORMAL: return ctx->log_normal ? 1 : 0;
case UTP_LOG_MTU: return ctx->log_mtu ? 1 : 0;
case UTP_LOG_DEBUG: return ctx->log_debug ? 1 : 0;
case UTP_TARGET_DELAY: return ctx->target_delay;
case UTP_SNDBUF: return ctx->opt_sndbuf;
case UTP_RCVBUF: return ctx->opt_rcvbuf;
}
return -1;
}
int utp_setsockopt(UTPSocket* conn, int opt, int val)
{
assert(conn);
if (!conn) return -1;
switch (opt) {
case UTP_SNDBUF:
assert(val >= 1);
conn->opt_sndbuf = val;
return 0;
case UTP_RCVBUF:
assert(val >= 1);
conn->opt_rcvbuf = val;
return 0;
case UTP_TARGET_DELAY:
conn->target_delay = val;
return 0;
}
return -1;
}
int utp_getsockopt(UTPSocket* conn, int opt)
{
assert(conn);
if (!conn) return -1;
switch (opt) {
case UTP_SNDBUF: return conn->opt_sndbuf;
case UTP_RCVBUF: return conn->opt_rcvbuf;
case UTP_TARGET_DELAY: return conn->target_delay;
}
return -1;
}
// Try to connect to a specified host.
int utp_connect(utp_socket *conn, const struct sockaddr *to, socklen_t tolen)
{
assert(conn);
if (!conn) return -1;
assert(conn->state == CS_UNINITIALIZED);
if (conn->state != CS_UNINITIALIZED) {
conn->state = CS_DESTROY;
return -1;
}
utp_initialize_socket(conn, to, tolen, true, 0, 0, 1);
assert(conn->cur_window_packets == 0);
assert(conn->outbuf.get(conn->seq_nr) == NULL);
assert(sizeof(PacketFormatV1) == 20);
conn->state = CS_SYN_SENT;
conn->ctx->current_ms = utp_call_get_milliseconds(conn->ctx, conn);
// Create and send a connect message
// used in parse_log.py
conn->log(UTP_LOG_NORMAL, "UTP_Connect conn_seed:%u packet_size:%u (B) "
"target_delay:%u (ms) delay_history:%u "
"delay_base_history:%u (minutes)",
conn->conn_seed, PACKET_SIZE, conn->target_delay / 1000,
CUR_DELAY_SIZE, DELAY_BASE_HISTORY);
// Setup initial timeout timer.
conn->retransmit_timeout = 3000;
conn->rto_timeout = conn->ctx->current_ms + conn->retransmit_timeout;
conn->last_rcv_win = conn->get_rcv_window();
// if you need compatibiltiy with 1.8.1, use this. it increases attackability though.
//conn->seq_nr = 1;
conn->seq_nr = utp_call_get_random(conn->ctx, conn);
// Create the connect packet.
const size_t header_size = sizeof(PacketFormatV1);
OutgoingPacket *pkt = (OutgoingPacket*)malloc(sizeof(OutgoingPacket) - 1 + header_size);
PacketFormatV1* p1 = (PacketFormatV1*)pkt->data;
memset(p1, 0, header_size);
// SYN packets are special, and have the receive ID in the connid field,
// instead of conn_id_send.
p1->set_version(1);
p1->set_type(ST_SYN);
p1->ext = 0;
p1->connid = conn->conn_id_recv;
p1->windowsize = (uint32)conn->last_rcv_win;
p1->seq_nr = conn->seq_nr;
pkt->transmissions = 0;
pkt->length = header_size;
pkt->payload = 0;
/*
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "Sending connect %s [%u].",
addrfmt(conn->addr, addrbuf), conn_seed);
#endif
*/
// Remember the message in the outgoing queue.
conn->outbuf.ensure_size(conn->seq_nr, conn->cur_window_packets);
conn->outbuf.put(conn->seq_nr, pkt);
conn->seq_nr++;
conn->cur_window_packets++;
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "incrementing cur_window_packets:%u", conn->cur_window_packets);
#endif
conn->send_packet(pkt);
return 0;
}
// Returns 1 if the UDP payload was recognized as a UTP packet, or 0 if it was not
int utp_process_udp(utp_context *ctx, const byte *buffer, size_t len, const struct sockaddr *to, socklen_t tolen)
{
assert(ctx);
if (!ctx) return 0;
assert(buffer);
if (!buffer) return 0;
assert(to);
if (!to) return 0;
const PackedSockAddr addr((const SOCKADDR_STORAGE*)to, tolen);
if (len < sizeof(PacketFormatV1)) {
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "recv %s len:%u too small", addrfmt(addr, addrbuf), (uint)len);
#endif
return 0;
}
const PacketFormatV1 *pf1 = (PacketFormatV1*)buffer;
const byte version = UTP_Version(pf1);
const uint32 id = uint32(pf1->connid);
if (version != 1) {
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "recv %s len:%u version:%u unsupported version", addrfmt(addr, addrbuf), (uint)len, version);
#endif
return 0;
}
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "recv %s len:%u id:%u", addrfmt(addr, addrbuf), (uint)len, id);
ctx->log(UTP_LOG_DEBUG, NULL, "recv id:%u seq_nr:%u ack_nr:%u", id, (uint)pf1->seq_nr, (uint)pf1->ack_nr);
#endif
const byte flags = pf1->type();
if (flags == ST_RESET) {
// id is either our recv id or our send id
// if it's our send id, and we initiated the connection, our recv id is id + 1
// if it's our send id, and we did not initiate the connection, our recv id is id - 1
// we have to check every case
UTPSocketKeyData* keyData;
if ( (keyData = ctx->utp_sockets->Lookup(UTPSocketKey(addr, id))) ||
((keyData = ctx->utp_sockets->Lookup(UTPSocketKey(addr, id + 1))) && keyData->socket->conn_id_send == id) ||
((keyData = ctx->utp_sockets->Lookup(UTPSocketKey(addr, id - 1))) && keyData->socket->conn_id_send == id))
{
UTPSocket* conn = keyData->socket;
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "recv RST for existing connection");
#endif
if (conn->close_requested)
conn->state = CS_DESTROY;
else
conn->state = CS_RESET;
utp_call_on_overhead_statistics(conn->ctx, conn, false, len + conn->get_udp_overhead(), close_overhead);
const int err = (conn->state == CS_SYN_SENT) ? UTP_ECONNREFUSED : UTP_ECONNRESET;
utp_call_on_error(conn->ctx, conn, err);
}
else {
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "recv RST for unknown connection");
#endif
}
return 1;
}
else if (flags != ST_SYN) {
UTPSocket* conn = NULL;
if (ctx->last_utp_socket && ctx->last_utp_socket->addr == addr && ctx->last_utp_socket->conn_id_recv == id) {
conn = ctx->last_utp_socket;
} else {
UTPSocketKeyData* keyData = ctx->utp_sockets->Lookup(UTPSocketKey(addr, id));
if (keyData) {
conn = keyData->socket;
ctx->last_utp_socket = conn;
}
}
if (conn) {
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "recv processing");
#endif
const size_t read = utp_process_incoming(conn, buffer, len);
utp_call_on_overhead_statistics(conn->ctx, conn, false, (len - read) + conn->get_udp_overhead(), header_overhead);
return 1;
}
}
// We have not found a matching utp_socket, and this isn't a SYN. Reject it.
const uint32 seq_nr = pf1->seq_nr;
if (flags != ST_SYN) {
ctx->current_ms = utp_call_get_milliseconds(ctx, NULL);
for (size_t i = 0; i < ctx->rst_info.GetCount(); i++) {
if ((ctx->rst_info[i].connid == id) &&
(ctx->rst_info[i].addr == addr) &&
(ctx->rst_info[i].ack_nr == seq_nr))
{
ctx->rst_info[i].timestamp = ctx->current_ms;
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "recv not sending RST to non-SYN (stored)");
#endif
return 1;
}
}
if (ctx->rst_info.GetCount() > RST_INFO_LIMIT) {
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "recv not sending RST to non-SYN (limit at %u stored)", (uint)ctx->rst_info.GetCount());
#endif
return 1;
}
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "recv send RST to non-SYN (%u stored)", (uint)ctx->rst_info.GetCount());
#endif
RST_Info &r = ctx->rst_info.Append();
r.addr = addr;
r.connid = id;
r.ack_nr = seq_nr;
r.timestamp = ctx->current_ms;
UTPSocket::send_rst(ctx, addr, id, seq_nr, utp_call_get_random(ctx, NULL));
return 1;
}
if (ctx->callbacks[UTP_ON_ACCEPT]) {
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "Incoming connection from %s", addrfmt(addr, addrbuf));
#endif
UTPSocketKeyData* keyData = ctx->utp_sockets->Lookup(UTPSocketKey(addr, id + 1));
if (keyData) {
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "rejected incoming connection, connection already exists");
#endif
return 1;
}
if (ctx->utp_sockets->GetCount() > 3000) {
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "rejected incoming connection, too many uTP sockets %d", ctx->utp_sockets->GetCount());
#endif
return 1;
}
// true means yes, block connection. false means no, don't block.
if (utp_call_on_firewall(ctx, to, tolen)) {
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "rejected incoming connection, firewall callback returned true");
#endif
return 1;
}
// Create a new UTP socket to handle this new connection
UTPSocket *conn = utp_create_socket(ctx);
utp_initialize_socket(conn, to, tolen, false, id, id+1, id);
conn->ack_nr = seq_nr;
conn->seq_nr = utp_call_get_random(ctx, NULL);
conn->fast_resend_seq_nr = conn->seq_nr;
conn->state = CS_SYN_RECV;
const size_t read = utp_process_incoming(conn, buffer, len, true);
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "recv send connect ACK");
#endif
conn->send_ack(true);
utp_call_on_accept(ctx, conn, to, tolen);
// we report overhead after on_accept(), because the callbacks are setup now
utp_call_on_overhead_statistics(conn->ctx, conn, false, (len - read) + conn->get_udp_overhead(), header_overhead); // SYN
utp_call_on_overhead_statistics(conn->ctx, conn, true, conn->get_overhead(), ack_overhead); // SYNACK
}
else {
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "rejected incoming connection, UTP_ON_ACCEPT callback not set");
#endif
}
return 1;
}
// Called by utp_process_icmp_fragmentation() and utp_process_icmp_error() below
static UTPSocket* parse_icmp_payload(utp_context *ctx, const byte *buffer, size_t len, const struct sockaddr *to, socklen_t tolen)
{
assert(ctx);
if (!ctx) return NULL;
assert(buffer);
if (!buffer) return NULL;
assert(to);
if (!to) return NULL;
const PackedSockAddr addr((const SOCKADDR_STORAGE*)to, tolen);
// ICMP packets are only required to quote the first 8 bytes of the layer4
// payload. The UDP payload is 8 bytes, and the UTP header is another 20
// bytes. So, in order to find the entire UTP header, we need the ICMP
// packet to quote 28 bytes.
if (len < sizeof(PacketFormatV1)) {
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "Ignoring ICMP from %s: runt length %d", addrfmt(addr, addrbuf), len);
#endif
return NULL;
}
const PacketFormatV1 *pf = (PacketFormatV1*)buffer;
const byte version = UTP_Version(pf);
const uint32 id = uint32(pf->connid);
if (version != 1) {
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "Ignoring ICMP from %s: not UTP version 1", addrfmt(addr, addrbuf));
#endif
return NULL;
}
UTPSocketKeyData* keyData;
if ( (keyData = ctx->utp_sockets->Lookup(UTPSocketKey(addr, id))) ||
((keyData = ctx->utp_sockets->Lookup(UTPSocketKey(addr, id + 1))) && keyData->socket->conn_id_send == id) ||
((keyData = ctx->utp_sockets->Lookup(UTPSocketKey(addr, id - 1))) && keyData->socket->conn_id_send == id))
{
return keyData->socket;
}
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "Ignoring ICMP from %s: No matching connection found for id %u", addrfmt(addr, addrbuf), id);
#endif
return NULL;
}
// Should be called when an ICMP Type 3, Code 4 packet (fragmentation needed) is received, to adjust the MTU
//
// Returns 1 if the UDP payload (delivered in the ICMP packet) was recognized as a UTP packet, or 0 if it was not
//
// @ctx: utp_context
// @buf: Contents of the original UDP payload, which the ICMP packet quoted. *Not* the ICMP packet itself.
// @len: buffer length
// @to: destination address of the original UDP pakcet
// @tolen: address length
// @next_hop_mtu:
int utp_process_icmp_fragmentation(utp_context *ctx, const byte* buffer, size_t len, const struct sockaddr *to, socklen_t tolen, uint16 next_hop_mtu)
{
UTPSocket* conn = parse_icmp_payload(ctx, buffer, len, to, tolen);
if (!conn) return 0;
// Constrain the next_hop_mtu to sane values. It might not be initialized or sent properly
if (next_hop_mtu >= 576 && next_hop_mtu < 0x2000) {
conn->mtu_ceiling = min<uint32>(next_hop_mtu, conn->mtu_ceiling);
conn->mtu_search_update();
// this is something of a speecial case, where we don't set mtu_last
// to the value in between the floor and the ceiling. We can update the
// floor, because there might be more network segments after the one
// that sent this ICMP with smaller MTUs. But we want to test this
// MTU size first. If the next probe gets through, mtu_floor is updated
conn->mtu_last = conn->mtu_ceiling;
} else {
// Otherwise, binary search. At this point we don't actually know
// what size the packet that failed was, and apparently we can't
// trust the next hop mtu either. It seems reasonably conservative
// to just lower the ceiling. This should not happen on working networks
// anyway.
conn->mtu_ceiling = (conn->mtu_floor + conn->mtu_ceiling) / 2;
conn->mtu_search_update();
}
conn->log(UTP_LOG_MTU, "MTU [ICMP] floor:%d ceiling:%d current:%d", conn->mtu_floor, conn->mtu_ceiling, conn->mtu_last);
return 1;
}
// Should be called when an ICMP message is received that should tear down the connection.
//
// Returns 1 if the UDP payload (delivered in the ICMP packet) was recognized as a UTP packet, or 0 if it was not
//
// @ctx: utp_context
// @buf: Contents of the original UDP payload, which the ICMP packet quoted. *Not* the ICMP packet itself.
// @len: buffer length
// @to: destination address of the original UDP pakcet
// @tolen: address length
int utp_process_icmp_error(utp_context *ctx, const byte *buffer, size_t len, const struct sockaddr *to, socklen_t tolen)
{
UTPSocket* conn = parse_icmp_payload(ctx, buffer, len, to, tolen);
if (!conn) return 0;
const int err = (conn->state == CS_SYN_SENT) ? UTP_ECONNREFUSED : UTP_ECONNRESET;
const PackedSockAddr addr((const SOCKADDR_STORAGE*)to, tolen);
switch(conn->state) {
// Don't pass on errors for idle/closed connections
case CS_IDLE:
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "ICMP from %s in state CS_IDLE, ignoring", addrfmt(addr, addrbuf));
#endif
return 1;
default:
if (conn->close_requested) {
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "ICMP from %s after close, setting state to CS_DESTROY and causing error %d", addrfmt(addr, addrbuf), err);
#endif
conn->state = CS_DESTROY;
} else {
#if UTP_DEBUG_LOGGING
ctx->log(UTP_LOG_DEBUG, NULL, "ICMP from %s, setting state to CS_RESET and causing error %d", addrfmt(addr, addrbuf), err);
#endif
conn->state = CS_RESET;
}
break;
}
utp_call_on_error(conn->ctx, conn, err);
return 1;
}
// Write bytes to the UTP socket. Returns the number of bytes written.
// 0 indicates the socket is no longer writable, -1 indicates an error
ssize_t utp_writev(utp_socket *conn, struct utp_iovec *iovec_input, size_t num_iovecs)
{
static utp_iovec iovec[UTP_IOV_MAX];
assert(conn);
if (!conn) return -1;
assert(iovec_input);
if (!iovec_input) return -1;
assert(num_iovecs);
if (!num_iovecs) return -1;
if (num_iovecs > UTP_IOV_MAX)
num_iovecs = UTP_IOV_MAX;
memcpy(iovec, iovec_input, sizeof(struct utp_iovec)*num_iovecs);
size_t bytes = 0;
size_t sent = 0;
for (size_t i = 0; i < num_iovecs; i++)
bytes += iovec[i].iov_len;
#if UTP_DEBUG_LOGGING
size_t param = bytes;
#endif
if (conn->state != CS_CONNECTED) {
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "UTP_Write %u bytes = false (not CS_CONNECTED)", (uint)bytes);
#endif
return 0;
}
if (conn->fin_sent) {
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "UTP_Write %u bytes = false (fin_sent already)", (uint)bytes);
#endif
return 0;
}
conn->ctx->current_ms = utp_call_get_milliseconds(conn->ctx, conn);
// don't send unless it will all fit in the window
size_t packet_size = conn->get_packet_size();
size_t num_to_send = min<size_t>(bytes, packet_size);
while (!conn->is_full(num_to_send)) {
// Send an outgoing packet.
// Also add it to the outgoing of packets that have been sent but not ACKed.
bytes -= num_to_send;
sent += num_to_send;
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "Sending packet. seq_nr:%u ack_nr:%u wnd:%u/%u/%u rcv_win:%u size:%u cur_window_packets:%u",
conn->seq_nr, conn->ack_nr,
(uint)(conn->cur_window + num_to_send),
(uint)conn->max_window, (uint)conn->max_window_user,
(uint)conn->last_rcv_win, num_to_send,
conn->cur_window_packets);
#endif
conn->write_outgoing_packet(num_to_send, ST_DATA, iovec, num_iovecs);
num_to_send = min<size_t>(bytes, packet_size);
if (num_to_send == 0) {
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "UTP_Write %u bytes = true", (uint)param);
#endif
return sent;
}
}
bool full = conn->is_full();
if (full) {
// mark the socket as not being writable.
conn->state = CS_CONNECTED_FULL;
}
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "UTP_Write %u bytes = %s", (uint)bytes, full ? "false" : "true");
#endif
// returns whether or not the socket is still writable
// if the congestion window is not full, we can still write to it
//return !full;
return sent;
}
void utp_read_drained(utp_socket *conn)
{
assert(conn);
if (!conn) return;
assert(conn->state != CS_UNINITIALIZED);
if (conn->state == CS_UNINITIALIZED) return;
const size_t rcvwin = conn->get_rcv_window();
if (rcvwin > conn->last_rcv_win) {
// If last window was 0 send ACK immediately, otherwise should set timer
if (conn->last_rcv_win == 0) {
conn->send_ack();
} else {
conn->ctx->current_ms = utp_call_get_milliseconds(conn->ctx, conn);
conn->schedule_ack();
}
}
}
// Should be called each time the UDP socket is drained
void utp_issue_deferred_acks(utp_context *ctx)
{
assert(ctx);
if (!ctx) return;
for (size_t i = 0; i < ctx->ack_sockets.GetCount(); i++) {
UTPSocket *conn = ctx->ack_sockets[i];
conn->send_ack();
i--;
}
}
// Should be called every 500ms
void utp_check_timeouts(utp_context *ctx)
{
assert(ctx);
if (!ctx) return;
ctx->current_ms = utp_call_get_milliseconds(ctx, NULL);
if (ctx->current_ms - ctx->last_check < TIMEOUT_CHECK_INTERVAL)
return;
ctx->last_check = ctx->current_ms;
for (size_t i = 0; i < ctx->rst_info.GetCount(); i++) {
if ((int)(ctx->current_ms - ctx->rst_info[i].timestamp) >= RST_INFO_TIMEOUT) {
ctx->rst_info.MoveUpLast(i);
i--;
}
}
if (ctx->rst_info.GetCount() != ctx->rst_info.GetAlloc()) {
ctx->rst_info.Compact();
}
utp_hash_iterator_t it;
UTPSocketKeyData* keyData;
while ((keyData = ctx->utp_sockets->Iterate(it))) {
UTPSocket *conn = keyData->socket;
conn->check_timeouts();
// Check if the object was deleted
if (conn->state == CS_DESTROY) {
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "Destroying");
#endif
delete conn;
}
}
}
int utp_getpeername(utp_socket *conn, struct sockaddr *addr, socklen_t *addrlen)
{
assert(addr);
if (!addr) return -1;
assert(addrlen);
if (!addrlen) return -1;
assert(conn);
if (!conn) return -1;
assert(conn->state != CS_UNINITIALIZED);
if (conn->state == CS_UNINITIALIZED) return -1;
socklen_t len;
const SOCKADDR_STORAGE sa = conn->addr.get_sockaddr_storage(&len);
*addrlen = min(len, *addrlen);
memcpy(addr, &sa, *addrlen);
return 0;
}
int utp_get_delays(UTPSocket *conn, uint32 *ours, uint32 *theirs, uint32 *age)
{
assert(conn);
if (!conn) return -1;
assert(conn->state != CS_UNINITIALIZED);
if (conn->state == CS_UNINITIALIZED) {
if (ours) *ours = 0;
if (theirs) *theirs = 0;
if (age) *age = 0;
return -1;
}
if (ours) *ours = conn->our_hist.get_value();
if (theirs) *theirs = conn->their_hist.get_value();
if (age) *age = (uint32)(conn->ctx->current_ms - conn->last_measured_delay);
return 0;
}
// Close the UTP socket.
// It is not valid for the upper layer to refer to socket after it is closed.
// Data will keep to try being delivered after the close.
void utp_close(UTPSocket *conn)
{
assert(conn);
if (!conn) return;
assert(conn->state != CS_UNINITIALIZED
&& conn->state != CS_DESTROY);
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "UTP_Close in state:%s", statenames[conn->state]);
#endif
switch(conn->state) {
case CS_CONNECTED:
case CS_CONNECTED_FULL:
conn->read_shutdown = true;
conn->close_requested = true;
if (!conn->fin_sent) {
conn->fin_sent = true;
conn->write_outgoing_packet(0, ST_FIN, NULL, 0);
} else if (conn->fin_sent_acked) {
conn->state = CS_DESTROY;
}
break;
case CS_SYN_SENT:
conn->rto_timeout = utp_call_get_milliseconds(conn->ctx, conn) + min<uint>(conn->rto * 2, 60);
// fall through
case CS_SYN_RECV:
// fall through
default:
conn->state = CS_DESTROY;
break;
}
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "UTP_Close end in state:%s", statenames[conn->state]);
#endif
}
void utp_shutdown(UTPSocket *conn, int how)
{
assert(conn);
if (!conn) return;
assert(conn->state != CS_UNINITIALIZED
&& conn->state != CS_DESTROY);
#if UTP_DEBUG_LOGGING
conn->log(UTP_LOG_DEBUG, "UTP_shutdown(%d) in state:%s", how, statenames[conn->state]);
#endif
if (how != SHUT_WR) {
conn->read_shutdown = true;
}
if (how != SHUT_RD) {
switch(conn->state) {
case CS_CONNECTED:
case CS_CONNECTED_FULL:
if (!conn->fin_sent) {
conn->fin_sent = true;
conn->write_outgoing_packet(0, ST_FIN, NULL, 0);
}
break;
case CS_SYN_SENT:
conn->rto_timeout = utp_call_get_milliseconds(conn->ctx, conn) + min<uint>(conn->rto * 2, 60);
default:
break;
}
}
}
utp_context* utp_get_context(utp_socket *socket) {
assert(socket);
return socket ? socket->ctx : NULL;
}
void* utp_set_userdata(utp_socket *socket, void *userdata) {
assert(socket);
if (socket) socket->userdata = userdata;
return socket ? socket->userdata : NULL;
}
void* utp_get_userdata(utp_socket *socket) {
assert(socket);
return socket ? socket->userdata : NULL;
}
void struct_utp_context::log(int level, utp_socket *socket, char const *fmt, ...)
{
if (!would_log(level)) {
return;
}
va_list va;
va_start(va, fmt);
log_unchecked(socket, fmt, va);
va_end(va);
}
void struct_utp_context::log_unchecked(utp_socket *socket, char const *fmt, ...)
{
va_list va;
char buf[4096];
va_start(va, fmt);
vsnprintf(buf, 4096, fmt, va);
buf[4095] = '\0';
va_end(va);
utp_call_log(this, socket, (const byte *)buf);
}
inline bool struct_utp_context::would_log(int level)
{
if (level == UTP_LOG_NORMAL) return log_normal;
if (level == UTP_LOG_MTU) return log_mtu;
if (level == UTP_LOG_DEBUG) return log_debug;
return true;
}
utp_socket_stats* utp_get_stats(utp_socket *socket)
{
#ifdef _DEBUG
assert(socket);
if (!socket) return NULL;
socket->_stats.mtu_guess = socket->mtu_last ? socket->mtu_last : socket->mtu_ceiling;
return &socket->_stats;
#else
return NULL;
#endif
}