372 lines
13 KiB
Go
372 lines
13 KiB
Go
package netlink
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import (
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"bytes"
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"encoding/binary"
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"errors"
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"fmt"
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"net"
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"github.com/vishvananda/netlink/nl"
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"golang.org/x/sys/unix"
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)
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// ConntrackTableType Conntrack table for the netlink operation
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type ConntrackTableType uint8
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const (
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// ConntrackTable Conntrack table
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// https://github.com/torvalds/linux/blob/master/include/uapi/linux/netfilter/nfnetlink.h -> #define NFNL_SUBSYS_CTNETLINK 1
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ConntrackTable = 1
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// ConntrackExpectTable Conntrack expect table
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// https://github.com/torvalds/linux/blob/master/include/uapi/linux/netfilter/nfnetlink.h -> #define NFNL_SUBSYS_CTNETLINK_EXP 2
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ConntrackExpectTable = 2
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)
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const (
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// For Parsing Mark
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TCP_PROTO = 6
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UDP_PROTO = 17
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)
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const (
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// backward compatibility with golang 1.6 which does not have io.SeekCurrent
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seekCurrent = 1
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)
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// InetFamily Family type
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type InetFamily uint8
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// -L [table] [options] List conntrack or expectation table
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// -G [table] parameters Get conntrack or expectation
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// -I [table] parameters Create a conntrack or expectation
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// -U [table] parameters Update a conntrack
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// -E [table] [options] Show events
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// -C [table] Show counter
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// -S Show statistics
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// ConntrackTableList returns the flow list of a table of a specific family
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// conntrack -L [table] [options] List conntrack or expectation table
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func ConntrackTableList(table ConntrackTableType, family InetFamily) ([]*ConntrackFlow, error) {
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return pkgHandle.ConntrackTableList(table, family)
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}
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// ConntrackTableFlush flushes all the flows of a specified table
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// conntrack -F [table] Flush table
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// The flush operation applies to all the family types
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func ConntrackTableFlush(table ConntrackTableType) error {
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return pkgHandle.ConntrackTableFlush(table)
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}
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// ConntrackDeleteFilter deletes entries on the specified table on the base of the filter
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// conntrack -D [table] parameters Delete conntrack or expectation
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func ConntrackDeleteFilter(table ConntrackTableType, family InetFamily, filter CustomConntrackFilter) (uint, error) {
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return pkgHandle.ConntrackDeleteFilter(table, family, filter)
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}
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// ConntrackTableList returns the flow list of a table of a specific family using the netlink handle passed
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// conntrack -L [table] [options] List conntrack or expectation table
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func (h *Handle) ConntrackTableList(table ConntrackTableType, family InetFamily) ([]*ConntrackFlow, error) {
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res, err := h.dumpConntrackTable(table, family)
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if err != nil {
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return nil, err
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}
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// Deserialize all the flows
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var result []*ConntrackFlow
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for _, dataRaw := range res {
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result = append(result, parseRawData(dataRaw))
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}
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return result, nil
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}
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// ConntrackTableFlush flushes all the flows of a specified table using the netlink handle passed
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// conntrack -F [table] Flush table
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// The flush operation applies to all the family types
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func (h *Handle) ConntrackTableFlush(table ConntrackTableType) error {
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req := h.newConntrackRequest(table, unix.AF_INET, nl.IPCTNL_MSG_CT_DELETE, unix.NLM_F_ACK)
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_, err := req.Execute(unix.NETLINK_NETFILTER, 0)
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return err
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}
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// ConntrackDeleteFilter deletes entries on the specified table on the base of the filter using the netlink handle passed
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// conntrack -D [table] parameters Delete conntrack or expectation
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func (h *Handle) ConntrackDeleteFilter(table ConntrackTableType, family InetFamily, filter CustomConntrackFilter) (uint, error) {
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res, err := h.dumpConntrackTable(table, family)
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if err != nil {
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return 0, err
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}
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var matched uint
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for _, dataRaw := range res {
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flow := parseRawData(dataRaw)
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if match := filter.MatchConntrackFlow(flow); match {
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req2 := h.newConntrackRequest(table, family, nl.IPCTNL_MSG_CT_DELETE, unix.NLM_F_ACK)
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// skip the first 4 byte that are the netfilter header, the newConntrackRequest is adding it already
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req2.AddRawData(dataRaw[4:])
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req2.Execute(unix.NETLINK_NETFILTER, 0)
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matched++
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}
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}
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return matched, nil
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}
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func (h *Handle) newConntrackRequest(table ConntrackTableType, family InetFamily, operation, flags int) *nl.NetlinkRequest {
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// Create the Netlink request object
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req := h.newNetlinkRequest((int(table)<<8)|operation, flags)
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// Add the netfilter header
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msg := &nl.Nfgenmsg{
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NfgenFamily: uint8(family),
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Version: nl.NFNETLINK_V0,
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ResId: 0,
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}
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req.AddData(msg)
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return req
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}
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func (h *Handle) dumpConntrackTable(table ConntrackTableType, family InetFamily) ([][]byte, error) {
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req := h.newConntrackRequest(table, family, nl.IPCTNL_MSG_CT_GET, unix.NLM_F_DUMP)
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return req.Execute(unix.NETLINK_NETFILTER, 0)
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}
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// The full conntrack flow structure is very complicated and can be found in the file:
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// http://git.netfilter.org/libnetfilter_conntrack/tree/include/internal/object.h
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// For the time being, the structure below allows to parse and extract the base information of a flow
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type ipTuple struct {
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SrcIP net.IP
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DstIP net.IP
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Protocol uint8
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SrcPort uint16
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DstPort uint16
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}
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type ConntrackFlow struct {
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FamilyType uint8
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Forward ipTuple
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Reverse ipTuple
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Mark uint32
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}
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func (s *ConntrackFlow) String() string {
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// conntrack cmd output:
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// udp 17 src=127.0.0.1 dst=127.0.0.1 sport=4001 dport=1234 [UNREPLIED] src=127.0.0.1 dst=127.0.0.1 sport=1234 dport=4001 mark=0
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return fmt.Sprintf("%s\t%d src=%s dst=%s sport=%d dport=%d\tsrc=%s dst=%s sport=%d dport=%d mark=%d",
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nl.L4ProtoMap[s.Forward.Protocol], s.Forward.Protocol,
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s.Forward.SrcIP.String(), s.Forward.DstIP.String(), s.Forward.SrcPort, s.Forward.DstPort,
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s.Reverse.SrcIP.String(), s.Reverse.DstIP.String(), s.Reverse.SrcPort, s.Reverse.DstPort, s.Mark)
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}
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// This method parse the ip tuple structure
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// The message structure is the following:
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// <len, [CTA_IP_V4_SRC|CTA_IP_V6_SRC], 16 bytes for the IP>
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// <len, [CTA_IP_V4_DST|CTA_IP_V6_DST], 16 bytes for the IP>
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// <len, NLA_F_NESTED|nl.CTA_TUPLE_PROTO, 1 byte for the protocol, 3 bytes of padding>
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// <len, CTA_PROTO_SRC_PORT, 2 bytes for the source port, 2 bytes of padding>
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// <len, CTA_PROTO_DST_PORT, 2 bytes for the source port, 2 bytes of padding>
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func parseIpTuple(reader *bytes.Reader, tpl *ipTuple) uint8 {
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for i := 0; i < 2; i++ {
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_, t, _, v := parseNfAttrTLV(reader)
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switch t {
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case nl.CTA_IP_V4_SRC, nl.CTA_IP_V6_SRC:
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tpl.SrcIP = v
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case nl.CTA_IP_V4_DST, nl.CTA_IP_V6_DST:
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tpl.DstIP = v
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}
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}
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// Skip the next 4 bytes nl.NLA_F_NESTED|nl.CTA_TUPLE_PROTO
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reader.Seek(4, seekCurrent)
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_, t, _, v := parseNfAttrTLV(reader)
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if t == nl.CTA_PROTO_NUM {
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tpl.Protocol = uint8(v[0])
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}
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// Skip some padding 3 bytes
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reader.Seek(3, seekCurrent)
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for i := 0; i < 2; i++ {
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_, t, _ := parseNfAttrTL(reader)
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switch t {
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case nl.CTA_PROTO_SRC_PORT:
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parseBERaw16(reader, &tpl.SrcPort)
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case nl.CTA_PROTO_DST_PORT:
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parseBERaw16(reader, &tpl.DstPort)
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}
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// Skip some padding 2 byte
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reader.Seek(2, seekCurrent)
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}
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return tpl.Protocol
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}
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func parseNfAttrTLV(r *bytes.Reader) (isNested bool, attrType, len uint16, value []byte) {
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isNested, attrType, len = parseNfAttrTL(r)
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value = make([]byte, len)
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binary.Read(r, binary.BigEndian, &value)
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return isNested, attrType, len, value
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}
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func parseNfAttrTL(r *bytes.Reader) (isNested bool, attrType, len uint16) {
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binary.Read(r, nl.NativeEndian(), &len)
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len -= nl.SizeofNfattr
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binary.Read(r, nl.NativeEndian(), &attrType)
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isNested = (attrType & nl.NLA_F_NESTED) == nl.NLA_F_NESTED
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attrType = attrType & (nl.NLA_F_NESTED - 1)
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return isNested, attrType, len
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}
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func parseBERaw16(r *bytes.Reader, v *uint16) {
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binary.Read(r, binary.BigEndian, v)
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}
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func parseRawData(data []byte) *ConntrackFlow {
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s := &ConntrackFlow{}
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var proto uint8
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// First there is the Nfgenmsg header
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// consume only the family field
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reader := bytes.NewReader(data)
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binary.Read(reader, nl.NativeEndian(), &s.FamilyType)
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// skip rest of the Netfilter header
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reader.Seek(3, seekCurrent)
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// The message structure is the following:
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// <len, NLA_F_NESTED|CTA_TUPLE_ORIG> 4 bytes
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// <len, NLA_F_NESTED|CTA_TUPLE_IP> 4 bytes
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// flow information of the forward flow
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// <len, NLA_F_NESTED|CTA_TUPLE_REPLY> 4 bytes
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// <len, NLA_F_NESTED|CTA_TUPLE_IP> 4 bytes
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// flow information of the reverse flow
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for reader.Len() > 0 {
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nested, t, l := parseNfAttrTL(reader)
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if nested && t == nl.CTA_TUPLE_ORIG {
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if nested, t, _ = parseNfAttrTL(reader); nested && t == nl.CTA_TUPLE_IP {
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proto = parseIpTuple(reader, &s.Forward)
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}
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} else if nested && t == nl.CTA_TUPLE_REPLY {
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if nested, t, _ = parseNfAttrTL(reader); nested && t == nl.CTA_TUPLE_IP {
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parseIpTuple(reader, &s.Reverse)
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// Got all the useful information stop parsing
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break
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} else {
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// Header not recognized skip it
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reader.Seek(int64(l), seekCurrent)
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}
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}
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}
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if proto == TCP_PROTO {
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reader.Seek(64, seekCurrent)
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_, t, _, v := parseNfAttrTLV(reader)
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if t == nl.CTA_MARK {
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s.Mark = uint32(v[3])
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}
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} else if proto == UDP_PROTO {
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reader.Seek(16, seekCurrent)
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_, t, _, v := parseNfAttrTLV(reader)
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if t == nl.CTA_MARK {
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s.Mark = uint32(v[3])
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}
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}
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return s
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}
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// Conntrack parameters and options:
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// -n, --src-nat ip source NAT ip
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// -g, --dst-nat ip destination NAT ip
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// -j, --any-nat ip source or destination NAT ip
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// -m, --mark mark Set mark
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// -c, --secmark secmark Set selinux secmark
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// -e, --event-mask eventmask Event mask, eg. NEW,DESTROY
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// -z, --zero Zero counters while listing
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// -o, --output type[,...] Output format, eg. xml
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// -l, --label label[,...] conntrack labels
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// Common parameters and options:
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// -s, --src, --orig-src ip Source address from original direction
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// -d, --dst, --orig-dst ip Destination address from original direction
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// -r, --reply-src ip Source addres from reply direction
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// -q, --reply-dst ip Destination address from reply direction
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// -p, --protonum proto Layer 4 Protocol, eg. 'tcp'
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// -f, --family proto Layer 3 Protocol, eg. 'ipv6'
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// -t, --timeout timeout Set timeout
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// -u, --status status Set status, eg. ASSURED
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// -w, --zone value Set conntrack zone
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// --orig-zone value Set zone for original direction
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// --reply-zone value Set zone for reply direction
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// -b, --buffer-size Netlink socket buffer size
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// --mask-src ip Source mask address
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// --mask-dst ip Destination mask address
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// Filter types
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type ConntrackFilterType uint8
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const (
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ConntrackOrigSrcIP = iota // -orig-src ip Source address from original direction
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ConntrackOrigDstIP // -orig-dst ip Destination address from original direction
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ConntrackNatSrcIP // -src-nat ip Source NAT ip
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ConntrackNatDstIP // -dst-nat ip Destination NAT ip
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ConntrackNatAnyIP // -any-nat ip Source or destination NAT ip
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)
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type CustomConntrackFilter interface {
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// MatchConntrackFlow applies the filter to the flow and returns true if the flow matches
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// the filter or false otherwise
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MatchConntrackFlow(flow *ConntrackFlow) bool
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}
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type ConntrackFilter struct {
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ipFilter map[ConntrackFilterType]net.IP
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}
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// AddIP adds an IP to the conntrack filter
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func (f *ConntrackFilter) AddIP(tp ConntrackFilterType, ip net.IP) error {
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if f.ipFilter == nil {
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f.ipFilter = make(map[ConntrackFilterType]net.IP)
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}
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if _, ok := f.ipFilter[tp]; ok {
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return errors.New("Filter attribute already present")
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}
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f.ipFilter[tp] = ip
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return nil
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}
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// MatchConntrackFlow applies the filter to the flow and returns true if the flow matches the filter
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// false otherwise
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func (f *ConntrackFilter) MatchConntrackFlow(flow *ConntrackFlow) bool {
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if len(f.ipFilter) == 0 {
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// empty filter always not match
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return false
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}
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match := true
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// -orig-src ip Source address from original direction
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if elem, found := f.ipFilter[ConntrackOrigSrcIP]; found {
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match = match && elem.Equal(flow.Forward.SrcIP)
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}
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// -orig-dst ip Destination address from original direction
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if elem, found := f.ipFilter[ConntrackOrigDstIP]; match && found {
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match = match && elem.Equal(flow.Forward.DstIP)
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}
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// -src-nat ip Source NAT ip
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if elem, found := f.ipFilter[ConntrackNatSrcIP]; match && found {
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match = match && elem.Equal(flow.Reverse.SrcIP)
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}
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// -dst-nat ip Destination NAT ip
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if elem, found := f.ipFilter[ConntrackNatDstIP]; match && found {
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match = match && elem.Equal(flow.Reverse.DstIP)
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}
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// -any-nat ip Source or destination NAT ip
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if elem, found := f.ipFilter[ConntrackNatAnyIP]; match && found {
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match = match && (elem.Equal(flow.Reverse.SrcIP) || elem.Equal(flow.Reverse.DstIP))
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}
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return match
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}
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var _ CustomConntrackFilter = (*ConntrackFilter)(nil)
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