161 lines
5.7 KiB
Go
161 lines
5.7 KiB
Go
package sctp
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import (
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"encoding/binary"
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"errors"
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"fmt"
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)
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/*
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chunkInitCommon represents an SCTP Chunk body of type INIT and INIT ACK
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Type = 1 | Chunk Flags | Chunk Length |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Initiate Tag |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Advertised Receiver Window Credit (a_rwnd) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Number of Outbound Streams | Number of Inbound Streams |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Initial TSN |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Optional/Variable-Length Parameters |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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The INIT chunk contains the following parameters. Unless otherwise
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noted, each parameter MUST only be included once in the INIT chunk.
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Fixed Parameters Status
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----------------------------------------------
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Initiate Tag Mandatory
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Advertised Receiver Window Credit Mandatory
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Number of Outbound Streams Mandatory
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Number of Inbound Streams Mandatory
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Initial TSN Mandatory
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*/
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type chunkInitCommon struct {
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initiateTag uint32
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advertisedReceiverWindowCredit uint32
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numOutboundStreams uint16
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numInboundStreams uint16
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initialTSN uint32
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params []param
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}
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const (
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initChunkMinLength = 16
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initOptionalVarHeaderLength = 4
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)
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var (
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errInitChunkParseParamTypeFailed = errors.New("failed to parse param type")
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errInitChunkUnmarshalParam = errors.New("failed unmarshalling param in Init Chunk")
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errInitAckMarshalParam = errors.New("unable to marshal parameter for INIT/INITACK")
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)
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func (i *chunkInitCommon) unmarshal(raw []byte) error {
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i.initiateTag = binary.BigEndian.Uint32(raw[0:])
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i.advertisedReceiverWindowCredit = binary.BigEndian.Uint32(raw[4:])
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i.numOutboundStreams = binary.BigEndian.Uint16(raw[8:])
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i.numInboundStreams = binary.BigEndian.Uint16(raw[10:])
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i.initialTSN = binary.BigEndian.Uint32(raw[12:])
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// https://tools.ietf.org/html/rfc4960#section-3.2.1
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//
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// Chunk values of SCTP control chunks consist of a chunk-type-specific
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// header of required fields, followed by zero or more parameters. The
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// optional and variable-length parameters contained in a chunk are
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// defined in a Type-Length-Value format as shown below.
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//
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// 0 1 2 3
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// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// | Parameter Type | Parameter Length |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// | |
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// | Parameter Value |
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// | |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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offset := initChunkMinLength
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remaining := len(raw) - offset
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for remaining > 0 {
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if remaining > initOptionalVarHeaderLength {
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pType, err := parseParamType(raw[offset:])
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if err != nil {
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return fmt.Errorf("%w: %v", errInitChunkParseParamTypeFailed, err)
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}
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p, err := buildParam(pType, raw[offset:])
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if err != nil {
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return fmt.Errorf("%w: %v", errInitChunkUnmarshalParam, err)
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}
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i.params = append(i.params, p)
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padding := getPadding(p.length())
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offset += p.length() + padding
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remaining -= p.length() + padding
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} else {
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break
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}
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}
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return nil
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}
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func (i *chunkInitCommon) marshal() ([]byte, error) {
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out := make([]byte, initChunkMinLength)
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binary.BigEndian.PutUint32(out[0:], i.initiateTag)
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binary.BigEndian.PutUint32(out[4:], i.advertisedReceiverWindowCredit)
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binary.BigEndian.PutUint16(out[8:], i.numOutboundStreams)
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binary.BigEndian.PutUint16(out[10:], i.numInboundStreams)
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binary.BigEndian.PutUint32(out[12:], i.initialTSN)
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for idx, p := range i.params {
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pp, err := p.marshal()
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if err != nil {
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return nil, fmt.Errorf("%w: %v", errInitAckMarshalParam, err)
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}
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out = append(out, pp...)
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// Chunks (including Type, Length, and Value fields) are padded out
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// by the sender with all zero bytes to be a multiple of 4 bytes
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// long. This padding MUST NOT be more than 3 bytes in total. The
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// Chunk Length value does not include terminating padding of the
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// chunk. *However, it does include padding of any variable-length
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// parameter except the last parameter in the chunk.* The receiver
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// MUST ignore the padding.
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if idx != len(i.params)-1 {
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out = padByte(out, getPadding(len(pp)))
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}
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}
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return out, nil
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}
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// String makes chunkInitCommon printable
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func (i chunkInitCommon) String() string {
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format := `initiateTag: %d
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advertisedReceiverWindowCredit: %d
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numOutboundStreams: %d
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numInboundStreams: %d
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initialTSN: %d`
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res := fmt.Sprintf(format,
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i.initiateTag,
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i.advertisedReceiverWindowCredit,
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i.numOutboundStreams,
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i.numInboundStreams,
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i.initialTSN,
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)
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for i, param := range i.params {
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res += fmt.Sprintf("Param %d:\n %s", i, param)
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}
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return res
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}
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