135 lines
4.5 KiB
Go
135 lines
4.5 KiB
Go
package sctp // nolint:dupl
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import (
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"errors"
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"fmt"
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)
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/*
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Init represents an SCTP Chunk of type INIT
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See chunkInitCommon for the fixed headers
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Variable Parameters Status Type Value
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-------------------------------------------------------------
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IPv4 IP (Note 1) Optional 5
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IPv6 IP (Note 1) Optional 6
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Cookie Preservative Optional 9
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Reserved for ECN Capable (Note 2) Optional 32768 (0x8000)
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Host Name IP (Note 3) Optional 11
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Supported IP Types (Note 4) Optional 12
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*/
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type chunkInit struct {
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chunkHeader
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chunkInitCommon
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}
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var (
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errChunkTypeNotTypeInit = errors.New("ChunkType is not of type INIT")
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errChunkValueNotLongEnough = errors.New("chunk Value isn't long enough for mandatory parameters exp")
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errChunkTypeInitFlagZero = errors.New("ChunkType of type INIT flags must be all 0")
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errChunkTypeInitUnmarshalFailed = errors.New("failed to unmarshal INIT body")
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errChunkTypeInitMarshalFailed = errors.New("failed marshaling INIT common data")
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errChunkTypeInitInitateTagZero = errors.New("ChunkType of type INIT ACK InitiateTag must not be 0")
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errInitInboundStreamRequestZero = errors.New("INIT ACK inbound stream request must be > 0")
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errInitOutboundStreamRequestZero = errors.New("INIT ACK outbound stream request must be > 0")
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errInitAdvertisedReceiver1500 = errors.New("INIT ACK Advertised Receiver Window Credit (a_rwnd) must be >= 1500")
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)
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func (i *chunkInit) unmarshal(raw []byte) error {
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if err := i.chunkHeader.unmarshal(raw); err != nil {
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return err
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}
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if i.typ != ctInit {
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return fmt.Errorf("%w: actually is %s", errChunkTypeNotTypeInit, i.typ.String())
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} else if len(i.raw) < initChunkMinLength {
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return fmt.Errorf("%w: %d actual: %d", errChunkValueNotLongEnough, initChunkMinLength, len(i.raw))
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}
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// The Chunk Flags field in INIT is reserved, and all bits in it should
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// be set to 0 by the sender and ignored by the receiver. The sequence
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// of parameters within an INIT can be processed in any order.
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if i.flags != 0 {
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return errChunkTypeInitFlagZero
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}
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if err := i.chunkInitCommon.unmarshal(i.raw); err != nil {
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return fmt.Errorf("%w: %v", errChunkTypeInitUnmarshalFailed, err)
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}
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return nil
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}
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func (i *chunkInit) marshal() ([]byte, error) {
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initShared, err := i.chunkInitCommon.marshal()
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if err != nil {
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return nil, fmt.Errorf("%w: %v", errChunkTypeInitMarshalFailed, err)
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}
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i.chunkHeader.typ = ctInit
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i.chunkHeader.raw = initShared
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return i.chunkHeader.marshal()
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}
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func (i *chunkInit) check() (abort bool, err error) {
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// The receiver of the INIT (the responding end) records the value of
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// the Initiate Tag parameter. This value MUST be placed into the
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// Verification Tag field of every SCTP packet that the receiver of
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// the INIT transmits within this association.
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//
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// The Initiate Tag is allowed to have any value except 0. See
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// Section 5.3.1 for more on the selection of the tag value.
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//
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// If the value of the Initiate Tag in a received INIT chunk is found
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// to be 0, the receiver MUST treat it as an error and close the
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// association by transmitting an ABORT.
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if i.initiateTag == 0 {
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abort = true
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return abort, errChunkTypeInitInitateTagZero
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}
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// Defines the maximum number of streams the sender of this INIT
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// chunk allows the peer end to create in this association. The
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// value 0 MUST NOT be used.
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//
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// Note: There is no negotiation of the actual number of streams but
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// instead the two endpoints will use the min(requested, offered).
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// See Section 5.1.1 for details.
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//
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// Note: A receiver of an INIT with the MIS value of 0 SHOULD abort
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// the association.
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if i.numInboundStreams == 0 {
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abort = true
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return abort, errInitInboundStreamRequestZero
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}
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// Defines the number of outbound streams the sender of this INIT
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// chunk wishes to create in this association. The value of 0 MUST
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// NOT be used.
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//
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// Note: A receiver of an INIT with the OS value set to 0 SHOULD
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// abort the association.
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if i.numOutboundStreams == 0 {
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abort = true
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return abort, errInitOutboundStreamRequestZero
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}
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// An SCTP receiver MUST be able to receive a minimum of 1500 bytes in
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// one SCTP packet. This means that an SCTP endpoint MUST NOT indicate
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// less than 1500 bytes in its initial a_rwnd sent in the INIT or INIT
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// ACK.
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if i.advertisedReceiverWindowCredit < 1500 {
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abort = true
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return abort, errInitAdvertisedReceiver1500
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}
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return false, nil
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}
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// String makes chunkInit printable
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func (i *chunkInit) String() string {
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return fmt.Sprintf("%s\n%s", i.chunkHeader, i.chunkInitCommon)
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}
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