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// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
// SPDX-License-Identifier: MIT
package extension
import (
"golang.org/x/crypto/cryptobyte"
)
// ConnectionID is a DTLS extension that provides an alternative to IP address
// and port for session association.
//
// https://tools.ietf.org/html/rfc9146
type ConnectionID struct {
// A zero-length connection ID indicates for a client or server that
// negotiated connection IDs from the peer will be sent but there is no need
// to respond with one
CID []byte // variable length
}
// TypeValue returns the extension TypeValue.
func (c ConnectionID) TypeValue() TypeValue {
return ConnectionIDTypeValue
}
// Marshal encodes the extension.
func (c *ConnectionID) Marshal() ([]byte, error) {
var b cryptobyte.Builder
b.AddUint16(uint16(c.TypeValue()))
b.AddUint16LengthPrefixed(func(b *cryptobyte.Builder) {
b.AddUint8LengthPrefixed(func(b *cryptobyte.Builder) {
b.AddBytes(c.CID)
})
})
return b.Bytes()
}
// Unmarshal populates the extension from encoded data.
func (c *ConnectionID) Unmarshal(data []byte) error {
val := cryptobyte.String(data)
var extension uint16
val.ReadUint16(&extension)
if TypeValue(extension) != c.TypeValue() {
return errInvalidExtensionType
}
var extData cryptobyte.String
val.ReadUint16LengthPrefixed(&extData)
var cid cryptobyte.String
if !extData.ReadUint8LengthPrefixed(&cid) {
return errInvalidCIDFormat
}
c.CID = make([]byte, len(cid))
if !cid.CopyBytes(c.CID) {
return errInvalidCIDFormat
}
return nil
}
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