cloudflared-mirror/quic/datagram.go

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package quic
import (
"fmt"
"github.com/google/uuid"
"github.com/lucas-clemente/quic-go"
"github.com/pkg/errors"
)
const (
MaxDatagramFrameSize = 1220
sessionIDLen = len(uuid.UUID{})
)
type DatagramMuxer struct {
ID uuid.UUID
session quic.Session
}
func NewDatagramMuxer(quicSession quic.Session) (*DatagramMuxer, error) {
muxerID, err := uuid.NewRandom()
if err != nil {
return nil, err
}
return &DatagramMuxer{
ID: muxerID,
session: quicSession,
}, nil
}
// SendTo suffix the session ID to the payload so the other end of the QUIC session can demultiplex
// the payload from multiple datagram sessions
func (dm *DatagramMuxer) SendTo(sessionID uuid.UUID, payload []byte) error {
if len(payload) > MaxDatagramFrameSize-sessionIDLen {
// TODO: TUN-5302 return ICMP packet too big message
return fmt.Errorf("origin UDP payload has %d bytes, which exceeds transport MTU %d", len(payload), MaxDatagramFrameSize-sessionIDLen)
}
msgWithID, err := SuffixSessionID(sessionID, payload)
if err != nil {
return errors.Wrap(err, "Failed to suffix session ID to datagram, it will be dropped")
}
if err := dm.session.SendMessage(msgWithID); err != nil {
return errors.Wrap(err, "Failed to send datagram back to edge")
}
return nil
}
// ReceiveFrom extracts datagram session ID, then sends the session ID and payload to session manager
// which determines how to proxy to the origin. It assumes the datagram session has already been
// registered with session manager through other side channel
func (dm *DatagramMuxer) ReceiveFrom() (uuid.UUID, []byte, error) {
msg, err := dm.session.ReceiveMessage()
if err != nil {
return uuid.Nil, nil, err
}
return ExtractSessionID(msg)
}
func (dm *DatagramMuxer) MTU() uint {
return MaxDatagramFrameSize
}
// Each QUIC datagram should be suffixed with session ID.
// ExtractSessionID extracts the session ID and a slice with only the payload
func ExtractSessionID(b []byte) (uuid.UUID, []byte, error) {
msgLen := len(b)
if msgLen < sessionIDLen {
return uuid.Nil, nil, fmt.Errorf("session ID has %d bytes, but data only has %d", sessionIDLen, len(b))
}
// Parse last 16 bytess as UUID and remove it from slice
sessionID, err := uuid.FromBytes(b[len(b)-sessionIDLen:])
if err != nil {
return uuid.Nil, nil, err
}
b = b[:len(b)-sessionIDLen]
return sessionID, b, nil
}
// SuffixSessionID appends the session ID at the end of the payload. Suffix is more performant than prefix because
// the payload slice might already have enough capacity to append the session ID at the end
func SuffixSessionID(sessionID uuid.UUID, b []byte) ([]byte, error) {
if len(b)+len(sessionID) > MaxDatagramFrameSize {
return nil, fmt.Errorf("datagram size exceed %d", MaxDatagramFrameSize)
}
b = append(b, sessionID[:]...)
return b, nil
}