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