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TUN-5593: Read full packet from UDP connection, even if it exceeds MTU of the transport. When packet length is greater than the MTU of the transport, we will silently drop packets (for now).

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This commit is contained in:
Igor Postelnik
2021-12-22 17:18:22 -06:00
parent 7a55208c61
commit 8445b88d3c
6 changed files with 28 additions and 19 deletions
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21
datagramsession/session.go
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@@ -7,6 +7,7 @@ import (
"time"
"github.com/google/uuid"
"github.com/rs/zerolog"
)
const (
@@ -17,7 +18,7 @@ func SessionIdleErr(timeout time.Duration) error {
return fmt.Errorf("session idle for %v", timeout)
}
// Each Session is a bidirectional pipe of datagrams between transport and dstConn
// Session is a bidirectional pipe of datagrams between transport and dstConn
// Currently the only implementation of transport is quic DatagramMuxer
// Destination can be a connection with origin or with eyeball
// When the destination is origin:
@@ -35,9 +36,10 @@ type Session struct {
// activeAtChan is used to communicate the last read/write time
activeAtChan chan time.Time
closeChan chan error
log *zerolog.Logger
}
func newSession(id uuid.UUID, transport transport, dstConn io.ReadWriteCloser) *Session {
func newSession(id uuid.UUID, transport transport, dstConn io.ReadWriteCloser, log *zerolog.Logger) *Session {
return &Session{
ID: id,
transport: transport,
@@ -47,6 +49,7 @@ func newSession(id uuid.UUID, transport transport, dstConn io.ReadWriteCloser) *
activeAtChan: make(chan time.Time, 2),
// capacity is 2 because close() and dstToTransport routine in Serve() can write to this channel
closeChan: make(chan error, 2),
log: log,
}
}
@@ -54,7 +57,8 @@ func (s *Session) Serve(ctx context.Context, closeAfterIdle time.Duration) (clos
go func() {
// QUIC implementation copies data to another buffer before returning https://github.com/lucas-clemente/quic-go/blob/v0.24.0/session.go#L1967-L1975
// This makes it safe to share readBuffer between iterations
readBuffer := make([]byte, s.transport.ReceiveMTU())
const maxPacketSize = 1500
readBuffer := make([]byte, maxPacketSize)
for {
if err := s.dstToTransport(readBuffer); err != nil {
s.closeChan <- err
@@ -103,8 +107,15 @@ func (s *Session) dstToTransport(buffer []byte) error {
n, err := s.dstConn.Read(buffer)
s.markActive()
if n > 0 {
if err := s.transport.SendTo(s.ID, buffer[:n]); err != nil {
return err
if n <= int(s.transport.MTU()) {
err = s.transport.SendTo(s.ID, buffer[:n])
} else {
// drop packet for now, eventually reply with ICMP for PMTUD
s.log.Debug().
Str("session", s.ID.String()).
Int("len", n).
Uint("mtu", s.transport.MTU()).
Msg("dropped packet exceeding MTU")
}
}
return err