func (sleeve *SleeveOverlay) handleFrame(sender *net.UDPAddr, fwd *sleeveForwarder, src []byte, dst []byte, frame []byte, dec *EthernetDecoder) {
dec.DecodeLayers(frame)
decodedLen := len(dec.decoded)
if decodedLen == 0 {
return
}
srcPeer := sleeve.peers.Fetch(mesh.PeerNameFromBin(src))
dstPeer := sleeve.peers.Fetch(mesh.PeerNameFromBin(dst))
if srcPeer == nil || dstPeer == nil {
return
}
// Handle special frames produced internally (rather than
// captured/forwarded) by the remote router.
//
// We really shouldn't be decoding these above, since they are
// not genuine Ethernet frames. However, it is actually more
// efficient to do so, as we want to optimise for the common
// (i.e. non-special) frames. These always need decoding, and
// detecting special frames is cheaper post decoding than pre.
if decodedLen == 1 && dec.IsSpecial() {
if srcPeer == fwd.remotePeer && dstPeer == fwd.sleeve.localPeer {
select {
case fwd.specialChan <- specialFrame{sender, frame}:
case <-fwd.finishedChan:
}
}
return
}
sleeve.sendToConsumer(srcPeer, dstPeer, frame, dec)
}
func (sleeve *SleeveOverlay) readUDP() {
defer sleeve.conn.Close()
dec := NewEthernetDecoder()
buf := make([]byte, MaxUDPPacketSize)
for {
n, sender, err := sleeve.conn.ReadFromUDP(buf)
if err == io.EOF {
return
} else if err != nil {
log.Print("ignoring UDP read error ", err)
continue
} else if n < NameSize {
log.Print("ignoring too short UDP packet from ", sender)
continue
}
fwdName := mesh.PeerNameFromBin(buf[:NameSize])
fwd := sleeve.lookupForwarder(fwdName)
if fwd == nil {
continue
}
packet := make([]byte, n-NameSize)
copy(packet, buf[NameSize:n])
err = fwd.crypto.Dec.IterateFrames(packet,
func(src []byte, dst []byte, frame []byte) {
sleeve.handleFrame(sender, fwd, src, dst, frame, dec)
})
if err != nil {
// Errors during UDP packet decoding /
// processing are non-fatal. One common cause
// is that we receive and attempt to decrypt a
// "stray" packet. This can actually happen
// quite easily if there is some connection
// churn between two peers. After all, UDP
// isn't a connection-oriented protocol, yet
// we pretend it is.
//
// If anything really is seriously,
// unrecoverably amiss with a connection, that
// will typically result in missed heartbeats
// and the connection getting shut down
// because of that.
log.Print(fwd.logPrefixFor(sender), err)
}
}
}