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Don't propagate errors from RelayBroadcast

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If forwarding of a broadcast frame resulted in a FrameTooBigError, we
would generate an ICMP "fragmentation needed" packet that contravened
RFC1122 on two counts: First, we should not produce a ICMP error
message in response to a broadcast/multicast packet.  Secondly, we
should not produce an IP packet with a broadcast/multicast source IP
address.  (It also gave an ethernet frame with a broadcast source MAC,
which probably contravenes some IEEE spec.)

So when RelayBroadcast gets a FrameTooBigError, it should just drop
the packet.

Futhermore, if we fail to relay a broadcast on one connection, that's
not a good reason to give up entirely - we can proceed to attempt to
relay on the other next hop connections.  Errors other than
FrameTooBigError that propagated upwards were simply logged, so that
logging is moved down into RelayBroadcast.
This commit is contained in:
David Wragg committed 2015-03-05 15:13:29 +00:00
1 parent 619ebc20a8
commit e543bff1ba
2 files changed
+12 -7
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router/local_peer.go
+8 -5
View File
@@ -32,8 +32,8 @@ func (peer *LocalPeer) Forward(dstPeer *Peer, df bool, frame []byte, dec *Ethern
return peer.Relay(peer.Peer, dstPeer, df, frame, dec)
}
func (peer *LocalPeer) Broadcast(df bool, frame []byte, dec *EthernetDecoder) error {
return peer.RelayBroadcast(peer.Peer, df, frame, dec)
func (peer *LocalPeer) Broadcast(df bool, frame []byte, dec *EthernetDecoder) {
peer.RelayBroadcast(peer.Peer, df, frame, dec)
}
func (peer *LocalPeer) Relay(srcPeer, dstPeer *Peer, df bool, frame []byte, dec *EthernetDecoder) error {
@@ -57,7 +57,7 @@ func (peer *LocalPeer) Relay(srcPeer, dstPeer *Peer, df bool, frame []byte, dec
dec)
}
func (peer *LocalPeer) RelayBroadcast(srcPeer *Peer, df bool, frame []byte, dec *EthernetDecoder) error {
func (peer *LocalPeer) RelayBroadcast(srcPeer *Peer, df bool, frame []byte, dec *EthernetDecoder) {
for _, conn := range peer.NextBroadcastHops(srcPeer) {
err := conn.Forward(df, &ForwardedFrame{
srcPeer: srcPeer,
@@ -65,10 +65,13 @@ func (peer *LocalPeer) RelayBroadcast(srcPeer *Peer, df bool, frame []byte, dec
frame: frame},
dec)
if err != nil {
return err
if ftbe, ok := err.(FrameTooBigError); ok {
log.Printf("dropping too big DF broadcast frame (%v -> %v): PMTU= %v\n", dec.ip.DstIP, dec.ip.SrcIP, ftbe.EPMTU)
} else {
log.Println(err)
}
}
}
return nil
}
func (peer *LocalPeer) NextBroadcastHops(srcPeer *Peer) []*LocalConnection {
router/router.go
+4 -2
View File
@@ -160,7 +160,8 @@ func (router *Router) handleCapturedPacket(frameData []byte, dec *EthernetDecode
copy(frameCopy, frameData)
if !found {
return checkFrameTooBig(router.Ourself.Broadcast(df, frameCopy, dec))
router.Ourself.Broadcast(df, frameCopy, dec)
return nil
} else {
return checkFrameTooBig(router.Ourself.Forward(dstPeer, df, frameCopy, dec))
}
@@ -344,7 +345,8 @@ func (router *Router) handleUDPPacketFunc(dec *EthernetDecoder, po PacketSink) F
dstPeer, found = router.Macs.Lookup(dstMac)
if !found || dstPeer != router.Ourself.Peer {
return checkFrameTooBig(router.Ourself.RelayBroadcast(srcPeer, df, frame, dec), srcPeer)
router.LogFrame("Relaying broadcast", frame, &dec.eth)
router.Ourself.RelayBroadcast(srcPeer, df, frame, dec)
}
return nil