From: Matteo Croce <mcr...@redhat.com> Date: Thu, 12 Oct 2017 16:12:37 +0200
> The ICMP implementation currently replies to an ICMP time exceeded message > (type 11) with an ICMP host unreachable message (type 3, code 1). > > However, time exceeded messages can either represent "time to live exceeded > in transit" (code 0) or "fragment reassembly time exceeded" (code 1). > > Unconditionally replying to "fragment reassembly time exceeded" with > host unreachable messages might cause unjustified connection resets > which are now easily triggered as UFO has been removed, because, in turn, > sending large buffers triggers IP fragmentation. > > The issue can be easily reproduced by running a lot of UDP streams > which is likely to trigger IP fragmentation: > > # start netserver in the test namespace > ip netns add test > ip netns exec test netserver > > # create a VETH pair > ip link add name veth0 type veth peer name veth0 netns test > ip link set veth0 up > ip -n test link set veth0 up > > for i in $(seq 20 29); do > # assign addresses to both ends > ip addr add dev veth0 192.168.$i.1/24 > ip -n test addr add dev veth0 192.168.$i.2/24 > > # start the traffic > netperf -L 192.168.$i.1 -H 192.168.$i.2 -t UDP_STREAM -l 0 & > done > > # wait > send_data: data send error: No route to host (errno 113) > netperf: send_omni: send_data failed: No route to host > > We need to differentiate instead: if fragment reassembly time exceeded > is reported, we need to silently drop the packet, > if time to live exceeded is reported, maintain the current behaviour. > In both cases increment the related error count "icmpInTimeExcds". > > While at it, fix a typo in a comment, and convert the if statement > into a switch to mate it more readable. > > Signed-off-by: Matteo Croce <mcr...@redhat.com> Looks good, applied, thank you!
