On Fri, Dec 22, 2017 at 04:28:07PM -0200, Marcelo Ricardo Leitner wrote: > On Fri, Dec 22, 2017 at 11:58:08AM +0100, Dmitry Vyukov wrote: > ... > > > Same with this one, perhaps related to / fixed by: > > > http://patchwork.ozlabs.org/patch/850957/ > > > > > > > > > > > Looking at the log, this one seems to be an infinite loop in SCTP code > > with console output in it. Kernel is busy printing gazilion of: > > > > [ 176.491099] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too > > low, using default minimum of 512 > > ** 110 printk messages dropped ** > > [ 176.503409] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too > > low, using default minimum of 512 > > ** 103 printk messages dropped ** > > ... > > [ 246.742374] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too > > low, using default minimum of 512 > > [ 246.742484] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too > > low, using default minimum of 512 > > [ 246.742590] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too > > low, using default minimum of 512 > > > > Looks like a different issue. > > > > Oh. I guess this is caused by the interface having a MTU smaller than > SCTP_DEFAULT_MINSEGMENT (512), as the icmp frag needed handler > (sctp_icmp_frag_needed) will trigger an instant retransmission. > But as the MTU is smaller, SCTP won't update it, but will issue the > retransmission anyway. > > I will test this soon. Should be fairly easy to trigger it.
Reproduced it. netns A veth0(1500) - veth1(1500) B veth2(508) - veth3(508) C When A sends a sctp packet bigger than 508, it triggers the issue as B will reply a icmp frag needed with a size that sctp won't accept but will retransmit anyway. Marcelo
