On Thu, Jan 4, 2018 at 6:59 AM, Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx> wrote: > Currently, if PMTU discovery is disabled on a given transport, but the > configured value is higher than the actual PMTU, it is likely that we > will get some icmp Frag Needed. The issue is, if PMTU discovery is > disabled, we won't update the information and will issue a > retransmission immediately, which may very well trigger another ICMP, > and another retransmission, leading to a loop. > > The fix is to simply not trigger immediate retransmissions if PMTU > discovery is disabled on the given transport. > > Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx> > --- > net/sctp/input.c | 17 +++++++++++------ > 1 file changed, 11 insertions(+), 6 deletions(-) > > diff --git a/net/sctp/input.c b/net/sctp/input.c > index 621b5ca3fd1c17c3d7ef7bb1c7677ab98cebbe77..4a8e76f4834c90de9398455862423e598b8354a7 100644 > --- a/net/sctp/input.c > +++ b/net/sctp/input.c > @@ -399,13 +399,18 @@ void sctp_icmp_frag_needed(struct sock *sk, struct sctp_association *asoc, > return; > } > > - if (t->param_flags & SPP_PMTUD_ENABLE) { > - /* Update transports view of the MTU */ > - sctp_transport_update_pmtu(t, pmtu); > + if (!(t->param_flags & SPP_PMTUD_ENABLE)) > + /* We can't allow retransmitting in such case, as the > + * retransmission would be sized just as before, and thus we > + * would get another icmp, and retransmit again. > + */ > + return; > > - /* Update association pmtu. */ > - sctp_assoc_sync_pmtu(asoc); > - } > + /* Update transports view of the MTU */ > + sctp_transport_update_pmtu(t, pmtu); > + > + /* Update association pmtu. */ > + sctp_assoc_sync_pmtu(asoc); > > /* Retransmit with the new pmtu setting. > * Normally, if PMTU discovery is disabled, an ICMP Fragmentation > -- > 2.14.3 > commit 52ccb8e90c0ace233b8b740f2fc5de0dbd706b27 Author: Frank Filz <ffilz@xxxxxxxxxx> Date: Thu Dec 22 11:36:46 2005 -0800 [SCTP]: Update SCTP_PEER_ADDR_PARAMS socket option to the latest api draft. It seemed intended to move sctp_retransmit out of 'if (SPP_PMTUD_ENABLE) {}' on the above commit with some notes: /* Retransmit with the new pmtu setting. * Normally, if PMTU discovery is disabled, an ICMP Fragmentation * Needed will never be sent, but if a message was sent before * PMTU discovery was disabled that was larger than the PMTU, it * would not be fragmented, so it must be re-transmitted fragmented. */ But this patch is equivalent to move it back into 'if (SPP_PMTUD_ENABLE) {}'. will there be no regression caused? -- To unsubscribe from this list: send the line "unsubscribe linux-sctp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html