Re: [PATCH net] sctp: use the pmtu from the icmp packet to update transport pathmtu
From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Date: 2018-10-16 06:14:26
Also in:
linux-sctp
On Mon, Oct 15, 2018 at 07:58:29PM +0800, Xin Long wrote:
Other than asoc pmtu sync from all transports, sctp_assoc_sync_pmtu is also processing transport pmtu_pending by icmp packets. But it's meaningless to use sctp_dst_mtu(t->dst) as new pmtu for a transport. The right pmtu value should come from the icmp packet, and it would be saved into transport->mtu_info in this patch and used later when the pmtu sync happens in sctp_sendmsg_to_asoc or sctp_packet_config. Besides, without this patch, as pmtu can only be updated correctly when receiving a icmp packet and no place is holding sock lock, it will take long time if the sock is busy with sending packets. Note that it doesn't process transport->mtu_info in .release_cb(), as there is no enough information for pmtu update, like for which asoc or transport. It is not worth traversing all asocs to check pmtu_pending. So unlike tcp, sctp does this in tx path, for which mtu_info needs to be atomic_t. Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
quoted hunk ↗ jump to hunk
--- include/net/sctp/structs.h | 2 ++ net/sctp/associola.c | 3 ++- net/sctp/input.c | 1 + net/sctp/output.c | 6 ++++++ 4 files changed, 11 insertions(+), 1 deletion(-)diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h index 28a7c8e..a11f937 100644 --- a/include/net/sctp/structs.h +++ b/include/net/sctp/structs.h@@ -876,6 +876,8 @@ struct sctp_transport { unsigned long sackdelay; __u32 sackfreq; + atomic_t mtu_info; + /* When was the last time that we heard from this transport? We use * this to pick new active and retran paths. */diff --git a/net/sctp/associola.c b/net/sctp/associola.c index 297d9cf..a827a1f 100644 --- a/net/sctp/associola.c +++ b/net/sctp/associola.c@@ -1450,7 +1450,8 @@ void sctp_assoc_sync_pmtu(struct sctp_association *asoc) /* Get the lowest pmtu of all the transports. */ list_for_each_entry(t, &asoc->peer.transport_addr_list, transports) { if (t->pmtu_pending && t->dst) { - sctp_transport_update_pmtu(t, sctp_dst_mtu(t->dst)); + sctp_transport_update_pmtu(t, + atomic_read(&t->mtu_info)); t->pmtu_pending = 0; } if (!pmtu || (t->pathmtu < pmtu))diff --git a/net/sctp/input.c b/net/sctp/input.c index 9bbc5f9..5c36a99 100644 --- a/net/sctp/input.c +++ b/net/sctp/input.c@@ -395,6 +395,7 @@ void sctp_icmp_frag_needed(struct sock *sk, struct sctp_association *asoc, return; if (sock_owned_by_user(sk)) { + atomic_set(&t->mtu_info, pmtu); asoc->pmtu_pending = 1; t->pmtu_pending = 1; return;diff --git a/net/sctp/output.c b/net/sctp/output.c index 7f849b0..67939ad 100644 --- a/net/sctp/output.c +++ b/net/sctp/output.c@@ -120,6 +120,12 @@ void sctp_packet_config(struct sctp_packet *packet, __u32 vtag, sctp_assoc_sync_pmtu(asoc); } + if (asoc->pmtu_pending) { + if (asoc->param_flags & SPP_PMTUD_ENABLE) + sctp_assoc_sync_pmtu(asoc); + asoc->pmtu_pending = 0; + } + /* If there a is a prepend chunk stick it on the list before * any other chunks get appended. */-- 2.1.0