sctp: use the pmtu from the icmp packet to update transport pathmtu (d805397c) · Commits · 戴 / test

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> Signed-off-by:

David S. Miller <davem@davemloft.net>

include/net/sctp/structs.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -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.
		*/

net/sctp/associola.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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))

net/sctp/input.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -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;

net/sctp/output.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -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.
		*/

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