linux-sctp.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Xin Long <lucien.xin@gmail.com>
To: network dev <netdev@vger.kernel.org>,
	davem@davemloft.net, kuba@kernel.org,
	Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>,
	linux-sctp@vger.kernel.org
Cc: David Laight <david.laight@aculab.com>
Subject: [PATCHv2 net-next 1/2] sctp: do black hole detection in search complete state
Date: Fri, 25 Jun 2021 22:40:54 -0400	[thread overview]
Message-ID: <1d298cde5971e080b56fb7aad24805b6812eb2f0.1624675179.git.lucien.xin@gmail.com> (raw)
In-Reply-To: <cover.1624675179.git.lucien.xin@gmail.com>

Currently the PLPMUTD probe will stop for a long period (interval * 30)
after it enters search complete state. If there's a pmtu change on the
route path, it takes a long time to be aware if the ICMP TooBig packet
is lost or filtered.

As it says in rfc8899#section-4.3:

  "A DPLPMTUD method MUST NOT rely solely on this method."
  (ICMP PTB message).

This patch is to enable the other method for search complete state:

  "A PL can use the DPLPMTUD probing mechanism to periodically
   generate probe packets of the size of the current PLPMTU."

With this patch, the probe will continue with the current pmtu every
'interval' until the PMTU_RAISE_TIMER 'timeout', which we implement
by adding raise_count to raise the probe size when it counts to 30
and removing the SCTP_PL_COMPLETE check for PMTU_RAISE_TIMER.

v1->v2:
  - do t->pl.raise_count++ and t->pl.raise_count check separately, as
    Marcelo suggested.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
 include/net/sctp/structs.h |  3 ++-
 net/sctp/transport.c       | 16 ++++++++--------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 9eaa701cda23..c4a4c1754be8 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -987,7 +987,8 @@ struct sctp_transport {
 		__u16 pmtu;
 		__u16 probe_size;
 		__u16 probe_high;
-		__u8 probe_count;
+		__u8 probe_count:3;
+		__u8 raise_count:5;
 		__u8 state;
 	} pl; /* plpmtud related */
 
diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index f27b856ea8ce..397a6244dd97 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -213,15 +213,10 @@ void sctp_transport_reset_reconf_timer(struct sctp_transport *transport)
 
 void sctp_transport_reset_probe_timer(struct sctp_transport *transport)
 {
-	int scale = 1;
-
 	if (timer_pending(&transport->probe_timer))
 		return;
-	if (transport->pl.state == SCTP_PL_COMPLETE &&
-	    transport->pl.probe_count == 1)
-		scale = 30; /* works as PMTU_RAISE_TIMER */
 	if (!mod_timer(&transport->probe_timer,
-		       jiffies + transport->probe_interval * scale))
+		       jiffies + transport->probe_interval))
 		sctp_transport_hold(transport);
 }
 
@@ -333,6 +328,7 @@ void sctp_transport_pl_recv(struct sctp_transport *t)
 		t->pl.probe_size += SCTP_PL_MIN_STEP;
 		if (t->pl.probe_size >= t->pl.probe_high) {
 			t->pl.probe_high = 0;
+			t->pl.raise_count = 0;
 			t->pl.state = SCTP_PL_COMPLETE; /* Search -> Search Complete */
 
 			t->pl.probe_size = t->pl.pmtu;
@@ -340,8 +336,12 @@ void sctp_transport_pl_recv(struct sctp_transport *t)
 			sctp_assoc_sync_pmtu(t->asoc);
 		}
 	} else if (t->pl.state == SCTP_PL_COMPLETE) {
-		t->pl.state = SCTP_PL_SEARCH; /* Search Complete -> Search */
-		t->pl.probe_size += SCTP_PL_MIN_STEP;
+		t->pl.raise_count++;
+		if (t->pl.raise_count == 30) {
+			/* Raise probe_size again after 30 * interval in Search Complete */
+			t->pl.state = SCTP_PL_SEARCH; /* Search Complete -> Search */
+			t->pl.probe_size += SCTP_PL_MIN_STEP;
+		}
 	}
 }
 
-- 
2.27.0


  reply	other threads:[~2021-06-26  2:41 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-26  2:40 [PATCHv2 net-next 0/2] sctp: make the PLPMTUD probe more effective and efficient Xin Long
2021-06-26  2:40 ` Xin Long [this message]
2021-06-26  2:40 ` [PATCHv2 net-next 2/2] sctp: send the next probe immediately once the last one is acked Xin Long
2021-06-28 16:54 ` [PATCHv2 net-next 0/2] sctp: make the PLPMTUD probe more effective and efficient Marcelo Ricardo Leitner
2021-06-28 20:38 ` David Miller

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1d298cde5971e080b56fb7aad24805b6812eb2f0.1624675179.git.lucien.xin@gmail.com \
    --to=lucien.xin@gmail.com \
    --cc=davem@davemloft.net \
    --cc=david.laight@aculab.com \
    --cc=kuba@kernel.org \
    --cc=linux-sctp@vger.kernel.org \
    --cc=marcelo.leitner@gmail.com \
    --cc=netdev@vger.kernel.org \
    --subject='Re: [PATCHv2 net-next 1/2] sctp: do black hole detection in search complete state' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).