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authorXin Long <lucien.xin@gmail.com>2021-06-22 14:04:54 -0400
committerDavid S. Miller <davem@davemloft.net>2021-06-22 11:28:52 -0700
commitb87641aff9e772fda15d3386d159646eada2ceef (patch)
treec95f58e778e645a748d69e49c5cb077cd39d450b /net/sctp
parent1dc68c194571acc4027de5f8378227d0c0ff7e13 (diff)
downloadlinux-b87641aff9e772fda15d3386d159646eada2ceef.tar.bz2
sctp: do state transition when a probe succeeds on HB ACK recv path
As described in rfc8899#section-5.2, when a probe succeeds, there might be the following state transitions: - Base -> Search, occurs when probe succeeds with BASE_PLPMTU, pl.pmtu is not changing, pl.probe_size increases by SCTP_PL_BIG_STEP, - Error -> Search, occurs when probe succeeds with BASE_PLPMTU, pl.pmtu is changed from SCTP_MIN_PLPMTU to SCTP_BASE_PLPMTU, pl.probe_size increases by SCTP_PL_BIG_STEP. - Search -> Search Complete, occurs when probe succeeds with the probe size SCTP_MAX_PLPMTU less than pl.probe_high, pl.pmtu is not changing, but update *pathmtu* with it, pl.probe_size is set back to pl.pmtu to double check it. - Search Complete -> Search, occurs when probe succeeds with the probe size equal to pl.pmtu, pl.pmtu is not changing, pl.probe_size increases by SCTP_PL_MIN_STEP. So search process can be described as: 1. When it just enters 'Search' state, *pathmtu* is not updated with pl.pmtu, and probe_size increases by a big step (SCTP_PL_BIG_STEP) each round. 2. Until pl.probe_high is set when a probe fails, and probe_size decreases back to pl.pmtu, as described in the last patch. 3. When the probe with the new size succeeds, probe_size changes to increase by a small step (SCTP_PL_MIN_STEP) due to pl.probe_high is set. 4. Until probe_size is next to pl.probe_high, the searching finishes and it goes to 'Complete' state and updates *pathmtu* with pl.pmtu, and then probe_size is set to pl.pmtu to confirm by once more probe. 5. This probe occurs after "30 * probe_inteval", a much longer time than that in Search state. Once it is done it goes to 'Search' state again with probe_size increased by SCTP_PL_MIN_STEP. As we can see above, during the searching, pl.pmtu changes while *pathmtu* doesn't. *pathmtu* is only updated when the search finishes by which it gets an optimal value for it. A big step is used at the beginning until it gets close to the optimal value, then it changes to a small step until it has this optimal value. The small step is also used in 'Complete' until it goes to 'Search' state again and the probe with 'pmtu + the small step' succeeds, which means a higher size could be used. Then probe_size changes to increase by a big step again until it gets close to the next optimal value. Note that anytime when black hole is detected, it goes directly to 'Base' state with pl.pmtu set to SCTP_BASE_PLPMTU, as described in the last patch. 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>
Diffstat (limited to 'net/sctp')
-rw-r--r--net/sctp/sm_statefuns.c2
-rw-r--r--net/sctp/transport.c38
2 files changed, 39 insertions, 1 deletions
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index 66c409e5b47c..d29b579da904 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -1274,7 +1274,7 @@ enum sctp_disposition sctp_sf_backbeat_8_3(struct net *net,
!sctp_transport_pl_enabled(link))
return SCTP_DISPOSITION_DISCARD;
- /* The actual handling will be performed here in a later patch. */
+ sctp_transport_pl_recv(link);
return SCTP_DISPOSITION_CONSUME;
}
diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index 99620d86e317..79ff5ca6b472 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -305,6 +305,44 @@ void sctp_transport_pl_send(struct sctp_transport *t)
t->pl.probe_count = 1;
}
+void sctp_transport_pl_recv(struct sctp_transport *t)
+{
+ pr_debug("%s: PLPMTUD: transport: %p, state: %d, pmtu: %d, size: %d, high: %d\n",
+ __func__, t, t->pl.state, t->pl.pmtu, t->pl.probe_size, t->pl.probe_high);
+
+ t->pl.pmtu = t->pl.probe_size;
+ t->pl.probe_count = 0;
+ if (t->pl.state == SCTP_PL_BASE) {
+ t->pl.state = SCTP_PL_SEARCH; /* Base -> Search */
+ t->pl.probe_size += SCTP_PL_BIG_STEP;
+ } else if (t->pl.state == SCTP_PL_ERROR) {
+ t->pl.state = SCTP_PL_SEARCH; /* Error -> Search */
+
+ t->pl.pmtu = t->pl.probe_size;
+ t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
+ sctp_assoc_sync_pmtu(t->asoc);
+ t->pl.probe_size += SCTP_PL_BIG_STEP;
+ } else if (t->pl.state == SCTP_PL_SEARCH) {
+ if (!t->pl.probe_high) {
+ t->pl.probe_size = min(t->pl.probe_size + SCTP_PL_BIG_STEP,
+ SCTP_MAX_PLPMTU);
+ return;
+ }
+ t->pl.probe_size += SCTP_PL_MIN_STEP;
+ if (t->pl.probe_size >= t->pl.probe_high) {
+ t->pl.probe_high = 0;
+ t->pl.state = SCTP_PL_COMPLETE; /* Search -> Search Complete */
+
+ t->pl.probe_size = t->pl.pmtu;
+ t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(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;
+ }
+}
+
bool sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
{
struct dst_entry *dst = sctp_transport_dst_check(t);