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sctp: fix an issue that plpmtu can never go to complete state

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When doing plpmtu probe, the probe size is growing every time when it
receives the ACK during the Search state until the probe fails. When
the failure occurs, pl.probe_high is set and it goes to the Complete
state.

However, if the link pmtu is huge, like 65535 in loopback_dev, the probe
eventually keeps using SCTP_MAX_PLPMTU as the probe size and never fails.
Because of that, pl.probe_high can not be set, and the plpmtu probe can
never go to the Complete state.

Fix it by setting pl.probe_high to SCTP_MAX_PLPMTU when the probe size
grows to SCTP_MAX_PLPMTU in sctp_transport_pl_recv(). Also, not allow
the probe size greater than SCTP_MAX_PLPMTU in the Complete state.

Fixes: b87641aff9 ("sctp: do state transition when a probe succeeds on HB ACK recv path")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Xin Long 2023-05-18 16:03:00 -04:00 committed by David S. Miller
parent 67caf26d76
commit 6ca328e985
1 changed files with 7 additions and 4 deletions
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11
net/sctp/transport.c
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@ -324,9 +324,12 @@ bool sctp_transport_pl_recv(struct sctp_transport *t)
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 false;
if (t->pl.probe_size < SCTP_MAX_PLPMTU) {
t->pl.probe_size = min(t->pl.probe_size + SCTP_PL_BIG_STEP,
SCTP_MAX_PLPMTU);
return false;
}
t->pl.probe_high = SCTP_MAX_PLPMTU;
}
t->pl.probe_size += SCTP_PL_MIN_STEP;
if (t->pl.probe_size >= t->pl.probe_high) {
@ -341,7 +344,7 @@ bool sctp_transport_pl_recv(struct sctp_transport *t)
} else if (t->pl.state == SCTP_PL_COMPLETE) {
/* 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;
t->pl.probe_size = min(t->pl.probe_size + SCTP_PL_MIN_STEP, SCTP_MAX_PLPMTU);
}
return t->pl.state == SCTP_PL_COMPLETE;