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sctp: do state transition when PROBE_COUNT == MAX_PROBES on HB send path

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The state transition is described in rfc8899#section-5.2,
PROBE_COUNT == MAX_PROBES means the probe fails for MAX times, and the
state transition includes:

  - Base -> Error, occurs when BASE_PLPMTU Confirmation Fails,
    pl.pmtu is set to SCTP_MIN_PLPMTU,
    probe_size is still SCTP_BASE_PLPMTU;

  - Search -> Base, occurs when Black Hole Detected,
    pl.pmtu is set to SCTP_BASE_PLPMTU,
    probe_size is set back to SCTP_BASE_PLPMTU;

  - Search Complete -> Base, occurs when Black Hole Detected
    pl.pmtu is set to SCTP_BASE_PLPMTU,
    probe_size is set back to SCTP_BASE_PLPMTU;

Note a black hole is encountered when a sender is unaware that packets
are not being delivered to the destination endpoint. So it includes the
probe failures with equal probe_size to pl.pmtu, and definitely not
include that with greater probe_size than pl.pmtu. The later one is the
normal probe failure where probe_size should decrease back to pl.pmtu
and pl.probe_high is set.  pl.probe_high would be used on HB ACK recv
path in the next 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>
This commit is contained in:
Xin Long 2021-06-22 14:04:53 -04:00 committed by David S. Miller
parent fe59379b9a
commit 1dc68c1945
3 changed files with 47 additions and 0 deletions
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1
include/net/sctp/structs.h
View File

@ -1023,6 +1023,7 @@ bool sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu);
void sctp_transport_immediate_rtx(struct sctp_transport *);
void sctp_transport_dst_release(struct sctp_transport *t);
void sctp_transport_dst_confirm(struct sctp_transport *t);
void sctp_transport_pl_send(struct sctp_transport *t);
/* This is the structure we use to queue packets as they come into

2
net/sctp/sm_statefuns.c
View File

@ -1109,6 +1109,8 @@ enum sctp_disposition sctp_sf_send_probe(struct net *net,
if (!sctp_transport_pl_enabled(transport))
return SCTP_DISPOSITION_CONSUME;
sctp_transport_pl_send(transport);
reply = sctp_make_heartbeat(asoc, transport, transport->pl.probe_size);
if (!reply)
return SCTP_DISPOSITION_NOMEM;

44
net/sctp/transport.c
View File

@ -261,6 +261,50 @@ void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk)
transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
}
void sctp_transport_pl_send(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);
if (t->pl.probe_count < SCTP_MAX_PROBES) {
t->pl.probe_count++;
return;
}
if (t->pl.state == SCTP_PL_BASE) {
if (t->pl.probe_size == SCTP_BASE_PLPMTU) { /* BASE_PLPMTU Confirmation Failed */
t->pl.state = SCTP_PL_ERROR; /* Base -> Error */
t->pl.pmtu = SCTP_MIN_PLPMTU;
t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
sctp_assoc_sync_pmtu(t->asoc);
}
} else if (t->pl.state == SCTP_PL_SEARCH) {
if (t->pl.pmtu == t->pl.probe_size) { /* Black Hole Detected */
t->pl.state = SCTP_PL_BASE; /* Search -> Base */
t->pl.probe_size = SCTP_BASE_PLPMTU;
t->pl.probe_high = 0;
t->pl.pmtu = SCTP_BASE_PLPMTU;
t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
sctp_assoc_sync_pmtu(t->asoc);
} else { /* Normal probe failure. */
t->pl.probe_high = t->pl.probe_size;
t->pl.probe_size = t->pl.pmtu;
}
} else if (t->pl.state == SCTP_PL_COMPLETE) {
if (t->pl.pmtu == t->pl.probe_size) { /* Black Hole Detected */
t->pl.state = SCTP_PL_BASE; /* Search Complete -> Base */
t->pl.probe_size = SCTP_BASE_PLPMTU;
t->pl.pmtu = SCTP_BASE_PLPMTU;
t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
sctp_assoc_sync_pmtu(t->asoc);
}
}
t->pl.probe_count = 1;
}
bool sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
{
struct dst_entry *dst = sctp_transport_dst_check(t);