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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id n16sm7414732wrx.85.2021.06.25.19.40.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Jun 2021 19:40:59 -0700 (PDT) From: Xin Long To: network dev , davem@davemloft.net, kuba@kernel.org, Marcelo Ricardo Leitner , linux-sctp@vger.kernel.org Cc: David Laight Subject: [PATCHv2 net-next 1/2] sctp: do black hole detection in search complete state Date: Fri, 25 Jun 2021 22:40:54 -0400 Message-Id: <1d298cde5971e080b56fb7aad24805b6812eb2f0.1624675179.git.lucien.xin@gmail.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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 --- 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; + } } }