By allowing the max timer backoff duration to be limited, a socket can
fast recover in case of intermittent network issues. Before this CL, the
exponential backoff algorithm could result in very long retry durations
(in the order of minutes), when connection has been lost or been flaky
for a long while.
Note that limiting the maximum backoff duration might require
compensating the maximum retransmission limit to avoid closing the
socket prematurely due to reaching the maximum retransmission limit much
faster than previously.
Bug: webrtc:13129
Change-Id: Ib94030d666433e3fa1a2c8ef69750a1afab8ef94
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/230702
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#34913}
dcSCTP seems to be able to provoke usrsctp to send ABORT in some
situations, as described in
https://github.com/sctplab/usrsctp/issues/597. Using a packetdrill
script, it seems as a contributing factor to this behavior is when a
FORWARD-TSN chunk is bundled with a DATA chunk. This is a valid and
recommended pattern in RFC3758:
"F2) The data sender SHOULD always attempt to bundle an outgoing
FORWARD TSN with outbound DATA chunks for efficiency."
However, that seems to be a rare event in usrsctp, which generally sends
each FORWARD-TSN in a separate packet.
By doing the same, the assumption is that this scenario will generally
be avoided.
With many browsers and other clients using usrsctp, and which will not
be upgraded for a long time, there is an advantage of avoiding the issue
even if it is according to specification.
Before this change, a FORWARD-TSN was bundled with outgoing DATA and due
to this, it wasn't rate limited as the overhead was very little. With
this change, a rate limiting behavior has been added to avoid sending
too many FORWARD-TSN in small packets. It will be sent every RTT, or
200 ms, whichever is smallest. This is also described in the RFC.
Bug: webrtc:12961
Change-Id: I3d8036a34f999f405958982534bfa0e99e330da3
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/229101
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34801}
This is mainly a refactoring commit, to break out packet sending to a
dedicated component.
Bug: webrtc:12943
Change-Id: I78f18933776518caf49737d3952bda97f19ef335
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/228565
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34772}
It is now allowed in WebRTC, so let's use it.
Bug: webrtc:12943
Change-Id: I74a0f2fd9c1b9e7b5613ae1c592cf26842b8dddd
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/228564
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34768}
To support implementing RTCSctpTransportStats, a few metrics are needed.
Some more were added that are useful for metric collection in SFUs.
Bug: webrtc:13052
Change-Id: Idafd49e1084922d01d3e6c5860715f63aea08b7d
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/228243
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34708}
While in the COOKIE ECHO state, there is a TCB and there might be data
in the send buffer, and RFC4960 allows the COOKIE ECHO chunk to bundle
additional DATA chunks in the same packet, but there mustn't be more
than one such packet sent, and that packet must have a COOKIE ECHO chunk
as the first chunk in it.
When the COOKIE ACK chunk has been received, the socket is allowed to
send multiple packets.
Previously, this was state managed by the socket and not the TCB, as
the socket is responsible for moving between the different states. And
when the COOKIE ECHO chunk was sent, the TCB was instructed to only send
a single packet by the socket.
However, if there were retransmissions or anything else that could
result in calling TransmissionControlBlock::SendBufferedChunks, it would
do as instructed and send those, even if the socket was in a state where
that wasn't allowed.
When the peer was dcSCTP, this didn't cause any issues as dcSCTP tries
to be tolerant in what it receives (but strict in what it sends, except
for when there are bugs). When the peer was usrsctp, it would send an
ABORT for each received packet that didn't have a COOKIE ECHO as the
first chunk, and then restart the handshake (sending an INIT). So this
resulted in a longer handshake, but the connection would eventually be
correctly established and any DATA chunks that resulted in the ABORTs
would've been retransmitted.
By making the TCB aware of that particular state, and to make it
responsible for creating the SCTP packet with the COOKIE ECHO chunk
first, and also to only send a single packet when it is in that state,
there will not be any way to bypass this limitation.
Also, while not explicitly mentioned in the RFC, the retransmission
timer will not affect resending any outstanding DATA chunks that were
bundled together with the COOKIE ECHO chunk, as then there would be two
timers that both would drive resending COOKIE ECHO and DATA chunks.
Bug: webrtc:12880
Change-Id: I76f215a03cceab5bafe9f16eb4775f3dc68a6f05
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/222645
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34329}
While it's not strictly defined, the expectation is that sending a
message with a lifetime parameter set to zero (0) ms should allow it to
be sent if it can be sent without being buffered. If it can't be
directly sent, it should be discarded.
This is initial support for it. Small messages can now be delivered fine
if they are not to be buffered, but fragmented messages could be partly
sent (if this fills up the congestion window), which means that the
message will then fail to be sent whenever the congestion window frees
up again. It would be better to - at a higher level - realize early that
the message can't be sent in full, and discard it without sending
anything. But that's an optimization that can be done later.
A few off-by-one errors were found when strictly defining that the
message is alive during its entire lifetime. It will expire just _after_
its lifetime.
Sending messages with a lifetime of zero may not supported in all
libraries, so a workaround would be to set a very small timeout instead,
which is tested as well.
Bug: webrtc:12614
Change-Id: I9a00bedb639ad7b3b565b750ef2a49c9020745f1
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/217562
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33977}
This is merely a container of components that have their lifetime
bound to when the socket is connected. If the socket gets disconnected
or restarted, this object (and everything it holds) will be released.
Bug: webrtc:12614
Change-Id: Ibd75760b7bf7efe9c26c4eb7cee62de8bba5410c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/214340
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33869}
