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Matthieu Baerts fd8acb5d4a net: mptcp: add TCPConn's MultipathTCP checker
This new TCPConn method returns whether the connection is using MPTCP or
if a fallback to TCP has been done, e.g. because the other peer doesn't
support MPTCP.

When working on the new E2E test linked to MPTCP (#56539), it looks like
the user might need to know such info to be able to do some special
actions (report, stop, etc.). This also improves the test to make sure
MPTCP has been used as expected.

Regarding the implementation, from kernel version 5.16, it is possible
to use:

    getsockopt(..., SOL_MPTCP, MPTCP_INFO, ...)

and check if EOPNOTSUPP (IPv4) or ENOPROTOOPT (IPv6) is returned. If it
is, it means a fallback to TCP has been done. See this link for more
details:

    https://github.com/multipath-tcp/mptcp_net-next/issues/294

Before v5.16, there is no other simple way, from the userspace, to check
if the created socket did a fallback to TCP. Netlink requests could be
done to try to find more details about a specific socket but that seems
quite a heavy machinery. Instead, only the protocol is checked on older
kernels.

The E2E test has been modified to check that the MPTCP connection didn't
do any fallback to TCP, explicitely validating the two methods
(SO_PROTOCOL and MPTCP_INFO) if it is supported by the host.

This work has been co-developed by Gregory Detal
<gregory.detal@tessares.net> and Benjamin Hesmans
<benjamin.hesmans@tessares.net>.

Fixes #59166

Change-Id: I5a313207146f71c66c349aa8588a2525179dd8b8
Reviewed-on: https://go-review.googlesource.com/c/go/+/471140
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
2023-04-18 13:48:22 +00:00
.github doc: normalize proposal-process links 2023-03-29 22:00:27 +00:00
api net: mptcp: add TCPConn's MultipathTCP checker 2023-04-18 13:48:22 +00:00
doc doc: correct spelling on placeholder 2023-04-13 23:15:09 +00:00
lib/time time/tzdata: generate zip constant during cmd/dist 2023-01-17 22:30:53 +00:00
misc cmd/go: add check for unknown godebug setting 2023-04-18 13:19:19 +00:00
src net: mptcp: add TCPConn's MultipathTCP checker 2023-04-18 13:48:22 +00:00
test Revert "cmd/compile: allow more inlining of functions that construct closures" 2023-04-17 21:45:00 +00:00
.gitattributes
.gitignore time/tzdata: generate zip constant during cmd/dist 2023-01-17 22:30:53 +00:00
CONTRIBUTING.md doc: normalize proposal-process links 2023-03-29 22:00:27 +00:00
LICENSE
PATENTS
README.md README: update from CC-BY-3.0 to CC-BY-4.0 2022-11-02 20:14:56 +00:00
SECURITY.md SECURITY.md: replace golang.org with go.dev 2022-04-26 19:59:47 +00:00
codereview.cfg
go.env cmd/go: introduce GOROOT/go.env and move proxy/sumdb config there 2023-01-17 23:10:39 +00:00

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