From: Jakub Kicinski <kuba@kernel.org>
To: Neil Spring <ntspring@meta.com>
Cc: netdev@vger.kernel.org, edumazet@google.com,
ncardwell@google.com, kuniyu@google.com, davem@davemloft.net,
dsahern@kernel.org, pabeni@redhat.com, horms@kernel.org,
shuah@kernel.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH net-next v6 0/2] tcp: rehash onto different local ECMP path on retransmit timeout
Date: Mon, 18 May 2026 13:08:24 -0700 [thread overview]
Message-ID: <20260518130824.2fe952ea@kernel.org> (raw)
In-Reply-To: <20260517174522.2232057-1-ntspring@meta.com>
On Sun, 17 May 2026 10:45:20 -0700 Neil Spring wrote:
> Currently sk_rethink_txhash() re-rolls the socket's txhash on RTO,
> PLB, and spurious-retransmission events, but the new hash is not
> propagated into the IPv6 ECMP path selection logic. The cached
> route is reused and fib6_select_path() is never re-invoked, so
> the connection stays on the same ECMP path.
>
> This series adds the two missing pieces:
>
> 1. __sk_dst_reset() alongside sk_rethink_txhash() so the cached dst
> is invalidated and the next transmit triggers a fresh route lookup.
>
> 2. fl6->mp_hash set from sk_txhash before each route lookup so
> fib6_select_path() picks a path based on the (potentially re-rolled)
> hash. This is conditioned on fib_multipath_hash_policy == 0 (L3)
> because policies 1-3 compute a deterministic hash from the flow
> keys which must not be overridden.
>
> Patch 1 is the kernel change; patch 2 adds selftests covering SYN
> rehash, SYN/ACK rehash, midstream RTO rehash, midstream ACK rehash
> (spurious retransmission), PLB rehash, a policy 1 negative test,
> a flowlabel leak regression test, and two dst rebuild consistency
> tests (normal and syncookie) verifying that natural route
> invalidation does not cause unintended path changes.
Still flakes:
https://netdev-ctrl.bots.linux.dev/logs/vmksft/net/results/652122/44-ecmp-rehash-sh/stdout
https://netdev-ctrl.bots.linux.dev/logs/vmksft/net-dbg/results/652122/34-ecmp-rehash-sh/stdout
--
pw-bot: cr
prev parent reply other threads:[~2026-05-18 20:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-17 17:45 [PATCH net-next v6 0/2] tcp: rehash onto different local ECMP path on retransmit timeout Neil Spring
2026-05-17 17:45 ` [PATCH net-next v6 1/2] " Neil Spring
2026-05-17 17:45 ` [PATCH net-next v6 2/2] selftests: net: add local ECMP rehash test Neil Spring
2026-05-18 20:08 ` Jakub Kicinski [this message]
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