netdev - Re: [PATCH net] netfilter: nft_flowtable.sh: re-run with random mtu sizes

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Message-ID: <20250829185624.16d49050@kernel.org>
Date: Fri, 29 Aug 2025 18:56:24 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Florian Westphal <fw@...len.de>
Cc: <netdev@...r.kernel.org>, Paolo Abeni <pabeni@...hat.com>, "David S.
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 <netfilter-devel@...r.kernel.org>, pablo@...filter.org
Subject: Re: [PATCH net] netfilter: nft_flowtable.sh: re-run with random mtu
 sizes

On Thu, 28 Aug 2025 23:49:18 +0200 Florian Westphal wrote:
> But all logs I saw show same scenario:
> 1. Failing tests have pmtu discovery off (i.e., ip fragmentation)
> 2. The test file is much larger than first-pass default (2M Byte)
> 3. peers have much larger MTUs compared to the 'network'.
> 
> These errors are very reproducible when re-running the test with
> the same commandline arguments.
> 
> The timeout became much more prominent with
> 1d2fbaad7cd8 ("tcp: stronger sk_rcvbuf checks"): reassembled packets
> typically have a skb->truesize more than double the skb length.
> 
> As that commit is intentional and pmtud-off with
> large-tcp-packets-as-fragments is not normal adjust the test to use a
> smaller file for the pmtu-off subtests.
> 
> While at it, add more information to pass/fail messages and
> also run the dscp alteration subtest with pmtu discovery enabled.

Thank you for fixing!