From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Kevin Mitchell <kevmitch@arista.com>
Cc: Jozsef Kadlecsik <kadlec@netfilter.org>,
Florian Westphal <fw@strlen.de>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] netfilter: conntrack: mark UDP zero checksum as CHECKSUM_UNNECESSARY
Date: Fri, 4 Feb 2022 06:09:07 +0100 [thread overview]
Message-ID: <Yfy08zMz6Duyz54/@salvia> (raw)
In-Reply-To: <20220115040050.187972-2-kevmitch@arista.com>
On Fri, Jan 14, 2022 at 08:00:50PM -0800, Kevin Mitchell wrote:
> The udp_error function verifies the checksum of incoming UDP packets if
> one is set. This has the desirable side effect of setting skb->ip_summed
> to CHECKSUM_COMPLETE, signalling that this verification need not be
> repeated further up the stack.
>
> Conversely, when the UDP checksum is empty, which is perfectly legal (at least
> inside IPv4), udp_error previously left no trace that the checksum had been
> deemed acceptable.
>
> This was a problem in particular for nf_reject_ipv4, which verifies the
> checksum in nf_send_unreach() before sending ICMP_DEST_UNREACH. It makes
> no accommodation for zero UDP checksums unless they are already marked
> as CHECKSUM_UNNECESSARY.
>
> This commit ensures packets with empty UDP checksum are marked as
> CHECKSUM_UNNECESSARY, which is explicitly recommended in skbuff.h.
Applied to nf-next
prev parent reply other threads:[~2022-02-04 5:09 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-15 4:00 [PATCH 0/1] UDP traceroute packets with no checksum Kevin Mitchell
2022-01-15 4:00 ` [PATCH 1/1] netfilter: conntrack: mark UDP zero checksum as CHECKSUM_UNNECESSARY Kevin Mitchell
2022-01-15 14:39 ` Florian Westphal
2022-02-04 5:09 ` Pablo Neira Ayuso [this message]
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