From: "Toke Høiland-Jørgensen" <toke@redhat•com>
To: Jakub Kicinski <kuba@kernel•org>
Cc: "David S. Miller" <davem@davemloft•net>,
netdev@vger•kernel.org, Jonathan Morton <chromatix99@gmail•com>,
Pete Heist <pete@heistp•net>
Subject: Re: [PATCH net] inet_ecn: Fix endianness of checksum update when setting ECT(1)
Date: Wed, 02 Dec 2020 11:07:15 +0100 [thread overview]
Message-ID: <87o8jccyi4.fsf@toke.dk> (raw)
In-Reply-To: <20201201172442.2d8dca75@kicinski-fedora-pc1c0hjn.DHCP.thefacebook.com>
Jakub Kicinski <kuba@kernel•org> writes:
> On Mon, 30 Nov 2020 19:37:05 +0100 Toke Høiland-Jørgensen wrote:
>> When adding support for propagating ECT(1) marking in IP headers it seems I
>> suffered from endianness-confusion in the checksum update calculation: In
>> fact the ECN field is in the *lower* bits of the first 16-bit word of the
>> IP header when calculating in network byte order. This means that the
>> addition performed to update the checksum field was wrong; let's fix that.
>>
>> Fixes: b723748750ec ("tunnel: Propagate ECT(1) when decapsulating as recommended by RFC6040")
>> Reported-by: Jonathan Morton <chromatix99@gmail•com>
>> Tested-by: Pete Heist <pete@heistp•net>
>> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat•com>
>
> Applied and queued, thanks!
>
>> diff --git a/include/net/inet_ecn.h b/include/net/inet_ecn.h
>> index e1eaf1780288..563457fec557 100644
>> --- a/include/net/inet_ecn.h
>> +++ b/include/net/inet_ecn.h
>> @@ -107,7 +107,7 @@ static inline int IP_ECN_set_ect1(struct iphdr *iph)
>> if ((iph->tos & INET_ECN_MASK) != INET_ECN_ECT_0)
>> return 0;
>>
>> - check += (__force u16)htons(0x100);
>> + check += (__force u16)htons(0x1);
>>
>> iph->check = (__force __sum16)(check + (check>=0xFFFF));
>> iph->tos ^= INET_ECN_MASK;
>
> This seems to be open coding csum16_add() - is there a reason and if
> not perhaps worth following up in net-next?
Hmm, good point. I think I originally just copied this from
IP_ECN_set_ce(), which comes all the way back from the initial
Linux-2.6.12-rc2 commit in git. So I suppose it may just predate the
csum helpers? I'll wait for this patch to get propagated to net-next,
then follow up with a fix there :)
-Toke
prev parent reply other threads:[~2020-12-02 10:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-30 18:37 [PATCH net] inet_ecn: Fix endianness of checksum update when setting ECT(1) Toke Høiland-Jørgensen
2020-12-02 1:24 ` Jakub Kicinski
2020-12-02 10:07 ` Toke Høiland-Jørgensen [this message]
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