From patchwork Thu Aug 8 07:59:02 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Asbj=C3=B8rn_Sloth_T=C3=B8nnesen?= X-Patchwork-Id: 818204 Received: from mail1.fiberby.net (mail1.fiberby.net [193.104.135.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CF00E186289; Thu, 8 Aug 2024 08:01:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.104.135.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723104066; cv=none; b=jaWjp6Rsfr0qNu5JotSIenobz2VfkXdpHFMqHGl0n0geAsT+BBbY8dfpuPbuwMg1ku9I/oT8dOlW7X0213d59CkkYrQ1QoUnReOaBam+0surArRAkE1HdUkAkw0EqY6C72VHUuyzD18/gcu6Irfw2A1CfhtNaY3dZiwTwhIIHeg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723104066; c=relaxed/simple; bh=RWh44ibT1OVXVkS6LOhCJHv00CcuvNPdegD/w3KXWug=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=Uj1ZditJrX9LhmMYrASNrvWo1UmmqRPY3rxuNqqseukICfeaGxLeNe3CjBErEyWhACDGhMJFXpTZfvP6zPy1n97BUCNPrfORkTAbMR1TjAt6kP0hB+qs39rY1jiw0xsjypOck7zQrlLoVXrbUmzmQvYBvJJGaYDzr0AgqixcQj8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=fiberby.net; spf=pass smtp.mailfrom=fiberby.net; dkim=pass (2048-bit key) header.d=fiberby.net header.i=@fiberby.net header.b=sP2joL0F; arc=none smtp.client-ip=193.104.135.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=fiberby.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=fiberby.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=fiberby.net header.i=@fiberby.net header.b="sP2joL0F" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=fiberby.net; s=202008; t=1723104058; bh=RWh44ibT1OVXVkS6LOhCJHv00CcuvNPdegD/w3KXWug=; h=From:To:Cc:Subject:Date:From; b=sP2joL0Fq8GhKMyYaxcHb9q2P9pmOFGuvSnf1Xsi41RdprY8zS8U3u927CeScJZDL optsYomQ9stB2MGKdzl0vAbIL/OlMyiBDt13gS9WiOUXRaVMM7e12kUREMP2YxPRqr ae8/FWD2wvv2pJ74NDWiRH5TS4z07wH6dh4ZN5RphIOkM+NhCYeU0lDjld++JOsFzN BTqHdDfiPeYmSAappR+ne5E8TbSWTq1XjWmQGr5PZ41QjlF1BrEjlvcLqf53HP9ONc aI4RmQ9CdxaM7NdvTVhIY+yw9VhMOnsDhC+o9jGGV2T+QyCnOwF153dHhhQOmVXj56 IWgjQjLVilGMQ== Received: from x201s (193-104-135-243.ip4.fiberby.net [193.104.135.243]) by mail1.fiberby.net (Postfix) with ESMTPSA id 1639C60078; Thu, 8 Aug 2024 07:59:18 +0000 (UTC) Received: by x201s (Postfix, from userid 1000) id BECD0202330; Thu, 08 Aug 2024 07:59:09 +0000 (UTC) From: =?utf-8?q?Asbj=C3=B8rn_Sloth_T=C3=B8nnesen?= To: bpf@vger.kernel.org Cc: =?utf-8?q?Asbj=C3=B8rn_Sloth_T=C3=B8nnesen?= , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Mykola Lysenko , Shuah Khan , Tushar Vyavahare , Magnus Karlsson , Willem de Bruijn , netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH bpf-next] selftests/bpf: Avoid subtraction after htons() in ipip tests Date: Thu, 8 Aug 2024 07:59:02 +0000 Message-ID: <20240808075906.1849564-1-ast@fiberby.net> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On little-endian systems, doing subtraction after htons() leads to interesting results: Given: MAGIC_BYTES = 123 = 0x007B aka. in big endian: 0x7B00 = 31488 sizeof(struct iphdr) = 20 Before this patch: __bpf_constant_htons(MAGIC_BYTES) - sizeof(struct iphdr) = 0x7AEC 0x7AEC = htons(0xEC7A) = htons(60538) So these were outer IP packets with a total length of 123 bytes, containing an inner IP packet with a total length of 60538 bytes. After this patch: __bpf_constant_htons(MAGIC_BYTES - sizeof(struct iphdr)) = htons(103) Now these packets are outer IP packets with a total length of 123 bytes, containing an inner IP packet with a total length of 103 bytes. Signed-off-by: Asbjørn Sloth Tønnesen --- I didn't target bpf and add a Fixes: e853ae776a58 ("selftests/bpf: support BPF_FLOW_DISSECTOR_F_STOP_AT_ENCAP"), since it only breaks when I change the BPF flow dissector to interact with tot_len. .../selftests/bpf/prog_tests/flow_dissector.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/flow_dissector.c b/tools/testing/selftests/bpf/prog_tests/flow_dissector.c index 9e5f38739104..6b3078dd5645 100644 --- a/tools/testing/selftests/bpf/prog_tests/flow_dissector.c +++ b/tools/testing/selftests/bpf/prog_tests/flow_dissector.c @@ -378,8 +378,8 @@ struct test tests[] = { .iph_inner.ihl = 5, .iph_inner.protocol = IPPROTO_TCP, .iph_inner.tot_len = - __bpf_constant_htons(MAGIC_BYTES) - - sizeof(struct iphdr), + __bpf_constant_htons(MAGIC_BYTES - + sizeof(struct iphdr)), .tcp.doff = 5, .tcp.source = 80, .tcp.dest = 8080, @@ -407,8 +407,8 @@ struct test tests[] = { .iph_inner.ihl = 5, .iph_inner.protocol = IPPROTO_TCP, .iph_inner.tot_len = - __bpf_constant_htons(MAGIC_BYTES) - - sizeof(struct iphdr), + __bpf_constant_htons(MAGIC_BYTES - + sizeof(struct iphdr)), .tcp.doff = 5, .tcp.source = 80, .tcp.dest = 8080, @@ -436,8 +436,8 @@ struct test tests[] = { .iph_inner.ihl = 5, .iph_inner.protocol = IPPROTO_TCP, .iph_inner.tot_len = - __bpf_constant_htons(MAGIC_BYTES) - - sizeof(struct iphdr), + __bpf_constant_htons(MAGIC_BYTES - + sizeof(struct iphdr)), .tcp.doff = 5, .tcp.source = 99, .tcp.dest = 9090,