From: Asbjørn Sloth Tønnesen Date: Thu, 8 Aug 2024 07:59:02 +0000 (+0000) Subject: selftests/bpf: Avoid subtraction after htons() in ipip tests X-Git-Tag: v6.12-rc1~232^2~191^2~2 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=92ec8b9367ab328cdd3d4409464137bc9775a2e5;p=thirdparty%2Fkernel%2Flinux.git selftests/bpf: Avoid subtraction after htons() in ipip tests 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 Reviewed-by: Toke Høiland-Jørgensen Link: https://lore.kernel.org/r/20240808075906.1849564-1-ast@fiberby.net Signed-off-by: Martin KaFai Lau --- diff --git a/tools/testing/selftests/bpf/prog_tests/flow_dissector.c b/tools/testing/selftests/bpf/prog_tests/flow_dissector.c index 9e5f38739104b..6b3078dd56455 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,