linux-kernel - [PATCH bpf-next v3 10/14] selftests/bpf: document pseudo-header checksum helpers

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Message-Id: <20241120-flow_dissector-v3-10-45b46494f937@bootlin.com>
Date: Wed, 20 Nov 2024 08:43:20 +0100
From: Alexis Lothoré (eBPF Foundation) <alexis.lothore@...tlin.com>
To: Andrii Nakryiko <andrii@...nel.org>, 
 Eduard Zingerman <eddyz87@...il.com>, Mykola Lysenko <mykolal@...com>, 
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, 
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
 Jiri Olsa <jolsa@...nel.org>, Shuah Khan <shuah@...nel.org>, 
 "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
 Jesper Dangaard Brouer <hawk@...nel.org>
Cc: ebpf@...uxfoundation.org, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 Bastien Curutchet <bastien.curutchet@...tlin.com>, bpf@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org, 
 netdev@...r.kernel.org, 
 Alexis Lothoré (eBPF Foundation) <alexis.lothore@...tlin.com>
Subject: [PATCH bpf-next v3 10/14] selftests/bpf: document pseudo-header
 checksum helpers

network_helpers.h provides helpers to compute checksum for pseudo
headers but no helpers to compute the global checksums.

Before adding those, clarify csum_tcpudp_magic and csum_ipv6_magic
purpose by adding some documentation.

Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@...tlin.com>
---
Changes in v3:
- instead of renaming the helpers, keep the original name (which is in
  sync with kernel helpers), and rather add documentation

Changes in v2:
- new patch
---
 tools/testing/selftests/bpf/network_helpers.h | 30 +++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/tools/testing/selftests/bpf/network_helpers.h b/tools/testing/selftests/bpf/network_helpers.h
index 5ef909f766eb9ac2dd5be67b99245b4676ce4f5f..6ca636643ea2b77fb5cc459b03bf7f8c4f749377 100644
--- a/tools/testing/selftests/bpf/network_helpers.h
+++ b/tools/testing/selftests/bpf/network_helpers.h
@@ -128,6 +128,21 @@ static inline __sum16 build_ip_csum(struct iphdr *iph)
 	return csum_fold(sum);
 }

+/**
+ * csum_tcpudp_magic - compute IP pseudo-header checksum
+ *
+ * Compute the IPv4 pseudo header checksum. The helper can take a
+ * accumulated sum from the transport layer to accumulate it and directly
+ * return the transport layer
+ *
+ * @saddr: IP source address
+ * @daddr: IP dest address
+ * @len: IP data size
+ * @proto: transport layer protocol
+ * @csum: The accumulated partial sum to add to the computation
+ *
+ * Returns the folded sum
+ */
 static inline __sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
 					__u32 len, __u8 proto,
 					__wsum csum)
@@ -143,6 +158,21 @@ static inline __sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
 	return csum_fold((__u32)s);
 }

+/**
+ * csum_ipv6_magic - compute IPv6 pseudo-header checksum
+ *
+ * Compute the ipv6 pseudo header checksum. The helper can take a
+ * accumulated sum from the transport layer to accumulate it and directly
+ * return the transport layer
+ *
+ * @saddr: IPv6 source address
+ * @daddr: IPv6 dest address
+ * @len: IPv6 data size
+ * @proto: transport layer protocol
+ * @csum: The accumulated partial sum to add to the computation
+ *
+ * Returns the folded sum
+ */
 static inline __sum16 csum_ipv6_magic(const struct in6_addr *saddr,
 				      const struct in6_addr *daddr,
 					__u32 len, __u8 proto,

-- 
2.47.0