netdev - [PATCH bpf-next v2 2/6] net: document inet[6]_lookup_reuseport sk

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Message-Id: <20230613-so-reuseport-v2-2-b7c69a342613@isovalent.com>
Date: Tue, 13 Jun 2023 11:14:57 +0100
From: Lorenz Bauer <lmb@...valent.com>
To: "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, David Ahern <dsahern@...nel.org>, 
 Willem de Bruijn <willemdebruijn.kernel@...il.com>, 
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
 Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>, 
 Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>, 
 KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>, 
 Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
 Joe Stringer <joe@...d.net.nz>, Mykola Lysenko <mykolal@...com>, 
 Shuah Khan <shuah@...nel.org>, Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: Hemanth Malla <hemanthmalla@...il.com>, netdev@...r.kernel.org, 
 linux-kernel@...r.kernel.org, bpf@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, Lorenz Bauer <lmb@...valent.com>
Subject: [PATCH bpf-next v2 2/6] net: document inet[6]_lookup_reuseport
 sk_state requirements

The current implementation was extracted from inet[6]_lhash2_lookup
in commit 80b373f74f9e ("inet: Extract helper for selecting socket
from reuseport group") and commit 5df6531292b5 ("inet6: Extract helper
for selecting socket from reuseport group"). In the original context,
sk is always in TCP_LISTEN state and so did not have a separate check.

Add documentation that specifies which sk_state are valid to pass to
the function.

Signed-off-by: Lorenz Bauer <lmb@...valent.com>
---
 net/ipv4/inet_hashtables.c  | 14 ++++++++++++++
 net/ipv6/inet6_hashtables.c | 14 ++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 920131e4a65d..91f9210d4e83 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -332,6 +332,20 @@ static inline int compute_score(struct sock *sk, struct net *net,
 	return score;
 }

+/**
+ * inet_lookup_reuseport() - execute reuseport logic on AF_INET socket if necessary.
+ * @net: network namespace.
+ * @sk: AF_INET socket, must be in TCP_LISTEN state for TCP or TCP_CLOSE for UDP.
+ * @skb: context for a potential SK_REUSEPORT program.
+ * @doff: header offset.
+ * @saddr: source address.
+ * @sport: source port.
+ * @daddr: destination address.
+ * @hnum: destination port in host byte order.
+ *
+ * Return: NULL if sk doesn't have SO_REUSEPORT set, otherwise a pointer to
+ *         the selected sock or an error.
+ */
 struct sock *inet_lookup_reuseport(struct net *net, struct sock *sk,
 				   struct sk_buff *skb, int doff,
 				   __be32 saddr, __be16 sport,
diff --git a/net/ipv6/inet6_hashtables.c b/net/ipv6/inet6_hashtables.c
index b7c56867314e..208998694ae3 100644
--- a/net/ipv6/inet6_hashtables.c
+++ b/net/ipv6/inet6_hashtables.c
@@ -111,6 +111,20 @@ static inline int compute_score(struct sock *sk, struct net *net,
 	return score;
 }

+/**
+ * inet6_lookup_reuseport() - execute reuseport logic on AF_INET6 socket if necessary.
+ * @net: network namespace.
+ * @sk: AF_INET6 socket, must be in TCP_LISTEN state for TCP or TCP_CLOSE for UDP.
+ * @skb: context for a potential SK_REUSEPORT program.
+ * @doff: header offset.
+ * @saddr: source address.
+ * @sport: source port.
+ * @daddr: destination address.
+ * @hnum: destination port in host byte order.
+ *
+ * Return: NULL if sk doesn't have SO_REUSEPORT set, otherwise a pointer to
+ *         the selected sock or an error.
+ */
 struct sock *inet6_lookup_reuseport(struct net *net, struct sock *sk,
 				    struct sk_buff *skb, int doff,
 				    const struct in6_addr *saddr,

-- 
2.40.1