linux-kernel - [PATCH bpf-next v5 4/7] net: document inet[6]_lookup_reuseport sk

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Message-Id: <20230613-so-reuseport-v5-4-f6686a0dbce0@isovalent.com>
Date:   Tue, 04 Jul 2023 14:46:26 +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 v5 4/7] 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.

Reviewed-by: Kuniyuki Iwashima <kuniyu@...zon.com>
Signed-off-by: Lorenz Bauer <lmb@...valent.com>
---
 net/ipv4/inet_hashtables.c  | 15 +++++++++++++++
 net/ipv6/inet6_hashtables.c | 15 +++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 352eb371c93b..64fc1bd3fb63 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -335,6 +335,21 @@ static inline int compute_score(struct sock *sk, struct net *net,
 
 INDIRECT_CALLABLE_DECLARE(inet_ehashfn_t udp_ehashfn);
 
+/**
+ * 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.
+ * @ehashfn: hash function used to generate the fallback hash.
+ *
+ * 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 3616225c89ef..f76dbbb29332 100644
--- a/net/ipv6/inet6_hashtables.c
+++ b/net/ipv6/inet6_hashtables.c
@@ -114,6 +114,21 @@ static inline int compute_score(struct sock *sk, struct net *net,
 
 INDIRECT_CALLABLE_DECLARE(inet6_ehashfn_t udp6_ehashfn);
 
+/**
+ * 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.
+ * @ehashfn: hash function used to generate the fallback hash.
+ *
+ * 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