[PATCH bpf-next v4 4/7] net: document inet[6]_lookup_reuseport sk_state requirements

[Lorenz Bauer <lmb@isovalent.com>]

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@isovalent.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 352eb371c93b..ac927a635a6f 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -335,6 +335,20 @@ 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.
+ *
+ * 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..d37602fabc00 100644
--- a/net/ipv6/inet6_hashtables.c
+++ b/net/ipv6/inet6_hashtables.c
@@ -114,6 +114,20 @@ 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.
+ *
+ * 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