[INET]: Generalise tcp_v4_lookup_listener

[acme@toy net-2.6.14]$ grep built-in /tmp/before /tmp/after
/tmp/before: 282560       13122    9312  304994   4a762 net/ipv4/built-in.o
/tmp/after:  282560       13122    9312  304994   4a762 net/ipv4/built-in.o

Will be used in DCCP, not exporting it right now not to get in Adrian
Bunk's exported-but-not-used-on-modules radar 8)

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 41 insertions, 0 deletions

diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 06cbc6f..88fcba05b 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -121,3 +121,44 @@ void inet_listen_wlock(struct inet_hashinfo *hashinfo)
 }
 
 EXPORT_SYMBOL(inet_listen_wlock);
+
+/*
+ * Don't inline this cruft. Here are some nice properties to exploit here. The
+ * BSD API does not allow a listening sock to specify the remote port nor the
+ * remote address for the connection. So always assume those are both
+ * wildcarded during the search since they can never be otherwise.
+ */
+struct sock *__inet_lookup_listener(const struct hlist_head *head, const u32 daddr,
+				    const unsigned short hnum, const int dif)
+{
+	struct sock *result = NULL, *sk;
+	const struct hlist_node *node;
+	int hiscore = -1;
+
+	sk_for_each(sk, node, head) {
+		const struct inet_sock *inet = inet_sk(sk);
+
+		if (inet->num == hnum && !ipv6_only_sock(sk)) {
+			const __u32 rcv_saddr = inet->rcv_saddr;
+			int score = sk->sk_family == PF_INET ? 1 : 0;
+
+			if (rcv_saddr) {
+				if (rcv_saddr != daddr)
+					continue;
+				score += 2;
+			}
+			if (sk->sk_bound_dev_if) {
+				if (sk->sk_bound_dev_if != dif)
+					continue;
+				score += 2;
+			}
+			if (score == 5)
+				return sk;
+			if (score > hiscore) {
+				hiscore	= score;
+				result	= sk;
+			}
+		}
+	}
+	return result;
+}