1 files changed, 41 insertions, 0 deletions

diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 06cbc6f689c5..88fcba05b7d6 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;
+}