udp6: Extract helper for selecting socket from reuseport group

Prepare for calling into reuseport from __udp6_lib_lookup as well.
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200717103536.397595-10-jakub@cloudflare.com

net/ipv6/udp.c

@@ -141,6 +141,27 @@ static int compute_score(struct sock *sk, struct net *net,
 	return score;
 }
 
+static inline struct sock *lookup_reuseport(struct net *net, struct sock *sk,
+					    struct sk_buff *skb,
+					    const struct in6_addr *saddr,
+					    __be16 sport,
+					    const struct in6_addr *daddr,
+					    unsigned int hnum)
+{
+	struct sock *reuse_sk = NULL;
+	u32 hash;
+
+	if (sk->sk_reuseport && sk->sk_state != TCP_ESTABLISHED) {
+		hash = udp6_ehashfn(net, daddr, hnum, saddr, sport);
+		reuse_sk = reuseport_select_sock(sk, hash, skb,
+						 sizeof(struct udphdr));
+		/* Fall back to scoring if group has connections */
+		if (reuseport_has_conns(sk, false))
+			return NULL;
+	}
+	return reuse_sk;
+}
+
 /* called with rcu_read_lock() */
 static struct sock *udp6_lib_lookup2(struct net *net,
 		const struct in6_addr *saddr, __be16 sport,
@@ -150,7 +171,6 @@ static struct sock *udp6_lib_lookup2(struct net *net,
 {
 	struct sock *sk, *result;
 	int score, badness;
-	u32 hash = 0;
 
 	result = NULL;
 	badness = -1;
@@ -158,16 +178,11 @@ static struct sock *udp6_lib_lookup2(struct net *net,
 		score = compute_score(sk, net, saddr, sport,
 				      daddr, hnum, dif, sdif);
 		if (score > badness) {
-			if (sk->sk_reuseport &&
-			    sk->sk_state != TCP_ESTABLISHED) {
-				hash = udp6_ehashfn(net, daddr, hnum,
-						    saddr, sport);
-
-				result = reuseport_select_sock(sk, hash, skb,
-							sizeof(struct udphdr));
-				if (result && !reuseport_has_conns(sk, false))
-					return result;
-			}
+			result = lookup_reuseport(net, sk, skb,
+						  saddr, sport, daddr, hnum);
+			if (result)
+				return result;
+
 			result = sk;
 			badness = score;
 		}