tcp: cleanup tcp_v[46]_inbound_md5_hash()

We'll soon have to call tcp_v[46]_inbound_md5_hash() twice.
Also add const attribute to the socket, as it might be the
unlocked listener for SYN packets.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_ipv4.c

@@ -1112,10 +1112,13 @@ int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
 }
 EXPORT_SYMBOL(tcp_v4_md5_hash_skb);
 
+#endif
+
 /* Called with rcu_read_lock() */
-static bool tcp_v4_inbound_md5_hash(struct sock *sk,
+static bool tcp_v4_inbound_md5_hash(const struct sock *sk,
 				    const struct sk_buff *skb)
 {
+#ifdef CONFIG_TCP_MD5SIG
 	/*
 	 * This gets called for each TCP segment that arrives
 	 * so we want to be efficient.
@@ -1165,8 +1168,9 @@ static bool tcp_v4_inbound_md5_hash(struct sock *sk,
 		return true;
 	}
 	return false;
-}
 #endif
+	return false;
+}
 
 static void tcp_v4_init_req(struct request_sock *req,
 			    const struct sock *sk_listener,
@@ -1607,16 +1611,8 @@ int tcp_v4_rcv(struct sk_buff *skb)
 	if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
 		goto discard_and_relse;
 
-#ifdef CONFIG_TCP_MD5SIG
-	/*
-	 * We really want to reject the packet as early as possible
-	 * if:
-	 *  o We're expecting an MD5'd packet and this is no MD5 tcp option
-	 *  o There is an MD5 option and we're not expecting one
-	 */
 	if (tcp_v4_inbound_md5_hash(sk, skb))
 		goto discard_and_relse;
-#endif
 
 	nf_reset(skb);
 

net/ipv6/tcp_ipv6.c

@@ -622,8 +622,12 @@ static int tcp_v6_md5_hash_skb(char *md5_hash,
 	return 1;
 }
 
-static bool tcp_v6_inbound_md5_hash(struct sock *sk, const struct sk_buff *skb)
+#endif
+
+static bool tcp_v6_inbound_md5_hash(const struct sock *sk,
+				    const struct sk_buff *skb)
 {
+#ifdef CONFIG_TCP_MD5SIG
 	const __u8 *hash_location = NULL;
 	struct tcp_md5sig_key *hash_expected;
 	const struct ipv6hdr *ip6h = ipv6_hdr(skb);
@@ -660,9 +664,9 @@ static bool tcp_v6_inbound_md5_hash(struct sock *sk, const struct sk_buff *skb)
 				     &ip6h->daddr, ntohs(th->dest));
 		return true;
 	}
+#endif
 	return false;
 }
-#endif
 
 static void tcp_v6_init_req(struct request_sock *req,
 			    const struct sock *sk_listener,
@@ -1408,10 +1412,8 @@ static int tcp_v6_rcv(struct sk_buff *skb)
 
 	tcp_v6_fill_cb(skb, hdr, th);
 
-#ifdef CONFIG_TCP_MD5SIG
 	if (tcp_v6_inbound_md5_hash(sk, skb))
 		goto discard_and_relse;
-#endif
 
 	if (sk_filter(sk, skb))
 		goto discard_and_relse;