tcp md5sig: Share MD5 Signature option parser between IPv4 and IPv6.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 715965f..dd4ddb3 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -844,43 +844,12 @@
 	struct tcp_md5sig_key *hash_expected;
 	struct ipv6hdr *ip6h = ipv6_hdr(skb);
 	struct tcphdr *th = tcp_hdr(skb);
-	int length = (th->doff << 2) - sizeof (*th);
 	int genhash;
-	u8 *ptr;
 	u8 newhash[16];
 
 	hash_expected = tcp_v6_md5_do_lookup(sk, &ip6h->saddr);
+	hash_location = tcp_parse_md5sig_option(th);
 
-	/* If the TCP option is too short, we can short cut */
-	if (length < TCPOLEN_MD5SIG)
-		return hash_expected ? 1 : 0;
-
-	/* parse options */
-	ptr = (u8*)(th + 1);
-	while (length > 0) {
-		int opcode = *ptr++;
-		int opsize;
-
-		switch(opcode) {
-		case TCPOPT_EOL:
-			goto done_opts;
-		case TCPOPT_NOP:
-			length--;
-			continue;
-		default:
-			opsize = *ptr++;
-			if (opsize < 2 || opsize > length)
-				goto done_opts;
-			if (opcode == TCPOPT_MD5SIG) {
-				hash_location = ptr;
-				goto done_opts;
-			}
-		}
-		ptr += opsize - 2;
-		length -= opsize;
-	}
-
-done_opts:
 	/* do we have a hash as expected? */
 	if (!hash_expected) {
 		if (!hash_location)