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

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

include/net/tcp.h

@@ -399,6 +399,8 @@ extern void			tcp_parse_options(struct sk_buff *skb,
 						  struct tcp_options_received *opt_rx,
 						  int estab);
 
+extern u8			*tcp_parse_md5sig_option(struct tcphdr *th);
+
 /*
  *	TCP v4 functions exported for the inet6 API
  */

net/ipv4/tcp_input.c

@@ -3450,6 +3450,43 @@ static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
 	return 1;
 }
 
+#ifdef CONFIG_TCP_MD5SIG
+/*
+ * Parse MD5 Signature option
+ */
+u8 *tcp_parse_md5sig_option(struct tcphdr *th)
+{
+	int length = (th->doff << 2) - sizeof (*th);
+	u8 *ptr = (u8*)(th + 1);
+
+	/* If the TCP option is too short, we can short cut */
+	if (length < TCPOLEN_MD5SIG)
+		return NULL;
+
+	while (length > 0) {
+		int opcode = *ptr++;
+		int opsize;
+
+		switch(opcode) {
+		case TCPOPT_EOL:
+			return NULL;
+		case TCPOPT_NOP:
+			length--;
+			continue;
+		default:
+			opsize = *ptr++;
+			if (opsize < 2 || opsize > length)
+				return NULL;
+			if (opcode == TCPOPT_MD5SIG)
+				return ptr;
+		}
+		ptr += opsize - 2;
+		length -= opsize;
+	}
+	return NULL;
+}
+#endif
+
 static inline void tcp_store_ts_recent(struct tcp_sock *tp)
 {
 	tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
@@ -5467,6 +5504,9 @@ EXPORT_SYMBOL(sysctl_tcp_ecn);
 EXPORT_SYMBOL(sysctl_tcp_reordering);
 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale);
 EXPORT_SYMBOL(tcp_parse_options);
+#ifdef CONFIG_TCP_MD5SIG
+EXPORT_SYMBOL(tcp_parse_md5sig_option);
+#endif
 EXPORT_SYMBOL(tcp_rcv_established);
 EXPORT_SYMBOL(tcp_rcv_state_process);
 EXPORT_SYMBOL(tcp_initialize_rcv_mss);

net/ipv4/tcp_ipv4.c

@@ -1134,52 +1134,12 @@ static int tcp_v4_inbound_md5_hash(struct sock *sk, struct sk_buff *skb)
 	struct tcp_md5sig_key *hash_expected;
 	const struct iphdr *iph = ip_hdr(skb);
 	struct tcphdr *th = tcp_hdr(skb);
-	int length = (th->doff << 2) - sizeof(struct tcphdr);
 	int genhash;
-	unsigned char *ptr;
 	unsigned char newhash[16];
 
 	hash_expected = tcp_v4_md5_do_lookup(sk, iph->saddr);
+	hash_location = tcp_parse_md5sig_option(th);
 
-	/*
-	 * If the TCP option length is less than the TCP_MD5SIG
-	 * option length, then we can shortcut
-	 */
-	if (length < TCPOLEN_MD5SIG) {
-		if (hash_expected)
-			return 1;
-		else
-			return 0;
-	}
-
-	/* Okay, we can't shortcut - we have to grub through the options */
-	ptr = (unsigned char *)(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)
-				goto done_opts;
-			if (opsize > length)
-				goto done_opts;
-
-			if (opcode == TCPOPT_MD5SIG) {
-				hash_location = ptr;
-				goto done_opts;
-			}
-		}
-		ptr += opsize-2;
-		length -= opsize;
-	}
-done_opts:
 	/* We've parsed the options - do we have a hash? */
 	if (!hash_expected && !hash_location)
 		return 0;

net/ipv6/tcp_ipv6.c

@@ -844,43 +844,12 @@ static int tcp_v6_inbound_md5_hash (struct sock *sk, struct sk_buff *skb)
 	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)