[NETFILTER]: make ipv6_find_hdr() find transport protocol header

The original ipv6_find_hdr() finds the specified header in IPv6 packets.
This makes it possible to get transport header so that we can kill similar
loop in ip6_match_packet().
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netfilter_ipv6/ip6_tables.h

@@ -474,7 +474,7 @@ extern unsigned int ip6t_do_table(struct sk_buff **pskb,
 extern int ip6t_ext_hdr(u8 nexthdr);
 /* find specified header and get offset to it */
 extern int ipv6_find_hdr(const struct sk_buff *skb, unsigned int *offset,
-			 u8 target);
+			 int target, unsigned short *fragoff);
 
 #define IP6T_ALIGN(s) (((s) + (__alignof__(struct ip6t_entry)-1)) & ~(__alignof__(struct ip6t_entry)-1))
 

net/ipv6/netfilter/ip6_tables.c

@@ -205,69 +205,21 @@ ip6_packet_match(const struct sk_buff *skb,
 
 	/* look for the desired protocol header */
 	if((ip6info->flags & IP6T_F_PROTO)) {
-		u_int8_t currenthdr = ipv6->nexthdr;
-		struct ipv6_opt_hdr _hdr, *hp;
-		u_int16_t ptr;		/* Header offset in skb */
-		u_int16_t hdrlen;	/* Header */
-		u_int16_t _fragoff = 0, *fp = NULL;
-
-		ptr = IPV6_HDR_LEN;
-
-		while (ip6t_ext_hdr(currenthdr)) {
-	                /* Is there enough space for the next ext header? */
-	                if (skb->len - ptr < IPV6_OPTHDR_LEN)
-	                        return 0;
-
-			/* NONE or ESP: there isn't protocol part */
-			/* If we want to count these packets in '-p all',
-			 * we will change the return 0 to 1*/
-			if ((currenthdr == IPPROTO_NONE) || 
-				(currenthdr == IPPROTO_ESP))
-				break;
-
-			hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
-			BUG_ON(hp == NULL);
-
-			/* Size calculation */
-	                if (currenthdr == IPPROTO_FRAGMENT) {
-				fp = skb_header_pointer(skb,
-						   ptr+offsetof(struct frag_hdr,
-								frag_off),
-						   sizeof(_fragoff),
-						   &_fragoff);
-				if (fp == NULL)
-					return 0;
-
-				_fragoff = ntohs(*fp) & ~0x7;
-	                        hdrlen = 8;
-	                } else if (currenthdr == IPPROTO_AH)
-	                        hdrlen = (hp->hdrlen+2)<<2;
-	                else
-	                        hdrlen = ipv6_optlen(hp);
+		int protohdr;
+		unsigned short _frag_off;
 
-			currenthdr = hp->nexthdr;
-	                ptr += hdrlen;
-			/* ptr is too large */
-	                if ( ptr > skb->len ) 
-				return 0;
-			if (_fragoff) {
-				if (ip6t_ext_hdr(currenthdr))
+		protohdr = ipv6_find_hdr(skb, protoff, -1, &_frag_off);
+		if (protohdr < 0)
 			return 0;
-				break;
-			}
-		}
-
-		*protoff = ptr;
-		*fragoff = _fragoff;
 
-		/* currenthdr contains the protocol header */
+		*fragoff = _frag_off;
 
 		dprintf("Packet protocol %hi ?= %s%hi.\n",
-				currenthdr, 
+				protohdr, 
 				ip6info->invflags & IP6T_INV_PROTO ? "!":"",
 				ip6info->proto);
 
-		if (ip6info->proto == currenthdr) {
+		if (ip6info->proto == protohdr) {
 			if(ip6info->invflags & IP6T_INV_PROTO) {
 				return 0;
 			}
@@ -2098,26 +2050,39 @@ static void __exit fini(void)
 }
 
 /*
- * find specified header up to transport protocol header.
- * If found target header, the offset to the header is set to *offset
- * and return 0. otherwise, return -1.
+ * find the offset to specified header or the protocol number of last header
+ * if target < 0. "last header" is transport protocol header, ESP, or
+ * "No next header".
+ *
+ * If target header is found, its offset is set in *offset and return protocol
+ * number. Otherwise, return -1.
+ *
+ * Note that non-1st fragment is special case that "the protocol number
+ * of last header" is "next header" field in Fragment header. In this case,
+ * *offset is meaningless and fragment offset is stored in *fragoff if fragoff
+ * isn't NULL.
  *
- * Notes: - non-1st Fragment Header isn't skipped.
- *	  - ESP header isn't skipped.
- *	  - The target header may be trancated.
  */
-int ipv6_find_hdr(const struct sk_buff *skb, unsigned int *offset, u8 target)
+int ipv6_find_hdr(const struct sk_buff *skb, unsigned int *offset,
+		  int target, unsigned short *fragoff)
 {
 	unsigned int start = (u8*)(skb->nh.ipv6h + 1) - skb->data;
 	u8 nexthdr = skb->nh.ipv6h->nexthdr;
 	unsigned int len = skb->len - start;
 
+	if (fragoff)
+		*fragoff = 0;
+
 	while (nexthdr != target) {
 		struct ipv6_opt_hdr _hdr, *hp;
 		unsigned int hdrlen;
 
-		if ((!ipv6_ext_hdr(nexthdr)) || nexthdr == NEXTHDR_NONE)
+		if ((!ipv6_ext_hdr(nexthdr)) || nexthdr == NEXTHDR_NONE) {
+			if (target < 0)
+				break;
 			return -1;
+		}
+
 		hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr);
 		if (hp == NULL)
 			return -1;
@@ -2131,8 +2096,17 @@ int ipv6_find_hdr(const struct sk_buff *skb, unsigned int *offset, u8 target)
 			if (fp == NULL)
 				return -1;
 
-			if (ntohs(*fp) & ~0x7)
+			_frag_off = ntohs(*fp) & ~0x7;
+			if (_frag_off) {
+				if (target < 0 &&
+				    ((!ipv6_ext_hdr(hp->nexthdr)) ||
+				     nexthdr == NEXTHDR_NONE)) {
+					if (fragoff)
+						*fragoff = _frag_off;
+					return hp->nexthdr;
+				}
 				return -1;
+			}
 			hdrlen = 8;
 		} else if (nexthdr == NEXTHDR_AUTH)
 			hdrlen = (hp->hdrlen + 2) << 2; 
@@ -2145,7 +2119,7 @@ int ipv6_find_hdr(const struct sk_buff *skb, unsigned int *offset, u8 target)
 	}
 
 	*offset = start;
-	return 0;
+	return nexthdr;
 }
 
 EXPORT_SYMBOL(ip6t_register_table);

net/ipv6/netfilter/ip6t_ah.c

@@ -54,7 +54,7 @@ match(const struct sk_buff *skb,
 	unsigned int ptr;
 	unsigned int hdrlen = 0;
 
-	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_AUTH) < 0)
+	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_AUTH, NULL) < 0)
 		return 0;
 
 	ah = skb_header_pointer(skb, ptr, sizeof(_ah), &_ah);

net/ipv6/netfilter/ip6t_dst.c

@@ -71,9 +71,9 @@ match(const struct sk_buff *skb,
        unsigned int optlen;
        
 #if HOPBYHOP
-	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_HOP) < 0)
+	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_HOP, NULL) < 0)
 #else
-	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_DEST) < 0)
+	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_DEST, NULL) < 0)
 #endif
 		return 0;
 

net/ipv6/netfilter/ip6t_esp.c

@@ -56,7 +56,7 @@ match(const struct sk_buff *skb,
 	/* Make sure this isn't an evil packet */
 	/*DEBUGP("ipv6_esp entered \n");*/
 
-	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_ESP) < 0)
+	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_ESP, NULL) < 0)
 		return 0;
 
 	eh = skb_header_pointer(skb, ptr, sizeof(_esp), &_esp);

net/ipv6/netfilter/ip6t_frag.c

@@ -52,7 +52,7 @@ match(const struct sk_buff *skb,
        const struct ip6t_frag *fraginfo = matchinfo;
        unsigned int ptr;
 
-	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_FRAGMENT) < 0)
+	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_FRAGMENT, NULL) < 0)
 		return 0;
 
 	fh = skb_header_pointer(skb, ptr, sizeof(_frag), &_frag);

net/ipv6/netfilter/ip6t_hbh.c

@@ -71,9 +71,9 @@ match(const struct sk_buff *skb,
        unsigned int optlen;
        
 #if HOPBYHOP
-	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_HOP) < 0)
+	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_HOP, NULL) < 0)
 #else
-	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_DEST) < 0)
+	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_DEST, NULL) < 0)
 #endif
 		return 0;
 

net/ipv6/netfilter/ip6t_rt.c

@@ -58,7 +58,7 @@ match(const struct sk_buff *skb,
        unsigned int ret = 0;
        struct in6_addr *ap, _addr;
 
-	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_ROUTING) < 0)
+	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_ROUTING, NULL) < 0)
 		return 0;
 
        rh = skb_header_pointer(skb, ptr, sizeof(_route), &_route);