ipv6: Add fragment reporting to ipv6_skip_exthdr().

While parsing through IPv6 extension headers, fragment headers are
skipped making them invisible to the caller.  This reports the
fragment offset of the last header in order to make it possible to
determine whether the packet is fragmented and, if so whether it is
a first or last fragment.
Signed-off-by: Jesse Gross <jesse@nicira.com>

include/net/ipv6.h

@@ -558,7 +558,7 @@ extern void			ipv6_push_frag_opts(struct sk_buff *skb,
 						    u8 *proto);
 
 extern int			ipv6_skip_exthdr(const struct sk_buff *, int start,
-					         u8 *nexthdrp);
+					         u8 *nexthdrp, __be16 *frag_offp);
 
 extern int 			ipv6_ext_hdr(u8 nexthdr);
 

net/bridge/br_multicast.c

@@ -1458,6 +1458,7 @@ static int br_multicast_ipv6_rcv(struct net_bridge *br,
 	const struct ipv6hdr *ip6h;
 	u8 icmp6_type;
 	u8 nexthdr;
+	__be16 frag_off;
 	unsigned len;
 	int offset;
 	int err;
@@ -1483,7 +1484,7 @@ static int br_multicast_ipv6_rcv(struct net_bridge *br,
 		return -EINVAL;
 
 	nexthdr = ip6h->nexthdr;
-	offset = ipv6_skip_exthdr(skb, sizeof(*ip6h), &nexthdr);
+	offset = ipv6_skip_exthdr(skb, sizeof(*ip6h), &nexthdr, &frag_off);
 
 	if (offset < 0 || nexthdr != IPPROTO_ICMPV6)
 		return 0;

net/bridge/netfilter/ebt_ip6.c

@@ -55,9 +55,10 @@ ebt_ip6_mt(const struct sk_buff *skb, struct xt_action_param *par)
 		return false;
 	if (info->bitmask & EBT_IP6_PROTO) {
 		uint8_t nexthdr = ih6->nexthdr;
+		__be16 frag_off;
 		int offset_ph;
 
-		offset_ph = ipv6_skip_exthdr(skb, sizeof(_ip6h), &nexthdr);
+		offset_ph = ipv6_skip_exthdr(skb, sizeof(_ip6h), &nexthdr, &frag_off);
 		if (offset_ph == -1)
 			return false;
 		if (FWINV(info->protocol != nexthdr, EBT_IP6_PROTO))

net/bridge/netfilter/ebt_log.c

@@ -113,6 +113,7 @@ ebt_log_packet(u_int8_t pf, unsigned int hooknum,
 		const struct ipv6hdr *ih;
 		struct ipv6hdr _iph;
 		uint8_t nexthdr;
+		__be16 frag_off;
 		int offset_ph;
 
 		ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
@@ -123,7 +124,7 @@ ebt_log_packet(u_int8_t pf, unsigned int hooknum,
 		printk(" IPv6 SRC=%pI6 IPv6 DST=%pI6, IPv6 priority=0x%01X, Next Header=%d",
 		       &ih->saddr, &ih->daddr, ih->priority, ih->nexthdr);
 		nexthdr = ih->nexthdr;
-		offset_ph = ipv6_skip_exthdr(skb, sizeof(_iph), &nexthdr);
+		offset_ph = ipv6_skip_exthdr(skb, sizeof(_iph), &nexthdr, &frag_off);
 		if (offset_ph == -1)
 			goto out;
 		print_ports(skb, nexthdr, offset_ph);

net/ipv6/exthdrs_core.c

@@ -57,6 +57,9 @@ int ipv6_ext_hdr(u8 nexthdr)
  *	    it returns NULL.
  *	  - First fragment header is skipped, not-first ones
  *	    are considered as unparsable.
+ *	  - Reports the offset field of the final fragment header so it is
+ *	    possible to tell whether this is a first fragment, later fragment,
+ *	    or not fragmented.
  *	  - ESP is unparsable for now and considered like
  *	    normal payload protocol.
  *	  - Note also special handling of AUTH header. Thanks to IPsec wizards.
@@ -64,10 +67,13 @@ int ipv6_ext_hdr(u8 nexthdr)
  * --ANK (980726)
  */
 
-int ipv6_skip_exthdr(const struct sk_buff *skb, int start, u8 *nexthdrp)
+int ipv6_skip_exthdr(const struct sk_buff *skb, int start, u8 *nexthdrp,
+		     __be16 *frag_offp)
 {
 	u8 nexthdr = *nexthdrp;
 
+	*frag_offp = 0;
+
 	while (ipv6_ext_hdr(nexthdr)) {
 		struct ipv6_opt_hdr _hdr, *hp;
 		int hdrlen;
@@ -87,7 +93,8 @@ int ipv6_skip_exthdr(const struct sk_buff *skb, int start, u8 *nexthdrp)
 			if (fp == NULL)
 				return -1;
 
-			if (ntohs(*fp) & ~0x7)
+			*frag_offp = *fp;
+			if (ntohs(*frag_offp) & ~0x7)
 				break;
 			hdrlen = 8;
 		} else if (nexthdr == NEXTHDR_AUTH)

net/ipv6/icmp.c

@@ -135,11 +135,12 @@ static int is_ineligible(struct sk_buff *skb)
 	int ptr = (u8 *)(ipv6_hdr(skb) + 1) - skb->data;
 	int len = skb->len - ptr;
 	__u8 nexthdr = ipv6_hdr(skb)->nexthdr;
+	__be16 frag_off;
 
 	if (len < 0)
 		return 1;
 
-	ptr = ipv6_skip_exthdr(skb, ptr, &nexthdr);
+	ptr = ipv6_skip_exthdr(skb, ptr, &nexthdr, &frag_off);
 	if (ptr < 0)
 		return 0;
 	if (nexthdr == IPPROTO_ICMPV6) {
@@ -596,6 +597,7 @@ static void icmpv6_notify(struct sk_buff *skb, u8 type, u8 code, __be32 info)
 	int inner_offset;
 	int hash;
 	u8 nexthdr;
+	__be16 frag_off;
 
 	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
 		return;
@@ -603,7 +605,8 @@ static void icmpv6_notify(struct sk_buff *skb, u8 type, u8 code, __be32 info)
 	nexthdr = ((struct ipv6hdr *)skb->data)->nexthdr;
 	if (ipv6_ext_hdr(nexthdr)) {
 		/* now skip over extension headers */
-		inner_offset = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr);
+		inner_offset = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr),
+						&nexthdr, &frag_off);
 		if (inner_offset<0)
 			return;
 	} else {

net/ipv6/ip6_input.c

@@ -280,6 +280,7 @@ int ip6_mc_input(struct sk_buff *skb)
 			u8 *ptr = skb_network_header(skb) + opt->ra;
 			struct icmp6hdr *icmp6;
 			u8 nexthdr = hdr->nexthdr;
+			__be16 frag_off;
 			int offset;
 
 			/* Check if the value of Router Alert
@@ -293,7 +294,7 @@ int ip6_mc_input(struct sk_buff *skb)
 					goto out;
 				}
 				offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
-							  &nexthdr);
+							  &nexthdr, &frag_off);
 				if (offset < 0)
 					goto out;
 

net/ipv6/ip6_output.c

@@ -329,10 +329,11 @@ static int ip6_forward_proxy_check(struct sk_buff *skb)
 {
 	struct ipv6hdr *hdr = ipv6_hdr(skb);
 	u8 nexthdr = hdr->nexthdr;
+	__be16 frag_off;
 	int offset;
 
 	if (ipv6_ext_hdr(nexthdr)) {
-		offset = ipv6_skip_exthdr(skb, sizeof(*hdr), &nexthdr);
+		offset = ipv6_skip_exthdr(skb, sizeof(*hdr), &nexthdr, &frag_off);
 		if (offset < 0)
 			return 0;
 	} else

net/ipv6/netfilter/ip6t_REJECT.c

@@ -49,6 +49,7 @@ static void send_reset(struct net *net, struct sk_buff *oldskb)
 	const __u8 tclass = DEFAULT_TOS_VALUE;
 	struct dst_entry *dst = NULL;
 	u8 proto;
+	__be16 frag_off;
 	struct flowi6 fl6;
 
 	if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) ||
@@ -58,7 +59,7 @@ static void send_reset(struct net *net, struct sk_buff *oldskb)
 	}
 
 	proto = oip6h->nexthdr;
-	tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data), &proto);
+	tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data), &proto, &frag_off);
 
 	if ((tcphoff < 0) || (tcphoff > oldskb->len)) {
 		pr_debug("Cannot get TCP header.\n");

net/netfilter/ipset/ip_set_getport.c

@@ -116,9 +116,11 @@ ip_set_get_ip6_port(const struct sk_buff *skb, bool src,
 {
 	int protoff;
 	u8 nexthdr;
+	__be16 frag_off;
 
 	nexthdr = ipv6_hdr(skb)->nexthdr;
-	protoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr);
+	protoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr,
+				   &frag_off);
 	if (protoff < 0)
 		return false;
 

net/netfilter/xt_AUDIT.c

@@ -98,6 +98,7 @@ static void audit_ip6(struct audit_buffer *ab, struct sk_buff *skb)
 	struct ipv6hdr _ip6h;
 	const struct ipv6hdr *ih;
 	u8 nexthdr;
+	__be16 frag_off;
 	int offset;
 
 	ih = skb_header_pointer(skb, skb_network_offset(skb), sizeof(_ip6h), &_ip6h);
@@ -108,7 +109,7 @@ static void audit_ip6(struct audit_buffer *ab, struct sk_buff *skb)
 
 	nexthdr = ih->nexthdr;
 	offset = ipv6_skip_exthdr(skb, skb_network_offset(skb) + sizeof(_ip6h),
-				  &nexthdr);
+				  &nexthdr, &frag_off);
 
 	audit_log_format(ab, " saddr=%pI6c daddr=%pI6c proto=%hhu",
 			 &ih->saddr, &ih->daddr, nexthdr);

net/netfilter/xt_TCPMSS.c

@@ -204,11 +204,12 @@ tcpmss_tg6(struct sk_buff *skb, const struct xt_action_param *par)
 {
 	struct ipv6hdr *ipv6h = ipv6_hdr(skb);
 	u8 nexthdr;
+	__be16 frag_off;
 	int tcphoff;
 	int ret;
 
 	nexthdr = ipv6h->nexthdr;
-	tcphoff = ipv6_skip_exthdr(skb, sizeof(*ipv6h), &nexthdr);
+	tcphoff = ipv6_skip_exthdr(skb, sizeof(*ipv6h), &nexthdr, &frag_off);
 	if (tcphoff < 0)
 		return NF_DROP;
 	ret = tcpmss_mangle_packet(skb, par->targinfo,

net/netfilter/xt_TCPOPTSTRIP.c

@@ -87,9 +87,10 @@ tcpoptstrip_tg6(struct sk_buff *skb, const struct xt_action_param *par)
 	struct ipv6hdr *ipv6h = ipv6_hdr(skb);
 	int tcphoff;
 	u_int8_t nexthdr;
+	__be16 frag_off;
 
 	nexthdr = ipv6h->nexthdr;
-	tcphoff = ipv6_skip_exthdr(skb, sizeof(*ipv6h), &nexthdr);
+	tcphoff = ipv6_skip_exthdr(skb, sizeof(*ipv6h), &nexthdr, &frag_off);
 	if (tcphoff < 0)
 		return NF_DROP;
 

net/netfilter/xt_hashlimit.c

@@ -445,6 +445,7 @@ hashlimit_init_dst(const struct xt_hashlimit_htable *hinfo,
 {
 	__be16 _ports[2], *ports;
 	u8 nexthdr;
+	__be16 frag_off;
 	int poff;
 
 	memset(dst, 0, sizeof(*dst));
@@ -480,7 +481,7 @@ hashlimit_init_dst(const struct xt_hashlimit_htable *hinfo,
 		      (XT_HASHLIMIT_HASH_DPT | XT_HASHLIMIT_HASH_SPT)))
 			return 0;
 		nexthdr = ipv6_hdr(skb)->nexthdr;
-		protoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr);
+		protoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr, &frag_off);
 		if ((int)protoff < 0)
 			return -1;
 		break;

net/netfilter/xt_socket.c

@@ -214,6 +214,7 @@ extract_icmp6_fields(const struct sk_buff *skb,
 	struct icmp6hdr *icmph, _icmph;
 	__be16 *ports, _ports[2];
 	u8 inside_nexthdr;
+	__be16 inside_fragoff;
 	int inside_hdrlen;
 
 	icmph = skb_header_pointer(skb, outside_hdrlen,
@@ -229,7 +230,8 @@ extract_icmp6_fields(const struct sk_buff *skb,
 		return 1;
 	inside_nexthdr = inside_iph->nexthdr;
 
-	inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + sizeof(_inside_iph), &inside_nexthdr);
+	inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + sizeof(_inside_iph),
+					 &inside_nexthdr, &inside_fragoff);
 	if (inside_hdrlen < 0)
 		return 1; /* hjm: Packet has no/incomplete transport layer headers. */
 

security/lsm_audit.c

@@ -114,6 +114,7 @@ int ipv6_skb_to_auditdata(struct sk_buff *skb,
 	int offset, ret = 0;
 	struct ipv6hdr *ip6;
 	u8 nexthdr;
+	__be16 frag_off;
 
 	ip6 = ipv6_hdr(skb);
 	if (ip6 == NULL)
@@ -126,7 +127,7 @@ int ipv6_skb_to_auditdata(struct sk_buff *skb,
 	offset = skb_network_offset(skb);
 	offset += sizeof(*ip6);
 	nexthdr = ip6->nexthdr;
-	offset = ipv6_skip_exthdr(skb, offset, &nexthdr);
+	offset = ipv6_skip_exthdr(skb, offset, &nexthdr, &frag_off);
 	if (offset < 0)
 		return 0;
 	if (proto)

security/selinux/hooks.c

@@ -3561,6 +3561,7 @@ static int selinux_parse_skb_ipv6(struct sk_buff *skb,
 	u8 nexthdr;
 	int ret = -EINVAL, offset;
 	struct ipv6hdr _ipv6h, *ip6;
+	__be16 frag_off;
 
 	offset = skb_network_offset(skb);
 	ip6 = skb_header_pointer(skb, offset, sizeof(_ipv6h), &_ipv6h);
@@ -3573,7 +3574,7 @@ static int selinux_parse_skb_ipv6(struct sk_buff *skb,
 
 	nexthdr = ip6->nexthdr;
 	offset += sizeof(_ipv6h);
-	offset = ipv6_skip_exthdr(skb, offset, &nexthdr);
+	offset = ipv6_skip_exthdr(skb, offset, &nexthdr, &frag_off);
 	if (offset < 0)
 		goto out;