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>

5 files changed, 20 insertions, 7 deletions

diff --git a/net/ipv6/exthdrs_core.c b/net/ipv6/exthdrs_core.c
index 37f548b7f6dc..72957f4a7c6c 100644
--- a/net/ipv6/exthdrs_core.c
+++ b/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)
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 9e2bdccf9143..01d46bff63c3 100644
--- a/net/ipv6/icmp.c
+++ b/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 {
diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index a46c64eb0a66..1ca5d45a12e8 100644
--- a/net/ipv6/ip6_input.c
+++ b/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;
 
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index a24e15557843..3221bc675654 100644
--- a/net/ipv6/ip6_output.c
+++ b/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
diff --git a/net/ipv6/netfilter/ip6t_REJECT.c b/net/ipv6/netfilter/ip6t_REJECT.c
index b5a2aa58a03a..aad2fa41cf46 100644
--- a/net/ipv6/netfilter/ip6t_REJECT.c
+++ b/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");