ipv4: Save nexthop address of LSRR/SSRR option to IPCB.

We can not update iph->daddr in ip_options_rcv_srr(), It is too early.
When some exception ocurred later (eg. in ip_forward() when goto
sr_failed) we need the ip header be identical to the original one as
ICMP need it.

Add a field 'nexthop' in struct ip_options to save nexthop of LSRR
or SSRR option.

Signed-off-by: Li Wei <lw@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 6 insertions, 3 deletions

diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
index b897d6e6d0a5..f941964a9931 100644
--- a/include/net/inet_sock.h
+++ b/include/net/inet_sock.h
@@ -31,6 +31,7 @@
 /** struct ip_options - IP Options
  *
  * @faddr - Saved first hop address
+ * @nexthop - Saved nexthop address in LSRR and SSRR
  * @is_data - Options in __data, rather than skb
  * @is_strictroute - Strict source route
  * @srr_is_hit - Packet destination addr was our one
@@ -41,6 +42,7 @@
  */
 struct ip_options {
         __be32          faddr;
+        __be32          nexthop;
         unsigned char   optlen;
         unsigned char   srr;
         unsigned char   rr;
diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c
index 3b34d1c86270..29a07b6c7168 100644
--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -84,7 +84,7 @@ int ip_forward(struct sk_buff *skb)
 
         rt = skb_rtable(skb);
 
-        if (opt->is_strictroute && ip_hdr(skb)->daddr != rt->rt_gateway)
+        if (opt->is_strictroute && opt->nexthop != rt->rt_gateway)
                 goto sr_failed;
 
         if (unlikely(skb->len > dst_mtu(&rt->dst) && !skb_is_gso(skb) &&
diff --git a/net/ipv4/ip_options.c b/net/ipv4/ip_options.c
index 05d20cca9d66..1e60f7679075 100644
--- a/net/ipv4/ip_options.c
+++ b/net/ipv4/ip_options.c
@@ -568,12 +568,13 @@ void ip_forward_options(struct sk_buff *skb)
                      ) {
                         if (srrptr + 3 > srrspace)
                                 break;
-                        if (memcmp(&ip_hdr(skb)->daddr, &optptr[srrptr-1], 4) == 0)
+                        if (memcmp(&opt->nexthop, &optptr[srrptr-1], 4) == 0)
                                 break;
                 }
                 if (srrptr + 3 <= srrspace) {
                         opt->is_changed = 1;
                         ip_rt_get_source(&optptr[srrptr-1], skb, rt);
+                        ip_hdr(skb)->daddr = opt->nexthop;
                         optptr[2] = srrptr+4;
                 } else if (net_ratelimit())
                         printk(KERN_CRIT "ip_forward(): Argh! Destination lost!\n");
@@ -640,7 +641,7 @@ int ip_options_rcv_srr(struct sk_buff *skb)
         }
         if (srrptr <= srrspace) {
                 opt->srr_is_hit = 1;
-                iph->daddr = nexthop;
+                opt->nexthop = nexthop;
                 opt->is_changed = 1;
         }
         return 0;