ipv4: defer fib_compute_spec_dst() call

ip_options_compile() can avoid calling fib_compute_spec_dst()
by default, and perform the call only if needed.

David suggested to add a helper to make the call only once.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/ip_options.c b/net/ipv4/ip_options.c
index 1f022510abe3431b75c1812ac5fe7be1836ca8d5..a19d6471a318addedaa714a890b55930735ba27e 100644 (file)
--- a/net/ipv4/ip_options.c
+++ b/net/ipv4/ip_options.c
@@ -242,6 +242,15 @@ void ip_options_fragment(struct sk_buff *skb)
        opt->ts_needtime = 0;
 }
 
+/* helper used by ip_options_compile() to call fib_compute_spec_dst()
+ * at most one time.
+ */
+static void spec_dst_fill(__be32 *spec_dst, struct sk_buff *skb)
+{
+       if (*spec_dst == htonl(INADDR_ANY))
+               *spec_dst = fib_compute_spec_dst(skb);
+}
+
 /*
  * Verify options and fill pointers in struct options.
  * Caller should clear *opt, and set opt->data.
@@ -251,7 +260,7 @@ void ip_options_fragment(struct sk_buff *skb)
 int ip_options_compile(struct net *net,
                       struct ip_options *opt, struct sk_buff *skb)
 {
-       __be32 spec_dst = (__force __be32) 0;
+       __be32 spec_dst = htonl(INADDR_ANY);
        unsigned char *pp_ptr = NULL;
        struct rtable *rt = NULL;
        unsigned char *optptr;
@@ -260,8 +269,6 @@ int ip_options_compile(struct net *net,
 
        if (skb != NULL) {
                rt = skb_rtable(skb);
-               if (rt)
-                       spec_dst = fib_compute_spec_dst(skb);
                optptr = (unsigned char *)&(ip_hdr(skb)[1]);
        } else
                optptr = opt->__data;
@@ -334,6 +341,7 @@ int ip_options_compile(struct net *net,
                                        goto error;
                                }
                                if (rt) {
+                                       spec_dst_fill(&spec_dst, skb);
                                        memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
                                        opt->is_changed = 1;
                                }
@@ -376,6 +384,7 @@ int ip_options_compile(struct net *net,
                                        }
                                        opt->ts = optptr - iph;
                                        if (rt)  {
+                                               spec_dst_fill(&spec_dst, skb);
                                                memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
                                                timeptr = &optptr[optptr[2]+3];
                                        }