net: ipv4: avoid repeated calls to ip_skb_dst_mtu helper

ip_skb_dst_mtu is small inline helper, but its called in several places.

before: 17061      44       0   17105    42d1 net/ipv4/ip_output.o
after:  16805      44       0   16849    41d1 net/ipv4/ip_output.o

Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 7 deletions

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 451b009dae75..d6dd8ba04441 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -84,6 +84,7 @@ int sysctl_ip_default_ttl __read_mostly = IPDEFTTL;
 EXPORT_SYMBOL(sysctl_ip_default_ttl);
 
 static int ip_fragment(struct sock *sk, struct sk_buff *skb,
+                       unsigned int mtu,
                        int (*output)(struct sock *, struct sk_buff *));
 
 /* Generate a checksum for an outgoing IP datagram. */
@@ -219,7 +220,8 @@ static inline int ip_finish_output2(struct sock *sk, struct sk_buff *skb)
         return -EINVAL;
 }
 
-static int ip_finish_output_gso(struct sock *sk, struct sk_buff *skb)
+static int ip_finish_output_gso(struct sock *sk, struct sk_buff *skb,
+                                unsigned int mtu)
 {
         netdev_features_t features;
         struct sk_buff *segs;
@@ -227,7 +229,7 @@ static int ip_finish_output_gso(struct sock *sk, struct sk_buff *skb)
 
         /* common case: locally created skb or seglen is <= mtu */
         if (((IPCB(skb)->flags & IPSKB_FORWARDED) == 0) ||
-              skb_gso_network_seglen(skb) <= ip_skb_dst_mtu(skb))
+              skb_gso_network_seglen(skb) <= mtu)
                 return ip_finish_output2(sk, skb);
 
         /* Slowpath -  GSO segment length is exceeding the dst MTU.
@@ -251,7 +253,7 @@ static int ip_finish_output_gso(struct sock *sk, struct sk_buff *skb)
                 int err;
 
                 segs->next = NULL;
-                err = ip_fragment(sk, segs, ip_finish_output2);
+                err = ip_fragment(sk, segs, mtu, ip_finish_output2);
 
                 if (err && ret == 0)
                         ret = err;
@@ -263,6 +265,8 @@ static int ip_finish_output_gso(struct sock *sk, struct sk_buff *skb)
 
 static int ip_finish_output(struct sock *sk, struct sk_buff *skb)
 {
+        unsigned int mtu;
+
 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
         /* Policy lookup after SNAT yielded a new policy */
         if (skb_dst(skb)->xfrm) {
@@ -270,11 +274,12 @@ static int ip_finish_output(struct sock *sk, struct sk_buff *skb)
                 return dst_output_sk(sk, skb);
         }
 #endif
+        mtu = ip_skb_dst_mtu(skb);
         if (skb_is_gso(skb))
-                return ip_finish_output_gso(sk, skb);
+                return ip_finish_output_gso(sk, skb, mtu);
 
-        if (skb->len > ip_skb_dst_mtu(skb))
-                return ip_fragment(sk, skb, ip_finish_output2);
+        if (skb->len > mtu)
+                return ip_fragment(sk, skb, mtu, ip_finish_output2);
 
         return ip_finish_output2(sk, skb);
 }
@@ -482,10 +487,10 @@ static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 }
 
 static int ip_fragment(struct sock *sk, struct sk_buff *skb,
+                       unsigned int mtu,
                        int (*output)(struct sock *, struct sk_buff *))
 {
         struct iphdr *iph = ip_hdr(skb);
-        unsigned int mtu = ip_skb_dst_mtu(skb);
 
         if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->ignore_df) ||
                      (IPCB(skb)->frag_max_size &&