ipv6: ip6_skb_dst_mtu() cleanups

Use const attribute where we can, and cache skb_dst()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20211119022355.2985984-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 5efd0b71dc6732d97257fae0637b67516a5b9261..ca2d6b60e1eceeb3839f413726fb4f93e1835a0e 100644 (file)
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -263,19 +263,19 @@ static inline bool ipv6_anycast_destination(const struct dst_entry *dst,
 int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
                 int (*output)(struct net *, struct sock *, struct sk_buff *));
 
-static inline unsigned int ip6_skb_dst_mtu(struct sk_buff *skb)
+static inline unsigned int ip6_skb_dst_mtu(const struct sk_buff *skb)
 {
-       unsigned int mtu;
-
-       struct ipv6_pinfo *np = skb->sk && !dev_recursion_level() ?
+       const struct ipv6_pinfo *np = skb->sk && !dev_recursion_level() ?
                                inet6_sk(skb->sk) : NULL;
+       const struct dst_entry *dst = skb_dst(skb);
+       unsigned int mtu;
 
        if (np && np->pmtudisc >= IPV6_PMTUDISC_PROBE) {
-               mtu = READ_ONCE(skb_dst(skb)->dev->mtu);
-               mtu -= lwtunnel_headroom(skb_dst(skb)->lwtstate, mtu);
-       } else
-               mtu = dst_mtu(skb_dst(skb));
-
+               mtu = READ_ONCE(dst->dev->mtu);
+               mtu -= lwtunnel_headroom(dst->lwtstate, mtu);
+       } else {
+               mtu = dst_mtu(dst);
+       }
        return mtu;
 }