ipv6: change inet6_sk_rebuild_header() to use inet->cork.fl.u.ip6

TCP v6 spends a good amount of time rebuilding a fresh fl6 at each
transmit in inet6_csk_xmit()/inet6_csk_route_socket().

TCP v4 caches the information in inet->cork.fl.u.ip4 instead.

This patch is a first step converting IPv6 to the same strategy:

Before this patch inet6_sk_rebuild_header() only validated/rebuilt
a dst. Automatic variable @fl6 content was lost.

After this patch inet6_sk_rebuild_header() also initializes
inet->cork.fl.u.ip6, which can be reused in the future.

This makes inet6_sk_rebuild_header() very similar to
inet_sk_rebuild_header().

Also remove the EXPORT_SYMBOL_GPL(), inet6_sk_rebuild_header()
is not called from any module.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260204163035.4123817-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index bd29840659f34b5754a182303d2871c5f884dfce..0476dbc8edb2b8273fd337b15c8196e9597753ef 100644 (file)
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -824,45 +824,42 @@ EXPORT_SYMBOL(inet6_unregister_protosw);
 int inet6_sk_rebuild_header(struct sock *sk)
 {
        struct ipv6_pinfo *np = inet6_sk(sk);
+       struct inet_sock *inet = inet_sk(sk);
+       struct in6_addr *final_p, final;
        struct dst_entry *dst;
+       struct flowi6 *fl6;
 
        dst = __sk_dst_check(sk, np->dst_cookie);
+       if (dst)
+               return 0;
+
+       fl6 = &inet->cork.fl.u.ip6;
+       memset(fl6, 0, sizeof(*fl6));
+       fl6->flowi6_proto = sk->sk_protocol;
+       fl6->daddr = sk->sk_v6_daddr;
+       fl6->saddr = np->saddr;
+       fl6->flowlabel = np->flow_label;
+       fl6->flowi6_oif = sk->sk_bound_dev_if;
+       fl6->flowi6_mark = sk->sk_mark;
+       fl6->fl6_dport = inet->inet_dport;
+       fl6->fl6_sport = inet->inet_sport;
+       fl6->flowi6_uid = sk_uid(sk);
+       security_sk_classify_flow(sk, flowi6_to_flowi_common(fl6));
 
-       if (!dst) {
-               struct inet_sock *inet = inet_sk(sk);
-               struct in6_addr *final_p, final;
-               struct flowi6 fl6;
-
-               memset(&fl6, 0, sizeof(fl6));
-               fl6.flowi6_proto = sk->sk_protocol;
-               fl6.daddr = sk->sk_v6_daddr;
-               fl6.saddr = np->saddr;
-               fl6.flowlabel = np->flow_label;
-               fl6.flowi6_oif = sk->sk_bound_dev_if;
-               fl6.flowi6_mark = sk->sk_mark;
-               fl6.fl6_dport = inet->inet_dport;
-               fl6.fl6_sport = inet->inet_sport;
-               fl6.flowi6_uid = sk_uid(sk);
-               security_sk_classify_flow(sk, flowi6_to_flowi_common(&fl6));
-
-               rcu_read_lock();
-               final_p = fl6_update_dst(&fl6, rcu_dereference(np->opt),
-                                        &final);
-               rcu_read_unlock();
-
-               dst = ip6_dst_lookup_flow(sock_net(sk), sk, &fl6, final_p);
-               if (IS_ERR(dst)) {
-                       sk->sk_route_caps = 0;
-                       WRITE_ONCE(sk->sk_err_soft, -PTR_ERR(dst));
-                       return PTR_ERR(dst);
-               }
+       rcu_read_lock();
+       final_p = fl6_update_dst(fl6, rcu_dereference(np->opt), &final);
+       rcu_read_unlock();
 
-               ip6_dst_store(sk, dst, false, false);
+       dst = ip6_dst_lookup_flow(sock_net(sk), sk, fl6, final_p);
+       if (IS_ERR(dst)) {
+               sk->sk_route_caps = 0;
+               WRITE_ONCE(sk->sk_err_soft, -PTR_ERR(dst));
+               return PTR_ERR(dst);
        }
 
+       ip6_dst_store(sk, dst, false, false);
        return 0;
 }
-EXPORT_SYMBOL_GPL(inet6_sk_rebuild_header);
 
 bool ipv6_opt_accepted(const struct sock *sk, const struct sk_buff *skb,
                       const struct inet6_skb_parm *opt)