tcp: populate inet->cork.fl.u.ip6 in tcp_v6_connect()

Instead of using private @fl6 and @final variables
use respectively inet->cork.fl.u.ip6 and np->final.

As explained in commit 85d05e281712 ("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.

After this patch, active TCP ipv6 flows have correctly initialized
inet->cork.fl.u.ip6 structure.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260206173426.1638518-6-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index c65a5bfd322a1db5dc3fbc406e577f0ccb044c23..0fbcb39b3aa709e936a518865e2d16c4027081dd 100644 (file)
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -138,15 +138,15 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
 {
        struct sockaddr_in6 *usin = (struct sockaddr_in6 *) uaddr;
        struct inet_connection_sock *icsk = inet_csk(sk);
-       struct in6_addr *saddr = NULL, *final_p, final;
        struct inet_timewait_death_row *tcp_death_row;
        struct ipv6_pinfo *np = tcp_inet6_sk(sk);
+       struct in6_addr *saddr = NULL, *final_p;
        struct inet_sock *inet = inet_sk(sk);
        struct tcp_sock *tp = tcp_sk(sk);
        struct net *net = sock_net(sk);
        struct ipv6_txoptions *opt;
        struct dst_entry *dst;
-       struct flowi6 fl6;
+       struct flowi6 *fl6;
        int addr_type;
        int err;
 
@@ -156,14 +156,15 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
        if (usin->sin6_family != AF_INET6)
                return -EAFNOSUPPORT;
 
-       memset(&fl6, 0, sizeof(fl6));
+       fl6 = &inet_sk(sk)->cork.fl.u.ip6;
+       memset(fl6, 0, sizeof(*fl6));
 
        if (inet6_test_bit(SNDFLOW, sk)) {
-               fl6.flowlabel = usin->sin6_flowinfo&IPV6_FLOWINFO_MASK;
-               IP6_ECN_flow_init(fl6.flowlabel);
-               if (fl6.flowlabel&IPV6_FLOWLABEL_MASK) {
+               fl6->flowlabel = usin->sin6_flowinfo & IPV6_FLOWINFO_MASK;
+               IP6_ECN_flow_init(fl6->flowlabel);
+               if (fl6->flowlabel & IPV6_FLOWLABEL_MASK) {
                        struct ip6_flowlabel *flowlabel;
-                       flowlabel = fl6_sock_lookup(sk, fl6.flowlabel);
+                       flowlabel = fl6_sock_lookup(sk, fl6->flowlabel);
                        if (IS_ERR(flowlabel))
                                return -EINVAL;
                        fl6_sock_release(flowlabel);
@@ -212,7 +213,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
        }
 
        sk->sk_v6_daddr = usin->sin6_addr;
-       np->flow_label = fl6.flowlabel;
+       np->flow_label = fl6->flowlabel;
 
        /*
         *      TCP over IPv4
@@ -260,24 +261,24 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
        if (!ipv6_addr_any(&sk->sk_v6_rcv_saddr))
                saddr = &sk->sk_v6_rcv_saddr;
 
-       fl6.flowi6_proto = IPPROTO_TCP;
-       fl6.daddr = sk->sk_v6_daddr;
-       fl6.saddr = saddr ? *saddr : np->saddr;
-       fl6.flowlabel = ip6_make_flowinfo(np->tclass, np->flow_label);
-       fl6.flowi6_oif = sk->sk_bound_dev_if;
-       fl6.flowi6_mark = sk->sk_mark;
-       fl6.fl6_dport = usin->sin6_port;
-       fl6.fl6_sport = inet->inet_sport;
-       if (IS_ENABLED(CONFIG_IP_ROUTE_MULTIPATH) && !fl6.fl6_sport)
-               fl6.flowi6_flags = FLOWI_FLAG_ANY_SPORT;
-       fl6.flowi6_uid = sk_uid(sk);
+       fl6->flowi6_proto = IPPROTO_TCP;
+       fl6->daddr = sk->sk_v6_daddr;
+       fl6->saddr = saddr ? *saddr : np->saddr;
+       fl6->flowlabel = ip6_make_flowinfo(np->tclass, np->flow_label);
+       fl6->flowi6_oif = sk->sk_bound_dev_if;
+       fl6->flowi6_mark = sk->sk_mark;
+       fl6->fl6_dport = usin->sin6_port;
+       fl6->fl6_sport = inet->inet_sport;
+       if (IS_ENABLED(CONFIG_IP_ROUTE_MULTIPATH) && !fl6->fl6_sport)
+               fl6->flowi6_flags = FLOWI_FLAG_ANY_SPORT;
+       fl6->flowi6_uid = sk_uid(sk);
 
        opt = rcu_dereference_protected(np->opt, lockdep_sock_is_held(sk));
-       final_p = fl6_update_dst(&fl6, opt, &final);
+       final_p = fl6_update_dst(fl6, opt, &np->final);
 
-       security_sk_classify_flow(sk, flowi6_to_flowi_common(&fl6));
+       security_sk_classify_flow(sk, flowi6_to_flowi_common(fl6));
 
-       dst = ip6_dst_lookup_flow(net, sk, &fl6, final_p);
+       dst = ip6_dst_lookup_flow(net, sk, fl6, final_p);
        if (IS_ERR(dst)) {
                err = PTR_ERR(dst);
                goto failure;
@@ -287,7 +288,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
        tcp_death_row = &sock_net(sk)->ipv4.tcp_death_row;
 
        if (!saddr) {
-               saddr = &fl6.saddr;
+               saddr = &fl6->saddr;
 
                err = inet_bhash2_update_saddr(sk, saddr, AF_INET6);
                if (err)