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To net-next: tcp/ipv6: re-resolve route after binding the ephemeral source port #2

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To net-next: tcp/ipv6: re-resolve route after binding the ephemeral source port #2

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24 changes: 24 additions & 0 deletions net/ipv6/tcp_ipv6.c
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Original file line number Diff line number Diff line change
Expand Up @@ -325,6 +325,30 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
if (err)
goto late_failure;

/* The route above was resolved before the ephemeral source port was
* bound: fl6->fl6_sport was 0 and FLOWI_FLAG_ANY_SPORT had
* rt6_multipath_hash() substitute a random source port, so under a
* port-based hash policy the next hop was picked for a port this
* connection does not use. Every later route rebuild goes through
* inet6_csk_route_socket(), which hashes the real source port, so the
* flow would move to a different next hop the first time the cached
* dst is invalidated. Re-resolve now that the port is final, as
* tcp_v4_connect() does via ip_route_newports(), so the next hop
* stored here is the one every later lookup selects. The source
* address is already final: the first lookup wrote it into fl6->saddr.
*/
if (fl6->fl6_sport != inet->inet_sport) {
fl6->fl6_sport = inet->inet_sport;
fl6->flowi6_flags &= ~FLOWI_FLAG_ANY_SPORT;
security_sk_classify_flow(sk, flowi6_to_flowi_common(fl6));
dst = ip6_dst_lookup_flow(net, sk, fl6, final_p);
if (IS_ERR(dst)) {
err = PTR_ERR(dst);
goto late_failure;
}
ip6_dst_store(sk, dst, false, false);
}

if (likely(!tp->repair)) {
union tcp_seq_and_ts_off st;

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