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Date: Thu, 6 Aug 2020 08:41:08 +0200 From: Tim Froidcoeur <tim.froidcoeur@...sares.net> To: "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Alexey Kuznetsov <kuznet@....inr.ac.ru>, Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>, KOVACS Krisztian <hidden@...abit.hu>, Patrick McHardy <kaber@...sh.net> Cc: Tim Froidcoeur <tim.froidcoeur@...sares.net>, Matthieu Baerts <matthieu.baerts@...sares.net>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: [PATCH net 2/2] net: initialize fastreuse on inet_inherit_port In the case of TPROXY, bind_conflict optimizations for SO_REUSEADDR or SO_REUSEPORT are broken, possibly resulting in O(n) instead of O(1) bind behaviour or in the incorrect reuse of a bind. the kernel keeps track for each bind_bucket if all sockets in the bind_bucket support SO_REUSEADDR or SO_REUSEPORT in two fastreuse flags. These flags allow skipping the costly bind_conflict check when possible (meaning when all sockets have the proper SO_REUSE option). For every socket added to a bind_bucket, these flags need to be updated. As soon as a socket that does not support reuse is added, the flag is set to false and will never go back to true, unless the bind_bucket is deleted. Note that there is no mechanism to re-evaluate these flags when a socket is removed (this might make sense when removing a socket that would not allow reuse; this leaves room for a future patch). For this optimization to work, it is mandatory that these flags are properly initialized and updated. When a child socket is created from a listen socket in __inet_inherit_port, the TPROXY case could create a new bind bucket without properly initializing these flags, thus preventing the optimization to work. Alternatively, a socket not allowing reuse could be added to an existing bind bucket without updating the flags, causing bind_conflict to never be called as it should. Call inet_csk_update_fastreuse when __inet_inherit_port decides to create a new bind_bucket or use a different bind_bucket than the one of the listen socket. Fixes: 093d282321da ("tproxy: fix hash locking issue when using port redirection in __inet_inherit_port()") Acked-by: Matthieu Baerts <matthieu.baerts@...sares.net> Signed-off-by: Tim Froidcoeur <tim.froidcoeur@...sares.net> --- net/ipv4/inet_hashtables.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c index 2bbaaf0c7176..006a34b18537 100644 --- a/net/ipv4/inet_hashtables.c +++ b/net/ipv4/inet_hashtables.c @@ -163,6 +163,7 @@ int __inet_inherit_port(const struct sock *sk, struct sock *child) return -ENOMEM; } } + inet_csk_update_fastreuse(tb, child); } inet_bind_hash(child, tb, port); spin_unlock(&head->lock); -- 2.25.1 -- Disclaimer: https://www.tessares.net/mail-disclaimer/ <https://www.tessares.net/mail-disclaimer/>
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