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Message-ID: <CAJnrk1ZTh89qcMoC4nzE8-E-Do9idwmjXAcV-J1THkPjaZGqFw@mail.gmail.com> Date: Fri, 23 Dec 2022 11:34:40 -0800 From: Joanne Koong <joannelkoong@...il.com> To: Kuniyuki Iwashima <kuniyu@...zon.com> Cc: davem@...emloft.net, edumazet@...gle.com, jirislaby@...nel.org, kuba@...nel.org, kuni1840@...il.com, netdev@...r.kernel.org, pabeni@...hat.com Subject: Re: [PATCH RFC net 1/2] tcp: Add TIME_WAIT sockets in bhash2. On Thu, Dec 22, 2022 at 5:55 PM Kuniyuki Iwashima <kuniyu@...zon.com> wrote: > > From: Joanne Koong <joannelkoong@...il.com> > Date: Thu, 22 Dec 2022 16:25:10 -0800 > > On Thu, Dec 22, 2022 at 3:27 PM Kuniyuki Iwashima <kuniyu@...zon.com> wrote: > > > > > > From: Joanne Koong <joannelkoong@...il.com> > > > Date: Thu, 22 Dec 2022 13:46:57 -0800 > > > > On Thu, Dec 22, 2022 at 7:06 AM Paolo Abeni <pabeni@...hat.com> wrote: > > > > > > > > > > On Thu, 2022-12-22 at 00:12 +0900, Kuniyuki Iwashima wrote: > > > > > > Jiri Slaby reported regression of bind() with a simple repro. [0] > > > > > > > > > > > > The repro creates a TIME_WAIT socket and tries to bind() a new socket > > > > > > with the same local address and port. Before commit 28044fc1d495 ("net: > > > > > > Add a bhash2 table hashed by port and address"), the bind() failed with > > > > > > -EADDRINUSE, but now it succeeds. > > > > > > > > > > > > The cited commit should have put TIME_WAIT sockets into bhash2; otherwise, > > > > > > inet_bhash2_conflict() misses TIME_WAIT sockets when validating bind() > > > > > > requests if the address is not a wildcard one. > > > > > > > > (resending my reply because it wasn't in plaintext mode) > > > > > > > > Thanks for adding this! I hadn't realized TIME_WAIT sockets also are > > > > considered when checking against inet bind conflicts. > > > > > > > > > > > > > > How does keeping the timewait sockets inside bhash2 affect the bind > > > > > loopup performance? I fear that could defeat completely the goal of > > > > > 28044fc1d495, on quite busy server we could have quite a bit of tw with > > > > > the same address/port. If so, we could even consider reverting > > > > > 28044fc1d495. > > > > > > It will slow down along the number of twsk, but I think it's still faster > > > than bhash if we listen() on multiple IP. If we don't, bhash is always > > > faster because of bhash2's additional locking. However, this is the > > > nature of bhash2 from the beginning. > > > > > > > > > > > > > > > > > > > Can you clarify what you mean by bind loopup? > > > > > > I think it means just bhash2 traversal. (s/loopup/lookup/) > > > > > > > > > > > > > [0]: https://lore.kernel.org/netdev/6b971a4e-c7d8-411e-1f92-fda29b5b2fb9@kernel.org/ > > > > > > > > > > > > Fixes: 28044fc1d495 ("net: Add a bhash2 table hashed by port and address") > > > > > > Reported-by: Jiri Slaby <jirislaby@...nel.org> > > > > > > Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com> > > > > > > --- > > > > > > include/net/inet_timewait_sock.h | 2 ++ > > > > > > include/net/sock.h | 5 +++-- > > > > > > net/ipv4/inet_hashtables.c | 5 +++-- > > > > > > net/ipv4/inet_timewait_sock.c | 31 +++++++++++++++++++++++++++++-- > > > > > > 4 files changed, 37 insertions(+), 6 deletions(-) > > > > > > > > > > > > diff --git a/include/net/inet_timewait_sock.h b/include/net/inet_timewait_sock.h > > > > > > index 5b47545f22d3..c46ed239ad9a 100644 > > > > > > --- a/include/net/inet_timewait_sock.h > > > > > > +++ b/include/net/inet_timewait_sock.h > > > > > > @@ -44,6 +44,7 @@ struct inet_timewait_sock { > > > > > > #define tw_bound_dev_if __tw_common.skc_bound_dev_if > > > > > > #define tw_node __tw_common.skc_nulls_node > > > > > > #define tw_bind_node __tw_common.skc_bind_node > > > > > > +#define tw_bind2_node __tw_common.skc_bind2_node > > > > > > #define tw_refcnt __tw_common.skc_refcnt > > > > > > #define tw_hash __tw_common.skc_hash > > > > > > #define tw_prot __tw_common.skc_prot > > > > > > @@ -73,6 +74,7 @@ struct inet_timewait_sock { > > > > > > u32 tw_priority; > > > > > > struct timer_list tw_timer; > > > > > > struct inet_bind_bucket *tw_tb; > > > > > > + struct inet_bind2_bucket *tw_tb2; > > > > > > }; > > > > > > #define tw_tclass tw_tos > > > > > > > > > > > > diff --git a/include/net/sock.h b/include/net/sock.h > > > > > > index dcd72e6285b2..aaec985c1b5b 100644 > > > > > > --- a/include/net/sock.h > > > > > > +++ b/include/net/sock.h > > > > > > @@ -156,6 +156,7 @@ typedef __u64 __bitwise __addrpair; > > > > > > * @skc_tw_rcv_nxt: (aka tw_rcv_nxt) TCP window next expected seq number > > > > > > * [union with @skc_incoming_cpu] > > > > > > * @skc_refcnt: reference count > > > > > > + * @skc_bind2_node: bind node in the bhash2 table > > > > > > * > > > > > > * This is the minimal network layer representation of sockets, the header > > > > > > * for struct sock and struct inet_timewait_sock. > > > > > > @@ -241,6 +242,7 @@ struct sock_common { > > > > > > u32 skc_window_clamp; > > > > > > u32 skc_tw_snd_nxt; /* struct tcp_timewait_sock */ > > > > > > }; > > > > > > + struct hlist_node skc_bind2_node; > > > > > > > > > > I *think* it would be better adding a tw_bind2_node field to the > > > > > inet_timewait_sock struct, so that we leave unmodified the request > > > > > socket and we don't change the struct sock binary layout. That could > > > > > affect performances moving hot fields on different cachelines. > > > > > > > > > +1. The rest of this patch LGTM. > > > > > > Then we can't use sk_for_each_bound_bhash2(), or we have to guarantee this. > > > > > > BUILD_BUG_ON(offsetof(struct sock, sk_bind2_node), > > > offsetof(struct inet_timewait_sock, tw_bind2_node)) > > > > > > Considering the number of members in struct sock, at least we have > > > to move sk_bind2_node forward. > > > > > > Another option is to have another TIME_WAIT list in inet_bind2_bucket like > > > tb2->deathrow or something. sk_for_each_bound_bhash2() is used only in > > > inet_bhash2_conflict(), so I think this is feasible. > > > > Oh I see, thanks for clarifying! > > > > I think we could also check sk_state (which is in __sk_common already) > > and if it's TCP_TIME_WAIT, then we know sk is at offsetof(struct > > inet_timewait_sock, tw_bind2_node), whereas otherwise it's at > > offsetof(struct sock, sk_bind2_node). This seems simpler/cleaner to me > > than the other approaches. What are your thoughts? > > Sorry, I don't get it. You mean we can check sk_state first and change > how we traverse ? But then we cannot know the offset of sk_state if we > don't know if the socket is TIME_WAIT ... ? I think the offset of sk_state is the same for both sockets because sk_state is in "struct sock_common" (__sk_common.skc_state) that both share.
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