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Wed, 20 Nov 2024 02:38:31 +0000 From: Kuniyuki Iwashima To: CC: , , , , , , , , , Subject: Re: kernel tcp sockets stuck in FIN_WAIT1 after call tcp_close Date: Tue, 19 Nov 2024 18:38:28 -0800 Message-ID: <20241120023828.907-1-kuniyu@amazon.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-ClientProxiedBy: EX19D035UWB002.ant.amazon.com (10.13.138.97) To EX19D004ANA001.ant.amazon.com (10.37.240.138) From: mengkanglai Date: Tue, 19 Nov 2024 08:38:26 +0000 > > > > From: mengkanglai > > Date: Wed, 13 Nov 2024 12:40:34 +0000 > > > Hello, Eric: > > > Commit 151c9c724d05 (tcp: properly terminate timers for kernel > > > sockets) introduce inet_csk_clear_xmit_timers_sync in tcp_close. > > > For kernel sockets it does not hold sk->sk_net_refcnt, if this is > > > kernel tcp socket it will call tcp_send_fin in __tcp_close to send FIN > > > packet to remotes server, > > > > Just curious which subsystem the kernel socket is created by. > > > > Recently, CIFS and sunrpc are (being) converted to hold net refcnt. > > > > CIFS: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ef7134c7fc48e1441b398e55a862232868a6f0a7 > > sunrpc: https://lore.kernel.org/netdev/20241112135434.803890-1-liujian56@huawei.com/ > > > > I remember RDS's listener does not hold refcnt but other client sockets (SMC, RDS, MPTCP, CIFS, sunrpc) do. > > > > I think all TCP kernel sockets should hold netns refcnt except for one created at pernet_operations.init() hook like RDS. > > > > > if this fin packet lost due to network faults, tcp should retransmit > > > this fin packet, but tcp_timer stopped by inet_csk_clear_xmit_timers_sync. > > > tcp sockets state will stuck in FIN_WAIT1 and never go away. I think > > > it's not right. > > > I found this problem when testing nfs. sunrpc: https://lore.kernel.org/netdev/20241112135434.803890-1-liujian56@huawei.com/ will solve this problem. > I agree with that all TCP kernel sockets should hold netns refcnt. > However, for kernel tcp sockets created by other kernel modules through > sock_create_kern or sk_alloc(kern=0), In the next cycle, I'll rename sock_create_kern() to sock_create_net_noref() and add sock_create_net() so that out-of-tree module will fail to build and such users will notice sock_create_net_noref() would trigger an issue. https://github.com/q2ven/linux/commits/427_2 > it means that they must now hold > sk_net_refcnf, otherwise fin will only be sent once and will not be > retransmitted when the socket is released.But other use tcp modules may > not be aware of hold sk_net_refcnt. should we add a check in tcp_close？ The check doesn't fix the issue for in-netns users. I'd rather print the allocator and change it to use sock_create_net() instead. ---8<--- diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 0d704bda6c41..7d6a1faa05a3 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3220,8 +3220,12 @@ void tcp_close(struct sock *sk, long timeout) lock_sock(sk); __tcp_close(sk, timeout); release_sock(sk); + +#ifdef CONFIG_NET_NS_REFCNT_TRACKER if (!sk->sk_net_refcnt) - inet_csk_clear_xmit_timers_sync(sk); + stack_depot_print(sk->ns_tracker); +#endif + sock_put(sk); } EXPORT_SYMBOL(tcp_close); ---8<--- > > --- > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c > index fb920369c..6b92026a4 100644 > --- a/net/ipv4/tcp.c > +++ b/net/ipv4/tcp.c > @@ -2804,7 +2804,7 @@ void tcp_close(struct sock *sk, long timeout) > lock_sock(sk); > __tcp_close(sk, timeout); > release_sock(sk); > - if (!sk->sk_net_refcnt) > + if (sk->net != &init_net && !sk->sk_net_refcnt) > inet_csk_clear_xmit_timers_sync(sk); > sock_put(sk); > }