kernel/git/stable/linux.git/net/rds/connection.c, branch linux-4.14.y

rds: tcp: correctly sequence cleanup on netns deletion.

2018-02-25T10:07:50+00:00

commit 681648e67d43cf269c5590ecf021ed481f4551fc upstream. Commit 8edc3affc077 ("rds: tcp: Take explicit refcounts on struct net") introduces a regression in rds-tcp netns cleanup. The cleanup_net(), (and thus rds_tcp_dev_event notification) is only called from put_net() when all netns refcounts go to 0, but this cannot happen if the rds_connection itself is holding a c_net ref that it expects to release in rds_tcp_kill_sock. Instead, the rds_tcp_kill_sock callback should make sure to tear down state carefully, ensuring that the socket teardown is only done after all data-structures and workqs that depend on it are quiesced. The original motivation for commit 8edc3affc077 ("rds: tcp: Take explicit refcounts on struct net") was to resolve a race condition reported by syzkaller where workqs for tx/rx/connect were triggered after the namespace was deleted. Those worker threads should have been cancelled/flushed before socket tear-down and indeed, rds_conn_path_destroy() does try to sequence this by doing /* cancel cp_send_w */ /* cancel cp_recv_w */ /* flush cp_down_w */ /* free data structures */ Here the "flush cp_down_w" will trigger rds_conn_shutdown and thus invoke rds_tcp_conn_path_shutdown() to close the tcp socket, so that we ought to have satisfied the requirement that "socket-close is done after all other dependent state is quiesced". However, rds_conn_shutdown has a bug in that it *always* triggers the reconnect workq (and if connection is successful, we always restart tx/rx workqs so with the right timing, we risk the race conditions reported by syzkaller). Netns deletion is like module teardown- no need to restart a reconnect in this case. We can use the c_destroy_in_prog bit to avoid restarting the reconnect. Fixes: 8edc3affc077 ("rds: tcp: Take explicit refcounts on struct net") Signed-off-by: Sowmini Varadhan Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

rds: reduce memory footprint for RDS when transport is RDMA

2017-08-03T16:27:59+00:00

RDS over IB does not use multipath RDS, so the array of additional rds_conn_path structures is always superfluous in this case. Reduce the memory footprint of the rds module by making this a dynamic allocation predicated on whether the transport is mp_capable. Signed-off-by: Sowmini Varadhan Acked-by: Santosh Shilimkar Tested-by: Efrain Galaviz Signed-off-by: David S. Miller

rds: cancel send/recv work before queuing connection shutdown

2017-07-17T02:07:35+00:00

We could end up executing rds_conn_shutdown before the rds_recv_worker thread, then rds_conn_shutdown -> rds_tcp_conn_shutdown can do a sock_release and set sock->sk to null, which may interleave in bad ways with rds_recv_worker, e.g., it could result in: "BUG: unable to handle kernel NULL pointer dereference at 0000000000000078" [ffff881769f6fd70] release_sock at ffffffff815f337b [ffff881769f6fd90] rds_tcp_recv at ffffffffa043c888 [rds_tcp] [ffff881769f6fdb0] rds_recv_worker at ffffffffa04a4810 [rds] [ffff881769f6fde0] process_one_work at ffffffff810a14c1 [ffff881769f6fe40] worker_thread at ffffffff810a1940 [ffff881769f6fec0] kthread at ffffffff810a6b1e Also, do not enqueue any new shutdown workq items when the connection is shutting down (this may happen for rds-tcp in softirq mode, if a FIN or CLOSE is received while the modules is in the middle of an unload) Signed-off-by: Sowmini Varadhan Signed-off-by: David S. Miller

rds: tcp: set linger to 1 when unloading a rds-tcp

2017-06-22T15:34:04+00:00

If we are unloading the rds_tcp module, we can set linger to 1 and drop pending packets to accelerate reconnect. The peer will end up resetting the connection based on new generation numbers of the new incarnation, so hanging on to unsent TCP packets via linger is mostly pointless in this case. Signed-off-by: Sowmini Varadhan Tested-by: Jenny Xu Signed-off-by: David S. Miller

rds: tcp: remove cp_outgoing

2017-06-16T16:45:14+00:00

After commit 1a0e100fb2c9 ("RDS: TCP: Force every connection to be initiated by numerically smaller IP address") we no longer need the logic associated with cp_outgoing, so clean up usage of this field. Signed-off-by: Sowmini Varadhan Tested-by: Imanti Mendez Signed-off-by: David S. Miller

rds: tcp: allow progress of rds_conn_shutdown if the rds_connection is marked ERROR by an intervening FIN

2017-04-03T02:41:00+00:00

rds_conn_shutdown() runs in workq context, and marks the rds_connection as DISCONNECTING before quiescing Tx/Rx paths. However, after all I/O has quiesced, we may still find the rds_connection state to be RDS_CONN_ERROR if an intervening FIN was processed in softirq context. This is not a fatal error: rds_conn_shutdown() should continue the shutdown, and there is no need to log noisy messages about this event. Signed-off-by: Sowmini Varadhan Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller

rds: tcp: Take explicit refcounts on struct net

2017-03-07T22:09:59+00:00

It is incorrect for the rds_connection to piggyback on the sock_net() refcount for the netns because this gives rise to a chicken-and-egg problem during rds_conn_destroy. Instead explicitly take a ref on the net, and hold the netns down till the connection tear-down is complete. Reported-by: Dmitry Vyukov Signed-off-by: Sowmini Varadhan Signed-off-by: David S. Miller

RDS: mark few internal functions static to make sparse build happy

2017-01-02T22:02:40+00:00

Fixes below warnings: warning: symbol 'rds_send_probe' was not declared. Should it be static? warning: symbol 'rds_send_ping' was not declared. Should it be static? warning: symbol 'rds_tcp_accept_one_path' was not declared. Should it be static? warning: symbol 'rds_walk_conn_path_info' was not declared. Should it be static? Signed-off-by: Santosh Shilimkar

RDS: TCP: Force every connection to be initiated by numerically smaller IP address

2016-11-17T18:35:18+00:00

When 2 RDS peers initiate an RDS-TCP connection simultaneously, there is a potential for "duelling syns" on either/both sides. See commit 241b271952eb ("RDS-TCP: Reset tcp callbacks if re-using an outgoing socket in rds_tcp_accept_one()") for a description of this condition, and the arbitration logic which ensures that the numerically large IP address in the TCP connection is bound to the RDS_TCP_PORT ("canonical ordering"). The rds_connection should not be marked as RDS_CONN_UP until the arbitration logic has converged for the following reason. The sender may start transmitting RDS datagrams as soon as RDS_CONN_UP is set, and since the sender removes all datagrams from the rds_connection's cp_retrans queue based on TCP acks. If the TCP ack was sent from a tcp socket that got reset as part of duel aribitration (but before data was delivered to the receivers RDS socket layer), the sender may end up prematurely freeing the datagram, and the datagram is no longer reliably deliverable. This patch remedies that condition by making sure that, upon receipt of 3WH completion state change notification of TCP_ESTABLISHED in rds_tcp_state_change, we mark the rds_connection as RDS_CONN_UP if, and only if, the IP addresses and ports for the connection are canonically ordered. In all other cases, rds_tcp_state_change will force an rds_conn_path_drop(), and rds_queue_reconnect() on both peers will restart the connection to ensure canonical ordering. A side-effect of enforcing this condition in rds_tcp_state_change() is that rds_tcp_accept_one_path() can now be refactored for simplicity. It is also no longer possible to encounter an RDS_CONN_UP connection in the arbitration logic in rds_tcp_accept_one(). Signed-off-by: Sowmini Varadhan Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller

RDS: TCP: Track peer's connection generation number

2016-11-17T18:35:18+00:00

The RDS transport has to be able to distinguish between two types of failure events: (a) when the transport fails (e.g., TCP connection reset) but the RDS socket/connection layer on both sides stays the same (b) when the peer's RDS layer itself resets (e.g., due to module reload or machine reboot at the peer) In case (a) both sides must reconnect and continue the RDS messaging without any message loss or disruption to the message sequence numbers, and this is achieved by rds_send_path_reset(). In case (b) we should reset all rds_connection state to the new incarnation of the peer. Examples of state that needs to be reset are next expected rx sequence number from, or messages to be retransmitted to, the new incarnation of the peer. To achieve this, the RDS handshake probe added as part of commit 5916e2c1554f ("RDS: TCP: Enable multipath RDS for TCP") is enhanced so that sender and receiver of the RDS ping-probe will add a generation number as part of the RDS_EXTHDR_GEN_NUM extension header. Each peer stores local and remote generation numbers as part of each rds_connection. Changes in generation number will be detected via incoming handshake probe ping request or response and will allow the receiver to reset rds_connection state. Signed-off-by: Sowmini Varadhan Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller