linux/net/tipc
Tuong Lien 91986ee166 tipc: fix link session and re-establish issues
When a link endpoint is re-created (e.g. after a node reboot or
interface reset), the link session number is varied by random, the peer
endpoint will be synced with this new session number before the link is
re-established.

However, there is a shortcoming in this mechanism that can lead to the
link never re-established or faced with a failure then. It happens when
the peer endpoint is ready in ESTABLISHING state, the 'peer_session' as
well as the 'in_session' flag have been set, but suddenly this link
endpoint leaves. When it comes back with a random session number, there
are two situations possible:

1/ If the random session number is larger than (or equal to) the
previous one, the peer endpoint will be updated with this new session
upon receipt of a RESET_MSG from this endpoint, and the link can be re-
established as normal. Otherwise, all the RESET_MSGs from this endpoint
will be rejected by the peer. In turn, when this link endpoint receives
one ACTIVATE_MSG from the peer, it will move to ESTABLISHED and start
to send STATE_MSGs, but again these messages will be dropped by the
peer due to wrong session.
The peer link endpoint can still become ESTABLISHED after receiving a
traffic message from this endpoint (e.g. a BCAST_PROTOCOL or
NAME_DISTRIBUTOR), but since all the STATE_MSGs are invalid, the link
will be forced down sooner or later!

Even in case the random session number is larger than the previous one,
it can be that the ACTIVATE_MSG from the peer arrives first, and this
link endpoint moves quickly to ESTABLISHED without sending out any
RESET_MSG yet. Consequently, the peer link will not be updated with the
new session number, and the same link failure scenario as above will
happen.

2/ Another situation can be that, the peer link endpoint was reset due
to any reasons in the meantime, its link state was set to RESET from
ESTABLISHING but still in session, i.e. the 'in_session' flag is not
reset...
Now, if the random session number from this endpoint is less than the
previous one, all the RESET_MSGs from this endpoint will be rejected by
the peer. In the other direction, when this link endpoint receives a
RESET_MSG from the peer, it moves to ESTABLISHING and starts to send
ACTIVATE_MSGs, but all these messages will be rejected by the peer too.
As a result, the link cannot be re-established but gets stuck with this
link endpoint in state ESTABLISHING and the peer in RESET!

Solution:

===========

This link endpoint should not go directly to ESTABLISHED when getting
ACTIVATE_MSG from the peer which may belong to the old session if the
link was re-created. To ensure the session to be correct before the
link is re-established, the peer endpoint in ESTABLISHING state will
send back the last session number in ACTIVATE_MSG for a verification at
this endpoint. Then, if needed, a new and more appropriate session
number will be regenerated to force a re-synch first.

In addition, when a link in ESTABLISHING state is reset, its state will
move to RESET according to the link FSM, along with resetting the
'in_session' flag (and the other data) as a normal link reset, it will
also be deleted if requested.

The solution is backward compatible.

Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Tuong Lien <tuong.t.lien@dektech.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2019-02-11 21:26:20 -08:00
..
addr.c tipc: handle collisions of 32-bit node address hash values 2018-03-23 13:12:18 -04:00
addr.h tipc: add 128-bit node identifier 2018-03-23 13:12:18 -04:00
bcast.c tipc: correct spelling errors for struct tipc_bc_base's comment 2018-09-03 22:03:07 -07:00
bcast.h tipc: make replicast a user selectable option 2017-01-20 12:10:17 -05:00
bearer.c tipc: fix a double free in tipc_enable_bearer() 2018-12-27 16:16:17 -08:00
bearer.h tipc: enable tracepoints in tipc 2018-12-19 11:49:24 -08:00
core.c net: Drop pernet_operations::async 2018-03-27 13:18:09 -04:00
core.h tipc: replace name table service range array with rb tree 2018-03-31 22:19:52 -04:00
diag.c tipc: switch to rhashtable iterator 2018-08-29 18:04:54 -07:00
discover.c tipc: fix lockdep warning when reinitilaizing sockets 2018-11-17 22:01:31 -08:00
discover.h tipc: some cleanups in the file discover.c 2018-03-23 13:12:17 -04:00
eth_media.c tipc: make media address offset a common define 2015-02-27 18:18:48 -05:00
group.c tipc: fix info leak from kernel tipc_event 2018-10-18 16:49:53 -07:00
group.h tipc: extend sock diag for group communication 2018-06-30 21:05:42 +09:00
ib_media.c tipc: rename media/msg related definitions 2015-02-27 18:18:48 -05:00
Kconfig tipc: implement socket diagnostics for AF_TIPC 2018-03-22 14:43:35 -04:00
link.c tipc: fix link session and re-establish issues 2019-02-11 21:26:20 -08:00
link.h tipc: add trace_events for tipc link 2018-12-19 11:49:24 -08:00
Makefile tipc: enable tracepoints in tipc 2018-12-19 11:49:24 -08:00
monitor.c tipc: make some functions static 2018-07-21 16:23:22 -07:00
monitor.h tipc: dump monitor attributes 2016-07-26 14:26:42 -07:00
msg.c tipc: buffer overflow handling in listener socket 2018-09-29 11:24:22 -07:00
msg.h tipc: fix link session and re-establish issues 2019-02-11 21:26:20 -08:00
name_distr.c tipc: eliminate message disordering during binding table update 2018-10-22 19:29:12 -07:00
name_distr.h tipc: permit overlapping service ranges in name table 2018-03-31 22:19:52 -04:00
name_table.c tipc: eliminate message disordering during binding table update 2018-10-22 19:29:12 -07:00
name_table.h tipc: eliminate message disordering during binding table update 2018-10-22 19:29:12 -07:00
net.c tipc: fix lockdep warning when reinitilaizing sockets 2018-11-17 22:01:31 -08:00
net.h tipc: fix lockdep warning when reinitilaizing sockets 2018-11-17 22:01:31 -08:00
netlink_compat.c tipc: fix uninit-value in tipc_nl_compat_doit 2019-01-15 20:29:21 -08:00
netlink.c tipc: switch to rhashtable iterator 2018-08-29 18:04:54 -07:00
netlink.h tipc: make cluster size threshold for monitoring configurable 2016-07-26 14:26:42 -07:00
node.c tipc: fix link session and re-establish issues 2019-02-11 21:26:20 -08:00
node.h tipc: enable tracepoints in tipc 2018-12-19 11:49:24 -08:00
socket.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-12-20 11:53:36 -08:00
socket.h tipc: add trace_events for tipc socket 2018-12-19 11:49:24 -08:00
subscr.c tipc: fix unbalanced reference counter 2018-04-12 21:46:10 -04:00
subscr.h tipc: replace name table service range array with rb tree 2018-03-31 22:19:52 -04:00
sysctl.c tipc: add trace_events for tipc socket 2018-12-19 11:49:24 -08:00
topsrv.c tipc: fix uninit-value in in tipc_conn_rcv_sub 2019-01-15 20:29:20 -08:00
topsrv.h tipc: rename tipc_server to tipc_topsrv 2018-02-16 15:26:34 -05:00
trace.c tipc: add trace_events for tipc socket 2018-12-19 11:49:24 -08:00
trace.h tipc: add trace_events for tipc bearer 2018-12-19 11:49:25 -08:00
udp_media.c tipc: compare remote and local protocols in tipc_udp_enable() 2018-12-14 13:28:03 -08:00
udp_media.h tipc: implement configuration of UDP media MTU 2018-04-20 11:04:05 -04:00