selftests: net: fix server bind failure in sctp_vrf.sh

sctp_vrf.sh could fail:

  TEST 12: bind vrf-2 & 1 in server, connect from client 1 & 2, N [FAIL]
  not ok 1 selftests: net: sctp_vrf.sh # exit=3

The failure happens when the server bind in a new run conflicts with an
existing association from the previous run:

[1] ip netns exec $SERVER_NS ./sctp_hello server ...
[2] ip netns exec $CLIENT_NS ./sctp_hello client ...
[3] ip netns exec $SERVER_NS pkill sctp_hello ...
[4] ip netns exec $SERVER_NS ./sctp_hello server ...

It occurs if the client in [2] sends a message and closes immediately.
With the message unacked, no SHUTDOWN is sent. Killing the server in [3]
triggers a SHUTDOWN the client also ignores due to the unacked message,
leaving the old association alive. This causes the bind at [4] to fail
until the message is acked and the client responds to a second SHUTDOWN
after the server’s T2 timer expires (3s).

This patch fixes the issue by preventing the client from sending data.
Instead, the client blocks on recv() and waits for the server to close.
It also waits until both the server and the client sockets are fully
released in stop_server and wait_client before restarting.

Additionally, replace 2>&1 >/dev/null with -q in sysctl and grep, and
drop other redundant 2>&1 >/dev/null redirections, and fix a typo from
N to Y (connect successfully) in the description of the last test.

Fixes: a61bd7b9fef3 ("selftests: add a selftest for sctp vrf")
Reported-by: Hangbin Liu <liuhangbin@gmail.com>
Tested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Link: https://patch.msgid.link/be2dacf52d0917c4ba5e2e8c5a9cb640740ad2b6.1760731574.git.lucien.xin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions