If something abnormal happened to QEMU, 'connect()' can block calling
thread (e.g. main thread of OVS) forever or for a really long time.
This can break whole application or block the reconnection thread.
Example with OVS:
ovs_rcu(urcu2)|WARN|blocked 512000 ms waiting for main to quiesce
(gdb) bt
#0 connect () from /lib64/libpthread.so.0
#1 vhost_user_create_client (vsocket=0xa816e0)
#2 rte_vhost_driver_register
#3 netdev_dpdk_vhost_user_construct
#4 netdev_open (name=0xa664b0 "vhost1")
[...]
#11 main
Fix that by setting non-blocking mode for client sockets for connection.
Fixes: 64ab701c3d1e ("vhost: add vhost-user client mode")
Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
81b5d22f1d