This series comes out of a discussion between myself & Yongji Xie in: https://lists.gnu.org/archive/html/qemu-devel/2019-01/msg01881.html
I eventually understood that the problem faced was that tcp_chr_wait_connected was racing with the background connection attempt previously started, causing two connections to be established. This broke because some vhost user servers only allow a single connection. After messing around with the code alot the final solution was in fact very easy. We simply have to delay the first background connection attempt until the main loop is running. It will then automatically turn into a no-op if tcp_chr_wait_connected has been run. This is dealt with in the last patch in this series I believe this should solve the problem Yongji Xie faced, and thus not require us to add support for "nowait" option with client sockets at all. The reconnect=1 option effectively already implements nowait semantics, and now plays nicely with tcp_chr_wait_connected. In investigating this I found various other bugs that needed fixing and identified some useful refactoring to simplify / clarify the code, hence this very long series. This series passes make check-unit & check-qtest (for x86_64 target). I did a test with tests/vhost-user-bridge too, which was in fact already broken for the same reason Yongji Xie found - it only accepts a single connection. This series fixes use of reconnect=1 with vhost-user-bridge. Despite me not adding new functionality in this series, I think we could probably do with further unit test cover for the socket chardev backend. I'll investigate this while waiting for reviews on this series so far. Daniel P. Berrangé (12): chardev: fix validation of options for QMP created chardevs chardev: forbid 'reconnect' option with server sockets chardev: forbid 'wait' option with client sockets chardev: remove many local variables in qemu_chr_parse_socket chardev: ensure qemu_chr_parse_compat reports missing driver error chardev: remove unused 'sioc' variable & cleanup paths chardev: split tcp_chr_wait_connected into two methods chardev: split up qmp_chardev_open_socket connection code chardev: use a state machine for socket connection state chardev: honour the reconnect setting in tcp_chr_wait_connected chardev: disallow TLS/telnet/websocket with tcp_chr_wait_connected chardev: fix race with client connections in tcp_chr_wait_connected chardev/char-socket.c | 428 +++++++++++++++++++++++---------- chardev/char.c | 2 + tests/ivshmem-test.c | 2 +- tests/libqtest.c | 4 +- tests/test-filter-redirector.c | 4 +- 5 files changed, 303 insertions(+), 137 deletions(-) -- 2.20.1
