Our default of a backlog of 1 connection is rather puny, particularly for scenarios where we expect multiple listeners to connect (such as qemu-nbd -e X). For Unix sockets, there's no real harm in supporting a larger backlog, and a definite benefit to the clients: at least on Linux, a client trying to connect to a Unix socket with a backlog gets an EAGAIN failure with no way to poll() for when the backlog is no longer present short of sleeping an arbitrary amount of time before retrying.
See https://bugzilla.redhat.com/1925045 for a demonstration of where our low backlog prevents libnbd from connecting as many parallel clients as it wants. Reported-by: Richard W.M. Jones <rjo...@redhat.com> Signed-off-by: Eric Blake <ebl...@redhat.com> --- util/qemu-sockets.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c index 8af0278f15c6..a7573e9f0fda 100644 --- a/util/qemu-sockets.c +++ b/util/qemu-sockets.c @@ -1059,7 +1059,7 @@ int unix_listen(const char *str, Error **errp) saddr = g_new0(UnixSocketAddress, 1); saddr->path = g_strdup(str); - sock = unix_listen_saddr(saddr, 1, errp); + sock = unix_listen_saddr(saddr, SOMAXCONN, errp); qapi_free_UnixSocketAddress(saddr); return sock; } -- 2.30.0