[Libguestfs] [libnbd PATCH 1/2] socket: Avoid SIGPIPE where possible

If the server hangs up while we are writing, we'd rather have send() fail with EPIPE than deal with a SIGPIPE signal - especially when we are being run as a library inside a larger program that may have other intentions on what signals should do for its other activities. At least Linux makes this easy with the MSG_NOSIGNAL flag (it requires that we use send() instead of write(), which in turn requires socketpair() rather than pipe() for nbd_connect_command - but we already do that). If we ever branch out into accepting pre-opened fds, we'll have to deal with SIGPIPE suppression for non-sockets at that time. --- lib/socket.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/lib/socket.c b/lib/socket.c index 8555855..a0f3d61 100644 --- a/lib/socket.c +++ b/lib/socket.c @@ -46,6 +46,13 @@ socket_send (struct nbd_handle *h, { ssize_t r; + /* We don't want to die from SIGPIPE, but also don't want to force a + * changed signal handler on the rest of the application. + */ +#ifdef MSG_NOSIGNAL + flags |= MSG_NOSIGNAL; +#endif + r = send (sock->u.fd, buf, len, flags); if (r == -1 && errno != EAGAIN && errno != EWOULDBLOCK) set_error (errno, "send"); -- 2.20.1