From: Eric Blake <eblake@redhat.com>
To: qemu-devel@nongnu.org
Cc: "Daniel P. Berrangé" <berrange@redhat.com>,
"Juan Quintela" <quintela@redhat.com>,
qemu-stable@nongnu.org,
"Richard W . M . Jones" <rjones@redhat.com>,
"Gerd Hoffmann" <kraxel@redhat.com>,
"Stefan Hajnoczi" <stefanha@redhat.com>,
"Stefano Garzarella" <sgarzare@redhat.com>
Subject: [PULL 1/1] sockets: update SOCKET_ADDRESS_TYPE_FD listen(2) backlog
Date: Tue, 11 May 2021 14:28:02 -0500 [thread overview]
Message-ID: <20210511192802.552706-2-eblake@redhat.com> (raw)
In-Reply-To: <20210511192802.552706-1-eblake@redhat.com>
From: Stefan Hajnoczi <stefanha@redhat.com>
socket_get_fd() fails with the error "socket_get_fd: too many
connections" if the given listen backlog value is not 1.
Not all callers set the backlog to 1. For example, commit
582d4210eb2f2ab5baac328fe4b479cd86da1647 ("qemu-nbd: Use SOMAXCONN for
socket listen() backlog") uses SOMAXCONN. This will always fail with in
socket_get_fd().
This patch calls listen(2) on the fd to update the backlog value. The
socket may already be in the listen state. I have tested that this works
on Linux 5.10 and macOS Catalina.
As a bonus this allows us to detect when the fd cannot listen. Now we'll
be able to catch unbound or connected fds in socket_listen().
Drop the num argument from socket_get_fd() since this function is also
called by socket_connect() where a listen backlog value does not make
sense.
Fixes: e5b6353cf25c99c3f08bf51e29933352f7140e8f ("socket: Add backlog parameter to socket_listen")
Reported-by: Richard W.M. Jones <rjones@redhat.com>
Cc: Juan Quintela <quintela@redhat.com>
Cc: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20210310173004.420190-1-stefanha@redhat.com>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
util/qemu-sockets.c | 29 ++++++++++++++++++++++-------
1 file changed, 22 insertions(+), 7 deletions(-)
diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
index 8af0278f15c6..2463c49773ea 100644
--- a/util/qemu-sockets.c
+++ b/util/qemu-sockets.c
@@ -1116,14 +1116,10 @@ fail:
return NULL;
}
-static int socket_get_fd(const char *fdstr, int num, Error **errp)
+static int socket_get_fd(const char *fdstr, Error **errp)
{
Monitor *cur_mon = monitor_cur();
int fd;
- if (num != 1) {
- error_setg_errno(errp, EINVAL, "socket_get_fd: too many connections");
- return -1;
- }
if (cur_mon) {
fd = monitor_get_fd(cur_mon, fdstr, errp);
if (fd < 0) {
@@ -1159,7 +1155,7 @@ int socket_connect(SocketAddress *addr, Error **errp)
break;
case SOCKET_ADDRESS_TYPE_FD:
- fd = socket_get_fd(addr->u.fd.str, 1, errp);
+ fd = socket_get_fd(addr->u.fd.str, errp);
break;
case SOCKET_ADDRESS_TYPE_VSOCK:
@@ -1187,7 +1183,26 @@ int socket_listen(SocketAddress *addr, int num, Error **errp)
break;
case SOCKET_ADDRESS_TYPE_FD:
- fd = socket_get_fd(addr->u.fd.str, num, errp);
+ fd = socket_get_fd(addr->u.fd.str, errp);
+ if (fd < 0) {
+ return -1;
+ }
+
+ /*
+ * If the socket is not yet in the listen state, then transition it to
+ * the listen state now.
+ *
+ * If it's already listening then this updates the backlog value as
+ * requested.
+ *
+ * If this socket cannot listen because it's already in another state
+ * (e.g. unbound or connected) then we'll catch the error here.
+ */
+ if (listen(fd, num) != 0) {
+ error_setg_errno(errp, errno, "Failed to listen on fd socket");
+ closesocket(fd);
+ return -1;
+ }
break;
case SOCKET_ADDRESS_TYPE_VSOCK:
--
2.31.1
next prev parent reply other threads:[~2021-05-11 19:29 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-11 19:28 [PULL 0/1] NBD patches for 2021-05-11 Eric Blake
2021-05-11 19:28 ` Eric Blake [this message]
2021-05-12 3:42 ` Philippe Mathieu-Daudé
2021-05-21 8:55 ` Peter Maydell
2021-05-24 19:30 ` Eric Blake
2021-05-21 11:02 ` Peter Maydell
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