sockets: update SOCKET_ADDRESS_TYPE_FD listen(2) backlog
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, commit582d4210eb
("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:e5b6353cf2
("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>
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@ -1116,14 +1116,10 @@ fail:
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return NULL;
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return NULL;
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}
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}
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static int socket_get_fd(const char *fdstr, int num, Error **errp)
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static int socket_get_fd(const char *fdstr, Error **errp)
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{
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{
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Monitor *cur_mon = monitor_cur();
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Monitor *cur_mon = monitor_cur();
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int fd;
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int fd;
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if (num != 1) {
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error_setg_errno(errp, EINVAL, "socket_get_fd: too many connections");
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return -1;
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}
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if (cur_mon) {
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if (cur_mon) {
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fd = monitor_get_fd(cur_mon, fdstr, errp);
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fd = monitor_get_fd(cur_mon, fdstr, errp);
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if (fd < 0) {
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if (fd < 0) {
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@ -1159,7 +1155,7 @@ int socket_connect(SocketAddress *addr, Error **errp)
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break;
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break;
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case SOCKET_ADDRESS_TYPE_FD:
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case SOCKET_ADDRESS_TYPE_FD:
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fd = socket_get_fd(addr->u.fd.str, 1, errp);
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fd = socket_get_fd(addr->u.fd.str, errp);
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break;
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break;
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case SOCKET_ADDRESS_TYPE_VSOCK:
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case SOCKET_ADDRESS_TYPE_VSOCK:
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@ -1187,7 +1183,26 @@ int socket_listen(SocketAddress *addr, int num, Error **errp)
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break;
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break;
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case SOCKET_ADDRESS_TYPE_FD:
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case SOCKET_ADDRESS_TYPE_FD:
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fd = socket_get_fd(addr->u.fd.str, num, errp);
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fd = socket_get_fd(addr->u.fd.str, errp);
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if (fd < 0) {
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return -1;
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}
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/*
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* If the socket is not yet in the listen state, then transition it to
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* the listen state now.
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*
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* If it's already listening then this updates the backlog value as
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* requested.
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*
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* If this socket cannot listen because it's already in another state
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* (e.g. unbound or connected) then we'll catch the error here.
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*/
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if (listen(fd, num) != 0) {
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error_setg_errno(errp, errno, "Failed to listen on fd socket");
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closesocket(fd);
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return -1;
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}
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break;
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break;
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case SOCKET_ADDRESS_TYPE_VSOCK:
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case SOCKET_ADDRESS_TYPE_VSOCK:
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