oslib-posix: Introduce qemu_socketpair()

qemu_socketpair() will create a pair of connected sockets
with FD_CLOEXEC set

Signed-off-by: Guoyi Tu <tugy@chinatelecom.cn>
Reviewed-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <17fa1eff729eeabd9a001f4639abccb127ceec81.1661240709.git.tugy@chinatelecom.cn>

include/qemu/sockets.h

@@ -14,6 +14,24 @@ int inet_aton(const char *cp, struct in_addr *ia);
 /* misc helpers */
 bool fd_is_socket(int fd);
 int qemu_socket(int domain, int type, int protocol);
+
+#ifndef WIN32
+/**
+ * qemu_socketpair:
+ * @domain: specifies a communication domain, such as PF_UNIX
+ * @type: specifies the socket type.
+ * @protocol: specifies a particular protocol to be used with the  socket
+ * @sv: an array to store the pair of socket created
+ *
+ * Creates an unnamed pair of connected sockets in the specified domain,
+ * of the specified type, and using the optionally specified protocol.
+ * And automatically set the close-on-exec flags on the returned sockets
+ *
+ * Return 0 on success.
+ */
+int qemu_socketpair(int domain, int type, int protocol, int sv[2]);
+#endif
+
 int qemu_accept(int s, struct sockaddr *addr, socklen_t *addrlen);
 int socket_set_cork(int fd, int v);
 int socket_set_nodelay(int fd);

util/oslib-posix.c

@@ -253,6 +253,25 @@ void qemu_set_cloexec(int fd)
     assert(f != -1);
 }
 
+int qemu_socketpair(int domain, int type, int protocol, int sv[2])
+{
+    int ret;
+
+#ifdef SOCK_CLOEXEC
+    ret = socketpair(domain, type | SOCK_CLOEXEC, protocol, sv);
+    if (ret != -1 || errno != EINVAL) {
+        return ret;
+    }
+#endif
+    ret = socketpair(domain, type, protocol, sv);;
+    if (ret == 0) {
+        qemu_set_cloexec(sv[0]);
+        qemu_set_cloexec(sv[1]);
+    }
+
+    return ret;
+}
+
 char *
 qemu_get_local_state_dir(void)
 {