nbd: ask and print error information from qemu-sockets

Before:

    $ qemu-system-x86_64 nbd:localhost:12345
    inet_connect_opts: connect(ipv4,yakj.usersys.redhat.com,127.0.0.1,12345): Connection refused
    qemu-system-x86_64: could not open disk image nbd:localhost:12345: Connection refused

After:

    $ x86_64-softmmu/qemu-system-x86_64 nbd:localhost:12345
    qemu-system-x86_64: Failed to connect to socket: Connection refused
    qemu-system-x86_64: could not open disk image nbd:localhost:12345: Connection refused

Signed-off-by: Paolo Bonzini <[email protected]>

nbd.c

@@ -208,7 +208,14 @@ int tcp_socket_outgoing(const char *address, uint16_t port)
 
 int tcp_socket_outgoing_spec(const char *address_and_port)
 {
-    return inet_connect(address_and_port, NULL);
+    Error *local_err = NULL;
+    int fd = inet_connect(address_and_port, &local_err);
+
+    if (local_err != NULL) {
+        qerror_report_err(local_err);
+        error_free(local_err);
+    }
+    return fd;
 }
 
 int tcp_socket_incoming(const char *address, uint16_t port)
@@ -220,22 +227,38 @@ int tcp_socket_incoming(const char *address, uint16_t port)
 
 int tcp_socket_incoming_spec(const char *address_and_port)
 {
-    char *ostr  = NULL;
-    int olen = 0;
-    return inet_listen(address_and_port, ostr, olen, SOCK_STREAM, 0, NULL);
+    Error *local_err = NULL;
+    int fd = inet_listen(address_and_port, NULL, 0, SOCK_STREAM, 0, &local_err);
+
+    if (local_err != NULL) {
+        qerror_report_err(local_err);
+        error_free(local_err);
+    }
+    return fd;
 }
 
 int unix_socket_incoming(const char *path)
 {
-    char *ostr = NULL;
-    int olen = 0;
+    Error *local_err = NULL;
+    int fd = unix_listen(path, NULL, 0, &local_err);
 
-    return unix_listen(path, ostr, olen, NULL);
+    if (local_err != NULL) {
+        qerror_report_err(local_err);
+        error_free(local_err);
+    }
+    return fd;
 }
 
 int unix_socket_outgoing(const char *path)
 {
-    return unix_connect(path, NULL);
+    Error *local_err = NULL;
+    int fd = unix_connect(path, &local_err);
+
+    if (local_err != NULL) {
+        qerror_report_err(local_err);
+        error_free(local_err);
+    }
+    return fd;
 }
 
 /* Basic flow for negotiation