unix: Make more descriptive error logging for ext socket restore failure

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

crtools.c

@@ -94,7 +94,7 @@ int main(int argc, char *argv[])
 			{ "log-file", required_argument, 0, 'o' },
 			{ "namespaces", required_argument, 0, 'n' },
 			{ "root", required_argument, 0, 'r' },
-			{ "ext-unix-sk", no_argument, 0, 'x' },
+			{ USK_EXT_PARAM, no_argument, 0, 'x' },
 			{ "help", no_argument, 0, 'h' },
 			{ SK_EST_PARAM, no_argument, 0, 42 },
 			{ "close", required_argument, 0, 43 },

include/sockets.h

@@ -83,4 +83,6 @@ static inline int sk_decode_shutdown(int val)
 	return hows[val];
 }
 
+#define USK_EXT_PARAM "ext-unix-sk"
+
 #endif /* __CR_SOCKETS_H__ */

sk-unix.c

@@ -819,18 +819,21 @@ int resolve_unix_peers(void)
 
 		peer = find_unix_sk_by_ino(ui->ue->peer);
 
+		if (!peer) {
+			pr_err("FATAL: Peer %#x unresolved for %#x\n",
+					ui->ue->peer, ui->ue->ino);
+			return -1;
+		}
+
 		/*
 		 * Connect to external sockets requires
 		 * special option to be passed.
 		 */
-		if (peer &&
-		    (peer->ue->uflags & USK_EXTERN) &&
-		    !(opts.ext_unix_sk))
-			peer = NULL;
-
-		if (!peer) {
-			pr_err("FATAL: Peer %#x unresolved for %#x\n",
-					ui->ue->peer, ui->ue->ino);
+		if ((peer->ue->uflags & USK_EXTERN) &&
+				!(opts.ext_unix_sk)) {
+			pr_err("External socket found in image. "
+					"Consider using the --" USK_EXT_PARAM " option "
+					"to allow restoring it.\n");
 			return -1;
 		}