[slam] Eliminate variable-length stack allocation

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/net/udp/slam.c

 static int slam_parse_multicast_address ( struct slam_request *slam,
 					  const char *path,
 					  struct sockaddr_in *address ) {
-	char path_dup[ strlen ( path ) /* no +1 */ ];
+	char *path_dup;
 	char *sep;
 	char *end;
+	int rc;
 
 	/* Create temporary copy of path, minus the leading '/' */
 	assert ( *path == '/' );
-	memcpy ( path_dup, ( path + 1 ) , sizeof ( path_dup ) );
+	path_dup = strdup ( path + 1 );
+	if ( ! path_dup ) {
+		rc = -ENOMEM;
+		goto err_strdup;
+	}
 
 	/* Parse port, if present */
 	sep = strchr ( path_dup, ':' );
 		if ( *end != '\0' ) {
 			DBGC ( slam, "SLAM %p invalid multicast port "
 			       "\"%s\"\n", slam, sep );
-			return -EINVAL;
+			rc = -EINVAL;
+			goto err_port;
 		}
 	}
 
 	if ( inet_aton ( path_dup, &address->sin_addr ) == 0 ) {
 		DBGC ( slam, "SLAM %p invalid multicast address \"%s\"\n",
 		       slam, path_dup );
-		return -EINVAL;
+		rc = -EINVAL;
+		goto err_addr;
 	}
 
-	return 0;
+	/* Success */
+	rc = 0;
+
+ err_addr:
+ err_port:
+	free ( path_dup );
+ err_strdup:
+	return rc;
 }
 
 /**