ip link: Allow to filter devices by master dev

Added 'master' option to 'ip link show' command
to filter devices by master dev.
Signed-off-by: Vadim Kochan <vadim4j@gmail.com>

ip/ipaddress.c

@@ -56,6 +56,7 @@ static struct
 	int flushp;
 	int flushe;
 	int group;
+	int master;
 } filter;
 
 static int do_link;
@@ -542,6 +543,14 @@ int print_linkinfo(const struct sockaddr_nl *who,
 			return -1;
 	}
 
+	if (tb[IFLA_MASTER]) {
+		int master = *(int*)RTA_DATA(tb[IFLA_MASTER]);
+		if (filter.master > 0 && master != filter.master)
+			return -1;
+	}
+	else if (filter.master > 0)
+		return -1;
+
 	if (n->nlmsg_type == RTM_DELLINK)
 		fprintf(fp, "Deleted ");
 
@@ -1277,6 +1286,13 @@ static int ipaddr_list_flush_or_save(int argc, char **argv, int action)
 			NEXT_ARG();
 			if (rtnl_group_a2n(&filter.group, *argv))
 				invarg("Invalid \"group\" value\n", *argv);
+		} else if (strcmp(*argv, "master") == 0) {
+			int ifindex;
+			NEXT_ARG();
+			ifindex = ll_name_to_index(*argv);
+			if (!ifindex)
+				invarg("Device does not exist\n", *argv);
+			filter.master = ifindex;
 		} else {
 			if (strcmp(*argv, "dev") == 0) {
 				NEXT_ARG();

ip/iplink.c

@@ -82,7 +82,7 @@ void iplink_usage(void)
 	fprintf(stderr, "			  [ master DEVICE ]\n");
 	fprintf(stderr, "			  [ nomaster ]\n");
 	fprintf(stderr, "			  [ addrgenmode { eui64 | none } ]\n");
-	fprintf(stderr, "       ip link show [ DEVICE | group GROUP ] [up]\n");
+	fprintf(stderr, "       ip link show [ DEVICE | group GROUP ] [up] [master DEV]\n");
 
 	if (iplink_have_newlink()) {
 		fprintf(stderr, "       ip link help [ TYPE ]\n");

man/man8/ip-link.8.in

@@ -145,9 +145,10 @@ ip-link \- network device configuration
 .B ip link show
 .RI "[ " DEVICE " | "
 .B group
-.IR GROUP " |"
-.B up
-]
+.IR GROUP " | "
+.BR up " | "
+.B master
+.IR DEVICE " ]"
 
 .SH "DESCRIPTION"
 .SS ip link add - add virtual link
@@ -678,6 +679,11 @@ specifies what group of devices to show.
 .B up
 only display running interfaces.
 
+.TP
+.BI master " DEVICE "
+.I DEVICE
+specifies the master device which enslaves devices to show.
+
 The show command has additional formatting options:
 
 .TP