ip vrf: Add name_is_vrf

Add name_is_vrf function to determine if given name corresponds to a
VRF device.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>

ip/ip_common.h

@@ -90,6 +90,8 @@ struct link_util *get_link_slave_kind(const char *slave_kind);
 
 void br_dump_bridge_id(const struct ifla_bridge_id *id, char *buf, size_t len);
 
+bool name_is_vrf(const char *name);
+
 #ifndef	INFINITY_LIFE_TIME
 #define     INFINITY_LIFE_TIME      0xFFFFFFFFU
 #endif

ip/iplink_vrf.c

@@ -96,3 +96,53 @@ struct link_util vrf_slave_link_util = {
 	.print_opt	= vrf_slave_print_opt,
 	.slave          = true,
 };
+
+bool name_is_vrf(const char *name)
+{
+	struct {
+		struct nlmsghdr		n;
+		struct ifinfomsg	i;
+		char			buf[1024];
+	} req = {
+		.n = {
+			.nlmsg_len   = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
+			.nlmsg_flags = NLM_F_REQUEST,
+			.nlmsg_type  = RTM_GETLINK,
+		},
+		.i = {
+			.ifi_family  = preferred_family,
+		},
+	};
+	struct {
+		struct nlmsghdr n;
+		char buf[8192];
+	} answer;
+	struct rtattr *tb[IFLA_MAX+1];
+	struct rtattr *li[IFLA_INFO_MAX+1];
+	struct ifinfomsg *ifi;
+	int len;
+
+	addattr_l(&req.n, sizeof(req), IFLA_IFNAME, name, strlen(name) + 1);
+
+	if (rtnl_talk(&rth, &req.n, &answer.n, sizeof(answer)) < 0)
+		return false;
+
+	ifi = NLMSG_DATA(&answer.n);
+	len = answer.n.nlmsg_len - NLMSG_LENGTH(sizeof(*ifi));
+	if (len < 0) {
+		fprintf(stderr, "BUG: Invalid response to link query.\n");
+		return false;
+	}
+
+	parse_rtattr(tb, IFLA_MAX, IFLA_RTA(ifi), len);
+
+	if (!tb[IFLA_LINKINFO])
+		return false;
+
+	parse_rtattr_nested(li, IFLA_INFO_MAX, tb[IFLA_LINKINFO]);
+
+	if (!li[IFLA_INFO_KIND])
+		return false;
+
+	return strcmp(RTA_DATA(li[IFLA_INFO_KIND]), "vrf") == 0;
+}