[iproute2,rfc,1/2] ip: add support for alternative name addition/deletion/list

diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index d36919fb4024..2386a3e94082 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -167,6 +167,9 @@  enum {
 	IFLA_NEW_IFINDEX,
 	IFLA_MIN_MTU,
 	IFLA_MAX_MTU,
+	IFLA_ALT_IFNAME_MOD, /* Alternative ifname to add/delete */
+	IFLA_ALT_IFNAME_LIST, /* nest */
+	IFLA_ALT_IFNAME, /* Alternative ifname */
 	__IFLA_MAX
 };
 
diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index 358e83ee134d..38a4f5b55e17 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -164,6 +164,13 @@  enum {
 	RTM_GETNEXTHOP,
 #define RTM_GETNEXTHOP	RTM_GETNEXTHOP
 
+	RTM_NEWALTIFNAME = 108,
+#define RTM_NEWALTIFNAME	RTM_NEWALTIFNAME
+	RTM_DELALTIFNAME,
+#define RTM_DELALTIFNAME	RTM_DELALTIFNAME
+	RTM_GETALTIFNAME,
+#define RTM_GETALTIFNAME	RTM_GETALTIFNAME
+
 	__RTM_MAX,
 #define RTM_MAX		(((__RTM_MAX + 3) & ~3) - 1)
 };
diff --git a/include/utils.h b/include/utils.h
index 794d36053634..2dd6443fc6ff 100644
--- a/include/utils.h
+++ b/include/utils.h
@@ -196,6 +196,7 @@  void duparg(const char *, const char *) __attribute__((noreturn));
 void duparg2(const char *, const char *) __attribute__((noreturn));
 int nodev(const char *dev);
 int check_ifname(const char *);
+int check_altifname(const char *);
 int get_ifname(char *, const char *);
 const char *get_ifname_rta(int ifindex, const struct rtattr *rta);
 bool matches(const char *prefix, const char *string);
diff --git a/ip/ipaddress.c b/ip/ipaddress.c
index bc8f5ba13c33..8060161dcf1a 100644
--- a/ip/ipaddress.c
+++ b/ip/ipaddress.c
@@ -1139,6 +1139,20 @@  int print_linkinfo(struct nlmsghdr *n, void *arg)
 		close_json_array(PRINT_JSON, NULL);
 	}
 
+	if (tb[IFLA_ALT_IFNAME_LIST]) {
+		struct rtattr *i, *alt_ifname_list = tb[IFLA_ALT_IFNAME_LIST];
+		int rem = RTA_PAYLOAD(alt_ifname_list);
+
+		open_json_array(PRINT_JSON, "altifnames");
+		for (i = RTA_DATA(alt_ifname_list); RTA_OK(i, rem);
+		     i = RTA_NEXT(i, rem)) {
+			print_nl();
+			print_string(PRINT_ANY, NULL,
+				     "    altname %s", rta_getattr_str(i));
+		}
+		close_json_array(PRINT_JSON, NULL);
+	}
+
 	print_string(PRINT_FP, NULL, "%s", "\n");
 	fflush(fp);
 	return 1;
diff --git a/ip/iplink.c b/ip/iplink.c
index 212a088535da..45f975f1dce9 100644
--- a/ip/iplink.c
+++ b/ip/iplink.c
@@ -1617,6 +1617,84 @@  static int iplink_afstats(int argc, char **argv)
 	return 0;
 }
 
+static int iplink_altname_mod(int argc, char **argv, struct iplink_req *req)
+{
+	char *name = NULL;
+	char *dev = NULL;
+
+	while (argc > 0) {
+		if (matches(*argv, "name") == 0) {
+			NEXT_ARG();
+			if (check_altifname(*argv))
+				invarg("not a valid altifname", *argv);
+			name = *argv;
+		} else if (matches(*argv, "help") == 0) {
+			usage();
+		} else {
+			if (strcmp(*argv, "dev") == 0)
+				NEXT_ARG();
+			if (dev)
+				duparg2("dev", *argv);
+			if (check_altifname(*argv))
+				invarg("\"dev\" not a valid altifname", *argv);
+			dev = *argv;
+		}
+		argv++; argc--;
+	}
+
+	if (!dev) {
+		fprintf(stderr, "Not enough of information: \"dev\" argument is required.\n");
+		exit(-1);
+	}
+
+	if (!name) {
+		if (req->n.nlmsg_type != RTM_NEWALTIFNAME) {
+			name = dev;
+		} else {
+			fprintf(stderr, "Not enough of information: \"name\" argument is required.\n");
+			exit(-1);
+		}
+	}
+
+	addattr_l(&req->n, sizeof(*req), IFLA_ALT_IFNAME,
+		  dev, strlen(dev) + 1);
+	addattr_l(&req->n, sizeof(*req), IFLA_ALT_IFNAME_MOD,
+		  name, strlen(name) + 1);
+
+	if (rtnl_talk(&rth, &req->n, NULL) < 0)
+		return -2;
+
+	return 0;
+}
+
+static int iplink_altname(int argc, char **argv)
+{
+	struct iplink_req req = {
+		.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
+		.n.nlmsg_flags = NLM_F_REQUEST,
+		.i.ifi_family = preferred_family,
+	};
+
+	if (argc <= 0) {
+		usage();
+		exit(-1);
+	}
+
+	if (matches(*argv, "add") == 0) {
+		req.n.nlmsg_flags |= NLM_F_EXCL | NLM_F_CREATE | NLM_F_APPEND;
+		req.n.nlmsg_type = RTM_NEWALTIFNAME;
+	} else if (matches(*argv, "del") == 0) {
+		req.n.nlmsg_flags |= RTM_DELLINK;
+		req.n.nlmsg_type = RTM_DELALTIFNAME;
+	} else if (matches(*argv, "help") == 0) {
+		usage();
+	} else {
+		fprintf(stderr, "Operator required\n");
+		exit(-1);
+	}
+	return iplink_altname_mod(argc - 1, argv + 1, &req);
+}
+
 static void do_help(int argc, char **argv)
 {
 	struct link_util *lu = NULL;
@@ -1674,6 +1752,9 @@  int do_iplink(int argc, char **argv)
 		return 0;
 	}
 
+	if (matches(*argv, "altname") == 0)
+		return iplink_altname(argc-1, argv+1);
+
 	if (matches(*argv, "help") == 0) {
 		do_help(argc-1, argv+1);
 		return 0;
diff --git a/lib/utils.c b/lib/utils.c
index 9ea21fa16503..80e025e96a5a 100644
--- a/lib/utils.c
+++ b/lib/utils.c
@@ -824,14 +824,10 @@  int nodev(const char *dev)
 	return -1;
 }
 
-int check_ifname(const char *name)
+static int __check_ifname(const char *name)
 {
-	/* These checks mimic kernel checks in dev_valid_name */
 	if (*name == '\0')
 		return -1;
-	if (strlen(name) >= IFNAMSIZ)
-		return -1;
-
 	while (*name) {
 		if (*name == '/' || isspace(*name))
 			return -1;
@@ -840,6 +836,19 @@  int check_ifname(const char *name)
 	return 0;
 }
 
+int check_ifname(const char *name)
+{
+	/* These checks mimic kernel checks in dev_valid_name */
+	if (strlen(name) >= IFNAMSIZ)
+		return -1;
+	return __check_ifname(name);
+}
+
+int check_altifname(const char *name)
+{
+	return __check_ifname(name);
+}
+
 /* buf is assumed to be IFNAMSIZ */
 int get_ifname(char *buf, const char *name)
 {