Add ability to set link state with ip

Exposes existing netlink operations to modify link state of devices.

ip/ip_common.h

+extern int get_operstate(const char *name);
 extern int print_linkinfo(const struct sockaddr_nl *who,
 			  struct nlmsghdr *n,
 			  void *arg);

ip/ipaddress.c

@@ -131,6 +131,16 @@ static void print_operstate(FILE *f, __u8 state)
 		fprintf(f, "state %s ", oper_states[state]);
 }
 
+int get_operstate(const char *name)
+{
+	int i;
+
+	for (i = 0; i < sizeof(oper_states)/sizeof(oper_states[0]); i++)
+		if (strcasecmp(name, oper_states[i]) == 0)
+			return i;
+	return -1;
+}
+
 static void print_queuelen(FILE *f, struct rtattr *tb[IFLA_MAX + 1])
 {
 	int qlen;

ip/iplink.c

@@ -437,6 +437,14 @@ int iplink_parse(int argc, char **argv, struct iplink_req *req,
 			if (mode < 0)
 				invarg("Invalid link mode\n", *argv);
 			addattr8(&req->n, sizeof(*req), IFLA_LINKMODE, mode);
+		} else if (strcmp(*argv, "state") == 0) {
+			int state;
+			NEXT_ARG();
+			state = get_operstate(*argv);
+			if (state < 0)
+				invarg("Invalid operstate\n", *argv);
+
+			addattr8(&req->n, sizeof(*req), IFLA_OPERSTATE, state);
 		} else {
 			if (strcmp(*argv, "dev") == 0) {
 				NEXT_ARG();

man/man8/ip-link.8

@@ -103,6 +103,9 @@ ip-link \- network device configuration
 .B mode
 .IR LINKMODE " |"
 .br
+.B state
+.IR LINKSTATE " |"
+.br
 .B master
 .IR DEVICE
 .br
@@ -259,6 +262,10 @@ the device will transistion to when it is brought up. Setting
 mode changes the behaviour so that device goes into DORMANT state instead
 of UP when driver is ready.
 
+.TP
+.BI state " LINKSTATE"
+allows setting the operational link state. The values (defined in RFC2863)
+are: UP, DOWN, TESTING, UNKNOWN, DORMANT, NOTPRESENT, LOWERLAYERDOWN.
 .TP
 .BI alias " NAME"
 give the device a symbolic name for easy reference.