iplink: support for WWAN devices

The WWAN subsystem has been extended to generalize the per data channel
network interfaces management. This change implements support for WWAN
links handling. And actively uses the earlier introduced ip-link
capability to specify the parent by its device name.

The WWAN interface for a new data channel should be created with a
command like this:

ip link add dev wwan0-2 parentdev wwan0 type wwan linkid 2

Where: wwan0 is the modem HW device name (should be taken from
/sys/class/wwan) and linkid is an identifier of the opened data
channel.

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Signed-off-by: David Ahern <dsahern@kernel.org>

ip/Makefile

@@ -11,7 +11,7 @@ IPOBJ=ip.o ipaddress.o ipaddrlabel.o iproute.o iprule.o ipnetns.o \
     iplink_bridge.o iplink_bridge_slave.o ipfou.o iplink_ipvlan.o \
     iplink_geneve.o iplink_vrf.o iproute_lwtunnel.o ipmacsec.o ipila.o \
     ipvrf.o iplink_xstats.o ipseg6.o iplink_netdevsim.o iplink_rmnet.o \
-    ipnexthop.o ipmptcp.o iplink_bareudp.o
+    ipnexthop.o ipmptcp.o iplink_bareudp.o iplink_wwan.o
 
 RTMONOBJ=rtmon.o
 

ip/iplink.c

@@ -56,7 +56,8 @@ void iplink_types_usage(void)
 		"          ipip | ipoib | ipvlan | ipvtap |\n"
 		"          macsec | macvlan | macvtap |\n"
 		"          netdevsim | nlmon | rmnet | sit | team | team_slave |\n"
-		"          vcan | veth | vlan | vrf | vti | vxcan | vxlan | xfrm }\n");
+		"          vcan | veth | vlan | vrf | vti | vxcan | vxlan | wwan |\n"
+		"          xfrm }\n");
 }
 
 void iplink_usage(void)

ip/iplink_wwan.c

@@ -0,0 +1,72 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <stdio.h>
+#include <linux/netlink.h>
+#include <linux/wwan.h>
+
+#include "utils.h"
+#include "ip_common.h"
+
+static void print_explain(FILE *f)
+{
+	fprintf(f,
+		"Usage: ... wwan linkid LINKID\n"
+		"\n"
+		"Where: LINKID := 0-4294967295\n"
+	);
+}
+
+static void explain(void)
+{
+	print_explain(stderr);
+}
+
+static int wwan_parse_opt(struct link_util *lu, int argc, char **argv,
+			  struct nlmsghdr *n)
+{
+	while (argc > 0) {
+		if (matches(*argv, "linkid") == 0) {
+			__u32 linkid;
+
+			NEXT_ARG();
+			if (get_u32(&linkid, *argv, 0))
+				invarg("linkid", *argv);
+			addattr32(n, 1024, IFLA_WWAN_LINK_ID, linkid);
+		} else if (matches(*argv, "help") == 0) {
+			explain();
+			return -1;
+		} else {
+			fprintf(stderr, "wwan: unknown command \"%s\"?\n",
+				*argv);
+			explain();
+			return -1;
+		}
+		argc--, argv++;
+	}
+
+	return 0;
+}
+
+static void wwan_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
+{
+	if (!tb)
+		return;
+
+	if (tb[IFLA_WWAN_LINK_ID])
+		print_uint(PRINT_ANY, "linkid", "linkid %u ",
+			   rta_getattr_u32(tb[IFLA_WWAN_LINK_ID]));
+}
+
+static void wwan_print_help(struct link_util *lu, int argc, char **argv,
+			    FILE *f)
+{
+	print_explain(f);
+}
+
+struct link_util wwan_link_util = {
+	.id		= "wwan",
+	.maxattr	= IFLA_WWAN_MAX,
+	.parse_opt	= wwan_parse_opt,
+	.print_opt	= wwan_print_opt,
+	.print_help	= wwan_print_help,
+};