networkctl: add support to delete virtual netdevs

We now don't have the support to delete netdevs and dependent
upon iproute to delete. With this we can delete via networkctl
and use in our test cases too.

Note that it supports deleting multiple links at once.

```
 sudo ./networkctl delete test1 test2 test3 test4
```

man/networkctl.xml

@@ -271,6 +271,13 @@ s - Service VLAN, m - Two-port MAC Relay (TPMR)
         </listitem>
       </varlistentry>
 
+       <varlistentry>
+        <term>
+          <command>delete</command>
+        </term>
+        <listitem><para>Deletes virtual netdevs. Takes interface name or index number.</para></listitem>
+      </varlistentry>
+
     </variablelist>
   </refsect1>
 

src/network/networkctl.c

@@ -28,6 +28,7 @@
 #include "pager.h"
 #include "parse-util.h"
 #include "pretty-print.h"
+#include "set.h"
 #include "socket-util.h"
 #include "sort-util.h"
 #include "sparse-endian.h"
@@ -1055,6 +1056,64 @@ static int link_lldp_status(int argc, char *argv[], void *userdata) {
         return 0;
 }
 
+static int link_delete_send_message(sd_netlink *rtnl, int index) {
+        _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *req = NULL;
+        int r;
+
+        assert(rtnl);
+
+        r = sd_rtnl_message_new_link(rtnl, &req, RTM_DELLINK, index);
+        if (r < 0)
+                return rtnl_log_create_error(r);
+
+        r = sd_netlink_call(rtnl, req, 0, NULL);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static int link_delete(int argc, char *argv[], void *userdata) {
+        _cleanup_(sd_netlink_unrefp) sd_netlink *rtnl = NULL;
+        _cleanup_set_free_ Set *indexes = NULL;
+        char ifname[IFNAMSIZ] = "";
+        int index, r, i;
+        Iterator j;
+
+        r = sd_netlink_open(&rtnl);
+        if (r < 0)
+                return log_error_errno(r, "Failed to connect to netlink: %m");
+
+        indexes = set_new(NULL);
+        if (!indexes)
+                return log_oom();
+
+        for (i = 1; i < argc; i++) {
+                r = parse_ifindex(argv[i], &index);
+                if (r < 0) {
+                        index = (int) if_nametoindex(argv[i]);
+                        if (index <= 0)
+                                return log_error_errno(r, "Failed to resolve interface %s", argv[i]);
+                }
+
+                r = set_put(indexes, INT_TO_PTR(index));
+                if (r < 0)
+                        return log_oom();
+        }
+
+        SET_FOREACH(index, indexes, j) {
+                r = link_delete_send_message(rtnl, index);
+                if (r < 0) {
+                        if (if_indextoname(index, ifname))
+                                return log_error_errno(r, "Failed to delete interface %s: %m", ifname);
+                        else
+                                return log_error_errno(r, "Failed to delete interface %d: %m", index);
+                }
+        }
+
+        return r;
+}
+
 static int help(void) {
         _cleanup_free_ char *link = NULL;
         int r;
@@ -1075,6 +1134,7 @@ static int help(void) {
                "  status [PATTERN...]   Show link status\n"
                "  lldp [PATTERN...]     Show LLDP neighbors\n"
                "  label                 Show current address label entries in the kernel\n"
+               "  delete DEVICES        Delete virtual netdevs\n"
                "\nSee the %s for details.\n"
                , program_invocation_short_name
                , link
@@ -1144,6 +1204,7 @@ static int networkctl_main(int argc, char *argv[]) {
                 { "status", VERB_ANY, VERB_ANY, 0,            link_status         },
                 { "lldp",   VERB_ANY, VERB_ANY, 0,            link_lldp_status    },
                 { "label",  VERB_ANY, VERB_ANY, 0,            list_address_labels },
+                { "delete", 2,        VERB_ANY, 0,            link_delete         },
                 {}
         };