ip link: Fix vlan proto, closes 8261 and 11638

The proto has to be passed in network byte-order.
While at it allow for
 ip link add link eth0 name eth0.2.24 type vlan proto 802.1ad id 24
 ip link del link eth0 name eth0.2.24 type vlan proto 802.1ad id 24
The del was lacking a dev_str and thus errored out. Fix by using
name/dev counterpart as fallback.

The proto identifier 802.1Q was not recognized, just it's lowercase
variant, fix that too.

function                                             old     new   delta
do_add_or_delete                                    1275    1376    +101
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/0 up/down: 101/0)             Total: 101 bytes

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

networking/libiproute/iplink.c

@@ -518,11 +518,11 @@ static void vlan_parse_opt(char **argv, struct nlmsghdr *n, unsigned int size)
 			id = get_u16(*argv, "id");
 			addattr_l(n, size, IFLA_VLAN_ID, &id, sizeof(id));
 		} else if (arg == ARG_protocol) {
-			arg = index_in_substrings(protocols, *argv);
+			arg = index_in_substrings(protocols, str_tolower(*argv));
 			if (arg == PROTO_8021Q)
-				proto = ETH_P_8021Q;
+				proto = htons(ETH_P_8021Q);
 			else if (arg == PROTO_8021AD)
-				proto = ETH_P_8021AD;
+				proto = htons(ETH_P_8021AD);
 			else
 				bb_error_msg_and_die("unknown VLAN encapsulation protocol '%s'",
 								     *argv);
@@ -673,13 +673,19 @@ static int do_add_or_delete(char **argv, const unsigned rtm)
 
 		linkinfo->rta_len = (void *)NLMSG_TAIL(&req.n) - (void *)linkinfo;
 	}
+	/* Allow "ip link add dev" and "ip link add name" */
+	if (!name_str)
+		name_str = dev_str;
+	else if (!dev_str)
+		dev_str = name_str;
+	/* else if (!strcmp(name_str, dev_str))
+		name_str = dev_str; */
+
 	if (rtm != RTM_NEWLINK) {
 		if (!dev_str)
 			return 1; /* Need a device to delete */
 		req.i.ifi_index = xll_name_to_index(dev_str);
 	} else {
-		if (!name_str)
-			name_str = dev_str;
 		if (link_str) {
 			int idx = xll_name_to_index(link_str);
 			addattr_l(&req.n, sizeof(req), IFLA_LINK, &idx, 4);