I went looking at -current's source to see which ethernet drivers
supported which ethercap bits.  Grepping for ETHERCAP in dev/sbus
turned up only one hit, be.c.  But one line looked odd:

	            len > ETHER_MAX_LEN + ETHERCAP_VLAN_MTU) {

Looking at the context, I find

	        if (len <= sizeof(struct ether_header) ||
	            len > ETHER_MAX_LEN + ETHERCAP_VLAN_MTU) {
	#ifdef BEDEBUG
...
	#endif
	                ifp->if_ierrors++;
	                return;
	        }

This doesn't look right to me.  Surely it should be
ETHER_VLAN_ENCAP_LEN, not ETHERCAP_VLAN_MTU?

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