bridge: add vlan filtering support

[ivy]

Summary

The new ifconfig options 'ifvlan', '+ifvlans' and '-ifvlans' allow the
vlan access list of a bridge port to be configured.

Incoming tagged frames will be dropped if the incoming vlan tag isn't
in the port's access list.

Outgoing frames will be dropped if the outgoing vlan ID isn't in the
port's access list (e.g., for BUM traffic).

This is only enabled if the port's pvid is set to something other than
zero, which is treated as the flag to enable vlan filtering.

[kevans]

sbin/ifconfig/ifbridge.c

161

Declaration needs to move up to the top of this block at a minimum, when someone provides more useful feedback to warrant another iteration.

[ivy]

sbin/ifconfig/ifbridge.c

161

i keep forgetting we're not allowed to do this. i'll fix it in my local branch.

[kp]

sbin/ifconfig/ifbridge.c

155

Maybe <= DOT1Q_VID_MAX ?

sys/net/if_bridge.c

1944

(Random example picked)

This might be easier if you used BITSET(9). It has macros for bitwise AND/OR/XOR/.. on the entire set at once.

[ivy]

update for new vlan filtering behaviour

[ivy]

sbin/ifconfig/ifbridge.c

155

we can't use DOT1Q_VID_* here since they're behind _KERNEL. i've been meaning to fix that and move them to a different header, but i might do that in a followup commit (and fix this at the same time) rather than adding more commits to this stack.

sys/net/if_bridge.c

1944

according to the manual page, bitset(9) isn't available to userland unless _WANT_FREEBSD_BITSET is defined, which means every userland program that includes if_bridgevar.h would have to do that. i'm not very fond of that since it makes the header unnecessarily difficult to use.

[ivy]

sbin/ifconfig/ifbridge.c

155

i decided to just do this: D50570. i'll fix this if that's approved.

[ivy]

use DOT1Q_VID_* constants consistently, now they're available to userland.

also neaten up parse_vlans() a little.

[kp]

sbin/ifconfig/ifbridge.c

766

We have three near-identical functions here. It might be worth doing something like

static void
setbridge_tagged(if_ctx *ctx, const char *ifn, const char *vlans, int cmd)
...

static void
addbridge_tagged(if_ctx *ctx, const char *ifn, const char *vlans)
{
    setbridge_tagged(ctx, ifn, vlans, BRDG_VLAN_OP_SET);
}

[ivy]

• remove some redundant code in ifconfig
• use bitset(9) for ifbvlan_set_t instead of rolling our own