well this is odd.
altq(4) clearly *indicates* that cxgbe(4) is supported.
"There were error(s) loading the rules: pfctl: cxgbe1: driver does not support altq - The line in question reads [0]:
2018-02-06 08:55:55"@¶
info ...
dmesg | grep cxgbe1
cxgbe1: <port 1> on t4nex0
cxgbe1: Ethernet address: 00:07:43:CA:BE:EF
cxgbe1: 12 txq, 8 rxq (NIC); 8 txq, 2 rxq (TOE)
cxgbe1: tso4 disabled due to -txcsum.
cxgbe1: enable txcsum first.
cxgbe1: cxgbe_media_change unimplemented.
cxgbe1: link state changed to DOWN
cxgbe1: link state changed to UP
ifconfig cxgbe1
cxgbe1: flags=8a43<UP,BROADCAST,RUNNING,ALLMULTI,SIMPLEX,MULTICAST> metric 0 mtu 9000
options=ec00b8<VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,VLAN_HWTSO,LINKSTATE,RXCSUM_IPV6,TXCSUM_IPV6>
ether 00:07:43:CA:BE:EF
hwaddr 00:07:43:CA:BE:EF
inet6 fe80::123:45ff:fe14:beef%cxgbe1 prefixlen 64 scopeid 0x4
inet 111.111.111.111 netmask 0xffffffff broadcast 111.111.111.111
inet 10.10.10.1 netmask 0xffffffff broadcast 10.10.10.1
nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
media: Ethernet 10Gbase-Twinax <full-duplex>
status: active