NG_VLAN(4)

💅 NG_VLAN(4) — the ng_vlan manual, bestie edition 🎀

okay so this is from the Kernel Interfaces Manual, section 4, and it's literally all about ng_vlan — the IEEE 802.1Q VLAN tagging netgraph node type. yes bestie, netgraph. we're doing this. sit down, grab a strawberry 🍓, it's gonna slay.

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✨ NAME ✨

ng_vlan — the IEEE 802.1Q VLAN tagging netgraph node type 🦋

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✨ SYNOPSIS ✨

#include <sys/types.h>
#include <netgraph.h>
#include <netgraph/ng_vlan.h>

like, just include these three and you're in, no cap 💜

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✨ DESCRIPTION ✨

The vlan node type multiplexes frames tagged according to the IEEE 802.1Q standard between different hooks. that's the whole vibe — it's a little traffic director for tagged frames 🌈

Every node has two special hooks, downstream and nomatch, plus an arbitrary number of “vlan” hooks, and each one of those is associated with a particular VLAN tag. so it's like the main character node with two besties and then a whole group chat of vlan hooks 💅

here's the tea on how frames flow:

• An ETHERTYPE_VLAN frame that shows up on the downstream hook with a tag the node has been configured to filter gets sent out the corresponding “vlan” hook. slay, matched ✨
• If it does not match any of the configured tags, or it isn't of type ETHERTYPE_VLAN, it gets sent out the nomatch hook instead. not me just yeeting it to nomatch 🙈
• real talk though: if the nomatch hook is not connected, the packet is dropped. 💀 gone. no forwarding, no rescue. keep that in mind.

and the other direction:

• An Ethernet frame received on the nomatch hook is passed unmodified to the downstream hook. untouched, iconic, no glow-up needed 🫶
• An Ethernet frame received on any of the “vlan” hooks gets tagged accordingly and sent out the downstream hook. now it's got a little tag, look at it go 🎀

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✨ HOOKS ✨

This node type supports the following hooks:

• downstream — typically this hook would be connected to a ng_ether(4) node, using the lower hook. that's the classic setup 🦋
• nomatch — typically this hook would also be connected to a ng_ether(4) type node, but using the upper hook this time. see what they did there 👑
• ⟨any valid name⟩ — any other hook name will be accepted and should later be associated with a particular tag. typically this hook would be attached to a ng_eiface(4) type node using the ether hook. name it whatever you want bestie, it's yours 💖

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✨ CONTROL MESSAGES ✨

This node type supports the generic control messages, plus the following. all three are giving very much "manage your filters" energy:

• NGM_VLAN_ADD_FILTER (also known as addfilter) — associates a hook with the tag. match made in heaven, periodt 💍
• NGM_VLAN_DEL_FILTER (also known as delfilter) — disassociates a hook from the tag. it's giving breakup era 😭
• NGM_VLAN_GET_TABLE (also known as gettable) — returns a table of all hook/tag associations. the receipts, literally 🧾

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✨ EXAMPLES ✨ 🍓

here's a whole little shell script, copy it exactly, don't @ me:

#!/bin/sh

ETHER_IF=rl0

ngctl -f- <<EOF
shutdown ${ETHER_IF}:
mkpeer ${ETHER_IF}: vlan lower downstream
name ${ETHER_IF}:lower vlan
connect ${ETHER_IF}: vlan: upper nomatch
EOF

ngctl mkpeer vlan: eiface vlan123 ether
ngctl msg vlan: addfilter '{ vlan=123 hook="vlan123" }'

look at that heredoc. the way that ngctl -f- <<EOF eats. 💅✨

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✨ SHUTDOWN ✨

This node shuts down upon receipt of a NGM_SHUTDOWN control message, or when all hooks have been disconnected. so either way, it knows when to leave the party 🫶 no dramatic exit needed.

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✨ SEE ALSO ✨

netgraph(4), ng_eiface(4), ng_ether(4), ngctl(8), nghook(8) — go read these too, iykyk 💜

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✨ HISTORY ✨

The ng_vlan node type appeared in FreeBSD 4.10. vintage, honestly 👑

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✨ AUTHORS ✨

Ruslan Ermilov <ru@FreeBSD.org> — thank you for your service, king 🫡🌸

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and that's the whole page bestie!! 🌈 this one came from Debian, dated March 1, 2004 — yes it's older than most of us, and it's still iconic. mwah 💋🎀✨