---
name: "ng_tee"
section: "4"
platform: "linux"
package: "freebsd-manpages"
version: "6.0-5"
release: "Debian 4.0 (Etch)"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/ng_tee"
---

# ng\_tee(4)

netgraph \`\`tee'' node type

## NAME

**ng\_tee** – netgraph \`\`tee'' node type

## SYNOPSIS

**#include \<sys/types.h\>**

**#include \<netgraph/ng\_tee.h\>**

## DESCRIPTION

The **tee** node type has a purpose similar to the [tee(1)](/tee/1.md) command. **Tee** nodes are useful for debugging or “snooping” on a connection between two netgraph nodes. **Tee** nodes have four hooks, right, left, right2left, and left2right. All data received on right is sent unmodified to *both* hooks left and right2left. Similarly, all data received on left is sent unmodified to both right and left2right.

Packets may also be received on right2left and left2right; if so, they are forwarded unchanged out hooks right and left, respectively.

## HOOKS

This node type supports the following hooks:

- right

  The connection to the node on the right.

- left

  The connection to the node on the left.

- right2left

  Tap for right to left traffic.

- left2right

  Tap for left to right traffic.

## CONTROL MESSAGES

This node type supports the generic control messages, plus the following.

- NGM\_TEE\_GET\_STATS

  Get statistics, returned as a struct ng\_tee\_stats.

- NGM\_TEE\_CLR\_STATS

  Clear statistics.

## SHUTDOWN

This node shuts down upon receipt of an NGM\_SHUTDOWN control message, or when all hooks have been disconnected. If both right and left hooks are present, node removes itself from the chain gently, connecting right and left together.

## SEE ALSO

[tee(1)](/tee/1.md), [netgraph(4)](/netgraph/4.md), [ngctl(8)](/ngctl/8.md)

## HISTORY

The **ng\_tee** node type was implemented in FreeBSD 4.0.

## AUTHORS

Julian Elischer ⟨julian@FreeBSD.org⟩