---
name: "ng_ipfw"
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_ipfw"
---

# ng\_ipfw(4)

interface between netgraph and IP firewall

## NAME

**ng\_ipfw** – interface between netgraph and IP firewall

## SYNOPSIS

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

## DESCRIPTION

The **ipfw** node implements interface between [ipfw(4)](/ipfw/4.md) and [netgraph(4)](/netgraph/4.md) subsystems.

## HOOKS

The **ipfw** node supports an arbitrary number of hooks, which must be named using only numeric characters.

## OPERATION

Once the **ng\_ipfw** module is loaded into the kernel, a single node named *ipfw* is automatically created. No more **ipfw** nodes can be created. Once destroyed, the only way to recreate the node is to reload the **ng\_ipfw** module.

Packets can be injected into [netgraph(4)](/netgraph/4.md) using either the **netgraph** or **ngtee** commands of the [ipfw(8)](/ipfw/8.md) utility. These commands require a numeric cookie to be supplied as an argument. Packets are sent out of the hook whose name equals the cookie value. If no hook matches, packets are discarded. Packets injected via the **netgraph** command are tagged with *struct ng\_ipfw\_tag*. This tag contains information that helps the packet to re-enter [ipfw(4)](/ipfw/4.md) processing, should the packet come back from [netgraph(4)](/netgraph/4.md) to [ipfw(4)](/ipfw/4.md).

```
struct ng_ipfw_tag {
	struct m_tag	mt;		/* tag header */
	struct ip_fw	*rule;		/* matching rule */
        struct ifnet	*ifp;		/* interface, for ip_output */
	int		dir;		/* packet direction */
#define	NG_IPFW_OUT	0
#define	NG_IPFW_IN	1
	int		flags;		/* flags, for ip_output() */
};
```

Packets received by a node from [netgraph(4)](/netgraph/4.md) must be tagged with *struct ng\_ipfw\_tag* tag. Packets re-enter IP firewall processing at the next rule. If no tag is supplied, packets are discarded.

## CONTROL MESSAGES

This node type supports only the generic control messages.

## SHUTDOWN

This node shuts down upon receipt of a NGM\_SHUTDOWN control message. Do not do this, since the new **ipfw** node can only be created by reloading the **ng\_ipfw** module.

## SEE ALSO

[ipfw(4)](/ipfw/4.md), [netgraph(4)](/netgraph/4.md), [ipfw(8)](/ipfw/8.md), [mbuf\_tags(9)](/mbuf_tags/9.md)

## HISTORY

The **ipfw** node type was implemented in FreeBSD 6.0.

## AUTHORS

The **ipfw** node was written by Gleb Smirnoff ⟨glebius@FreeBSD.org⟩.