---
name: "ipq_set_mode"
section: "3"
platform: "linux"
package: "iptables"
version: "1:1.8.13-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/ipq_set_mode"
---

# ipq\_set\_mode(3)

set the ip\_queue queuing mode

## NAME

ipq\_set\_mode — set the ip\_queue queuing mode

## SYNOPSIS

**#include \<linux/netfilter.h\>**\
 **#include \<libipq.h\>**

**int ipq\_set\_mode(const struct ipq\_handle \****h***, uint8\_t** *mode***, size\_t** *range***);**

## DESCRIPTION

The **ipq\_set\_mode** function sends a message to the kernel ip\_queue module, specifying whether packet metadata only, or packet payloads as well as metadata should be copied to userspace.

The *h* parameter is a context handle which must previously have been returned  successfully from a call to **ipq\_create\_handle**.

The *mode* parameter must be one of:

- **IPQ\_COPY\_META**

  Copy only packet metadata to userspace.

- **IPQ\_COPY\_PACKET**

  Copy packet metadata and packet payloads to userspace.

The *range* parameter is used to specify how many bytes of the payload to copy to userspace.  It is only valid for **IPQ\_COPY\_PACKET** mode and is otherwise ignored.  The maximum useful value for *range* is 65535 (greater values will be clamped to this by ip\_queue).

**ipq\_set\_mode** is usually used immediately following **ipq\_create\_handle** to enable the flow of packets to userspace.

Note that as the underlying Netlink messaging transport is connectionless, the ip\_queue module does not know that a userspace application is ready to communicate until it receives a message such as this.

## RETURN VALUE

On failure, -1 is returned.\
 On success, a non-zero positive value is returned.

## ERRORS

On failure, a descriptive error message will be available via the **ipq\_errstr** function.

## DIAGNOSTICS

A relatively common failure may occur if the ip\_queue module is not loaded. In this case, the following code excerpt:

```
status = ipq_set_mode(h, IPQ_COPY_META, 0);
if (status < 0) {
	ipq_perror("myapp");
	ipq_destroy_handle(h);
	exit(1);
}
```

would generate the following output:

*myapp: Failed to send netlink message: Connection refused*

## BUGS

None known.

## AUTHOR

James Morris \<jmorris@intercode.com.au\>

## COPYRIGHT

Copyright (c) 2000-2001 Netfilter Core Team.

Distributed under the GNU General Public License.

## SEE ALSO

[**libipq**(3)](/libipq/3.md), [**iptables**(8)](/iptables/8.md).