---
name: "resolv_wrapper"
section: "1"
platform: "linux"
package: "libresolv-wrapper"
version: "1.1.8-3"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/resolv_wrapper"
---

# resolv\_wrapper(1)

A wrapper for dns name resolving or dns faking.

## NAME

resolv\_wrapper - A wrapper for dns name resolving or dns faking.

## SYNOPSIS

LD\_PRELOAD=libresolv\_wrapper.so RESOLV\_WRAPPER\_CONF="/path/to/resolv.conf" **./myapplication**

## DESCRIPTION

resolv\_wrapper makes it possible on most UNIX platforms to contact your own DNS implementation in your test environment. It requires socket\_wrapper to be able to contact it. If it doesn’t work on a special platform the wrapper is able to fake DNS queries and return valid responses to your application.

• Redirects name queries to the nameservers specified in your resolv.conf

• Can fake DNS queries using a simple formatted DNS hosts file.

## ENVIRONMENT VARIABLES

**RESOLV\_WRAPPER\_CONF**

This is used to specify the resolv.conf to use. The format of the resolv.conf file is defined in the manpage *[resolv.conf(5)](/resolv.conf/5.md)*. Currently only the **namserver** directive is supported.

In order that this works with socket\_wrapper. The res\_\* symbols need to be in a separate libresolv library. If they are part of libc this wont work. This is the case with glibc \>= 2.34.

**RESOLV\_WRAPPER\_HOSTS**

This environment variable is used for faking DNS queries. It must point to a hosts-like text file that specifies fake records for custom queries. The format of the file looks like this:

```
TYPE    RECORD_NAME RECORD_VALUE
```

For example:

```
A       dc.cwrap.org 127.0.0.10
AAAA    dc.cwrap.org fd00::5357:5f0a
CNAME   kerberos.cwrap.org dc.cwrap.org
SRV     _kerberos._tcp.cwrap.org kerberos.cwrap.org 88
URI     _vpn.cwrap.org https://vpn.cwrap.org/VPN
TXT     cwrap.org v=spf1 mx
```

**RESOLV\_WRAPPER\_DEBUGLEVEL**

If you need to see what is going on in resolv\_wrapper itself or try to find a bug, you can enable logging support in resolv\_wrapper if you built it with debug symbols.

• 0 = ERROR

• 1 = WARNING

• 2 = DEBUG

• 3 = TRACE

**RESOLV\_WRAPPER\_DISABLE\_DEEPBIND**

This allows you to disable deep binding in resolv\_wrapper. This is useful for running valgrind tools or sanitizers like (address, undefined, thread).

## EXAMPLE

The following command would trick *[kinit(1)](/kinit/1.md)* into using DNS servers from "./resolv.conf" for Kerberos service resolution:

```
$ LD_PRELOAD=libresolv_wrapper.so RESOLV_WRAPPER_CONF="./resolv.conf" kinit user@EXAMPLE.COM
```

## AUTHOR

The Samba Team