Man page - resolv_wrapper(1)

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Manual

RESOLV_WRAPPER

NAME
SYNOPSIS
DESCRIPTION
ENVIRONMENT VARIABLES
EXAMPLE
AUTHOR

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) . 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) 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