---
name: "dns_ip6_qualify"
section: "3diet"
platform: "linux"
package: "libowfat-dev"
version: "0.28-2"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/dns_ip6_qualify/3diet"
---

# dns\_ip6\_qualify(3diet)

qualify name and look up IPv6 addresses

## NAME

dns\_ip6\_qualify - qualify name and look up IPv6 addresses

## SYNTAX

**#include \<dns.h\>**

int **dns\_ip6\_qualify**(stralloc\* *out*,stralloc\* *fqdn*,\
                     const stralloc\* *udn*);

## DESCRIPTION

dns\_ip6\_qualify feeds the name *udn* through qualification and looks up 16-byte IPv6 addresses for the result. It puts the fully qualified domain name into *fqdn*, puts the concatenation of the IP addresses into *out*, and returns 0. If the domain does not exist in DNS, or has no IP addresses, *out* will be empty.

dns\_ip6\_qualify also looks up 4-byte IPv4 addresses and converts them into IPv4-mapped IPv6 addresses (::ffff:1.2.3.4) to provide easy backwards compatibility for IPv6 applications.

If dns\_ip6\_qualify has trouble with the qualification, has trouble with DNS, or runs out of memory, it returns -1, setting errno appropriately. It may or may not change *out* and *fqdn*.

## QUALIFICATION

See http://cr.yp.to/djbdns/qualification.html

## SEE ALSO

[dns\_ip6(3)](/dns_ip6/3.md), [dns\_ip6\_packet(3)](/dns_ip6_packet/3.md), [dns\_ip4\_qualify(3)](/dns_ip4_qualify/3.md)