.TH dns_ip6 3
.SH NAME
dns_ip6 \- find IPv6 addresses for FQDNs
.SH SYNTAX
.B #include <dns.h>

int \fBdns_ip6\fP(&\fIout\fR,&\fIfqdn\fR);
.br
int \fBdns_ip6_4mapped\fP(&\fIout\fR,&\fIfqdn\fR);
.br
int \fBdns_ip6_packet\fP(&\fIout\fR,char *\fIbuf\fR,unsigned int \fIlen\fR);

stralloc \fIout\fR = {0};
.br
stralloc \fIfqdn\fR = {0};

.SH DESCRIPTION
.B dns_ip6
looks up 16-byte IPv6 addresses for the fully-qualified domain name in
\fIfqdn\fR. It puts the concatenation of the IP addresses into \fIout\fR and returns
0. If the domain does not exist in DNS, or has no IP addresses, \fIout\fR will
be empty.

If \fBdns_ip6\fR has trouble with the DNS lookup or runs out of memory, it
returns -1, setting \fIerrno\fR appropriately. It may or may not change \fIout\fR.

If \fIfqdn\fR is a dotted-decimal IP address, \fBdns_ip6\fR converts
that IP address into IPv4-mapped IPv6 representation and puts it
into \fIout\fR without checking DNS.  Likewise, if \fIfqdn\fR is an IPv6
address, \fBdns_ip6\fR puts that address into \fIout\fR without checking
DNS.

\fBdns_ip6\fR performs IPv6 and IPv4 lookups on \fIfqdn\fR, appending
the IPv4 addresses in IPv4-mapped IPv6 representation.

.B dns_ip6_4mapped
uses \fBdns_ip4\fR and returns the addresses in IPv4-mapped IPv6
representation.

.B dns_ip6_packet
is a low-level component of \fBdns_ip6\fR, designed to support
asynchronous DNS lookups. It reads a DNS packet of length \fIlen\fR from \fIbuf\fR,
extracts IP addresses from the answer section of the packet, puts the
addresses into \fIout\fR, and returns 0 or -1 the same way as \fIdns_ip6\fR.

.SH "SEE ALSO"
dns_ip6_qualify(3), dns_ip4(3), dns_name6(3)