.Dd December 13, 2021
.Dt GETDNSCOFIG 2
.Os
.Sh NAME
.Nm getdnsconfig ,
.Nm setdnsconfig
.Nd get and set the kernel DNS resolver list
.Sh SYNOPSIS
.In sys/dnsconfig.h
.Fd #define DNSCONFIG_MAX_SERVERS 3
.Ft int
.Fn getdnsconfig "struct dnsconfig *cfg"
.Ft int
.Fn getdnsconfig "const struct dnsconfig *cfg"
.Sh DESCRIPTION
.Fn getdnsconfig
gets and
.Fn setdnsconfig
sets the kernel DNS resolver list.
.Pp
.Fa cfg
points to a
.Vt struct dnsconfig
structure.
The
.Fa servers
array can contain up to
.Dv DNSCONFIG_MAX_SERVERS
DNS resolvers.
The
.Fa servers_count
field marks how many of the entries in
.Fa servers
are populated.
.Bd -literal
struct dnsconfig {
	size_t servers_count;
	struct dnsconfig_server servers[DNSCONFIG_MAX_SERVERS];
}
.Ed
.Pp
Each DNS resolver in the
.Fa servers
array is described by a
.Vt struct dnsconfig_server
structure.
The resolver can be defined by either an IPv4 or an IPv6 address.
.Pp
For an IPv4 address
.Fa family
is
.Dv AF_INET ,
.Fa addrsize
is
.Fn sizeof "struct in_addr" ,
and the address is stored in the
.Fa in
field of the
.Fa addr
union.
.Pp
For an IPv6 address
.Fa family
is
.Dv AF_INET6 ,
.Fa addrsize
is
.Fn sizeof "struct in_addr6" ,
and the address is stored in the
.Fa in6
field of the
.Fa addr
union.
.Bd -literal
union dnsconfig_server_union {
	struct in_addr in;
	struct in6_addr in6;
}

struct dnsconfig_server {
	sa_family_t family;
	size_t addrsize;
	union dnsconfig_server_union addr;
}
.Ed
.Sh RETURN VALUES
On success 0 is returned.
On error -1 is returned, and
.Va errno
is set appropriately.
.Sh ERRORS
.Fn getdnsconfig
and
.Fn setdnsconfig
will fail if:
.Bl -tag -width "12345678"
.It Er EFAULT
.Fa cfg
points to an invalid address.
.El
.Pp
.Fn setdnsconfig
will additionally fail if:
.Bl -tag -width "12345678"
.It Er EAFNOSUPPORT
.Fa family
is set to an address family other than
.Dv AF_INET
or
.Dv AF_INET6 .
.It Er EINVAL
.Fa servers_count
is larger than
.Dv DNSCONFIG_MAX_SERVERS .
.It Er EINVAL
.Fa addrsize
does not match the size of the address corresponding to
.Fa family .
.El
.Sh SEE ALSO
.Xr inet 4 ,
.Xr inet6 4 ,
.Xr dhclient 8 ,
.Xr dnsconfig 8
.Sh HISTORY
The
.Fn getdnsconfig
and
.Fn setdnsconfig
system calls originally appeared in Sortix 1.1.