Implement EDNS0 support, as EDNS0 support will be made mandatory for

IPv6 transport-ready resolvers/DNS servers.  Need careful configuration
when enable it. (default config is not affected).
See manpage for details.

XXX visible symbol __res_opt() is added, however, it is not supposed to be
called from outside, libc minor is not bumped.

Obtained from:	KAME/NetBSD

1 files changed, 14 insertions, 1 deletions

diff --git a/lib/libc/net/resolver.3 b/lib/libc/net/resolver.3
index 1fb97f5..e06a5fd 100644
--- a/lib/libc/net/resolver.3
+++ b/lib/libc/net/resolver.3
@@ -119,7 +119,7 @@ are defined in
 and are as follows.
 Options are stored as a simple bit mask containing the bitwise ``or''
 of the options enabled.
-.Bl -tag -width RES_DEFNAMES
+.Bl -tag -width RES_USE_INET6
 .It Dv RES_INIT
 True if the initial name server address and default domain name are
 initialized (i.e.,
@@ -176,6 +176,19 @@ This option is enabled by default.
 This option turns off the user level aliasing feature controlled by the
 .Dq Ev HOSTALIASES
 environment variable.  Network daemons should set this option.
+.It Dv RES_USE_INET6
+Enables support for IPv6-only applications.
+This causes IPv4 addresses to be returned as an IPv4 mapped address.
+For example, 10.1.1.1 will be returned as ::ffff:10.1.1.1.
+The option is meaningful with certain kernel configuration only.
+.It Dv RES_USE_EDNS0
+Enables support for OPT pseudo-RR for EDNS0 extension.
+With the option, resolver code will attach OPT pseudo-RR into DNS queries,
+to inform of our receive buffer size.
+The option will allow DNS servers to take advantage of non-default receive
+buffer size, and to send larger replies.
+DNS query packets with EDNS0 extension is not compatible with
+non-EDNS0 DNS servers.
 .El
 .Pp
 The