resolv.conf.5: Document 'edns0' option

Reported-by: Walter Jontofsohn <wjontofs@atriumberlin.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man5/resolv.conf.5 b/man5/resolv.conf.5
index 41fd5b86ef1825fa318fc84eed6691ad2cf1832a..c75227fbb818e64731005481be088cd10045bf03 100644 (file)
--- a/man5/resolv.conf.5
+++ b/man5/resolv.conf.5
@@ -163,6 +163,7 @@ an error to the calling application.
 The default is
 .BR RES_DFLRETRY
 (currently 2, see \fI<resolv.h>\fP).
+The maximum value for this option is silently capped to 5.
 .TP
 .B rotate
 sets
@@ -191,6 +192,13 @@ This has the effect of trying a AAAA query before an A query inside the
 .BR gethostbyname (3)
 function, and of mapping IPv4 responses in IPv6 "tunneled form"
 if no AAAA records are found but an A record set exists.
+.TP
+.BR edns0 " (since glibc 2.6)"
+sets
+.BR RES_USE_EDNSO
+in
+.IR _res.options .
+This enables support for the DNS extensions described in RFC\ 2671.
 .RE
 .LP
 The \fIdomain\fP and \fIsearch\fP keywords are mutually exclusive.