Bug 206165 - resolv.conf(5) is missing documentation on options
Summary: resolv.conf(5) is missing documentation on options
Status: Open
Alias: None
Product: Documentation
Classification: Unclassified
Component: Manual Pages (show other bugs)
Version: Latest
Hardware: Any Any
: --- Affects Only Me
Assignee: freebsd-bugs (Nobody)
Keywords: easy, patch
Depends on:
Reported: 2016-01-12 19:37 UTC by Mark Felder
Modified: 2021-10-01 06:43 UTC (History)
7 users (show)

See Also:

resolver(5) / resolv.conf(5) patch (3.67 KB, patch)
2021-09-20 06:48 UTC, Felix Johnson
no flags Details | Diff

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Description Mark Felder freebsd_committer 2016-01-12 19:37:08 UTC
There is no mention of the various options available to the resolver in resolv.conf(5). A common option is "edns0" and grepping the source shows there are others that should be documented as well:

		/* search for and process individual options */
				printf(";; res_setoptions(\"%s\", \"%s\")..\n",
				       options, source);
			statp->options |= RES_NOTLDQUERY;
			statp->options |= RES_USE_INET6;
		       statp->options |= RES_INSECURE1;
		       statp->options |= RES_INSECURE2;
			statp->options |= RES_ROTATE;
			statp->options |= RES_NOCHECKNAME;
			statp->options |= RES_USE_EDNS0;
			statp->options |= RES_USE_DNAME;
				statp->options |= RES_NO_NIBBLE2;
				statp->options &=
	statp->options &= ~RES_INIT;
Comment 1 Jason Mader 2017-09-13 11:51:42 UTC
Here's the edns0 options from the NetBSD man page. The other missing options are documented there as well. Since a fresh FreeBSD installation includes the line,

options edns0

It would be best to at least include this one,


attach OPT pseudo-RR for ENDS0 extension
specified in RFC 2671, to inform DNS server
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.  The option must be used only
when all the DNS servers listed in nameserver
lines are able to handle EDNS0 extension.
Comment 2 Miroslav Lachman 2019-02-23 22:10:23 UTC
Any progress on this one? Todya I tried to find what edns0 means in man resolv.conf and found nothing. Quick web search takes me to this PR.
I am on FreeBSD 11.2.
Comment 3 Felix Johnson freebsd_triage 2021-09-20 06:48:39 UTC
Created attachment 228042 [details]
resolver(5) / resolv.conf(5) patch

Document available options. Not all options in resolver(3) are exposed as options in resolv.conf.