1 files changed, 33 insertions, 3 deletions

diff --git a/README b/README
index c67fc25..cc15197 100644
--- a/README
+++ b/README
@@ -18,7 +18,7 @@ Configure the IRC channel or server if possible:
 	- use a bot to set XMPP users to have +o, +v or +h to prevent flood kicks
 	- disable invite-only mode on channel. you may use IRC channel passwords.
 
-Required environment variables for configuration:
+Required environment variables for configuration of a bridge:
 	- IX_JID	JID of ircxmpp user on XMPP server to connect with
 	- IX_PASS	password for XMPP authentication of ircxmpp user
 	- IX_HOST	hostname of the IRC server, prefix the value with # to connect with TLS
@@ -26,9 +26,14 @@ Required environment variables for configuration:
 	- IX_CHANNEL	channel on IRC server to bridge
 	- IX_MUC	multi-user chat on XMPP server to bridge
 
-Optional environment variables for configuration:
+Optional environment variables for configuration of a bridge:
 	- IX_CHPASS	set to IRC channel password if channel on IRC is password protected
+	- IX_DOMAIN	start the built in DNS server and spoof IRC hostnames (more info below)
+
+Optional environment variables for global configuration: (those do not have numbered counterparts)
 	- IX_LOOPDELAY	delay after each event loop cycle in microseconds, defaults to 10 ms.
+	- IX_DNS_PORT	port on which the DNS server should run, if it's enabled, by default 53
+	- IX_DNS_IP	IP on which to listen for DNS queries. by default this is INADDR_ANY-0.0.0.0
 
 Operation principle:
 	- ircxmpp initiates two control connections, one to XMPP server, one to IRC server, and joins
@@ -47,7 +52,6 @@ To implement:
 	- ctcp messages (ACTION - /me) and perhaps file upload (that'd be hard)
 	- subject changing
 	- automatic +v/+h/+o botnet juggling between bridge IRC connections and control IRC conn
-	- setting user@host of bridge bots on IRC to JIDs of XMPP users by temporary changing rDNS
 	- reusing bridge and control connections with same nick to different channels on same network
 
 Notes:
@@ -93,4 +97,30 @@ Using as a library:
 Gentoo/openrc?:
 	- http://github.com/OpenRC/openrc/pull/517 needs to be merged before for increased security
 
+Built-in DNS server for spoofing IRC hostnames:
+	- IRC hostnames can be spoofed so that they look like the XMPP JID domain of the XMPP user
+	- you need to run the program with CAP_NET_BIND_SERVICE, on debian systemd this is by default
+	- you need a domain name, on which you set a wildcard record to A record to server's IP
+		+ for example *.ircxmpp.example. IN A 192.168.0.2 (this is for IRC PTR verification)
+	- in the in-addr.arpa zone for you IP address, add a NS record pointing to your server
+		+ for example 2.0.168.193.in-addr.arpa. IN NS server.ircxmpp.example.
+	- start ircxmpp with the configuration variable IX_DOMAIN=ircxmpp.example.
+	- read the logs! the built in DNS server might spam bind: permission denied errors
+	- when a bridge will connect to IRC, the IRC server will query the ircxmpp NS for PTR
+	- when a request is received by the ircxmpp NS, last XMPP user's JID hostname will be sent
+		+ let's say xmpp.server.de.ircxmpp.example; ircxmpp.example appended for verification
+	- IRC server will then verify that this domain really points to your IP address-that wildcard
+
+Built-in DNS server for spoofing IRC hostnames when using the program as a library:
+	- call ircxmpp_set_domain with your domain suffix to which JID host and dot will be prepended
+	- you can set your callback with ircxmpp_set_set_domain_setter
+	- callback is called when domain change is wanted even if ircxmpp_set_dns is false
+	- with this you can differently publish the domain name for spoofing, perhaps with nsupdate
+	- otherwise if ircxmpp_set_dns is true, internal DNS server works as described above
+
+IPv6:
+	- Haha, remember this is C you're talking about! That'd require writing code!
+	- TODO: add support in DNS server for ip6 (binding to AF_INET6 sockets, ip6 memmem, ...)
+	- TODO: use irc_connect6 somehow in libircclient, libstrophe should already work with IPv6
+
  -- Anton Luka Šijanec <anton@sijanec.eu>  Fri, 29 Apr 2022 17:00:00 +0200