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DNS Lookup

MariaDB SQL Trigger for SRV based DNS lookup using PowerDNS 4.2 This provides access to the AllStar Link database via DNS.

Requirements

This code requires that you already have a working Asterisk Realtime setup and are familiar with storing usernames and passwords for IAX2 clients in a database.

This code has been successfully used with Asterisk 13 as it was the version of Asterisk that powered ASL Registration servers. The code in this repository should work with any version of Asterisk Realtime that uses the same database format as Asterisk 13.

Note: Information on setting up Asterisk Realtime is beyond the scope of this document. You can find information regarding Asterisk Realtime at https://wiki.asterisk.org/wiki/display/AST/Realtime+Database+Configuration

Overview

This supports the following records under the subdomain of nodes.allstarlink.org:

  • SRV
  • TXT
  • A

This is based on the AllStar Link DNS lookup standard provided on the wiki.

On any update to users_Nodes, the trigger is run and it updates the records in the records table. This has negligible additional load on the database as the trigger executes in .005 seconds or less.

There is no provision to remove records from the records table when removing an entry in the users_Nodes table. This has to be done manually.

Example Queries

SRV

This is used to find the port and hostname of the node and if it's a remotebase

dig SRV _iax._udp.2020.nodes.allstarlink.org

; <<>> DiG 9.10.3-P4-Ubuntu <<>> SRV _iax._udp.2020.nodes.allstarlink.org
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 25251
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1452
;; QUESTION SECTION:
;_iax._udp.2020.nodes.allstarlink.org. IN SRV

;; ANSWER SECTION:
_iax._udp.2020.nodes.allstarlink.org. 30 IN SRV 10 10 4572 2020.nodes.allstarlink.org.

This returns the port, 4572 and the hostname of the server as 2020.nodes.allstarlink.org. If this was a remotebase the hostname would be returned as 2020.remotebase.nodes.allstarlink.org.

A

This is used to resolve the hostname from the SRV into an IP address.

dig A 2020.nodes.allstarlink.org.

; <<>> DiG 9.10.3-P4-Ubuntu <<>> A 2020.nodes.allstarlink.org.
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 28603
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1452
;; QUESTION SECTION:
;2020.nodes.allstarlink.org.    IN      A

;; ANSWER SECTION:
2020.nodes.allstarlink.org. 30  IN      A       73.11.141.48

TXT

The TXT record is optional, but gives debugging info about the status of the registration of a node.

dig TXT 2560.nodes.allstarlink.org

; <<>> DiG 9.10.3-P4-Ubuntu <<>> TXT 2560.nodes.allstarlink.org
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 23328
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1452
;; QUESTION SECTION:
;2560.nodes.allstarlink.org.    IN      TXT

;; ANSWER SECTION:
2560.nodes.allstarlink.org. 30  IN      TXT     "NN=2560" "RT=2019-05-29 08:12:33" "RB=0" "IP=173.82.59.253" "PIP=" "PT=4569" "RH=register-fnt"

The records returned are:

  • NN - Node Number as seen in the database
  • RT - Registration time as seen in the database converted to UTC from unixtime
  • RB - Remote base 1 if true, 0 if not remote base
  • IP - IP address of the node doing the registration via IAX2
  • PIP - Proxy IP address if set
  • PT - Port to connect to
  • RH - Registration server hostname that processed the registration request

Notes

The proc_domain_id must match the ID number of the specialSubDomain in the domains table. This used to be read on the fly, but statically defining this yielded a 10000% speedup. This should never change in production. If it does, you've messed up big time.

Static records can be defined in the normal records fields, and the pdnsutil command can provision/test these if needed. This does open up the possibility that multiple A/SRV/TXT records can be defined, and the SQL/pdns will handle it, as it's valid. Asterisk is expecting to see a single SRV and A record returned to it for a node number via DNS, so this may break asterisk if a static record is made and then a dynamic generated record is returned.

The TTL must be different than proc_ttl (default 30) for any manually created records.

The records returned here are not aged out after 10 minuted like the nodeslist. There is little point to this, as freshness can be queried via the TXT record. In any event if a server is not updating it's registration, connections to and from it will fail, just as with the nodelist.

How to install

This is really intended for internal ASL use, but it's provided as it may be usefull for the community.

This is using pdns server 4.2 and needs access to the ASL databse on the dns server.

First install and configure pdns on the server.

You will need to add the NS records and RR records to the toplevel domain, and an SOA record in the database too

  • gmysql.conf
# config for pdns
# MySQL Configuration
#
# Launch gmysql backend
launch+=gmysql
# gmysql parameters
gmysql-host=127.0.0.1
gmysql-port=3306
gmysql-dbname=<your realtime asterisk database name>
gmysql-user=<username here>
gmysql-password=<password here>
gmysql-dnssec=yes
# gmysql-socket=

Now insert the tables into the allstar database if they don't exist:

mysql allstar --comments <pdns-42-schema.sql

We need a custom index on the records table

ALTER TABLE records ADD CONSTRAINT nameTypeTTL UNIQUE KEY (name, type, ttl);

Now each stored procedure:

mysql allstar --comments <DNS_Trigger.sql

Test

Test dns lookups for TXT, SRV and A records

Aditional procs

DNS_build_records.sql is included, this will populate the records table if you don't want to run in real time.

installing this

mysql allstar --comments <DNS_build_records.sql

Disable the mysqlprocs in the pdns.conf file

Old files

The original process was running a sproc for every lookup. This worked but was way too slow. These are in the old directory.

Authors

License

This project is licensed under the GNU Affero General Public License v3.0 - see the LICENSE file for details.

Acknowledgments

  • Tom Hayward (KD7LXL) for his help with the SRV records (who knew they existed!)
  • Stacy Olivas (KG7QIN) for his help with the internals of asterisk