[asterisk-bugs] [JIRA] (ASTERISK-26113) res_pjsip: Lots of DNS lookups of local hostname

[Mark Michelson (JIRA)]

    [ https://issues.asterisk.org/jira/browse/ASTERISK-26113?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=234376#comment-234376 ] 

Mark Michelson commented on ASTERISK-26113:
-------------------------------------------

I agree with Marek. The linked issue was one where we found that RTCP packet generation/reception resulted in DNS lookups of the hostname if the host was not defined in {{/etc/hosts}}

With that issue in mind, here are your list of options:
* Place the hostname in {{/etc/hosts}}
* Set {{bind_rtp_to_media_address=yes}} and then set a {{media_address}} for your endpoints. ({{bind_rtp_to_media_address}} was added in version 13.8.0)
* Upgrade to 13.12.0 (or newer), where Asterisk only looks up the hostname once for each new RTP session, rather than on every RTCP send/receive.

The first two suggestions will eliminate DNS lookups of the hostname entirely. The final option will significantly reduce the number of DNS lookups of the hostname, but will not eliminate them entirely.

> res_pjsip: Lots of DNS lookups of local hostname
> ------------------------------------------------
>
>                 Key: ASTERISK-26113
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-26113
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Resources/res_pjsip
>    Affects Versions: SVN
>         Environment: CentOS 6.5 and Fedora 23.
>            Reporter: Ross Beer
>            Assignee: Unassigned
>            Severity: Minor
>         Attachments: pjsip.conf, pjsip_inbound.conf
>
>
> Asterisk is performing thousands of DNS lookups per minute. 
> The lookups are for its own host name for A and AAAA records. These are milliseconds apart and produce a DoS attack on the name servers.
> This can be confirmed by having incoming calls and performing a wireshark.



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