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List:       netfilter
Subject:    Re: NAT - how external source port is selected
From:       Daniel <tech () tootai ! net>
Date:       2021-08-18 16:43:07
Message-ID: 82442129-99d3-8add-cd6f-8882070eb000 () tootai ! net
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Le 18/08/2021 à 18:16, Florian Westphal a écrit  :

> Daniel <tech@tootai.net> wrote:
>>>> Also, SNOM phones are systematically using port 2048 as source port of the
>>>> WAN ip. Is there a mechanism to allow such behavior ?
>>> What do you mean? The initiator is free to pick whatever source port they like.
>> Well, how he will know that the port is free ?
> bind() fails for listener socket, connect() fails for outgoing (if
> everything is full).
>
> On conntrack machine, connection tracking table gets queried after SNAT
> to see if the new tuple is still unique.
Thanks to all for the explanation.

-- 
Daniel
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