Mailing List Archive

On 21/11/2022 08:14, Laura Williamson via Exim-users wrote:
> Have a bit of an issue. When sending out emails out exim select an interface like this
>
> interface = ${lookup sqlite {SQLITE_Q_USERINTERFACE select ip from interface where active='Y' order by random() limit 1}{$value}}
> helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}{$primary_hostname}}
>
> Which works perfectly fine, however, if the server we send to has greylisting it will try again but every time it will select a new interface IP and therefore might get greylisted again (as the IP now is different), is there a way around this?

Nothing built-in.

You'd have to craft something involving remembering what interface you last
tried, and preferring it after a defer. That probably requires using an
event to write a DB entry on defer.

Or set up a static mapping from destination (host or domain) to
interface.

Or, stop trying to be clever with these multiple interfaces.
--
Cheers,
Jeremy


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On Mon, Nov 21, 2022 at 08:14:41AM +0000, Laura Williamson via Exim-users wrote:
> interface = ${lookup sqlite {SQLITE_Q_USERINTERFACE select ip from interface
> where active='Y' order by random() limit 1}{$value}}
> helo_data = ${lookup
> dnsdb{ptr=$sending_ip_address}{$value}{$primary_hostname}}
>
> Which works perfectly fine, however, if the server we send to has
> greylisting it will try again but every time it will select a new interface
> IP and therefore might get greylisted again (as the IP now is different), is
> there a way around this?

The counter-question is "Why do you do it?" Probably you want to use
IP-address randomization as a tool to overcome connectivity problems.
I don't know other reasons to use rotary IP pools (but they may exist).

However, if connection was successful and host replies with 4xx status code,
there is no connectivity problem. Hence IP rotation should be stopped or
suspended for some reasonable time (~ 30m-2h).
--
Eugene Berdnikov

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Hi,

> Have a bit of an issue. When sending out emails out exim select
> an interface like this
>
> interface = ${lookup sqlite {SQLITE_Q_USERINTERFACE select ip
> from interface where active='Y' order by random() limit
> 1}{$value}}
> helo_data = ${lookup
> dnsdb{ptr=$sending_ip_address}{$value}{$primary_hostname}}
>
> Which works perfectly fine, however, if the server we send to
> has greylisting it will try again but every time it will select
> a new interface IP and therefore might get greylisted again (as
> the IP now is different), is there a way around this?

Depending on what goals you were trying to achieve with the
multiple-interfaces, one option might be to swap the "random()" for
something based on a consistent hash of message properties.

That way you could still get load balanced over the interfaces but a given
message would always select the same interface and you wouldn't have to
store any extra state.




Best wishes,
@ndy

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andyjpb@ashurst.eu.org
http://www.ashurst.eu.org/
0x7EBA75FF

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On 2022-11-21, Laura Williamson via Exim-users <exim-users@exim.org> wrote:
> Have a bit of an issue. When sending out emails out exim select an
> interface like this
>
> interface = ${lookup sqlite {SQLITE_Q_USERINTERFACE select ip from
> interface where active='Y' order by random() limit 1}{$value}}
> helo_data = ${lookup
> dnsdb{ptr=$sending_ip_address}{$value}{$primary_hostname}}
>
> Which works perfectly fine, however, if the server we send to has
> greylisting it will try again but every time it will select a new
> interface IP and therefore might get greylisted again (as the IP now is
> different), is there a way around this?

don't use random, use somethign repeatable instead eg:

${listextract{${eval:1+(${base62d:${substr_14_2:$message_exim_id}}%5)}}{\
10.0.0.1:10.0.0.2:10.0.0.3:10.0.0.4:10.0.0.5}{$value}{10.0.0.1}}

Here the feactional-seconds part of $message_exim_id is used as a
repeatable pseudo-random number. the range is (0..499)

you can possibly use the sha1 function to get repeatable pseudo-random
values by salting the ip-address with the exim-id of the message.

interface = ${lookup sqlite {SQLITE_Q_USERINTERFACE select ip from \
interface where active='Y' \
order by sha1(ip || '${quote_sqlite:$message_exim_id}' ) \
limit 1}{$value}}

--
Jasen.

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