[exim-dev] [Bug 2149] Add option to prefer IPv4

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Author: admin
Date:  
To: exim-dev
Old-Topics: [exim-dev] [Bug 2149] New: Add option to prefer IPv4
Subject: [exim-dev] [Bug 2149] Add option to prefer IPv4
https://bugs.exim.org/show_bug.cgi?id=2149

Phil Pennock <pdp@???> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pdp@???


--- Comment #4 from Phil Pennock <pdp@???> ---
In the below, taken from my configs, there's two approaches used for Google's
peculiar treatment of IPv6; one is to apply rules on a domain basis, which
handles IP changes and lists becoming stale, while the other is to list the
IPv6 address-blocks which are Google, to handle all the Google-hosted domains.

The `conditionally_disable_ipv6` hostlist evaluates to "the entire IPv6
address-space" if and only if the key "disableipv6" is in the "key1=v1 key=v2"
list of data in $address_data.

The CDB referenced is built from plaintext which looks like this, you don't
need to use CDB:
gmail.com:      tls=yes tlshigh=yes tlsverify=MXHOST disableipv6=yes




# Google IPv6 blocks from <https://ipinfo.io/AS15169>
# cidrmerge is your friend
hostlist google_ipv6 = <; 2001:4860::/32 ; 2401:fa00::/32 ; 2404:6800::/32 ;
2600:1900::/28 ; 2605:ef80::/32 ; 2607:f8b0::/32 ; 2620:0:1000::/40 ;
2620:120:e000::/40 ; 2620:15c::/36 ; 2800:3f0::/32 ; 2a00:1450::/32 ;
2a00:79e0::/32 ; 2a03:ace0::/32 ; 2c0f:fb50::/32

# Disable IPv6 based on recipient domain
hostlist conditionally_disable_ipv6 = <;
${extract{disableipv6}{$address_data}{::0/0}{}} ; +google_ipv6

# begin routers

dnslookup:
  driver        = dnslookup
  domains       = ! +local_domains
  transport     = remote_smtp
  ignore_target_hosts = ... : +conditionally_disable_ipv6
  dnssec_request_domains = *
  address_data  = ${lookup {$domain}cdb{CDBMAILTABLES/remote_properties.cdb}}
  no_more


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