Disable IPv6 for Postfix #420
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@daveross came across an interesting bug with the default configuration -- since the `inet_protocols` defaults to "all", some network configurations will default to trying IPv6 and then giving up when an MX record won't resolve to it. (Try it yourself -- send to addresses at 10up.com vs. get10up.com). Disabling IPv6 and forcing IPv4 for all smtp connections seems to make this work correctly.
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Looks good, thanks for waiting. :) It may be worth moving to an external config file at some point, but I'm not sure how much we'll ever config postfix after this. |
jeremyfelt
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In #420, we added a line to provisioning that attempts to set "ipv4" as the only allowed protocol for postfix due to issues in how network connections managed the ipv6 connection. Because the config file does not yet exist during initial provisioning, that caused an error message saying as much. See #628. It turns out that this line hasn't been doing anything. :) I first went down the path of using `debconf-set-selections` to set the protocol value. This works, but then disables ipv6 entirely as a valid protocol. Since we haven't heard of any other issues besides the original in #420, I think it's safe to not make any change here and then watch for any problems. I have a feeling that postfix has gotten better about this. In the documentation for the `inet_protocols` config, it's mentioned that "versions before 2.8 attempt to connect via IPv6 before attempting to use IPv4." http://www.postfix.org/postconf.5.html#inet_protocols Now that we're past 2.8, it's entirely possible that the protocol detection has gotten better. If we do run into an issue, there is a newer `smtp_address_preference` config that allows us to specify which protocol should be attempted first. http://www.postfix.org/postconf.5.html#smtp_address_preference In that case, we may need to create our own custom config file as it's not entirely obvious that `debconf-set-selections` will work for this value. See #420. Fixes #628.
tomjn
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Mar 7, 2017
In Varying-Vagrant-Vagrants#420, we added a line to provisioning that attempts to set "ipv4" as the only allowed protocol for postfix due to issues in how network connections managed the ipv6 connection. Because the config file does not yet exist during initial provisioning, that caused an error message saying as much. See Varying-Vagrant-Vagrants#628. It turns out that this line hasn't been doing anything. :) I first went down the path of using `debconf-set-selections` to set the protocol value. This works, but then disables ipv6 entirely as a valid protocol. Since we haven't heard of any other issues besides the original in Varying-Vagrant-Vagrants#420, I think it's safe to not make any change here and then watch for any problems. I have a feeling that postfix has gotten better about this. In the documentation for the `inet_protocols` config, it's mentioned that "versions before 2.8 attempt to connect via IPv6 before attempting to use IPv4." http://www.postfix.org/postconf.5.html#inet_protocols Now that we're past 2.8, it's entirely possible that the protocol detection has gotten better. If we do run into an issue, there is a newer `smtp_address_preference` config that allows us to specify which protocol should be attempted first. http://www.postfix.org/postconf.5.html#smtp_address_preference In that case, we may need to create our own custom config file as it's not entirely obvious that `debconf-set-selections` will work for this value. See Varying-Vagrant-Vagrants#420. Fixes Varying-Vagrant-Vagrants#628.
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@daveross came across an interesting bug with the default configuration -- since the
inet_protocolsdefaults to "all", some network configurations will default to trying IPv6 and then giving up when an MX record won't resolve to it. (Try it yourself -- send to addresses at 10up.com vs. get10up.com). Disabling IPv6 and forcing IPv4 for all smtp connections seems to make this work correctly.