[paho-dev] python: persistent connection failures when v6 doesn't work

[Greg Troxel <gdt@xxxxxxxxxx>]

I have a machine that has IPv4 connectivity to the broker, but IPv6
fails -- no ICMP, just no delivery.  This is due to a failed tunnel
server in an ISP.

A program in python using paho-mqtt is configured to use foo.example.com
as the broker, and that name has an A and an AAAA.   As far as I can
tell there is a TCP connection in SYN_SENT to the AAAA record value, and
it never tries the other one.

It seems to me that a client should try every value in the union of the
AAAA and A records in sequence, in some unspecified order, arguably the
v6 ones first, given the deployment doctrine.

Is anybody else seeing this kind of problem?

Greg

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