AT&T mobile intercepting TCP sockets?
Chris Adams
cma at cmadams.net
Mon May 21 19:35:55 UTC 2018
I ran into an odd issue with access to a website I manage from AT&T
mobile devices this weekend. The website worked for everybody not on
AT&T mobile, and AT&T mobile users could access other sites; the problem
was just this combination.
Android and iOS phones, as well as a Linux system tethered to an Android
phone, all had the same problem. On the Linux system, I disabled IPv6
in Firefox, and it could then connect. Browsers got various "connection
reset" type errors; on Linux, I could telnet to port 80 or 443, and it
would connect and immediately close.
The site does have an IPv6 address, but I had missed getting the
webserver to listen on IPv6 (my mistake). Adding that looks to have
solved the problem.
When I ran tcpdump on the server and had someone try to connect from
their AT&T mobile iPhone, I saw three connection attempts a few tenths
of a second apart (all refused by the server).
My question is this: is AT&T mobile intercepting the TCP socket (and
not handling "connection refused" correctly)? Is that a known thing?
--
Chris Adams <cma at cmadams.net>
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