[Discuss] [EXT] Problem accessing blu.org

[cra at WPI.EDU (Chuck Anderson)]

On Tue, May 19, 2020 at 09:01:12AM -0400, Jerry Feldman wrote:
> I have Xfinity internet at home. In the past few weeks I can't access
> blu.org. Ping and website times out from phone over wifi and desktop fedora
> 32 connected by cable to the gateway. If I turn wifo off on my phone I am
> able to ping, sdh, and get web site from my wireless carrier. It seems to
> be related to my Wan address since other Comcast users can access Blu. John
> and I have checked our server and nothing appears to be blocking my Wan
> address. One interacting anomaly is that when I reset the gateway I am able
> to access the site for a short period of time, such as 10 mins. I've been
> on chats and phone calls with Xfinity, but they can't find any issues. I am
> able to access all other web sites and can ping other hosts. It is only
> blu.org that is the problem.
> 
> Since it appears to only be my home that is affected, I don't think Comcast
> is blacklisting Blu. I don't have any evidence that the BLU server is
> blocking my ip address.
> 
> Looking for ideas

Since it is possible to coordinte both ends in this instance, can you
try running tcpdump or wireshark on your end, while someone runs
tcpdump on the blu.org server, and see where the conversation is being
lost or getting stuck?  Use the IP of blu.org and your router's public
IP to filter the tcpdumps like this (substitute the correct names of
the network intefaces):

client> sudo tcpdump -i <interface> -nnn -s0 -vvv -w clientside.pcap host 216.235.254.230

server> sudo tcpdump -i <interface> -nnn -s0 -vvv -w serverside.pcap host <your-router-public-ip>

Then do a ping:

>ping 216.235.254.230
PING 216.235.254.230 (216.235.254.230) 56(84) bytes of data.
64 bytes from 216.235.254.230: icmp_seq=1 ttl=59 time=14.8 ms
64 bytes from 216.235.254.230: icmp_seq=2 ttl=59 time=13.2 ms
64 bytes from 216.235.254.230: icmp_seq=3 ttl=59 time=169 ms
^C
--- 216.235.254.230 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 13.247/65.789/169.346/73.228 ms

Then do a telnet to port 80 test.  If it connects, type "HEAD / HTTP/1.0" and hit enter twice:

>telnet 216.235.254.230 80
Trying 216.235.254.230...
Connected to 216.235.254.230.
Escape character is '^]'.
HEAD / HTTP/1.0

HTTP/1.1 200 OK
Date: Tue, 19 May 2020 13:32:54 GMT
Server: Apache
X-Powered-By: PHP/5.4.16
Connection: close
Content-Type: text/html; charset=UTF-8

Connection closed by foreign host.

You can send the pcaps along to the list (or me privately if you wish).