[BUG] Can't connect to any server in 5.0.0.0/8 IP range

NOTE: If anybody knows where the best place to submit this bug report for tripwire to receive the message, please tell me either as a reply or a PM.



I have been trying to work out why I haven't been able to connect to my server through the server browser for over a month now, and finally have the answer (well, I've found the reason anyway).



I noticed that I couldn't connect via the server browser, or by typing "open 5.135.154.174", but I COULD connect by typing "kf.gravitygunonly.com". This led me to determine that I couldn't connect to my server using it's IP address directly.



I later noticed that two other servers I manage also had the same issue when I ran Killing Floor on them, they were 5.39.87.163 and 5.39.92.147. I thought it was unlikely that there was a correlation between the IP range and the connection issue, but I began to test the theory.



I tested several of my other servers on different IP ranges, all of which worked perfectly, covering a range of platforms and environments (including identical environments to my servers which didn't work).



Finally, I went on the "Internet Games" list in the server browser, and went through the list trying every server I found that was in the 5.0.0.0/8 IP block, and found that they all suffered from the same connection issue. I initially thought this might just be an issue with OVH's 5.x.x.x IP block, but after further investigation via whois, I found that this affected a variety of IP block owners.



I next tried to determine if the issue was due to the Killing Floor server, or the client. I performed a TCP dump (using wireshark), and found that whenever connecting to a server in 5.0.0.0/8, no packets were sent to the server by the client. This makes me believe that the bug exists within the client rather than in the server (although I can not say for certain).



I also asked several people on different ISPs, even in different countries, to test this as well, to make sure that nothing relating to my own internet connection was causing this bug to appear, but everybody had the same results as me.



In summary, I believe there is a bug in the Killing Floor client which fails to connect to any server running in the 5.0.0.0/8 IP range. I don't have an exhaustive list but I found over a dozen servers which are currently inaccessible due to this, so I would regard this as a rather important bug.



Thank you for your time.



-Jonathan



Below I have included a table of results I gathered while testing this bug:



IPs that DON'T work (combination of servers I manage and servers from the master server list):

5.9.158.195

5.35.253.135

5.39.18.121

5.39.87.163

5.39.92.147

5.45.100.43

5.45.102.250

5.45.105.138

5.45.107.188

5.62.97.179

5.62.97.184

5.62.109.163

5.62.124.27

5.135.154.174

5.135.177.222

5.159.230.239

5.189.176.182

5.189.189.41



IPs that DO work (with the exception of the 2.x.x.x, these are all servers I manage):

NOTE: I don't have the killing floor server process running on any of these any more

2.111.68.87 (proves that it can handle single digit first block)

86.180.113.187

91.121.170.61

192.99.14.101

192.95.38.20

178.32.219.153

178.32.221.227

198.245.60.228