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Webscrab proxy creates loads of TCP6 connections despite IPV6 being down

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# 1  
Old 01-29-2020
Webscrab proxy creates loads of TCP6 connections despite IPV6 being down

I am working in Kali Linux. I have disabled ipv6 by the command, "sysctl -w net.ipv6.conf.all.disable_ipv6=1". Below output of "ifconfig -a" shows no IPV6.

inet netmask broadcast ether 08:00:27:ac:d6:52 txqueuelen 1000 (Ethernet) RX packets 3464 bytes 265390 (259.1 KiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 185 bytes 29219 (28.5 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 eth1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet netmask broadcast ether 08:00:27:42:25:3e txqueuelen 1000 (Ethernet) RX packets 6695 bytes 427120 (417.1 KiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 27 bytes 2250 (2.1 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

But when I enable "Webscrab" proxy, I see loads of TCP6 connection as below:
tcp6       0      0          ESTABLISHED
tcp6       0      0         ESTABLISHED

tcp6       0      0          ESTABLISHED
tcp6       0      0          ESTABLISHED
tcp6       0      0          CLOSE_WAIT

Any pointer toward the solution will be highly appreciated.
# 2  
Old 01-29-2020
I believe these loopbacks are not "true network connections" and so IPV6 traffic will not pass since you blocked IPV6 networking.

The title of your post is:

Webscrab proxy creates loads of TCP6 connections despite IPV6 being down
These internal loopbacks are not "true connections" per se.

Did you actually try to pass IPV6 traffic thought that host? If you did, I would be surprised if any IPV6 traffic would pass since you have already disabled IPV6 networking via "sysctl -w net.ipv6.conf.all.disable_ipv6=1".

You might want to check to make sure when you installed your proxy server that it did not unintentionally enable your intended block / disabled setup.

PS: You should use CODE tags when you post and insure your posts are well formatted and easy for everyone to read.
# 3  
Old 01-30-2020

The IP address is a special-purpose IPv4 address called localhost or loopback address. All computers use this address as their own but it doesn't let them communicate with other devices as a real IP address does.

Your computer might have the private IP address assigned to it so that it can communicate with a router and other networked devices. However, it still has this special address attached to it to mean "this computer," or the one you're currently on.

The loopback address is only used by the computer you're on, and only for special circumstances - unlike a regular IP address that is used to transfer files to and from other networked devices.
See also, for example: IP Address Explained


Quote: is localhost, it's the address of the current machine, accessed through a loopback interface (not through the network adapter - this works even if there is no network chips in the system).
# 4  
Old 01-30-2020

If you do not want your proxy server to listen on the kernel loopback interface (, you can easily fix this by configuring your proxy server to only listen on an IP address.

Just like mysql and other daemon processes, you can configure it to listen on or not.

For example, many people configure mysql to only listen on because they do not want any external connections to mysql; and does not permit external connections.

If you don't want your proxy server to listen on, then you simply configure your proxy server to not listen on

From the linux code base:

/* The loopback device is special if any other network devices
 * is present in a network namespace the loopback device must
 * be present. Since we now dynamically allocate and free the
 * loopback device ensure this invariant is maintained by
 * keeping the loopback device as the first device on the
 * list of network devices.  Ensuring the loopback devices
 * is the first device that appears and the last network device
 * that disappears.

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