[BitTorrent] ipv6

Christoph Hohmann reboot78 at freenet.de
Mon Jan 24 09:17:14 EST 2005

Justin Cormack wrote:

>> The bigger problem I encountered when I tried to make an
>> IPv6 version of Bittorrent is that most trackers don't
>> accept IPs provided by the peer and use the source IP which
>> it also checked with the NAT check to verify that it is
>> correct.
>What does the NAT check do? Presumably it shouldnt be done for ipv6
>as there is no NAT anyway...

As fas as I know the tracker connects to the peer and
validates the peer id. If that fails the peer is remembered
as being behind a NAT gateway and is not returned to other
peers. The NAT check is done for the source IP of the
tracker connection and in most cases the IP that is provided
by the peer is ignored. Even if the IP is not ignored and
tested that will not work for IPv4 only trackers when they
receive IPv6 addresses by a peer.

>> If you want to keep a NAT check to make sure that Bittorrent
>> is not used to start DDoS attacks the actual NAT check would
>> have to be done by the other peers. An IPv4 only tracker can
>> not do NAT check for IPv6 clients. Only other IPv6 clients
>> could provide this information to the tracker. My idea was
>> to give each IP a trust value and when more peers report
>> that they successfully connected to the IP the trust
>> increases or decreases if the connection failed. The more
>> trust a peer has the more often it is returned to other
>> peers.
>Not sure if the complexity of this is manageable.

The NAT check is also a security check. Imagine that a peer
provides a false IP of some webserver of a company and
suddenly hundrets of peers connect to this webserver. When
the tracker should accept IPs that it can not validate the
check has to be done by someone else.

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