[tor-dev] Understanding Tor and SOCKS

Yawning Angel yawning at schwanenlied.me
Sun Oct 26 17:31:09 UTC 2014

On Sun, 26 Oct 2014 14:34:59 +0100
Rob van der Hoeven <robvanderhoeven at ziggo.nl> wrote:
> So, the SOCKS protocol supports redirection to another SOCKS server.
> An all-zero address/port simply means: use the server/port that you
> are currently connected to.

That's a really interesting way of interpreting that part of the RFC.

The reason why BND.ADDR and BND.PORT are supplied in a SOCKS5 response
is to provide the client with the information equivalent to calling
getsockname() on a non-proxied socket.

In the context of tor, the reason why BND.ADDR and BND.PORT are all NUL
bytes is because the RELAY_CONNECTED cell does not propagate BND.PORT
backwards to the client from the exit.  BND.ADDR could technically be
filled in (since the tor client knows where it is exiting from), but I
don't see much point (and this information is useless at best in the
context of HSes).


Yawning Angel
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