Hello,

I noticed that libcurl doesn't currently have SOCKS4a support, which is
especially interesting for tor and other anonymizing networks because it
avoids (non-anonymized) DNS lookups.

So here is a quick patch against current CVS for SOCKS4a. It's quite small,
the differences between v4 and v4a are really minimal. It has been lightly
tested and seems to work fine: HTTP downloads with "curl --socks4a" through
tor no longer trigger tor's "Your application is giving Tor only an IP
address" message, plus you can actually download from .onion sites! :)
The test suite continues to work after applying my patch.

I'm assuming that hostnames can have arbitrary lengths, which complicates
things a bit - Curl_write() is called a second time to send long hostnames.
I've tested my code with SOCKS4REQLEN set to 12, that code path seems to
work.

Cheers,

  Richard

PS: ObLegal: My contribution has the same license as libcurl's.

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