Bugs item #3033966, was opened at 2010-07-24 11:51
Message generated for change (Comment added) made by bagder
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Category: libcurl
Group: wrong behaviour
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Robin Cornelius (robincornelius)
Assigned to: Daniel Stenberg (bagder)
Summary: SOCKS proxies do not work with multi interface

Initial Comment:
I have found that connections via a SOCKS5 proxy are failing when using the multi interface. The symptoms are that the proxy does not receive the setup packets/auth packets and instead libcurl sends the request data directly resulting in a socks protocol error. I have looked through the code in git and done some tests, it appears that libcurl 7.20.0 works fine but 7.20.1 results in socks protocol errors. (I noticed this when upgrading libcurl used by my app from 7.19.6 to 7.21.0.

Further tests indicate that Commit:4b351d018e3d6691191fd653a17f14f4a31e0b4c introduced un expected behaviour with socks proxies and the multi interface.

The problem occurs in the multi interface state machine, because on the multi interface connects are non blocking have have a timeout of 0, the STATE_CONNECT returns before the socket to the proxy is connected and we enter the STATE_WAITCONNECT

case CURLM_STATE_WAITCONNECT:
      /* awaiting a completion of an asynch connect */
      easy->result = Curl_is_connected(easy->easy_conn,
                                       FIRSTSOCKET,
                                       &connected);
      if(connected) {
        /* see if we need to do any proxy magic first once we connected */
        easy->result = Curl_connected_proxy(easy->easy_conn);

Curl_is_connected() since 4b351d018 sets conn->bits.tcpconnect = TRUE;

Curl_connected_proxy() tests for conn->bits.tcpconnect == TRUE and returns with out setting up the proxy

Attached is a patch that allows Curl_connected_proxy() to run when conn->bits.tcpconnect == TRUE and the multi interface is in use, comments in that function seem to suguest that this should have been allowed?

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>Comment By: Daniel Stenberg (bagder)
Date: 2010-07-24 23:50

Message:
Thanks a lot for your report and your help to improve libcurl!

Hm, doesn't this patch go against the fix the 4b351d018e commit
introduced?

In general I think checks for interface in use is suspicious and I'm far
from convinced right now that this patch really is the right thing.

To me, it looks like we should do something about the confusion around the
bits.tcpconnect struct memmber that seems to be used for a bit too many
purposes. Its name suggests it is about "TCP connect" but still it is also
used to check if the connection with the proxy is completed or whatever
that those two things are just not the same and I'm sure that's one reason
why we still get problems like this.

Possibly we should convert it to a state variable: NONE. TCPCONNECTING,
PROXYING, DONE and we should let everyone wait for DONE before we can
actually assume anything.

Thoughts?

(it's a bit late here and I'm on vacation so I'm sorry if I overlooked
something obvious...)

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You can respond by visiting:
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Received on 2010-07-24