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Re: GSOC 2012
From: SAI LAKSHMI Bhavana <oslbhavana () gmail com>
Date: Wed, 4 Apr 2012 11:37:20 +0530

You are getting the right idea. Let me ask you some questions to help
clarify your thinking. Suppose you have some pseudocode like this:
       struct proxy proxy1 = { PROXY_SOCKS4A, "proxy1", 9100 };
       struct proxy proxy2 = { PROXY_HTTP, "proxy2", 8080 };
       struct proxy proxy3 = { PROXY_SOCKS5, "proxy3", 3128 };
       nsock_add_proxy(nsp, &proxy1);
       nsock_add_proxy(nsp, &proxy2);
       nsock_add_proxy(nsp, &proxy3);
       nsock_connect_tcp(nsp, handle_connect, "target", 80);
You need to think about it in terms of events and callbacks. So for
example, I think that the final function call above will call
nsock_connect_tcp_primitive(nsp, handle_socks4a_proxy_connect, "proxy1", 9100).
The handle_socks4a_proxy_connect callback function will send the SOCKS
proxy request for proxy2:8080, and register its own callback to read the
response. The read callback will then (assuming the proxy request
succeeds) send the next HTTP request, and so on.
What
internal callback functions do you think will be necessary? It may help
to walk through the example I gave you, knowing that you have to make it
work as several function calls that you don't control directly, not just
a simple blocking while loop.

Hello Sir,

For the above given example
handle_socks4a_proxy_connect callback on success of the connect event
      creates a ms_event of type NSE_WRITE and sends socks proxy
request for proxy2:8080
      *nse = new ms_event(*nsp, NSE_WRITE, *ms_iod, timeout_secs,
handle_socks4a_proxy_write, *userdata);
handle_socks4a_proxy_write callback on success of write event creates
a NSE_READ event
      *nse = new ms_event(*nsp, NSE_READ, *ms_iod, timeout_secs,
handle_socks4a_proxy_read, *userdata);
handle_socks4a_proxy_read callback on success of read event creates a
NSE_WRITE event for the next proxy in chain so on.



What new event types do you think will be necessary (if any)?

I think of having a new event type NSE_TYPE_PROXY_CONNECT;

How will you remember your position in the proxy list between function
calls? I suspect we will need to add a new member to nsock_iod. Is there
any other new state you think will be needed?


we can create a gh_list of the proxy structs as gh_list proxy_chain.
This list can be made a member of mspool struct
Another member *next_proxy to know the next proxy to be handled in the
proxy chain.

A new state NSE_STATUS_PROCESS is necessary to represent that the
proxy chain is being handled.

(P.S. Your step (2) above should send a SOCKS request to proxy1, not an
HTTP request.)

   yes :)
the request to be sent for a particular proxy HTTP or SOCKS can be
known from two methods that can  be included  namely
req_http_proxy(url), req_socks_proxy(url)

I don't understand what these functions do. What do they return, a
string containing the request text? In what other functions will these
functions be called?

yes, these functions just return a string containing the request text
this will help up having just one callback such as handle_proxy_write
rather than having handle_socks4a_proxy_write and
handle_http_proxy_write.

Sir please let me know how to write a good proposal :)

Suggestions are most welcomed :)
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