socks4/5 proxy question

carrotcake1029 · 11-27-2008, 08:41 AM

I am in the process of writing my own socks4/5 proxy. I am to the point where the client has connected, sent the data with the requested ip, and have connected to that ip.

From other topics I have seen terms like blocking/nonblocking and I think that one of these apply here.

I have one main do loop that is basically is a recv() loop. When I make the connection to the server, where do I insert that recv?

initconn() makes a connection to the server. I only support socks4 atm.

Code:

	do 
	{
        err = recv(sckclient, recvbuf, 2048, 0);
        if (err > 0) 
		{
			msgnum++;
			if (msgnum == 1)
			{
				if ((recvbuf[0] == 0x04) && (recvbuf[1] == 0x01))
				{
					sckdestin = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
				    if (sckdestin == INVALID_SOCKET) 
					{
						printf("Invalid Socket\n");
				        errout(WSAGetLastError());
				        WSACleanup();
				        return 1;
				    }
					
					err = initconn(sckdestin, destinservice);
					if (acceptdeny(sckclient, err) == 0x01)
						return 1;
					printf("SOCKS 4 Connection established with TCP/IP stream connection\n");
				}
				else
				{
					printf("SOCKS 4 Connection failed\n");
					acceptdeny(sckclient, 0x02);
				}
				
			}
			else
			{
				printf("Message Received\n");
			}
		}
        else if (err == 0)
            printf("Connection closing...\n");
        else  
		{
            errout(WSAGetLastError());
            closesocket(sckclient);
            WSACleanup();
            return 1;
        }

    } while (err > 0);

**Salem** · 11-27-2008, 10:11 AM

> err = initconn(sckdestin, destinservice);
So where did these two parameters get defined?

Also, your initial recv() makes no account of fragmentation.

carrotcake1029 · 11-27-2008, 10:38 AM

Sorry for maybe not being as clear as I'd hoped, but here is how they are defined...

Code:

SOCKET sckdestin;
struct sockaddr_in destinservice;

I am unsure what you mean by how recv makes no account of fragmentation.

My question is just a logic one. If my client recv loop is always looping, where do I put my server recv loop in order for me to not lose data from either one.

**Salem** · 11-27-2008, 11:02 AM

destinservice = someRandomBitOfMagic;
Is that what happens, or is there something else?

> I am unsure what you mean by how recv makes no account of fragmentation.
If you send 10 bytes in a single send() call, then there's NO guarantee that the recv() will get those 10 bytes in a single call.
You could easily get them as 6 bytes + 4 bytes.
Or in extreme cases, 1 at a time.
If your code doesn't allow for that, then it's not going to work.

carrotcake1029 · 11-27-2008, 11:11 AM

Good point about the fragmentation thing, shouldn't be too hard to fix. I remember having issues like that from my BASIC days.

If you really want to know about destinservice, here is how it gets modified:

Code:

	serv.sin_family = AF_INET;
    serv.sin_addr.s_addr = ip;
    serv.sin_port = port;

That is inside my initconn function.
I tend to write code to get the job done first, then make it all spiffy-like later.

My real question though is how do I get my program to be able to receive data on 2 different sockets at the same time.

root4 · 11-27-2008, 11:16 AM

use either select() or poll().

carrotcake1029 · 11-27-2008, 11:51 AM

Thank you.

I am assuming select() is for Win32 and poll() is for unix variants?

root4 · 11-27-2008, 12:44 PM

both exist on unix. I don't know for windows.

11-27-2008, 10:11 AM	#2
Salem and the hat of Jobseeking Join Date: Aug 2001 Location: The edge of the known universe Posts: 21,650	> err = initconn(sckdestin, destinservice); So where did these two parameters get defined? Also, your initial recv() makes no account of fragmentation. __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
Salem is offline

11-27-2008, 10:38 AM	#3
carrotcake1029 Registered User Join Date: Apr 2008 Posts: 309	Sorry for maybe not being as clear as I'd hoped, but here is how they are defined... Code: SOCKET sckdestin; struct sockaddr_in destinservice; I am unsure what you mean by how recv makes no account of fragmentation. My question is just a logic one. If my client recv loop is always looping, where do I put my server recv loop in order for me to not lose data from either one.
carrotcake1029 is offline

11-27-2008, 11:02 AM	#4
Salem and the hat of Jobseeking Join Date: Aug 2001 Location: The edge of the known universe Posts: 21,650	destinservice = someRandomBitOfMagic; Is that what happens, or is there something else? > I am unsure what you mean by how recv makes no account of fragmentation. If you send 10 bytes in a single send() call, then there's NO guarantee that the recv() will get those 10 bytes in a single call. You could easily get them as 6 bytes + 4 bytes. Or in extreme cases, 1 at a time. If your code doesn't allow for that, then it's not going to work. __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
Salem is offline

11-27-2008, 11:11 AM	#5
carrotcake1029 Registered User Join Date: Apr 2008 Posts: 309	Good point about the fragmentation thing, shouldn't be too hard to fix. I remember having issues like that from my BASIC days. If you really want to know about destinservice, here is how it gets modified: Code: serv.sin_family = AF_INET; serv.sin_addr.s_addr = ip; serv.sin_port = port; That is inside my initconn function. I tend to write code to get the job done first, then make it all spiffy-like later. My real question though is how do I get my program to be able to receive data on 2 different sockets at the same time.
carrotcake1029 is offline

11-27-2008, 11:16 AM	#6
root4 Registered User Join Date: Apr 2008 Posts: 282	use either select() or poll().
root4 is offline

11-27-2008, 11:51 AM	#7
carrotcake1029 Registered User Join Date: Apr 2008 Posts: 309	Thank you. I am assuming select() is for Win32 and poll() is for unix variants?
carrotcake1029 is offline

11-27-2008, 12:44 PM	#8
root4 Registered User Join Date: Apr 2008 Posts: 282	both exist on unix. I don't know for windows.
root4 is offline

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