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Date: Mon, 8 Dec 1997 09:54:53 -0500 (EST)
From: Feiyi Wang <fwang2@unity.ncsu.edu>
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To: Ruslan Ermilov <ru@ucb.crimea.ua>
cc: hackers@FreeBSD.ORG
Subject: Re: help: divert sockets question
In-Reply-To: <199712081231.OAA07525@relay.ucb.crimea.ua>
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Hi, 

It will work. Here is the way I did it

-- snip --


/* this is readIncoming() */

 inbytes = recvfrom( fd,
                      inPacketBuf,
                      sizeof inPacketBuf,
                      0,
                      (struct sockaddr*) &inPacketAddr,
                      &addrsize);


/* this is writeIncoming() */

writeIncoming(int fd)
{
  int wrote;
  wrote = sendto( fd,
                  inPacketBuf,
                  inPacketLen,
                  0,
                  (struct sockaddr *) &inPacketAddr,
                  sizeof inPacketAddr);

  if ( wrote != inPacketLen ) 
    fprintf(stderr, "failed to write packet back\n");
  else
    return wrote;
}



On Mon, 8 Dec 1997, Ruslan Ermilov wrote:

> Hi, Hackers!
> 
> I'm in process of writing a small `iptunnel' program
> which lets me tunnel IP traffic thru UDP.
> 
> My program uses two sockets: UDP and divert.
> 
> It reads IP-packet from divert socket and
> sends it to the remote machine thru UDP.
> Remote machine then reads it from UDP and
> reinjects the IP-packet by writing it to the
> divert socket.
> 
> And vice versa.
> 
> It works greatly!
> 
> Problem:
> 
> I want to reinject received thru UDP IP-packet
> as incoming. `man ipdivert' says that I should
> use sendto() syscall with a destination address
> equal to IP address of some my local interface.
> 
> I did it and it doesn't works.
> 
> It seems to me like a kernel is just dropping such a packet.
> But no error returned from sendto(), no packets travel
> thru the firewall.
> 
> Can anyone point me a way to write packet as incoming?
> Should I change some IP-packet fields?
> 
> TIA,
> -- 
> Ruslan A. Ermilov	System Administrator
> ru@ucb.crimea.ua	United Commercial Bank
> +380-652-247647 	Simferopol, Crimea
> 2426679 		ICQ Network, UIN
>