I haven't yet got a response for this on the users list and so, am forwarding it to the devel list.
Hope someone out here knows the answer to this. Thanks! Harsha ---------------------------------------------------------------------------- University of Washington | http://www.cs.washington.edu/homes/harsha/ har...@cs.washington.edu | http://harshaandsports.blogspot.com/ ---------------------------------------------------------------------------- ---------- Forwarded message ---------- List-Post: openvpn-devel@lists.sourceforge.net Date: Mon, 16 May 2005 00:17:21 -0700 (PDT) From: Harsha V. Madhyastha <har...@cs.washington.edu> To: openvpn-us...@lists.sourceforge.net Subject: What happens to raw IP packets written to the TUN device? Hi everyone, I had written about this problem to the list a couple of months back and hadn't received any relevant response. So, I am presenting the same problem in a different light now. Hopefully one of you will be able to help me out. The basic question is as follows. Suppose I open a WIN32 HANDLE on the TUN/TAP device and then write a raw packet inclusive of IP header to it (the packet is destined to destination D), is it reasonable to expect that the packet will be sent out to D via the normal eth0 interface? (assuming the routing table is such that packets to destination D should be routed to eth0). Similarly, on Linux, if I open a file descriptor on /dev/net/tun and write a raw packet to it, will it be forwarded to the eth0 interface? One of the responses to my previous email had suggested that I did not have forwarding enabled, and as suggested, I executed on Linux "echo 1 > /proc/sys/net/ipv4/ip_forward" and also, added "iptables -A FORWARD -j ACCEPT", but that did not help. The main point of confusion is that when I write raw packets with local IP address as the destination address, the packet gets forwarded to the appropriate application, but when I write raw packets destined to other addresses, the packet just disappears! So, I am beginning to doubt whether the TUN interface is meant to be such that raw packets will get forwarded to the appropriate interface. Please note that I am using the TUN/TAP device installed by OpenVPN on Windows XP and I'm using the standard /dev/net/tun device on Linux, and the same problem is seen on both. Please let me know if you need more details to understand the problem. I would be glad to divulge as much information as you need. I hope one of you will respond to my call for help! Thanks! Harsha ---------------------------------------------------------------------------- University of Washington | http://www.cs.washington.edu/homes/harsha/ har...@cs.washington.edu | http://harshaandsports.blogspot.com/ ----------------------------------------------------------------------------
