Re: the tun device's pointopoint link and source address check

From: Sven-Haegar Koch
Date: Fri Oct 28 2005 - 14:32:39 EST


On Fri, 28 Oct 2005, Ritesh Kumar wrote:

While experimenting with the tun device I found that I was not
able to receive packets on the tun interface (i.e. a udp listener for
packets couldn't get the packets transmitted from the program which
wrote to /dev/net/tun), if the source address of the packet was not
equal to end point IP address of the tun pointopoint link. It seemed
that internally, linux dropped a packet it saw on the tun interface
(tcpdump on the tun interface shows the packet) because its source
address didn't match the IP address of the pointopoint end host of the
tun interface.
My question is, can this check be disabled?

Just a wild guess:
echo 0 >/proc/sys/net/ipv4/conf/tunX/rp_filter
or
echo 0 >/proc/sys/net/ipv4/conf/all/rp_filter

c'ya
sven

--

The Internet treats censorship as a routing problem, and routes around it.
(John Gilmore on http://www.cygnus.com/~gnu/)
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