Subject: Re: tap(4) and netbsd-2
To: Quentin Garnier <>
From: Stefan Wurstbauer <>
List: current-users
Date: 01/27/2005 13:09:16
Hi Quentin,

I use the tap interface as a bridge to my ethernet interface ex0.
Exactly I use openvpn as a lan-lan tunnel. All packets from ex0 are 
tunneled through tap0 to the remote machine.

The Problem is, there is only sometimes a real crash. I don't get an db> 
prompt on the console but the machine stopps responding on every 
interface. Only a reboot will solve this problem.
In the other case here is the backtrace:

login: uvm_fault(0xc6e91898, 0, 0, 1) -> 0xe
kernel: page fault trap, code=0
Stopped in pid 496.1 (mp3blaster) at    netbsd:m_adj+0x5c:      movl 
db> trace
m_adj(c0e3e800,fffffffc,c724ad28,c037bd13,5ee) at netbsd:m_adj+0x5c
ether_input(c0da4038,c0e3e800,c724ad78,c0d03c60,c0e3e800) at 
ex_intr(c0da4000,5,c0dd0010,c0d00030,c7240010) at netbsd:ex_intr+0x332
Xintr_legacy12() at netbsd:Xintr_legacy12+0xa8
--- interrupt ---
sbappendaddr(c0edd780,c724af08,c0d00e00,c0d00e00,c0d00e00) at 
udp4_sendup(c0dd0300,1c,c724af08,c0edd708,ffffffff) at 
udp4_realinput(c724af08,c724aef8,c0dd0300,14,c0da4038) at 
udp_input(c0dd0300,14,11,c0da4038,c0da4000) at netbsd:udp_input+0x159
ip_input(c0dd0300,c0d03f20,0,7,0) at netbsd:ip_input+0x579
ipintr(83b001f,4820001f,4820001f,80e001f,80793e0) at netbsd:ipintr+0x71
DDB lost frame for netbsd:Xsoftnet+0x40, trying 0xc724afa8
Xsoftnet() at netbsd:Xsoftnet+0x40
--- interrupt ---

Quentin Garnier wrote:
> On Wed, Jan 26, 2005 at 10:51:55PM +0100, Stefan Wurstbauer wrote:
>>Hi CÚsar,
>>works the tap-lkm for your requirement? I use the tap-lkm on a 2.0
>>system with an openvpn tunnel. My experiences are not good enough for a
>>productive environment. On heavy load through the tunnel the system
>>crashes with error messages from the underlying ethernet interface (in
>>my case ex0). 
> What do you mean by underlying ethernet device?  And how exactly do you
> use it with openvpn?  What is the _precise_ backtrace of the crash?
> Oh, and what is the PR number of that issue?