collisions on tun interfaces ...

[YongHyeon PYUN]

On Fri, Apr 29, 2011 at 12:52:31PM +0300, Zeus V Panchenko wrote:
> Hi,
> 
> may somebody epxplain it for me, what can cause collisions on tun
> interfaces created by ppp(8) and openvpn?
> 
> > uname -a
> FreeBSD 8.2-STABLE #0 i386
> 
> > netstat -i
> Name    Mtu Network       Address              Ipkts Ierrs Idrop    Opkts Oerrs  Coll
> tun0   1492 <Link#7>                        18940349     0     0 15737760     0 45668
> tun0   1492 A.B.C.D A-B-C-D.domain          15623965     -     - 12429351     -     -
> tun1   1500 <Link#8>                        12721670     0     0  9957662     0 11161
> tun1   1500 E.F.G.H E-F-G-H.vpn     	        6454     -     -   445751     -     -
> 
> 
> rl0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
>      options=3808<VLAN_MTU,WOL_UCAST,WOL_MCAST,WOL_MAGIC>
>      ether 00:30:4f:67:cf:81
>      media: Ethernet autoselect (100baseTX <full-duplex>)
>      status: active
> tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> metric 0 mtu 1492
>       options=80000<LINKSTATE>
>       inet A.B.C.D --> A1.B1.C1.D1 netmask 0xffffffff 
>       Opened by PID 3943
> tun1: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> metric 0 mtu 1500
>       options=80000<LINKSTATE>
>       inet E.F.G.H --> E1.F1.G1.H1 netmask 0xffffffff 
>       Opened by PID 1387
> 
> tun0 is created by ppp(8)
> 
> in /etc/ppp.conf is:
> default:
>  set log Phase Chat LCP IPCP CCP tun command
>  set server /var/run/ppp/internet "" 0177
>  set device PPPoE:rl0
>  set speed sync
>  enable lqr echo
>  set lqrperiod 30
>  set login
>  set ctsrts off
>  add default HISADDR
>  set timeout 0
>  set redial 0 0
>  set cd 5
> 
> tun1 is created by OpenVPN with configuration:
> client
> dev tun1
> proto udp
> ...
> 
> so, what can cause the collisions and can i fix them?
> 

It seems tun(4) just increments collision counter whenever it
can't enqueue packet. Because it's not collision at all I think
it's a bug that had been there from day 1. Just nuking updating the
counter will address the issue. You still can get the previous
collision counter of tun(4) with d option of netstat which shows
number of packets dropped due to send queue full.
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