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List:       bochs-dev
Subject:    [Bochs-developers] problems with tuntap
From:       Cristian CONSTANTIN <constantin () fokus ! fraunhofer ! de>
Date:       2004-07-29 14:15:18
Message-ID: 20040729141518.GF13005 () terix ! fokus ! gmd ! de
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hi!

I'm trying to have an working network connection for a bochs; sometimes it
fails... here is my configuration and an description of the problem I
have seen.

- host: dell 1750 running debian testing/unstable, kernel 2.6.3,
bochs 2.1.1-5; the network for bochs is configured like:

ne2k: ioaddr=0x240, irq=9, mac=fe:fd:00:00:00:01, ethmod=tuntap,
ethdev=tun, script=/store/bochs/tunconf.sh

- guest: openbsd 3.5 (if that matters)

the host tuntap interface is 10.100.0.1; guest ne0 interface is
10.100.0.2.
when I ping from the host the guest, bochs barks with lots of:

13854460000i[NE2K ] packet too short (42), padding to 60
13914760000i[NE2K ] tuntap read returned 42 bytes

on the host ping reports:

galador:/home/cco# ping 10.100.0.2
PING 10.100.0.2 (10.100.0.2) 56(84) bytes of data.
From 10.100.0.1 icmp_seq=1 Destination Host Unreachable
From 10.100.0.1 icmp_seq=2 Destination Host Unreachable

tcpdump on the tuntap interface on the host reveals:

16:51:05.045874 0:ff:82:d6:92:c1 ff:ff:ff:ff:ff:ff 0806 42: arp who-has
10.100.0.2 tell 10.100.0.1
16:51:06.045450 0:ff:82:d6:92:c1 ff:ff:ff:ff:ff:ff 0806 42: arp who-has
10.100.0.2 tell 10.100.0.1

so, no answer to the arp requests comes from the bochs. 
as soon as I start tcpdump on the openbsd running inside bochs, the host
machine starts receving icmp replies. after I stop the tcpdump on the
openbsd and the arp cahe expires on the host ping stops working as well. 
maybe it has to do with the promiscous mode of the interface on the 
guest machine because as soon as I start tcpdump on the guest machine,
it responds to the arp request:

17:13:51.591554 fe:fd:0:0:0:1 0:ff:82:d6:92:c1 0806 60: arp reply
10.100.0.2 is-at fe:fd:0:0:0:1

it is worth mentioning that networking for uml using tuntap 
works without problems on the same host machine having the same
configuration/kernel.

thanks a lot!
bye now!
cristian
-- 
 _          | There are many people who use UNIX or Linux  
(_'_        | who IMHO do not understand UNIX.
  (_'rist   |              --David Korn  
GPG public key at wwwkeys.de.pgp.net

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