Re: [Xen-devel] kernel oops/IRQ exception when networking between many domUs

[Nils Toedtmann <xen-devel@xxxxxxxxxxxxxxxxxx>]

Am Mittwoch, den 08.06.2005, 14:34 +0200 schrieb Nils Toedtmann:
[...] 
> Ok, reproduced the dom0 kernel panic in a simpler situation:
> 
> * create some domUs, each having 1 interface in the same subnet
> * bridge all the interfaces together (dom0 not having an ip on that
>   bridge)
> * trigger unicast traffic as much as you want (like unicast flood
>   pings): No problem.
> * Now trigger some broadcast traffic between the domUs:
> 
>     ping -i 0,1 -b 192.168.0.255
> 
>   BOOOM.
> 
> 
> Instead, you may down all vifs first, start the flood broadcast ping in
> the first domU and bring up one vif after the other (wait each time
> >15sec until the bridge put the added port in forwarding state). After
> bringing up 10-15 vifs, dom0 panics. 
> 
> I could _not_ reproduce this with massive unicast traffic. The problem
> disappears if i set "net.ipv4.icmp_echo_ignore_broadcasts=1" in all
> domains. Maybe the probem rises if to many domUs answer to broadcasts at
> the same time (collisions?).


More testing: again doing a 

  [root@domUtest01 ~]# ping -f -b 192.168.0.255

into the bridged vif-subnet. With all domains having
"net.ipv4.icmp_echo_ignore_broadcasts=1" (so noone answers the pings)
everything is fine. When i switch in the pinging domUtest01 itself (and
_only_ in that domain) to "net.ipv4.icmp_echo_ignore_broadcasts=0", dom0
immediately panics (if there are 15-20 domUs in that bridged subnet).

Another test: putting dom0's vif0.0 on the bridge too, pinging from
dom0. Then in needed (yet) all domains to have
"net.ipv4.icmp_echo_ignore_broadcasts=0" to get my oops.

The oopses happen in different places, not all contain
"net_rx_action" (all are "Fatal exception in interupt". These "dumps"
may contain typos because i copied them from monitor by hand):

  [...] 
  error_code
  kfree_skbmem
  __kfree_skb
  net_rx_action
  tasklet_action
  __do_softirq
  soft_irq
  irq_exit
  do_IRQ
  evtchn_do_upcall
  hypervisor_callback
  __wake_up
  sock_def_readable
  unix_stream_sendmsg
  sys_sendto
  sys_send
  sys_socketcall
  syscall_call

or

  [...] 
  error_code
  tasklet_action
  __do_softirq
  soft_irq
  irq_exit
  do_IRQ
  evtchn_do_upcall
  hypervisor_callback

or

  [...] 
  error_code
  tasklet_action
  __do_softirq
  soft_irq
  evtchn_do_upcall
  hypervisor_callback
  cpu_idle
  start_kernel

or

  [...] 
  error_code
  kfree_skbmem
  __kfree_skb
  net_rx_action
  tasklet_action
  __do_softirq
  soft_irq
  irq_exit
  do_IRQ
  evtchn_do_upcall
  hypervisor_callback
  __mmx_memcpy
  memcpy
  dup_task_struct
  copy_process
  do_fork
  sys_clone
  syscall_call

or

  [...] 
  error_code
  kfree_skbmem
  __kfree_skb
  net_rx_action
  tasklet_action
  __do_softirq
  soft_irq
  irq_exit
  do_IRQ
  evtchn_do_upcall
  hypervisor_callback
  __wake_up
  sock_def_readable
  unix_stream_sendmsg
  sys_sendto
  sys_send
  sys_socketcall
  syscall_call

or

  [...] 
  error_code
  kfree_skbmem
  __kfree_skb
  net_rx_action
  tasklet_action
  __do_softirq
  do_softirq
  local_bh_enable
  dev_queue_xmit
  nf_hook_slow
  ip_finish_output
  dst_output
  ip_push_pending_frames
  raw_sendmsg
  sock_sendmsg
  sys_sendmsg
  sys_socketcall
  syscall_call

and more ...


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