RE: [Xen-devel] network hang trigger

["Charles Coffing" <ccoffing@xxxxxxxxxx>]

I was able to reproduce the hang easily.  "ping -s 1473" worked, but
"ping -s 1499" hung.  While it was hung, I tried pinging the other
direction and that hung too.

My setup:
Pinging from DOMU to DOM0
Changeset 1.1307
DOM0: 2.6.8.1, Stock configuration
DOMU: 2.6.8.1, Stock, except writable pagetables are disabled

ccoffing2:~ # ping -s 1499 137.65.171.60
PING 137.65.171.60 (137.65.171.60) 1499(1527) bytes of data.
1507 bytes from 137.65.171.60: icmp_seq=1 ttl=64 time=0.455 ms
ping: sendmsg: No buffer space available
ping: sendmsg: No buffer space available
ping: sendmsg: No buffer space available
ping: sendmsg: No buffer space available
ping: sendmsg: No buffer space available
ping: sendmsg: No buffer space available
ping: sendmsg: No buffer space available
>From 137.65.171.60: icmp_seq=2 Frag reassembly time exceeded
>From 137.65.171.60 icmp_seq=2 Frag reassembly time exceeded
1507 bytes from 137.65.171.60: icmp_seq=3 ttl=64 time=28980 ms
1507 bytes from 137.65.171.60: icmp_seq=4 ttl=64 time=27980 ms
1507 bytes from 137.65.171.60: icmp_seq=5 ttl=64 time=26980 ms

--- 137.65.171.60 ping statistics ---
15 packets transmitted, 4 received, +2 errors, 73% packet loss, time
33213ms
rtt min/avg/max/mdev = 0.455/20985.849/28980.992/12136.540 ms, pipe 11





>>> "James Harper" <JamesH@xxxxxxxxxxxxxxxx> 09/15/04 8:43 AM >>>
Hmmmm... are you running 2.6 and pinging from xenU to xen0?

I've read your other emails, and I can still get it to fail if I remove
vif1.0 from the bridge and give it its own ip address, but to properly
exclude bridging I guess I'd have to boot up the computer with bridging
never having been started...

I'm running code checked out and compiled yesterday (15th AEST), and
have writable pagetables on but only since that last compile. It fails
either way. I have no iptables/conntrack related modules loaded in
either domain.

I think we'll have to start comparing .config's, but I need to get some
sleep.

James

> -----Original Message-----
> From: Keir Fraser [mailto:Keir.Fraser@xxxxxxxxxxxx]
> Sent: Wednesday, 15 September 2004 19:55
> To: James Harper
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-devel] network hang trigger
> 
> 
> I can't reproduce this. e.g.,
>  [root@druid-0 root]# ping -s 2473 128.232.39.40
>  PING 128.232.39.40 (128.232.39.40) 2473(2501) bytes of data.
>  2481 bytes from 128.232.39.40: icmp_seq=0 ttl=64 time=0.074 ms
>  2481 bytes from 128.232.39.40: icmp_seq=1 ttl=64 time=0.057 ms
>  2481 bytes from 128.232.39.40: icmp_seq=2 ttl=64 time=0.055 ms
>  2481 bytes from 128.232.39.40: icmp_seq=3 ttl=64 time=0.057 ms
> 
> Both domains have 256MB memory. MTU for both is 1500.
> 
>  -- Keir
> 
> > I have found that simply doing a ping with packetsize > 1500 (maybe
> > mtu???) causes the network to hang for a short time. This is from
xenU
> > and xen0 on the same machine.
> >
> > Can someone else _please_ test this? I am able to make the network
hang
> > by saying from domU:
> > ping -s 1473 <dom0 ip>
> > (1473 + 28 byte header = 1501 byte packet)
> >
> > I'll do more testing tomorrow.
> >
> > thanks
> >
> > James
> >
> >
> > -------------------------------------------------------
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>  -=- MIME -=- 
> 
> 
> I have found that simply doing a ping with packetsize > 1500 (maybe
> mtu???) causes the network to hang for a short time. This is from xenU
> and xen0 on the same machine.
> 
> Can someone else _please_ test this? I am able to make the network
hang
> by saying from domU:
> ping -s 1473 <dom0 ip>
> (1473 + 28 byte header =3D 1501 byte packet)
> 
> I'll do more testing tomorrow.
> 
> thanks
> 
> James
> 
> 
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