icmp packets on em larger than 1472 [SEC=UNCLASSIFIED]

[Kirill Yelizarov]

--- On Thu, 11/11/10, Kevin Oberman <oberman at es.net> wrote:

> From: Kevin Oberman <oberman at es.net>
> Subject: Re: icmp packets on em larger than 1472 [SEC=UNCLASSIFIED]
> To: "Wilkinson, Alex" <alex.wilkinson at dsto.defence.gov.au>
> Cc: freebsd-stable at freebsd.org
> Date: Thursday, November 11, 2010, 8:26 AM
> > Date: Thu, 11 Nov 2010 13:01:26
> +0800
> > From: "Wilkinson, Alex" <alex.wilkinson at dsto.defence.gov.au>
> > Sender: owner-freebsd-stable at freebsd.org
> > 
> > 
> >     0n Wed, Nov 10, 2010 at
> 04:21:12AM -0800, Kirill Yelizarov wrote: 
> > 
> >     >All my em cards running
> 8.1 stable don't reply to icmp echo requests packets larger
> than 1472 bytes.
> >     >
> >     >On stable 7.2 the same
> hardware works as expected:
> >     ># ping -s 1500
> 192.168.64.99
> >     >PING 192.168.64.99
> (192.168.64.99): 1500 data bytes
> >     >1508 bytes from
> 192.168.64.99: icmp_seq=0 ttl=63 time=1.249 ms
> >     >1508 bytes from
> 192.168.64.99: icmp_seq=1 ttl=63 time=1.158 ms
> >     >
> >     >Here is the dump on em
> interface
> >     >15:06:31.452043 IP
> 192.168.66.65 > *****: ICMP echo request, id 28729, seq
> 5, length 1480
> >     >15:06:31.452047 IP
> 192.168.66.65 > ****: icmp
> >     >15:06:31.452069 IP ****
> > 192.168.66.65: ICMP echo reply, id 28729, seq 5, length
> 1480
> >     >15:06:31.452071 IP ***
> > 192.168.66.65: icmp
> >     > 
> >     >Same ping from same source
> (it's a 8.1 stable with fxp interface) to em card running
> 8.1 stable
> >     >#pciconf -lv
> > 
>    >em0 at pci0:3:4:0:   
> class=0x020000 card=0x10798086 chip=0x10798086 rev=0x03
> hdr=0x00
> >     >    vendor 
>    = 'Intel Corporation'
> >     >    device 
>    = 'Dual Port Gigabit Ethernet Controller
> (82546EB)'
> >     >    class 
>     = network
> >     >   
> subclass   = ethernet
> >     >
> >     ># ping -s 1472
> 192.168.64.200
> >     >PING 192.168.64.200
> (192.168.64.200): 1472 data bytes
> >     >1480 bytes from
> 192.168.64.200: icmp_seq=0 ttl=63 time=0.848 ms
> >     >^C
> >     >
> >     ># ping -s 1473
> 192.168.64.200
> >     >PING 192.168.64.200
> (192.168.64.200): 1473 data bytes
> >     >^C
> >     >--- 192.168.64.200 ping
> statistics ---
> >     >4 packets transmitted, 0
> packets received, 100.0% packet loss
> > 
> > works fine for me:
> > 
> > FreeBSD 8.1-STABLE #0 r213395
> > 
> > em0 at pci0:0:25:0:class=0x020000 card=0x3035103c
> chip=0x10de8086 rev=0x02 hdr=0x00
> >     vendor 
>    = 'Intel Corporation'
> >     device 
>    = 'Intel Gigabit network connection
> (82567LM-3 )'
> >     class      =
> network
> >     subclass   =
> ethernet
> > 
> > #ping -s 1473 host
> > PING host(192.168.1.1): 1473 data bytes
> > 1481 bytes from 192.168.1.1: icmp_seq=0 ttl=253
> time=31.506 ms
> > 1481 bytes from 192.168.1.1: icmp_seq=1 ttl=253
> time=31.493 ms
> > 1481 bytes from 192.168.1.1: icmp_seq=2 ttl=253
> time=31.550 ms
> > ^C
> 
> The reason the '-s 1500' worked was that the packets were
> fragmented. If
> I add the '-D' option, '-s 1473' fails on v7 and v8. Are
> the V8 systems
> where you see if failing without the '-D' on the same
> network segment?
> If not, it is likely that an intervening device is refusing
> to fragment
> the packet. (Some routers deliberately don't fragment ICMP
> Echos Request
> packets.) 

If i set -D -s 1473 sender side refuses to ping and that is correct. All mentioned above machines are behind the same router and switch. Same hardware running v7 is working while v8 is not. And i never saw such problems before.  Also correct me if i'm wrong but the dump shows that the packet arrived. I'll try driver from head and will post here results. 

Kirill
> -- 
> R. Kevin Oberman, Network Engineer
> Energy Sciences Network (ESnet)
> Ernest O. Lawrence Berkeley National Laboratory (Berkeley
> Lab)
> E-mail: oberman at es.net   
>         Phone: +1 510
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