Network troubles after 8.3 -> 8.4 upgrade

[Andrea Venturoli]

Hello.

Three days ago I upgraded an amd64 8.3 box to the latest 8.4.
Since then the outside network is misbehaving: large mails are not 
sended (although small ones do), svn operations will work for a while, 
then come to a sudden stop, etc...
Perhaps the most evident test is "wget"ting a big file: it will download 
some chunk, halt; restart after a while and download another chunk; lose 
the connection once again, then restart and so on.

I remember a couple of similar experiences in the past, from which I got 
out by disabling TSO; however those box had fxp cards, while this has an em.
In any case disabling TSO did not help.

This is the relevant part of rc.conf:
> cloned_interfaces="lagg0 vlan1 vlan2 vlan3 carp0 carp1 carp3 carp4 carp6 carp7 carp9 carp10"
> ifconfig_igb0="up"
> ifconfig_igb1="up"
> ifconfig_lagg0="laggproto lacp laggport igb0 laggport igb1 192.168.101.4 netmask 255.255.255.0"
> ifconfig_lagg0_alias0="inet 192.168.101.101 netmask 0xffffffff"
> ifconfig_carp0="vhid 1 advskew 100 pass xxxxxxx 192.168.101.10"
> ifconfig_carp1="vhid 2 pass xxxxxxxx 192.168.101.10"
> ifconfig_em0="up"
> ifconfig_vlan1="inet 81.174.30.11 netmask 255.255.255.248 vlan 4 vlandev em0"
> ifconfig_vlan2="inet 83.211.188.186 netmask 255.255.255.248 vlan 2 vlandev em0"
> ifconfig_vlan3="inet 192.168.2.202 netmask 255.255.255.0 vlan 3 vlandev em0"
> ifconfig_carp3="vhid 4 advskew 100 pass xxxx 81.174.30.12"
> ifconfig_carp4="vhid 5 pass xxxxxxx 81.174.30.12"
> ifconfig_carp6="vhid 7 advskew 100 pass xxxxxx 83.211.188.187"
> ifconfig_carp7="vhid 8 pass xxxxxxxxxxx 83.211.188.187"
> ifconfig_carp9="vhid 10 advskew 100 pass xxxxxxxx 192.168.2.203"
> ifconfig_carp10="vhid 11 pass xxxxxxxx 192.168.2.203"
> ifconfig_lo0_alias0="inet 127.0.0.2 netmask 0xffffffff"
> ifconfig_lo0_alias1="inet 127.0.0.3 netmask 0xffffffff"
> ifconfig_lo0_alias2="inet 127.0.0.4 netmask 0xffffffff"

As you can see the setup is quite complicated, but worked like a charm 
until the upgrade; actually the internal net (igb+lagg+carp) still does, 
so this is what points me toward em0, where I cannot seem to get any 
kind of stability.

The card is
> em0 at pci0:6:0:0: class=0x020000 card=0x10828086 chip=0x107d8086 rev=0x06 hdr=0x00
>     vendor     = 'Intel Corporation'
>     device     = 'PRO/1000 PT'
>     class      = network
>     subclass   = ethernet

I tried disabling TSO, RXCSUM, TXCSUM, VLANHWTAG, VLANHWCSUM, VLANHWTSO...
I tried putting the card into 10baseT/UTP <half-duplex> mode...
I tried sysctl net.inet.tcp.tso=0...

None helped.

Maybe I'm barking up the wrong tree, but nothing is in the logs to help...

Nor did Google or wading through bug reports.



Now I could restore the dumps I made before upgrading to 8.4 (but I'd 
really like to avoid this), try to upgrade even further to 9.2 (although 
this will be a lot of work and I'm not looking forward to it as a shot 
in the dark), drop in another NIC...
What I'd really like, however, is some insight.

Is this a known problem of some sort? Is this card or this driver known 
to be broken?
Is there any way I could get some debugging info?

Any hint is appreciated (and I need it badly :( !!!).

  bye & Thanks
	av.