more UDP packet loss?

[Urban Boquist <urban%boquist.net@localhost>]

Hi all,

some other people have reported UDP packet loss between domU and dom0
(in bridge mode) but I understood that has mostly been under high
traffic load? I seem to get loss also with no load at all.

Every time I start a domU I see lost DHCP replies and lots of NFS
retransmits. This is for a domU with root on NFS but I get the DHCP
problems also for a domU on local disk. At the same time the other
running domU:s seem to "freeze". After the domU is started it uses NFS
over TCP and that seems to work better.

Below are packet captures during boot, up to the NFS mount root
call. The DHCP offers come back from the DHCP server on physical wm0
but the first 7 never reaches the domU XVIF interface. Netstat shows
no packet loss.

This is on a 8GB Quad core Xeon system - with zero CPU load in dom0
and a couple of other domUs. Week old -current amd64 dom0.

I tried increasing the UDP send/receive buffers in dom0 but it made no
difference.

Any ideas?
    -- Urban

domU xvif:
No.     Time            Source                Destination           Protocol 
Info
      1 11:01:36.718159 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
      2 11:01:37.718119 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
      4 11:01:39.718100 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
      6 11:01:42.718037 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
      7 11:01:46.717970 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
      8 11:01:51.717910 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
      9 11:01:56.717828 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
     12 11:02:01.717769 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
     13 11:02:01.719371 192.168.1.27          192.168.1.29          DHCP     
DHCP Offer    - Transaction ID 0x1ffffff
     14 11:02:01.719409 0.0.0.0               255.255.255.255       DHCP     
DHCP Request  - Transaction ID 0x1ffffff
     15 11:02:01.720906 192.168.1.27          192.168.1.29          DHCP     
DHCP ACK      - Transaction ID 0x1ffffff
     16 11:02:01.721083 Xensourc_2c:68:57     Broadcast             ARP      
Gratuitous ARP for 192.168.1.29 (Request)
     25 11:02:04.717719 Xensourc_2c:68:57     Broadcast             ARP      
Who has 192.168.1.43?  Tell 192.168.1.29
     26 11:02:04.718361 Asiarock_f5:2c:a0     Xensourc_2c:68:57     ARP      
192.168.1.43 is at 00:0b:6a:f5:2c:a0
     27 11:02:04.718381 192.168.1.29          192.168.1.43          Portmap  V2 
GETPORT Call (Reply In 28) MOUNT(100005) V:3 UDP

physical wm0:
No.     Time            Source                Destination           Protocol 
Info
      1 11:01:36.718167 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
      2 11:01:36.719828 192.168.1.27          192.168.1.29          DHCP     
DHCP Offer    - Transaction ID 0x1ffffff
      3 11:01:37.718125 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
      4 11:01:37.719748 192.168.1.27          192.168.1.29          DHCP     
DHCP Offer    - Transaction ID 0x1ffffff
      5 11:01:39.718106 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
      6 11:01:39.719587 192.168.1.27          192.168.1.29          DHCP     
DHCP Offer    - Transaction ID 0x1ffffff
      7 11:01:42.718043 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
      8 11:01:42.719348 192.168.1.27          192.168.1.29          DHCP     
DHCP Offer    - Transaction ID 0x1ffffff
      9 11:01:46.717975 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
     10 11:01:46.719411 192.168.1.27          192.168.1.29          DHCP     
DHCP Offer    - Transaction ID 0x1ffffff
     11 11:01:51.717915 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
     12 11:01:51.719779 192.168.1.27          192.168.1.29          DHCP     
DHCP Offer    - Transaction ID 0x1ffffff
     13 11:01:56.717901 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
     14 11:01:56.719762 192.168.1.27          192.168.1.29          DHCP     
DHCP Offer    - Transaction ID 0x1ffffff
     15 11:02:01.717836 0.0.0.0               255.255.255.255       DHCP     
DHCP Discover - Transaction ID 0x1ffffff
     16 11:02:01.719363 192.168.1.27          192.168.1.29          DHCP     
DHCP Offer    - Transaction ID 0x1ffffff
     17 11:02:01.719413 0.0.0.0               255.255.255.255       DHCP     
DHCP Request  - Transaction ID 0x1ffffff
     18 11:02:01.720899 192.168.1.27          192.168.1.29          DHCP     
DHCP ACK      - Transaction ID 0x1ffffff
     19 11:02:01.721147 Xensourc_2c:68:57     Broadcast             ARP      
Gratuitous ARP for 192.168.1.29 (Request)
     20 11:02:04.717723 Xensourc_2c:68:57     Broadcast             ARP      
Who has 192.168.1.43?  Tell 192.168.1.29
     21 11:02:04.718354 Asiarock_f5:2c:a0     Xensourc_2c:68:57     ARP      
192.168.1.43 is at 00:0b:6a:f5:2c:a0
     22 11:02:04.718384 192.168.1.29          192.168.1.43          Portmap  V2 
GETPORT Call (Reply In 23) MOUNT(100005) V:3 UDP