closing that old report, as it has not got recent comment.

** Changed in: xen-3.3 (Ubuntu)
       Status: Incomplete => Invalid

** Changed in: xen-3.2 (Ubuntu)
       Status: Confirmed => Invalid

** Changed in: xen-3.1 (Ubuntu)
       Status: Confirmed => Invalid

** Changed in: linux (Ubuntu)
       Status: Incomplete => Invalid

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https://bugs.launchpad.net/bugs/154271

Title:
  xenU sending too big packets

Status in linux package in Ubuntu:
  Invalid
Status in xen-3.1 package in Ubuntu:
  Invalid
Status in xen-3.2 package in Ubuntu:
  Invalid
Status in xen-3.3 package in Ubuntu:
  Invalid

Bug description:
  etup: amd64, xen0 = ubuntu 7.10 ("gutsy"), xenU = ubuntu 7.10 ("gutsy"),
  network config with xenU routing via xen0.

  scp xenU:file .         very slow, ~50KB/s
  scp xen0:file .         several MB/s

  on xen0:
  scp xenU:file .         many MB/s

  had a look at tcpdump, I see lines like this:
  10:55:30.319389 IP (tos 0x8, ttl 64, id 59286, offset 0, flags [DF], proto TCP
  (6), length 2948) xenU.22 > desktop: . 47785:50681(2896) ack 0 win 404
  <nop,nop,timestamp 20681576 687514747>
  10:55:30.319399 IP (tos 0xc8, ttl 64, id 52994, offset 0, flags [none], proto
  ICMP (1), length 576) xen0 > xenU: ICMP desktop unreachable - need to frag
  (mtu 1500), length 556 IP (tos 0x8, ttl 64, id 59286, offset 0, flags [DF],
  proto TCP (6), length 2948) xenU.22 > desktop.41056: . 47785:50681(2896) ack
  0 win 404 <nop,nop,timestamp 20681576 687514747>[|icmp]

  so the xenU is sending packets with size 2948? why?
  ifconfig on xenU:

  eth0      Link encap:Ethernet  HWaddr 00:16:3E:6D:03:2D
            inet addr:xenU  Bcast:...  Mask:255.255.255.255
            inet6 addr: fe80::216:3eff:fe6d:32d/64 Scope:Link
            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
            RX packets:34918213 errors:0 dropped:0 overruns:0 frame:0
            TX packets:34262839 errors:0 dropped:0 overruns:0 carrier:0
            collisions:0 txqueuelen:1000
            RX bytes:12337072144 (11.4 GB)  TX bytes:48486812526 (45.1 GB)

  so the MTU is 1500 which is fine. xenU sending too big packets.

  == WORK AROUND ==

  It seems that turning off TX checksum offloading within the domU
  eliminates the issue:

      ethtool -K ethN tx off

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