[Qemu-devel] [Bug 1192464] [NEW] udp checksum computed as 0 not converted to 0xffff, from guest os that share a common linux bridge among multiple guest os

[bk.rakesh]

Public bug reported:

UDP checksum computed as '0' during transmission of packets that uses
e1000 NIC in the Guest as well as emulated h/w in the qemu layer, That
needs to be converted to 0xffff, This occurs only when Hardware checksum
offload is been set in the guest OS NIC and made it as a transmitter.
The guest O.S use the N/W interface that is been shared to the linux
brige created in the host (used source=<bridge>) in the xml tags of
libvirt.

As per RFC768(http://tools.ietf.org/html/rfc768 [^]), If the computed
checksum is zero, it is transmitted as all ones (the equivalent in one's
complement arithmetic). An all zero transmitted checksum value means
that the transmitter generated no checksum (for debugging or for higher
level protocols that don't care).

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1192464

Title:
  udp checksum computed as 0 not converted to 0xffff, from guest os that
  share a common linux bridge among multiple guest os

Status in QEMU:
  New

Bug description:
  UDP checksum computed as '0' during transmission of packets that uses
  e1000 NIC in the Guest as well as emulated h/w in the qemu layer, That
  needs to be converted to 0xffff, This occurs only when Hardware
  checksum offload is been set in the guest OS NIC and made it as a
  transmitter. The guest O.S use the N/W interface that is been shared
  to the linux brige created in the host (used source=<bridge>) in the
  xml tags of libvirt.

  As per RFC768(http://tools.ietf.org/html/rfc768 [^]), If the computed
  checksum is zero, it is transmitted as all ones (the equivalent in
  one's complement arithmetic). An all zero transmitted checksum value
  means that the transmitter generated no checksum (for debugging or for
  higher level protocols that don't care).

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