** Changed in: isc-dhcp (Ubuntu Quantal)
Status: New => In Progress
** Changed in: isc-dhcp (Ubuntu Quantal)
Assignee: (unassigned) => Stéphane Graber (stgraber)
** Description changed:
- Tested with dhcp3-server ver. 3.1.3-2ubuntu3.3 in Ubuntu 10.04.3
- Server, x64.
+ == Rationale ==
+ Machines using virtio (kvm/xen) and running a dhcp server in a VM won't
receive the proper udp checksums which leads to dhcpd dropping the packets.
+ This patch forces the checksum to be calculated in such case.
+
+ == Test case ==
+ 1) Install a dhcp server in a VM using kvm/xen
+ 2) Make sure you don't have iptables re-calculating the checksums for you
+ 3) Check that the requests go through as expected
+
+ == Regression potential ==
+ Raring has had that fix for a while, so does redhat, so it looks pretty safe
to me.
+
+
+ --- original bug report ---
+ Tested with dhcp3-server ver. 3.1.3-2ubuntu3.3 in Ubuntu 10.04.3 Server,
x64.
The DHCP server reports that UDP packets sent to it have bad checksums:
Feb 11 06:57:18 ... dhcpd: 5 bad udp checksums in 5 packets
Feb 11 06:58:22 ... dhcpd: last message repeated 7 times
Feb 11 06:59:17 ... dhcpd: last message repeated 7 times
The DHCP server host is a KVM virtual machine using a virtio-based
virtual NIC.
This problem has been reported for other distros using KVM and virtio:
https://bugs.mageia.org/show_bug.cgi?id=1243
http://www.mail-archive.com/[email protected]/msg41958.html
- - suggests using iptables to write in a checksum
+ - suggests using iptables to write in a checksum
http://pkgs.fedoraproject.org/gitweb/?p=dhcp.git;a=blob;f=dhcp-4.2.2-xen-checksum.patch;h=038d346d726e131f1ab2579fe015a72b49733a0d;hb=HEAD
- - Fedora patch to dhcp to avoid this
+ - Fedora patch to dhcp to avoid this
The simplest workaround is to change the virtual NIC type from virtio to
Intel e1000 in KVM. Apparently this driver calculates checksums. But
virtio is the default driver type.
Thanks,
Tim Miller Dyck
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https://bugs.launchpad.net/bugs/930962
Title:
dhcp3-server reports many bad udp checksums to syslog using virtio NIC
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