So the reason is that LVS cann't transmit skbs of greater than MTU that have been aggregated by GRO. And Simon Horman gived a patch to make LVS deaggregate skbs that's greater than MTU by GSO. ( http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=8f1b03a4c18e8f3f0801447b62330faa8ed3bb37 )
Great! Thank you very much! :) On Sat, Dec 15, 2012 at 12:38 AM, Jesper Dangaard Brouer <bro...@redhat.com>wrote: > On Wed, 2012-12-12 at 10:05 +0100, Florian Crouzat wrote: > > Le 11/12/2012 22:00, Thomas Bätzler a écrit : > [...] > > > > > > I don't have any answers, but I can confirm the problem (and the > > > workaround) on a box running Debian "Squeeze" with 2.6.32 directing > > > traffic from a VIP bound to lo via NAT to an active/backup bonding > > > interface on the backend. With "gro on" for the bonded interfaces to > the > > > backend real servers, throughput was ~64K/s. With "gro off" it was > > > ~50MB/s. It's not a general networking problem since a direct > connection > > > to the real server via a DNAT port forward was not impacted. > > > > > >>From what I gleaned from a cursory look with tcpdump it seems that the > > > problem is caused by incorrectly calculated tcp checksums. > > > > > > Anybody interested in pursuing this further? > > As Julian notes, this have already been fixed in upstream kernels. > ( > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=8f1b03a4c18e8f3f0801447b62330faa8ed3bb37 > ) > > And I have recently (Aug 2012) also fixed this for IPv6. > ( > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=590e3f79a21edd2e9857ac3ced25ba6b2a491ef8 > ) > > > > Yes, I can relate. > > I had the same conclusions, incorrectly calculated TCP checksums leading > > to packet drops by the next firewall (in my architecture). > > Also fixed by disabling gro. > > Its not related to incorrect checksums, but (as you noticed) the GRO > (Generic Receive Offload) feature. (Adjusted via ethtool -K ethX) > > > > CentOS 6.2, ipvsadm-1.25-9.el6.x86_64, kernel 2.6.32-220.23.1.el6.x86_64 > > FYI: I have already backported support (for GRO) for the upcoming > RHEL6.4 and RHEL5.9 kernels. (Its also in zstream for 5.8 in > kernel-2.6.18-308.19.1.el5) > > To be exact, this fixed in kernel releases (and beyond): > RHEL6 kernel-2.6.32-328.el6 > RHEL5 kernel-2.6.18-340.el5 > > If someone needs this before its officially part of a RHEL release, I > think I'm allowed to give you the kernel with this fix as a test kernel. > Just let me now directly. > > -- > Best regards, > Jesper Dangaard Brouer > MSc.CS, Sr. Network Kernel Developer at Red Hat > Author of http://www.iptv-analyzer.org > LinkedIn: http://www.linkedin.com/in/brouer > > > -- Stephen Lao _______________________________________________ Please read the documentation before posting - it's available at: http://www.linuxvirtualserver.org/ LinuxVirtualServer.org mailing list - lvs-users@LinuxVirtualServer.org Send requests to lvs-users-requ...@linuxvirtualserver.org or go to http://lists.graemef.net/mailman/listinfo/lvs-users
