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On Mon, Dec 08, 2008 at 09:40:12PM +0000, Daniel Drown wrote:
> I have a need for multiple local nodes in LVS. I started from the patch from
> 2005:
> http://archive.linuxvirtualserver.org/html/lvs-users/2005-06/msg00113.html
>
> I found three problems with it:
> 1. packet checksums were not calculated correctly
> 2. having stats enabled would deadlock the kernel in the stats update function
> (ip_vs_in_stats/ip_vs_out_stats)
> 3. the kernel would deadlock in the packet recieve function (ip_vs_in)
>
> For #1, I believe this was because the existing code assumes the TCP/UDP
> checksums are correct (which is not true for locally generated packets with
> hardware checksum). I just used the same code that the tcp and udp functions
> use.
>
> For #2 and #3, the problem was that the majority of the code runs as a bottom
> handler. Locally generated packets are run as a normal kernel context. If a
> network interrupt happens while the kernel is holding a IPVS lock for sending
> a local packet, it can schedule the bottom handler. The bottom handler can
> then try to acquire the same lock, and this is a deadlock. To prevent this
> from happening, I've disabled bottom handlers (local_bh_disable) in the local
> packet output function I created (ip_vs_out_nobh).
>
> I've tested this and it works on a RH5/CentOS5 2.6.18.92.1.17.el5 kernel:
> http://dan.drown.org/software/ipvs-2.6.18-92.1.17.el5-multiple-local-nodes.patch
>
> I've ported it to a stock 2.6.27.7 kernel, but I haven't had time to test it
> out yet:
> http://dan.drown.org/software/ipvs-2.6.27.7-multiple-local-nodes.patch
>
> I welcome any comments or criticism on the code.
Hi Daniel,
sorry to take so long to respond, I have been meaning to do so.
Your patch seems good to me (though I am somewhat biases as I wrote
the patch you based your patch on). Would it be possible for you to
a) update the code to either DaveM's net-next-2.6 tree on git.kernel.org,
or at the very least one of the 2.6.29-rc releases? In particular
please note that the lvs code has moved from net/ipv4/ipvs/ to
net/netfilter/ipvs/ . Also, I think that you will need to rework
your checksum code changes a little to accomodate IPv6, which
has been merged into IPVS recently.
b) Provide a Signed-off-by line, an explanation of which can be found at
http://linux.yyz.us/patch-format.html
--
Simon Horman
VA Linux Systems Japan K.K., Sydney, Australia Satellite Office
H: www.vergenet.net/~horms/ W: www.valinux.co.jp/en
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