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[PATCH 4.4 0/5] DHCP client support when receiving "delayed" replies
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Patryk Mungai <patryk.mungai-ndungu.kx@...>
Dear All,
When running dhcp tests using the 4.4.y (and 4.4.y-cip kernel as well), I encountered an issue where the dhcp client in the kernel could not get an IP address when multiple network devices were enabled. It seems that the current implementation of the dhcp client in the 4.4 kernel is send dhcp request via device 1 -> wait <1s for response from server on device 1 -> if no response, switch to device 2 -> repeat process on device 2 ...etc. When the dhcp server is slow to respond, this means it is impossible to get a dhcp address. This series backported from upstream fixes the issue, is it possible to apply this to 4.4.y and/or 4.4.y-cip? Thanks, Patryk Geert Uytterhoeven (1): net: ipconfig: Fix NULL pointer dereference on RARP/BOOTP/DHCP timeout Thierry Reding (1): net: ipconfig: Fix more use after free Uwe Kleine-König (3): net: ipconfig: Support using "delayed" DHCP replies net: ipconfig: drop inter-device timeout net: ipconfig: fix use after free net/ipv4/ipconfig.c | 61 ++++++++++++++++++++++++----------------------------- 1 file changed, 28 insertions(+), 33 deletions(-) -- 2.7.4
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Pavel Machek
Hi!
When running dhcp tests using the 4.4.y (and 4.4.y-cip kernel as well), IOk, so first patch adds support for using "delayed" DHCP replies, then there are three more patches to fix up issues it creates. Which tells me that maybe this is not quite suitable for -stable. How long do your dhcp servers take to reply? Can you solve the problem some other way, like for example increasing timeouts? Thanks, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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Sasha Levin <sashal@...>
On Fri, Apr 05, 2019 at 11:47:31AM +0100, Patryk Mungai wrote:
Dear All,This is something that seems more suited for the CIP kernel as it adds new functionality. -- Thanks, Sasha
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Patryk Mungai Ndungu <patryk.mungai-ndungu.kx@...>
Hello Pavel,
toggle quoted messageShow quoted text
-----Original Message-----It varies: the fastest reply I've seen is 0.12931s, the slowest is in the region is just over 1.007s. In the tests I've run, I measured the time between the kernel sending out the DHCP request and receiving a DHCP offer from the server. After running 50 tests, in around half of them, it takes just over 1s for the DHCP offer to arrive. But this is rarely over 1s +1 jiffie, hence why I think the code is able to cope with it most of the time. However, the DHCP servers network is not at all loaded (at most only has 4 devices trying to connect to it at once), and yet I've seen this failure multiple times, so I'm not sure what would happen in a loaded network. I think at least for CIP we need a kernel that is able to cope with however long the server takes to reply. Can you solve the problemI've tried increasing CONF_INTER_TIMEOUT to 2Hz and I haven't seen it fail in 50 boots. Though this is an simple workaround, it can prolong boot up time and the DHCP client is still time dependent with regards to listening for a reply on a network device. Thanks, Patryk
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Greg KH <gregkh@...>
On Sat, Apr 06, 2019 at 09:53:50AM -0400, Sasha Levin wrote:
On Fri, Apr 05, 2019 at 11:47:31AM +0100, Patryk Mungai wrote:I agree, this is a new feature. If someone wants this, they should useDear All,This is something that seems more suited for the CIP kernel as it adds a newer kernel please. Like 4.19.y :) thanks, greg k-h
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