FIX "No such device" when adding unreachable routes for kernels >= 4.16 #19
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christf
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a debian package based on master containing the patch is available here: |
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Patch tested on Linux 4.17.0 and 4.14.52, network with 7 nodes. Has anyone tested compatibility with older kernels? |
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The patch does not set the onlink flag in case the route is unreachable. As your test shows this works with kernels older as well as newer than 4.16 when the behavior changed. |
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Tested on 4.17.8 and it looks like no routes go missing, the errors I mentioned in #14 don't appear anymore, yay! |
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@jech is there anything wrong with that patch? |
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Why is this line needed? Other than that, it looks good to me. |
It is used to unset rtm->rtm_flags &= ~RTNH_F_ONLINK; |
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It is used to unset RTNH_F_ONLINK flag, according to the top post.
But I think it would be better if written as:
+ rtm->rtm_flags &= ~RTNH_F_ONLINK;
Why would it be set at this point?
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christf
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indeed the line should not be required. I removed the line and adjusted the coding style to match the rest of the file. edit: I have to say though, I do like { } |
When adding unreachable routes and setting the RTNH_F_ONLINK flag, a device is required to be specified. In Linux kernel 4.16 support for this flag was added. Until now it was ignored. If RTNH_F_ONLINK is specified while the device is missing, newer kernels will respond with No such device. The result is: * spam in the log file * missing routes for both ipv4 and ipv6
christf
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Applied to master, thanks. I'll release a 1.8.3 when I've got a chance to do some more extensive testing. |
When adding unreachable routes and setting the RTNH_F_ONLINK flag, a
device is required to be specified. In Linux kernel 4.16 support for
this flag was added https://kernelnewbies.org/LinuxChanges#Linux_4.16.Networking. Until now it was ignored.
If RTNH_F_ONLINK is specified while the device is missing, newer kernels
will respond with No such device.
The result is:
This fixes #14.
This patch will mean that for unreachable routes, ONLINK is not set but in all other cases.
I am not entirely sure why the ONLINK flag is actually needed. Setting the flag in babeld was introduced in c10a4da.
Since https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fc1e64e1092f62290d59151d16f9de0210e303c8 a device is required when the flag is set.
We also need this in the unicast branch. I did direct this at the master branch because running babel on modern kernels yields a broken network due to missing routes. Also it fills the harddrive rather quickly (3gb per hour on my system) with log data. It might even be justified to consider a patch release with this.