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FS#97 - dnsmasq doesn't receive updated dns servers when running inside ujail #5221

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openwrt-bot opened this issue Aug 17, 2016 · 5 comments
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@openwrt-bot
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@openwrt-bot openwrt-bot commented Aug 17, 2016

dangowrt:

Bind-mounting /tmp/resolv.conf.auto apparently doesn't forward inotify events arriving from the kernel when resolv.conf.auto was changed (e.g. upstream DNS servers were received by a DHCP client or pppd). Restarting dnsmasq or running it without ujail solves the issue.

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@openwrt-bot openwrt-bot commented Aug 18, 2016

champtar:

Hi Daniel,
can you check if the inode number of /tmp/resolv.conf.auto change when such events happen
(ls -i /tmp/resolv.conf.auto)

@openwrt-bot
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@openwrt-bot openwrt-bot commented Aug 30, 2016

dangowrt:

Yes, apparently it does.

root@test:# ls -i /tmp/resolv.conf.auto
3400 /tmp/resolv.conf.auto
root@test:
# /etc/init.d/network restart
root@test:# ls -i /tmp/resolv.conf.auto
3897 /tmp/resolv.conf.auto
root@test:
#

@openwrt-bot
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@openwrt-bot openwrt-bot commented Sep 4, 2016

champtar:

Hi Daniel,
It's one of the limitations of bind mounts, what you see in the jail is the file with inode 3400 and never the one with inode 3897, because what you really changed is /tmp

There is 2 workarounds:

  1. write to the file instead of replacing it with a new one (with mv/rename). With this option you loose the atomicity of the rename
  2. bind mount the parent dir of the file, bind mouting /tmp is not a good idea but maybe you can move resolv.conf.auto in a dnsmasq dir

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@openwrt-bot openwrt-bot commented Oct 9, 2017

nwf:

May I propose that netifd write not to /tmp/resolv.conf.auto but to /tmp/netifd/resolv.conf or similar, so that /tmp/netifd can be mounted into the jail as a directory and inotify will work?

@dave14305
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@dave14305 dave14305 commented May 17, 2022

Fixed by cd48d8d

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