[Buildroot] [git commit] busybox: udhcpc.script: fix resolv.conf handling with multiple interfaces
Arnout Vandecappelle
arnout at mind.be
Wed Jun 26 17:13:30 UTC 2013
On 26/06/13 15:20, Peter Korsgaard wrote:
> commit: http://git.buildroot.net/buildroot/commit/?id=584f418ec1ae3f0b5e09c10133c82578d78a3e03
> branch: http://git.buildroot.net/buildroot/commit/?id=refs/heads/master
>
> When udhcpc is used on multiple network devices at the same time (or a mix
> of dhcp and fixed configuration), /etc/resolv.conf should contain the
> union of information from all the interfaces.
>
> Currently that's not the case. The udhcpc script simply overwrites
> resolv.conf with the information from the specific interface on each dhcp
> bound/renew event.
>
> Fix it by tagging lines with the interface they came from when added,
> and drop the affected lines on deconfig/renew. As /etc/resolv.conf is
> often a symlink to /tmp (and rootfs might be read only), special care
> has to be taken when it is updated.
>
> Notice that I'm not really aware of any official documentation requiring
> that '#' comments in /etc/resolv.conf must be supported, but atleast
> glibc and uClibc do.
>
> Signed-off-by: Peter Korsgaard <jacmet at sunsite.dk>
> ---
> package/busybox/udhcpc.script | 19 ++++++++++++++++---
> 1 files changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/package/busybox/udhcpc.script b/package/busybox/udhcpc.script
> index f7beb56..43742fb 100755
> --- a/package/busybox/udhcpc.script
> +++ b/package/busybox/udhcpc.script
> @@ -13,6 +13,13 @@ case "$1" in
> /sbin/ifconfig $interface up
> /sbin/ifconfig $interface 0.0.0.0
>
> + # drop info from this interface
> + # resolv.conf may be a symlink to /tmp/, so take care
> + TMPFILE=$(mktemp)
> + grep -vE "# $interface\$" $RESOLV_CONF > $TMPFILE
> + cat $TMPFILE > $RESOLV_CONF
Isn't the non-atomicity of this line a potential race condition?
mv -f $TMPFILE $(readlink -f $RESOLV_CONF)
might be a better idea.
Regards,
Arnout
> + rm -f $TMPFILE
> +
> if [ -x /usr/sbin/avahi-autoipd ]; then
> /usr/sbin/avahi-autoipd -k $interface
> fi
> @@ -41,11 +48,17 @@ case "$1" in
> done
> fi
>
> - echo -n > $RESOLV_CONF
> - [ -n "$domain" ] && echo search $domain >> $RESOLV_CONF
> + # drop info from this interface
> + # resolv.conf may be a symlink to /tmp/, so take care
> + TMPFILE=$(mktemp)
> + grep -vE "# $interface\$" $RESOLV_CONF > $TMPFILE
> + cat $TMPFILE > $RESOLV_CONF
> + rm -f $TMPFILE
> +
> + [ -n "$domain" ] && echo "search $domain # $interface" >> $RESOLV_CONF
> for i in $dns ; do
> echo adding dns $i
> - echo nameserver $i >> $RESOLV_CONF
> + echo "nameserver $i # $interface" >> $RESOLV_CONF
> done
> ;;
> esac
> _______________________________________________
> buildroot mailing list
> buildroot at busybox.net
> http://lists.busybox.net/mailman/listinfo/buildroot
>
>
--
Arnout Vandecappelle arnout at mind be
Senior Embedded Software Architect +32-16-286500
Essensium/Mind http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint: 7CB5 E4CC 6C2E EFD4 6E3D A754 F963 ECAB 2450 2F1F
More information about the buildroot
mailing list