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busybox: udhcpc.script: fix resolv.conf handling with multiple interfaces 

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@sunsite.dk>
This commit is contained in:
Peter Korsgaard 2013-06-26 15:01:46 +02:00
parent 8432d81a84
commit 584f418ec1
1 changed files with 16 additions and 3 deletions
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19
package/busybox/udhcpc.script
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@ -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
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