busybox/examples/udhcp/simple.script
Rolf Eike Beer 7180d9ed86 examples/udhcp/simple.script: fix resolv.conf update if it is a dangling symlink
If /etc/resolv.conf is a symlink to a tmpfs and the actual file does not
already exist, "readlink -f" will not detect it as symlink. Explicitely check
for that condition before and touch the file, making the other code work as
intended.

Signed-off-by: Rolf Eike Beer <eb@emlix.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2019-04-13 16:58:00 +02:00

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#!/bin/sh
# udhcpc script edited by Tim Riker <Tim@Rikers.org>
RESOLV_CONF="/etc/resolv.conf"
[ -n "$1" ] || { echo "Error: should be called from udhcpc"; exit 1; }
NETMASK=""
if command -v ip >/dev/null; then
[ -n "$subnet" ] && NETMASK="/$subnet"
else
[ -n "$subnet" ] && NETMASK="netmask $subnet"
fi
BROADCAST="broadcast +"
[ -n "$broadcast" ] && BROADCAST="broadcast $broadcast"
case "$1" in
deconfig)
echo "Setting IP address 0.0.0.0 on $interface"
if command -v ip >/dev/null; then
ip addr flush dev $interface
else
ifconfig $interface 0.0.0.0
fi
;;
renew|bound)
echo "Setting IP address $ip on $interface"
if command -v ip >/dev/null; then
ip addr add $ip$NETMASK $BROADCAST dev $interface
else
ifconfig $interface $ip $NETMASK $BROADCAST
fi
if [ -n "$router" ] ; then
echo "Deleting routers"
while route del default gw 0.0.0.0 dev $interface ; do
:
done
metric=0
for i in $router ; do
echo "Adding router $i"
if [ "$subnet" = "255.255.255.255" ]; then
# special case for /32 subnets:
# /32 instructs kernel to always use routing for all outgoing packets
# (they can never be sent to local subnet - there is no local subnet for /32).
# Used in datacenters, avoids the need for private ip-addresses between two hops.
ip route add $i dev $interface
fi
route add default gw $i dev $interface metric $((metric++))
done
fi
echo "Recreating $RESOLV_CONF"
# If the file is a symlink somewhere (like /etc/resolv.conf
# pointing to /run/resolv.conf), make sure things work.
if test -L "$RESOLV_CONF"; then
# If it's a dangling symlink, try to create the target.
test -e "$RESOLV_CONF" || touch "$RESOLV_CONF"
fi
realconf=$(readlink -f "$RESOLV_CONF" 2>/dev/null || echo "$RESOLV_CONF")
tmpfile="$realconf-$$"
> "$tmpfile"
[ -n "$domain" ] && echo "search $domain" >> "$tmpfile"
for i in $dns ; do
echo " Adding DNS server $i"
echo "nameserver $i" >> "$tmpfile"
done
mv "$tmpfile" "$realconf"
;;
esac
exit 0