Revert "Revert "Clear DNS configuration received from DHCP during net…

…working reconfiguration in Linux. (sonic-net#13516)" (sonic-net#14902)"

This reverts commit 72c52bc.

build_debian.sh

@@ -400,6 +400,7 @@ sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y in
  jq \
  auditd \
  linux-perf \
+ resolvconf \
  lsof \
  sysstat
 
@@ -762,7 +763,11 @@ sudo rm -f $ONIE_INSTALLER_PAYLOAD $FILESYSTEM_SQUASHFS
 ## Note: -x to skip directories on different file systems, such as /proc
 sudo du -hsx $FILESYSTEM_ROOT
 sudo mkdir -p $FILESYSTEM_ROOT/var/lib/docker
-sudo cp files/image_config/resolv-config/resolv.conf $FILESYSTEM_ROOT/etc/resolv.conf
+
+## Clear DNS configuration inherited from the build server
+sudo rm -f $FILESYSTEM_ROOT/etc/resolvconf/resolv.conf.d/original
+sudo cp files/image_config/resolv-config/resolv.conf.head $FILESYSTEM_ROOT/etc/resolvconf/resolv.conf.d/head
+
 sudo mksquashfs $FILESYSTEM_ROOT $FILESYSTEM_SQUASHFS -comp zstd -b 1M -e boot -e var/lib/docker -e $PLATFORM_DIR
 
 # Ensure admin gid is 1000

files/image_config/interfaces/interfaces-config.sh

@@ -60,6 +60,9 @@ for intf_pid in $(ls -1 /var/run/dhclient*.Ethernet*.pid 2> /dev/null); do
  [[ -f ${intf_pid} ]] && kill `cat ${intf_pid}` && rm -f ${intf_pid}
 done
 
+[[ -f /var/run/resolvconf/interface/eth0.dhclient ]] && rm -f /var/run/resolvconf/interface/eth0.dhclient
+[[ -f /var/run/resolvconf/interface/eth0.ip6.dhclient ]] && rm -f /var/run/resolvconf/interface/eth0.ip6.dhclient
+
 # Read sysctl conf files again
 sysctl -p /etc/sysctl.d/90-dhcp6-systcl.conf
 

files/image_config/resolv-config/resolv.conf.head

@@ -0,0 +1,2 @@
+# Dynamic resolv.conf(5) file generated by resolvconf(8)
+# The content of this file may be overwritten during a config reload.