sonic-buildimage/files/image_config/interfaces/interfaces-config.sh

#!/bin/bash

ifdown --force eth0

# Check if ZTP DHCP policy has been installed
if [ -e /etc/network/ifupdown2/policy.d/ztp_dhcp.json ]; then
    # Obtain port operational state information
    redis-dump -d 0 -k "PORT_TABLE:Ethernet*"  -y > /tmp/ztp_port_data.json

    if [ $? -ne 0 ] || [ ! -e /tmp/ztp_port_data.json ] || [ "$(cat /tmp/ztp_port_data.json)" = "" ]; then
        echo "{}" > /tmp/ztp_port_data.json
    fi

    # Create an input file with ztp input information
    echo "{ \"PORT_DATA\" : $(cat /tmp/ztp_port_data.json) }" > \
          /tmp/ztp_input.json
else
    echo "{ \"ZTP_DHCP_DISABLED\" : \"true\" }" > /tmp/ztp_input.json
fi

# Create /e/n/i file for existing and active interfaces, dhcp6 sytcl.conf and dhclient.conf
CFGGEN_PARAMS=" \
    -d -j /tmp/ztp_input.json \
    -t /usr/share/sonic/templates/interfaces.j2,/etc/network/interfaces \
    -t /usr/share/sonic/templates/90-dhcp6-systcl.conf.j2,/etc/sysctl.d/90-dhcp6-systcl.conf \
    -t /usr/share/sonic/templates/dhclient.conf.j2,/etc/dhcp/dhclient.conf \
"
sonic-cfggen $CFGGEN_PARAMS

[ -f /var/run/dhclient.eth0.pid ] && kill `cat /var/run/dhclient.eth0.pid` && rm -f /var/run/dhclient.eth0.pid
[ -f /var/run/dhclient6.eth0.pid ] && kill `cat /var/run/dhclient6.eth0.pid` && rm -f /var/run/dhclient6.eth0.pid

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

# Read sysctl conf files again
sysctl -p /etc/sysctl.d/90-dhcp6-systcl.conf

systemctl restart networking

# Clean-up created files
rm -f /tmp/ztp_input.json /tmp/ztp_port_data.json