From e6cda8a0406c4763324a881142fb96284289775f Mon Sep 17 00:00:00 2001
From: Rajendra Dendukuri <rajendra.dendukuri@broadcom.com>
Date: Tue, 6 Aug 2019 18:59:45 -0700
Subject: [PATCH 1/5] ZTP infrastructure changes to support DHCP discovery
 provisioning data

- Dynamically generate DHCP client configuration based on current ZTP state
- Added support to request and process hostname when using DHCPv6
- Do not process graphservice url dhcp option if ZTP is enabled, ZTP service
will process it
- Generate /e/n/i file with all active interfaces seeking address assignment
via DHCP. Only interfaces that are created in Linux will be added to /e/n/i.
Also DHCP is started only on linked up in-band interfaces.

Signed-off-by: Rajendra Dendukuri <rajendra.dendukuri@broadcom.com>
---
 build_debian.sh                               |  2 +-
 .../build_templates/sonic_debian_extension.j2 |  4 ++
 files/dhcp/dhclient.conf                      | 24 ----------
 files/dhcp/dhclient.conf.j2                   | 45 +++++++++++++++++++
 files/dhcp/graphserviceurl                    | 26 ++++++-----
 files/dhcp/rfc3442-classless-routes           |  7 ++-
 files/dhcp/sethostname6                       | 14 ++++++
 .../interfaces/interfaces-config.sh           | 28 +++++++++++-
 files/image_config/interfaces/interfaces.j2   | 34 ++++++++++++++
 src/sonic-config-engine/sonic-cfggen          |  9 ++++
 10 files changed, 154 insertions(+), 39 deletions(-)
 delete mode 100644 files/dhcp/dhclient.conf
 create mode 100644 files/dhcp/dhclient.conf.j2
 create mode 100644 files/dhcp/sethostname6

diff --git a/build_debian.sh b/build_debian.sh
index fcb26f16b52..4672b71383f 100755
--- a/build_debian.sh
+++ b/build_debian.sh
@@ -428,10 +428,10 @@ EOF
 
 sudo cp files/dhcp/rfc3442-classless-routes $FILESYSTEM_ROOT/etc/dhcp/dhclient-exit-hooks.d
 sudo cp files/dhcp/sethostname $FILESYSTEM_ROOT/etc/dhcp/dhclient-exit-hooks.d/
+sudo cp files/dhcp/sethostname6 $FILESYSTEM_ROOT/etc/dhcp/dhclient-exit-hooks.d/
 sudo cp files/dhcp/graphserviceurl $FILESYSTEM_ROOT/etc/dhcp/dhclient-exit-hooks.d/
 sudo cp files/dhcp/snmpcommunity $FILESYSTEM_ROOT/etc/dhcp/dhclient-exit-hooks.d/
 sudo cp files/dhcp/vrf $FILESYSTEM_ROOT/etc/dhcp/dhclient-exit-hooks.d/
-sudo cp files/dhcp/dhclient.conf $FILESYSTEM_ROOT/etc/dhcp/
 
 ## Version file
 sudo mkdir -p $FILESYSTEM_ROOT/etc/sonic
diff --git a/files/build_templates/sonic_debian_extension.j2 b/files/build_templates/sonic_debian_extension.j2
index 0f27c15273c..fdd7884db57 100644
--- a/files/build_templates/sonic_debian_extension.j2
+++ b/files/build_templates/sonic_debian_extension.j2
@@ -187,6 +187,10 @@ sudo cp $IMAGE_CONFIGS/interfaces/interfaces-config.sh $FILESYSTEM_ROOT/usr/bin/
 sudo cp $IMAGE_CONFIGS/interfaces/*.j2 $FILESYSTEM_ROOT_USR_SHARE_SONIC_TEMPLATES/
 echo "interfaces-config.service" | sudo tee -a $GENERATED_SERVICE_FILE
 
+# Copy dhcp client configuration template and create an initial configuration
+sudo cp files/dhcp/dhclient.conf.j2 $FILESYSTEM_ROOT_USR_SHARE_SONIC_TEMPLATES/
+j2 files/dhcp/dhclient.conf.j2 | sudo tee $FILESYSTEM_ROOT/etc/dhcp/dhclient.conf
+
 # Copy initial interfaces configuration file, will be overwritten on first boot
 sudo cp $IMAGE_CONFIGS/interfaces/init_interfaces $FILESYSTEM_ROOT/etc/network/interfaces
 sudo mkdir -p $FILESYSTEM_ROOT/etc/network/interfaces.d
diff --git a/files/dhcp/dhclient.conf b/files/dhcp/dhclient.conf
deleted file mode 100644
index 6a542e069fa..00000000000
--- a/files/dhcp/dhclient.conf
+++ /dev/null
@@ -1,24 +0,0 @@
-# Configuration file for /sbin/dhclient, which is included in Debian's
-#       dhcp3-client package.
-#
-# This is a sample configuration file for dhclient. See dhclient.conf's
-#       man page for more information about the syntax of this file
-#       and a more comprehensive list of the parameters understood by
-#       dhclient.
-#
-# Normally, if the DHCP server provides reasonable information and does
-#       not leave anything out (like the domain name, for example), then
-#       few changes must be made to this file, if any.
-#
-
-option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;
-option snmp-community code 224 = text;
-option minigraph-url code 225 = text;
-option acl-url code 226 = text;
-
-send host-name = gethostname();
-request subnet-mask, broadcast-address, time-offset, routers,
-        domain-name, domain-name-servers, domain-search, host-name,
-        dhcp6.name-servers, dhcp6.domain-search, interface-mtu,
-        rfc3442-classless-static-routes, ntp-servers, 
-        snmp-community, minigraph-url, acl-url;
diff --git a/files/dhcp/dhclient.conf.j2 b/files/dhcp/dhclient.conf.j2
new file mode 100644
index 00000000000..2a6f6fa84fb
--- /dev/null
+++ b/files/dhcp/dhclient.conf.j2
@@ -0,0 +1,45 @@
+{% block banner %}
+# =============== Managed by SONiC Config Engine DO NOT EDIT! ===============
+# generated from /usr/share/sonic/templates/dhclient.conf.j2 using sonic-cfggen
+# file: /etc/dhcp/dhclient.conf
+#
+{% endblock banner %}
+# Configuration file for /sbin/dhclient, which is included in Debian's
+#       dhcp3-client package.
+#
+# This is a sample configuration file for dhclient. See dhclient.conf's
+#       man page for more information about the syntax of this file
+#       and a more comprehensive list of the parameters understood by
+#       dhclient.
+#
+# Normally, if the DHCP server provides reasonable information and does
+#       not leave anything out (like the domain name, for example), then
+#       few changes must be made to this file, if any.
+#
+
+option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;
+option snmp-community code 224 = text;
+option minigraph-url code 225 = text;
+option acl-url code 226 = text;
+option tftp-server-name code 66 = text;
+option bootfile-name code 67 = text;
+option user-class code 77 = text;
+option provisioning-script-url code 239 = text;
+option dhcp6.user-class code 15 = text;
+option dhcp6.provisioning-script-url code 239 = text;
+option dhcp6.boot-file-url code 59 = text;
+
+send host-name = gethostname();
+request subnet-mask, broadcast-address, time-offset, routers,
+        domain-name, domain-name-servers, domain-search, host-name,
+        dhcp6.name-servers, dhcp6.domain-search, interface-mtu, dhcp6.fqdn,
+        rfc3442-classless-static-routes, ntp-servers, log-servers,
+{%- if ZTP is defined and ZTP_DHCP_DISABLED is not defined -%}bootfile-name, provisioning-script-url, tftp-server-name,
+        dhcp6.provisioning-script-url, dhcp6.boot-file-url,{%- endif -%}
+        snmp-community, minigraph-url, acl-url;
+{% if ZTP is defined and ZTP_DHCP_DISABLED is not defined %}
+send user-class "SONiC-ZTP";
+send dhcp6.user-class "SONiC-ZTP";
+send dhcp-client-identifier "SONiC##{{ ZTP['mode']['product-name'] }}##{{ ZTP['mode']['serial-no'] }}";
+retry 60;
+{% endif %}
diff --git a/files/dhcp/graphserviceurl b/files/dhcp/graphserviceurl
index f255cdff987..9bd5fded4b8 100644
--- a/files/dhcp/graphserviceurl
+++ b/files/dhcp/graphserviceurl
@@ -1,12 +1,14 @@
-case $reason in
-    BOUND|RENEW|REBIND|REBOOT)
-        if [ -n "$new_minigraph_url" ]; then
-            echo $new_minigraph_url > /tmp/dhcp_graph_url
-        else
-            echo "N/A" > /tmp/dhcp_graph_url
-        fi
-        if [ -n "$new_acl_url" ]; then
-            echo $new_acl_url > /tmp/dhcp_acl_url
-        fi
-        ;;
-esac
+if [ ! -e /usr/bin/ztp ] || [ "$(ztp status -c)" = "0:DISABLED" ]; then
+    case $reason in
+        BOUND|RENEW|REBIND|REBOOT)
+            if [ -n "$new_minigraph_url" ]; then
+                echo $new_minigraph_url > /tmp/dhcp_graph_url
+            else
+                echo "N/A" > /tmp/dhcp_graph_url
+            fi
+            if [ -n "$new_acl_url" ]; then
+                echo $new_acl_url > /tmp/dhcp_acl_url
+            fi
+         ;;
+    esac
+fi
diff --git a/files/dhcp/rfc3442-classless-routes b/files/dhcp/rfc3442-classless-routes
index 64e24192816..797a0d24429 100644
--- a/files/dhcp/rfc3442-classless-routes
+++ b/files/dhcp/rfc3442-classless-routes
@@ -55,8 +55,13 @@ if [ "$RUN" = "yes" ]; then
 				fi
 
 				# set route (ip detects host routes automatically)
-				ip -4 route add "${net_address}/${net_length}" \
+                                if echo $interface | grep -v Ethernet ; then
+   				     ip -4 route add "${net_address}/${net_length}" \
 					${via_arg} dev "${interface}" table default >/dev/null 2>&1
+                                else
+   				     ip -4 route add "${net_address}/${net_length}" \
+					${via_arg} dev "${interface}" >/dev/null 2>&1
+                                fi
 			done
 		fi
 	fi
diff --git a/files/dhcp/sethostname6 b/files/dhcp/sethostname6
new file mode 100644
index 00000000000..6ca5d8dbc99
--- /dev/null
+++ b/files/dhcp/sethostname6
@@ -0,0 +1,14 @@
+case $reason in
+    BOUND6|RENEW6|REBIND6|REBOOT)
+        current_dhcp6_fqdn=`hostname`
+        if [ "$current_dhcp6_fqdn" != "$new_dhcp6_fqdn" ] && [ -n "$new_dhcp6_fqdn" ]
+        then
+            echo $new_dhcp6_fqdn > /etc/hostname
+            hostname -F /etc/hostname
+            sed -i "/\s$current_dhcp6_fqdn$/d" /etc/hosts
+            sed -i "/\s$new_dhcp6_fqdn$/d" /etc/hosts
+            echo "127.0.0.1 $new_dhcp6_fqdn" >> /etc/hosts
+            echo ":: $new_dhcp6_fqdn" >> /etc/hosts
+        fi
+        ;;
+esac
diff --git a/files/image_config/interfaces/interfaces-config.sh b/files/image_config/interfaces/interfaces-config.sh
index a702917419c..829d40e5e39 100755
--- a/files/image_config/interfaces/interfaces-config.sh
+++ b/files/image_config/interfaces/interfaces-config.sh
@@ -2,10 +2,36 @@
 
 ifdown --force eth0
 
-sonic-cfggen -d -t /usr/share/sonic/templates/interfaces.j2 > /etc/network/interfaces
+# 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 [ ! -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
+sonic-cfggen -d -j /tmp/ztp_input.json -t /usr/share/sonic/templates/interfaces.j2 > /etc/network/interfaces
 
 [ -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
+
+sonic-cfggen -d -j /tmp/ztp_input.json -t /usr/share/sonic/templates/dhclient.conf.j2 > /etc/dhcp/dhclient.conf
 systemctl restart networking
 
+# Clean-up created files
+rm -f /tmp/ztp_input.json /tmp/ztp_port_data.json
+
 ifdown lo && ifup lo
diff --git a/files/image_config/interfaces/interfaces.j2 b/files/image_config/interfaces/interfaces.j2
index e0f9a290d18..c86dc295c9b 100644
--- a/files/image_config/interfaces/interfaces.j2
+++ b/files/image_config/interfaces/interfaces.j2
@@ -26,6 +26,39 @@ iface lo {{ 'inet' if prefix | ipv4 else 'inet6' }} static
 
 # The management network interface
 auto eth0
+{% if (ZTP_DHCP_DISABLED is not defined) and (ZTP is defined) and (ZTP['mode'] is defined and ZTP['mode']['profile'] == 'active') %}
+
+
+# ZTP out-of-band interface
+allow-hotplug eth0
+{% if ZTP['mode']['ipv4'] == 'true' %}
+iface eth0 inet dhcp
+{% endif %}
+{% if ZTP['mode']['ipv6'] == 'true' %}
+iface eth0 inet6 dhcp
+{% endif %}
+
+{% if ZTP['mode']['inband'] == 'true' %}
+{% for port in PORT %}
+{% set var = {'port_exists': True if port | is_intf_exists else False } %}
+{% if var.port_exists %}
+
+# ZTP in-band interface {{ port }}
+auto {{ port }}
+allow-hotplug {{ port }}
+{% if PORT_DATA['PORT_TABLE:'+port] is defined and PORT_DATA['PORT_TABLE:'+port]['value']['oper_status'] == 'up' %}
+{% if ZTP['mode']['ipv4'] == 'true' %}
+iface {{ port }} inet dhcp
+{% endif %}
+{% if ZTP['mode']['ipv6'] == 'true' %}
+iface {{ port }} inet6 dhcp
+{% endif %}
+{% endif %}
+{% endif %}
+{% endfor %}
+{% endif %}
+
+{% else %}
 {% if MGMT_INTERFACE %}
 {% for (name, prefix) in MGMT_INTERFACE|pfx_filter %}
 iface eth0 {{ 'inet' if prefix | ipv4 else 'inet6' }} static
@@ -70,6 +103,7 @@ iface eth0 inet dhcp
     down cgdelete -g l3mdev:mgmt
 {% endif %}
 {% endif %}
+{% endif %}
 #
 source /etc/network/interfaces.d/*
 #
diff --git a/src/sonic-config-engine/sonic-cfggen b/src/sonic-config-engine/sonic-cfggen
index abf858782f3..4d2a0d61c91 100755
--- a/src/sonic-config-engine/sonic-cfggen
+++ b/src/sonic-config-engine/sonic-cfggen
@@ -103,6 +103,14 @@ def pfx_filter(value):
         table[key] = val
     return table
 
+def is_intf_exists(value):
+    if not value:
+        return False
+    link_state = '/sys/class/net/'+value+'/operstate'
+    if os.path.isfile(link_state):
+        return True
+    return False
+
 class FormatConverter:
     """Convert config DB based schema to legacy minigraph based schema for backward capability.
 We will move to DB schema and remove this class when the config templates are modified.
@@ -247,6 +255,7 @@ def main():
 
         env = jinja2.Environment(loader=loader, trim_blocks=True)
         env.filters['sort_by_port_index'] = sort_by_port_index
+        env.filters['is_intf_exists'] = is_intf_exists
         env.filters['ipv4'] = is_ipv4
         env.filters['ipv6'] = is_ipv6
         env.filters['unique_name'] = unique_name

From 421e6ce811d59a0c7b0cd4d67c545e6c572c50af Mon Sep 17 00:00:00 2001
From: Rajendra Dendukuri <rajendra.dendukuri@broadcom.com>
Date: Mon, 19 Aug 2019 10:49:16 -0400
Subject: [PATCH 2/5] Added exit code check for redis-dump command. Fixed code
 indenation to 4 space.

---
 files/image_config/interfaces/interfaces-config.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/files/image_config/interfaces/interfaces-config.sh b/files/image_config/interfaces/interfaces-config.sh
index 829d40e5e39..31763ebf0f5 100755
--- a/files/image_config/interfaces/interfaces-config.sh
+++ b/files/image_config/interfaces/interfaces-config.sh
@@ -7,7 +7,7 @@ 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 [ ! -e /tmp/ztp_port_data.json ] || [ "$(cat /tmp/ztp_port_data.json)" = "" ]; then
+    if [ $? -ne 0 ] || [ ! -e /tmp/ztp_port_data.json ] || [ "$(cat /tmp/ztp_port_data.json)" = "" ]; then
         echo "{}" > /tmp/ztp_port_data.json
     fi
 
@@ -25,7 +25,7 @@ sonic-cfggen -d -j /tmp/ztp_input.json -t /usr/share/sonic/templates/interfaces.
 [ -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}
+    [ -f ${intf_pid} ] && kill `cat ${intf_pid}` && rm -f ${intf_pid}
 done
 
 sonic-cfggen -d -j /tmp/ztp_input.json -t /usr/share/sonic/templates/dhclient.conf.j2 > /etc/dhcp/dhclient.conf

From 364dd3153c06ac824510fdc7073c5cbfd565fa12 Mon Sep 17 00:00:00 2001
From: Rajendra Dendukuri <rajendra.dendukuri@broadcom.com>
Date: Mon, 2 Sep 2019 22:20:31 -0400
Subject: [PATCH 3/5] Allow router advertisements to be accepted by eth0 when
 DHCPv6 discovery is in progress.

---
 files/image_config/interfaces/interfaces.j2 | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/files/image_config/interfaces/interfaces.j2 b/files/image_config/interfaces/interfaces.j2
index c86dc295c9b..51f6dd4557b 100644
--- a/files/image_config/interfaces/interfaces.j2
+++ b/files/image_config/interfaces/interfaces.j2
@@ -36,6 +36,8 @@ iface eth0 inet dhcp
 {% endif %}
 {% if ZTP['mode']['ipv6'] == 'true' %}
 iface eth0 inet6 dhcp
+    up sysctl net.ipv6.conf.eth0.accept_ra=1
+    down sysctl net.ipv6.conf.eth0.accept_ra=0
 {% endif %}
 
 {% if ZTP['mode']['inband'] == 'true' %}

From 7d7b5a4934d14e34b3741f9ed669602259f75902 Mon Sep 17 00:00:00 2001
From: Rajendra Dendukuri <rajendra.dendukuri@broadcom.com>
Date: Mon, 16 Sep 2019 22:47:14 -0700
Subject: [PATCH 4/5] Assign IPv6 address to OOB using DHCPv6 if static address
 is not defined in MGMT_INTERFACE table.

---
 build_debian.sh                                    |  3 ---
 files/build_templates/sonic_debian_extension.j2    |  2 ++
 files/dhcp/90-dhcp6-systcl.conf.j2                 |  7 +++++++
 files/dhcp/ifupdown2_policy.json                   | 12 ++++++++++++
 files/image_config/interfaces/interfaces-config.sh |  4 ++++
 files/image_config/interfaces/interfaces.j2        |  3 +++
 6 files changed, 28 insertions(+), 3 deletions(-)
 create mode 100644 files/dhcp/90-dhcp6-systcl.conf.j2
 create mode 100644 files/dhcp/ifupdown2_policy.json

diff --git a/build_debian.sh b/build_debian.sh
index 4672b71383f..0aab8c396a1 100755
--- a/build_debian.sh
+++ b/build_debian.sh
@@ -393,9 +393,6 @@ set /files/etc/sysctl.conf/net.ipv6.conf.default.keep_addr_on_down 1
 set /files/etc/sysctl.conf/net.ipv6.conf.all.keep_addr_on_down 1
 set /files/etc/sysctl.conf/net.ipv6.conf.eth0.keep_addr_on_down 1
 
-set /files/etc/sysctl.conf/net.ipv6.conf.eth0.accept_ra_defrtr 0
-set /files/etc/sysctl.conf/net.ipv6.conf.eth0.accept_ra 0
-
 set /files/etc/sysctl.conf/net.ipv4.tcp_l3mdev_accept 1
 set /files/etc/sysctl.conf/net.ipv4.udp_l3mdev_accept 1
 
diff --git a/files/build_templates/sonic_debian_extension.j2 b/files/build_templates/sonic_debian_extension.j2
index fdd7884db57..80bdf6e2ccb 100644
--- a/files/build_templates/sonic_debian_extension.j2
+++ b/files/build_templates/sonic_debian_extension.j2
@@ -190,6 +190,8 @@ echo "interfaces-config.service" | sudo tee -a $GENERATED_SERVICE_FILE
 # Copy dhcp client configuration template and create an initial configuration
 sudo cp files/dhcp/dhclient.conf.j2 $FILESYSTEM_ROOT_USR_SHARE_SONIC_TEMPLATES/
 j2 files/dhcp/dhclient.conf.j2 | sudo tee $FILESYSTEM_ROOT/etc/dhcp/dhclient.conf
+sudo cp files/dhcp/ifupdown2_policy.json $FILESYSTEM_ROOT/etc/network/ifupdown2/policy.d
+sudo cp files/dhcp/90-dhcp6-systcl.conf.j2 $FILESYSTEM_ROOT_USR_SHARE_SONIC_TEMPLATES/
 
 # Copy initial interfaces configuration file, will be overwritten on first boot
 sudo cp $IMAGE_CONFIGS/interfaces/init_interfaces $FILESYSTEM_ROOT/etc/network/interfaces
diff --git a/files/dhcp/90-dhcp6-systcl.conf.j2 b/files/dhcp/90-dhcp6-systcl.conf.j2
new file mode 100644
index 00000000000..addb9467525
--- /dev/null
+++ b/files/dhcp/90-dhcp6-systcl.conf.j2
@@ -0,0 +1,7 @@
+{% if MGMT_INTERFACE %}
+net.ipv6.conf.eth0.accept_ra_defrtr = 0
+net.ipv6.conf.eth0.accept_ra = 0
+{% else %}
+net.ipv6.conf.eth0.accept_ra_defrtr = 1
+net.ipv6.conf.eth0.accept_ra = 1
+{% endif %}
diff --git a/files/dhcp/ifupdown2_policy.json b/files/dhcp/ifupdown2_policy.json
new file mode 100644
index 00000000000..9a5010dead8
--- /dev/null
+++ b/files/dhcp/ifupdown2_policy.json
@@ -0,0 +1,12 @@
+{
+  "dhcp" : {
+    "defaults" : {
+       "dhcp-wait" : "no"
+    },
+    "iface_defaults" : {
+     "eth0" : {
+         "dhcp6-duid" : "LL"
+      }
+    }
+  }
+}
diff --git a/files/image_config/interfaces/interfaces-config.sh b/files/image_config/interfaces/interfaces-config.sh
index 31763ebf0f5..8dddc215bbd 100755
--- a/files/image_config/interfaces/interfaces-config.sh
+++ b/files/image_config/interfaces/interfaces-config.sh
@@ -28,6 +28,10 @@ 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
 
+sonic-cfggen -d -j /tmp/ztp_input.json -t /usr/share/sonic/templates/90-dhcp6-systcl.conf.j2 > /etc/sysctl.d/90-dhcp6-systcl.conf
+# Read sysctl conf files again
+sysctl -p /etc/sysctl.d/90-dhcp6-systcl.conf
+
 sonic-cfggen -d -j /tmp/ztp_input.json -t /usr/share/sonic/templates/dhclient.conf.j2 > /etc/dhcp/dhclient.conf
 systemctl restart networking
 
diff --git a/files/image_config/interfaces/interfaces.j2 b/files/image_config/interfaces/interfaces.j2
index 51f6dd4557b..d6f7ba296bf 100644
--- a/files/image_config/interfaces/interfaces.j2
+++ b/files/image_config/interfaces/interfaces.j2
@@ -104,6 +104,9 @@ iface eth0 inet dhcp
     up cgset -r l3mdev.master-device=mgmt mgmt
     down cgdelete -g l3mdev:mgmt
 {% endif %}
+iface eth0 inet6 dhcp
+    up sysctl net.ipv6.conf.eth0.accept_ra=1
+    down sysctl net.ipv6.conf.eth0.accept_ra=0
 {% endif %}
 {% endif %}
 #

From fa71ce32940d4e69980ca3fb9c3cef58bd96af35 Mon Sep 17 00:00:00 2001
From: Rajendra Dendukuri <rajendra.dendukuri@broadcom.com>
Date: Fri, 6 Dec 2019 11:37:57 -0800
Subject: [PATCH 5/5] Remove interface exists in kernel check.

---
 files/image_config/interfaces/interfaces.j2 | 3 ---
 src/sonic-config-engine/sonic-cfggen        | 9 ---------
 2 files changed, 12 deletions(-)

diff --git a/files/image_config/interfaces/interfaces.j2 b/files/image_config/interfaces/interfaces.j2
index bbbc351c07b..6b6970bf431 100644
--- a/files/image_config/interfaces/interfaces.j2
+++ b/files/image_config/interfaces/interfaces.j2
@@ -50,8 +50,6 @@ iface eth0 inet6 dhcp
 
 {% if ZTP['mode']['inband'] == 'true' %}
 {% for port in PORT %}
-{% set var = {'port_exists': True if port | is_intf_exists else False } %}
-{% if var.port_exists %}
 
 # ZTP in-band interface {{ port }}
 auto {{ port }}
@@ -64,7 +62,6 @@ iface {{ port }} inet dhcp
 iface {{ port }} inet6 dhcp
 {% endif %}
 {% endif %}
-{% endif %}
 {% endfor %}
 {% endif %}
 
diff --git a/src/sonic-config-engine/sonic-cfggen b/src/sonic-config-engine/sonic-cfggen
index 51799562dc9..7cff6c9fb38 100755
--- a/src/sonic-config-engine/sonic-cfggen
+++ b/src/sonic-config-engine/sonic-cfggen
@@ -114,14 +114,6 @@ def pfx_filter(value):
         table[key] = val
     return table
 
-def is_intf_exists(value):
-    if not value:
-        return False
-    link_state = '/sys/class/net/'+value+'/operstate'
-    if os.path.isfile(link_state):
-        return True
-    return False
-
 def ip_network(value):
     """ Extract network for network prefix """
     try:
@@ -289,7 +281,6 @@ def main():
         redis_bcc = RedisBytecodeCache(SonicV2Connector(host='127.0.0.1'))
         env = jinja2.Environment(loader=loader, trim_blocks=True, bytecode_cache=redis_bcc)
         env.filters['sort_by_port_index'] = sort_by_port_index
-        env.filters['is_intf_exists'] = is_intf_exists
         env.filters['ipv4'] = is_ipv4
         env.filters['ipv6'] = is_ipv6
         env.filters['unique_name'] = unique_name