Refactor DHCP relay docker in sonicv2 style (#217)

* Refactor DHCP relay docker in sonicv2 style

dockers/docker-dhcp-relay/Dockerfile

@@ -10,9 +10,11 @@ RUN apt-get update                          \
     && apt-get autoclean -y                 \
     && apt-get autoremove -y
 
-COPY isc-dhcp-relay /etc/default/isc-dhcp-relay
+COPY ["isc-dhcp-relay.j2", "/usr/share/dhcp-relay/"]
+COPY ["config.sh", "/usr/bin/"]
 
-ENTRYPOINT service rsyslog start    \
+ENTRYPOINT /usr/bin/config.sh       \
+    && service rsyslog start        \
     && service isc-dhcp-relay start \
     && /bin/bash
 

dockers/docker-dhcp-relay/config.sh

@@ -0,0 +1,4 @@
+#!/bin/bash
+
+sonic-cfggen -m /etc/sonic/minigraph.xml -y /etc/sonic/dhcp_relay.yml -t /usr/share/dhcp-relay/isc-dhcp-relay.j2 > /etc/default/isc-dhcp-relay
+

dockers/docker-dhcp-relay/isc-dhcp-relay

@@ -1,6 +0,0 @@
-SERVERS=""
-
-INTERFACES=""
-
-#-a provides option 82 circuit id information
-OPTIONS="-a"

dockers/docker-dhcp-relay/isc-dhcp-relay.j2

@@ -0,0 +1,7 @@
+SERVERS="{{ dhcp_servers | join(' ') }}"
+
+INTERFACES="{{ minigraph_vlan_interfaces | join(' ') }}"
+
+# '-a' option provides option 82 circuit id information
+OPTIONS="-a"
+