[DHCP Relay]: Support Multiple VLANs (Separate DHCP Relay Agents, One Per VLAN) (#999)

* [DHCP Relay]: Support new <DhcpRelays> minigraph tag; support multiple VLANs

* Don't start dhcrelay in quiet mode so as to get startup output in syslog

* Update sonic-cfggen tests to support new '<DhcpRelays>' tag

* <DhcpRelays> tag is only present for VLANs which require a DHCP relay agent -- only parse if present

* Don't attempt to configure a DHCP relay agent for VLANs without specified DHCP servers

* Modify to work with Taoyu's minigraph/DB changes (#942)

* Reduce number of DHCP servers in sonic-cfggen unit tests from 4 to 2

* Remove isc-dhcp-relay sample output file from sonic-cfggen test, as we no longer generate that file

* Update Option 82 isc-dhcp-relay patch to load all interface name-alias maps into memory once at start instead of calling sonic-cfggen on each packet we relay

* Remove executable permission from Jinja2 template

* Set max hop count to 1 so that DHCP relay will only relay packets with a hop count of zero

* Replace tabs with spaces

* Modify overlooked sonic-cfggen call, use Config DB instead of minigraph

* Also ensure > 1 VLAN requires a DHCP relay agent before outputting to template

* Generate port name-alias map file using sonic-cfggen and parse that in lieu of parsing port_config.ini directly

* No longer drop packets with hop count > 0; Instead, drop packets which already contain agent info

Author: jleveque

dockers/docker-dhcp-relay/Dockerfile.j2

@@ -22,9 +22,7 @@ RUN dpkg_apt() { [ -f $1 ] && { dpkg -i $1 || apt-get -y install -f; } || return
 RUN apt-get clean -y; apt-get autoclean -y; apt-get autoremove -y
 RUN rm -rf /debs
 
-COPY ["start.sh", "isc-dhcp-relay.sh", "/usr/bin/"]
-COPY ["supervisord.conf", "/etc/supervisor/conf.d/"]
-COPY ["isc-dhcp-relay.j2", "/usr/share/sonic/templates/"]
-COPY ["wait_for_intf.sh.j2", "/usr/share/sonic/templates/"]
+COPY ["docker_init.sh", "start.sh", "/usr/bin/"]
+COPY ["docker-dhcp-relay.supervisord.conf.j2", "wait_for_intf.sh.j2", "/usr/share/sonic/templates/"]
 
-ENTRYPOINT ["/usr/bin/supervisord"]
+ENTRYPOINT ["/usr/bin/docker_init.sh"]

dockers/docker-dhcp-relay/docker-dhcp-relay.supervisord.conf.j2

@@ -0,0 +1,67 @@
+[supervisord]
+logfile_maxbytes=1MB
+logfile_backups=2
+nodaemon=true
+
+[program:start.sh]
+command=/usr/bin/start.sh
+priority=1
+autostart=true
+autorestart=false
+stdout_logfile=syslog
+stderr_logfile=syslog
+
+[program:rsyslogd]
+command=/usr/sbin/rsyslogd -n
+priority=2
+autostart=false
+autorestart=false
+stdout_logfile=syslog
+stderr_logfile=syslog
+
+{# If our configuration has VLANs... #}
+{% if VLAN %}
+{# Count how many VLANs require a DHCP relay agent... #}
+{% set num_relays = { 'count': 0 } %}
+{% for vlan_name in VLAN %}
+{% if VLAN[vlan_name]['dhcp_servers'] %}
+{% set _dummy = num_relays.update({'count': num_relays.count + 1}) %}
+{% endif %}
+{% endfor %}
+{# If one or more of the VLANs require a DHCP relay agent... #}
+{% if num_relays.count > 0 %}
+[group:isc-dhcp-relay]
+programs=
+{%- set add_preceding_comma = { 'flag': False } -%}
+{%- for vlan_name in VLAN -%}
+{%- if VLAN[vlan_name]['dhcp_servers'] -%}
+{%- if add_preceding_comma.flag %},{% endif -%}
+{%- set _dummy = add_preceding_comma.update({'flag': True}) -%}
+isc-dhcp-relay-{{ vlan_name }}
+{%- endif %}
+{% endfor %}
+
+
+{# Create a program entry for each DHCP relay agent instance #}
+{% for vlan_name in VLAN -%}
+{%- if VLAN[vlan_name]['dhcp_servers'] -%}
+[program:isc-dhcp-relay-{{ vlan_name }}]
+command=/usr/sbin/dhcrelay -d -m discard -a %%h:%%p %%P --name-alias-map-file /tmp/port-name-alias-map.txt -i {{ vlan_name }}
+{%- for (name, prefix) in INTERFACE -%}
+{%- if prefix | ipv4 %} -i {{ name }}{% endif -%}
+{%- endfor -%}
+{%- for (name, prefix) in PORTCHANNEL_INTERFACE -%}
+{%- if prefix | ipv4 %} -i {{ name }}{% endif -%}
+{%- endfor -%}
+{%- for dhcp_server in VLAN[vlan_name]['dhcp_servers'] %} {{ dhcp_server }}{% endfor %}
+
+priority=3
+autostart=false
+autorestart=false
+stdout_logfile=syslog
+stderr_logfile=syslog
+
+{% endif %}
+{% endfor %}
+{% endif %}
+{% endif %}

dockers/docker-dhcp-relay/docker_init.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+
+# Generate supervisord config file
+mkdir -p /etc/supervisor/conf.d/
+sonic-cfggen -d -t /usr/share/sonic/templates/docker-dhcp-relay.supervisord.conf.j2 > /etc/supervisor/conf.d/docker-dhcp-relay.supervisord.conf
+
+# Generate the script that waits for all interfaces to come up and make it executable
+sonic-cfggen -d -t /usr/share/sonic/templates/wait_for_intf.sh.j2 > /usr/bin/wait_for_intf.sh
+chmod +x /usr/bin/wait_for_intf.sh
+
+# Generate port name-alias map for isc-dhcp-relay to parse. Each line contains one
+# name-alias pair of the form "<name> <alias>"
+sonic-cfggen -d --var-json "PORT" | python -c "import sys, json, os; [sys.stdout.write('%s %s\n' % (k, v['alias'] if 'alias' in v else k)) for (k, v) in json.load(sys.stdin).iteritems()]" > /tmp/port-name-alias-map.txt
+
+# The docker container should start this script as PID 1, so now that supervisord is
+# properly configured, we exec supervisord so that it runs as PID 1 for the
+# duration of the container's lifetime
+exec /usr/bin/supervisord

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

@@ -1,16 +1,13 @@
 #!/usr/bin/env bash
 
-# Create isc-dhcp-relay config file
-sonic-cfggen -d -t /usr/share/sonic/templates/isc-dhcp-relay.j2 > /etc/default/isc-dhcp-relay
-
+# Remove stale rsyslog PID file if it exists
 rm -f /var/run/rsyslogd.pid
 
+# Start rsyslog
 supervisorctl start rsyslogd
 
-# Wait for all interfaces to come up before starting the DHCP relay
-sonic-cfggen -d -t /usr/share/sonic/templates/wait_for_intf.sh.j2 > /usr/bin/wait_for_intf.sh
-chmod +x /usr/bin/wait_for_intf.sh
+# Wait for all interfaces to come up before starting the DHCP relay agent(s)
 /usr/bin/wait_for_intf.sh
 
-# Start the DHCP relay
-supervisorctl start isc-dhcp-relay
+# Start the DHCP relay agent(s)
+supervisorctl start isc-dhcp-relay:*

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

@@ -25,4 +25,3 @@ wait_until_iface_exists {{ name }}
 {% for (name, prefix) in PORTCHANNEL_INTERFACE %}
 wait_until_iface_exists {{ name }}
 {% endfor %}
-