[orchagent]: Add ARP update script to maintain VLAN neighbors (#401)

- Extend ARP reachable time to 30min
- Add arping to docker-swss
- Add arp_update script to routinely probe neighbors

Signed-off-by: Shuotian Cheng <shuche@microsoft.com>

build_debian.sh

@@ -232,6 +232,8 @@ set /files/etc/sysctl.conf/net.ipv4.conf.all.arp_filter 0
 set /files/etc/sysctl.conf/net.ipv4.conf.all.arp_notify 1
 set /files/etc/sysctl.conf/net.ipv4.conf.all.arp_ignore 2
 
+set /files/etc/sysctl.conf/net.ipv4.neigh.default.base_reachable_time_ms 1800000
+
 set /files/etc/sysctl.conf/net.ipv6.conf.default.forwarding 1
 set /files/etc/sysctl.conf/net.ipv6.conf.all.forwarding 1
 set /files/etc/sysctl.conf/net.ipv6.conf.eth0.forwarding 0

dockers/docker-orchagent/Dockerfile.j2

@@ -5,7 +5,7 @@ ENV DEBIAN_FRONTEND=noninteractive
 
 RUN apt-get update
 
-RUN apt-get install -f -y ifupdown libdbus-1-3 libdaemon0 libjansson4
+RUN apt-get install -f -y ifupdown arping libdbus-1-3 libdaemon0 libjansson4
 
 ## Install redis-tools dependencies
 ## TODO: implicitly install dependencies
@@ -26,7 +26,7 @@ debs/{{ deb }}{{' '}}
 RUN apt-get clean -y; apt-get autoclean -y; apt-get autoremove -y
 RUN rm -rf /debs
 
-COPY ["start.sh", "orchagent.sh", "swssconfig.sh", "/usr/bin/"]
+COPY ["arp_update", "start.sh", "orchagent.sh", "swssconfig.sh", "/usr/bin/"]
 COPY ["supervisord.conf", "/etc/supervisor/conf.d/"]
 COPY ["ipinip.json.j2", "/usr/share/sonic/templates/"]
 COPY ["mirror.json.j2", "/usr/share/sonic/templates/"]

dockers/docker-orchagent/arp_update

@@ -0,0 +1,17 @@
+#!/bin/bash
+#
+# usage:
+# arp_update: Send gratuitous ARP requests to VLAN member neighbors to refresh
+# the neighbors state.
+
+VLAN=`sonic-cfggen -m /etc/sonic/minigraph.xml -v 'minigraph_vlans.keys() | join(" ")'`
+for vlan in $VLAN; do
+    # generate a list of arping commands:
+    #   arping -q -w 0 -c 1 -i <VLAN interface> <IP 1>;
+    #   arping -q -w 0 -c 1 -i <VLAN interface> <IP 2>;
+    #   ...
+    arpingcmd="sed -e 's/ / -i /' -e 's/^/arping -q -w 0 -c 1 /' -e 's/$/;/'"
+    ipcmd="ip -4 neigh show | grep $vlan | cut -d ' ' -f 1,3 | $arpingcmd"
+
+    eval `eval $ipcmd`
+done

dockers/docker-orchagent/start.sh

@@ -32,3 +32,8 @@ supervisorctl start neighsyncd
 
 supervisorctl start swssconfig
 
+# Start arp_update when VLAN exists
+VLAN=`sonic-cfggen -m /etc/sonic/minigraph.xml -v 'minigraph_vlans.keys() | join(" ")'`
+if [ "$VLAN" != "" ]; then
+    supervisorctl start arp_update
+fi

dockers/docker-orchagent/supervisord.conf

@@ -59,3 +59,10 @@ autorestart=false
 stdout_logfile=syslog
 stderr_logfile=syslog
 
+[program:arp_update]
+command=bash -c "/usr/bin/arp_update && sleep 300"
+priority=8
+autostart=false
+autorestart=true
+stdout_logfile=syslog
+stderr_logfile=syslog