From 95c7e7251d6e938691e2984bd70bcb80f590650d Mon Sep 17 00:00:00 2001
From: Joe LeVeque <jolevequ@microsoft.com>
Date: Tue, 21 Nov 2017 01:25:38 +0000
Subject: [PATCH 1/2] [DHCP relay]: Wait for all interfaces to be assigned IPv4
 addresses before starting relay agent

---
 dockers/docker-dhcp-relay/wait_for_intf.sh.j2 | 29 ++++++++++++++-----
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/dockers/docker-dhcp-relay/wait_for_intf.sh.j2 b/dockers/docker-dhcp-relay/wait_for_intf.sh.j2
index 1524b322131..80e75fd037b 100644
--- a/dockers/docker-dhcp-relay/wait_for_intf.sh.j2
+++ b/dockers/docker-dhcp-relay/wait_for_intf.sh.j2
@@ -1,27 +1,42 @@
 #!/usr/bin/env bash
 
-function wait_until_iface_exists
+function wait_until_iface_ready
 {
     IFACE=$1
 
-    echo "Waiting for interface ${IFACE}..."
+    echo "Waiting until interface $IFACE is up..."
 
     # Wait for the interface to come up (i.e., 'ip link show' returns 0)
-    until ip link show $IFACE > /dev/null 2>&1; do
+    until ip link show dev $IFACE up > /dev/null 2>&1; do
         sleep 1
     done
 
-    echo "Interface ${IFACE} is created"
+    echo "Interface $IFACE is up"
+
+    echo "Waiting until interface $IFACE has an IPv4 address..."
+
+    # Wait until the interface gets assigned an IPv4 address
+    while true; do
+        IP=$(ip -4 addr show dev $IFACE | grep "inet " | awk '{ print $2 }' | cut -d '/' -f1)
+
+        if [ -n "$IP" ]; then
+            break
+        fi
+
+        sleep 1
+    done
+
+    echo "Interface $IFACE is configured with IP $IP"
 }
 
 
 # Wait for all interfaces to come up before starting the DHCP relay
 {% for (name, prefix) in INTERFACE %}
-wait_until_iface_exists {{ name }}
+wait_until_iface_ready {{ name }}
 {% endfor %}
 {% for (name, prefix) in VLAN_INTERFACE %}
-wait_until_iface_exists {{ name }}
+wait_until_iface_ready {{ name }}
 {% endfor %}
 {% for (name, prefix) in PORTCHANNEL_INTERFACE %}
-wait_until_iface_exists {{ name }}
+wait_until_iface_ready {{ name }}
 {% endfor %}

From d13e14b53d75d98def45c57deab94ad7fa533b21 Mon Sep 17 00:00:00 2001
From: Joe LeVeque <jolevequ@microsoft.com>
Date: Tue, 21 Nov 2017 01:57:56 +0000
Subject: [PATCH 2/2] Add comments

---
 dockers/docker-dhcp-relay/start.sh            | 7 ++++++-
 dockers/docker-dhcp-relay/wait_for_intf.sh.j2 | 2 +-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/dockers/docker-dhcp-relay/start.sh b/dockers/docker-dhcp-relay/start.sh
index b53d7e4e238..2ee80c4e338 100755
--- a/dockers/docker-dhcp-relay/start.sh
+++ b/dockers/docker-dhcp-relay/start.sh
@@ -6,7 +6,12 @@ rm -f /var/run/rsyslogd.pid
 # Start rsyslog
 supervisorctl start rsyslogd
 
-# Wait for all interfaces to come up before starting the DHCP relay agent(s)
+# Wait for all interfaces to come up and be assigned IPv4 addresses before
+# starting the DHCP relay agent(s). If an interface the relay should listen
+# on is down, the relay agent will not start. If an interface the relay should
+# listen on is up but does not have an IP address assigned when the relay
+# agent starts, it will not listen or send on that interface for the lifetime
+# of the process.
 /usr/bin/wait_for_intf.sh
 
 # Start the DHCP relay agent(s)
diff --git a/dockers/docker-dhcp-relay/wait_for_intf.sh.j2 b/dockers/docker-dhcp-relay/wait_for_intf.sh.j2
index 80e75fd037b..037dc66ead6 100644
--- a/dockers/docker-dhcp-relay/wait_for_intf.sh.j2
+++ b/dockers/docker-dhcp-relay/wait_for_intf.sh.j2
@@ -30,7 +30,7 @@ function wait_until_iface_ready
 }
 
 
-# Wait for all interfaces to come up before starting the DHCP relay
+# Wait for all interfaces to come up and have IPv4 addresses assigned
 {% for (name, prefix) in INTERFACE %}
 wait_until_iface_ready {{ name }}
 {% endfor %}