Azure/personal/dns warning

lib/common.sh

@@ -134,6 +134,21 @@ is_ip_port_reachable()
     nc -w 3 -z $ip $port > /dev/null 2>&1
 }
 
+#
+# Verify if FQDN is resolved into ipv4_addr by /etc/hosts entry.
+#
+is_present_in_etc_hosts() {
+    local ip="$1"
+    local hostname="$2"
+
+    # Search for the entry in /etc/hosts
+    if grep -qE "^[[:space:]]*$ip[[:space:]]+[^#]*\<$hostname\>" /etc/hosts; then
+        return 0
+    fi
+
+    return 1
+}
+
 #
 # Blob fqdn to IPv4 adddress.
 # Caller must make sure that it is called only for hostname and not IP address.
@@ -144,6 +159,7 @@ is_ip_port_reachable()
 resolve_ipv4()
 {
     local hname="$1"
+    local fail_if_present_in_etc_hosts="$2"
     local RETRIES=3
 
     # Some retries for resilience.
@@ -213,6 +229,21 @@ resolve_ipv4()
         return 1
     fi
 
+    #
+    # Check if the IP-FQDN pair is present in /etc/hosts
+    # 
+    if is_present_in_etc_hosts "$ipv4_addr" "$hname"; then
+        if [ "$fail_if_present_in_etc_hosts" == "true" ]; then
+            eecho "[FATAL] Detected entry $ipv4_addr $hname in /etc/hosts."
+            eecho "$hname is resolving into $ipv4_addr from /etc/hosts."
+            eecho "Remove the entry for "$hname" in /etc/hosts to ensure proper handling of endpoint IP address changes by AZNFS."
+            return 1
+        else
+            wecho "[FATAL] Detected entry $ipv4_addr $hname in /etc/hosts." 1>/dev/null
+            wecho "Remove the entry for "$hname" in /etc/hosts to ensure proper handling of endpoint IP address changes by AZNFS." 1>/dev/null
+        fi
+    fi
+
     echo $ipv4_addr
     return 0
 }

src/aznfswatchdog

@@ -312,7 +312,7 @@ while :; do
         # Check if blob endpoint IP address changed.
         # This is the migration check.
         #
-        new_ip=$(resolve_ipv4 "$l_host")
+        new_ip=$(resolve_ipv4 "$l_host" "false")
 
         # If we fail to resolve the host name, try next time.
         if [ $? -ne 0 ]; then

src/mountscript.sh

@@ -636,10 +636,12 @@ if ! is_valid_blob_fqdn "$nfs_host"; then
     exit 1
 fi
 
-nfs_ip=$(resolve_ipv4 "$nfs_host")
+# Resolve the IP address for the NFS host
+nfs_ip=$(resolve_ipv4 "$nfs_host" "true")
 if [ $? -ne 0 ]; then
     echo "$nfs_ip"
     eecho "Cannot resolve IP address for ${nfs_host}!"
+    eecho "Mount failed!"
     exit 1
 fi