Dynamically assign DNS IP using cni-env

addons/common/utils.sh

@@ -31,3 +31,61 @@ use_addon_manifest() {
     use_manifest_result="$?"
     rm "${tmp_manifest}"
 }
+
+# Function to convert an IP address to a decimal number
+ip_to_decimal() {
+    local ip="$1"
+    echo $(( $(echo "$ip" | awk -F'.' '{print ($1*256^3)+($2*256^2)+($3*256^1)+$4}') ))
+}
+
+# Function to convert a decimal number to an IP address
+decimal_to_ip() {
+    local decimal="$1"
+    echo "$(( (decimal >> 24) & 255 )).$(( (decimal >> 16) & 255 )).$(( (decimal >> 8) & 255 )).$(( decimal & 255 ))"
+}
+
+# Function to validate if an IP address is within the CIDR range
+ip_in_cidr() {
+    local ip="$1"
+    local cidr="$2"
+
+    local cidr_ip=$(echo "$cidr" | cut -d'/' -f1)
+    local cidr_mask=$(echo "$cidr" | cut -d'/' -f2)
+
+    local ip_decimal=$(ip_to_decimal "$ip")
+    local cidr_ip_decimal=$(ip_to_decimal "$cidr_ip")
+
+    local bitmask=$((2**(32-cidr_mask)-1))
+    local network_ip_decimal=$((cidr_ip_decimal & ~bitmask))
+
+    local cidr_start_decimal=$((network_ip_decimal + 1))
+    local cidr_end_decimal=$((network_ip_decimal + bitmask - 1))
+
+    [ $ip_decimal -ge $cidr_start_decimal ] && [ $ip_decimal -le $cidr_end_decimal ]
+}
+
+# Function to choose a random valid IP address from the CIDR range
+choose_random_ip() {
+    local cidr="$1"
+    local ip
+    local count=0
+    local max_attempts=100
+
+    local cidr_ip=$(echo "$cidr" | cut -d'/' -f1)
+    local base_ip="${cidr_ip%.*}."
+
+    while [ "$count" -lt "$max_attempts" ]; do
+        ip=$(shuf -i 1-254 -n 1)
+        chosen_ip="${base_ip}$ip"
+
+    if ip_in_cidr "$chosen_ip" "$cidr"; then
+        echo "$chosen_ip"
+        return 0
+    fi
+
+    ((count++))
+    done
+
+    echo "Failed to find a valid IP address after $max_attempts attempts."
+    return 1
+}

addons/dns/enable

@@ -47,7 +47,12 @@ else
   echo "Will use ${nameserver_str} as upstream nameservers"
 fi
 
-DNSIP="10.152.183.10"
+if [ -e "${SNAP_DATA}/args/cni-env" ]; then
+  source "${SNAP_DATA}/args/cni-env"
+fi
+# Choose a random IP address from the service cidr.
+DNSIP=$(choose_random_ip "$IPv4_SERVICE_CIDR" || true)
+echo "Will use ${DNSIP} as dns service ip address"
 
 DNSIPARG=$2
 if [[ -n "$DNSIPARG" ]]; then