modifymacip.sh: drop state file, discover entries from bridge on delete

The state file was fragile: it could be left behind after a crash or
missed during host migration. Delete now queries the bridge neighbour
table directly with 'ip neigh show dev <bridge>' and removes every entry
whose lladdr matches the MAC, along with its corresponding host route.
This makes delete idempotent and self-healing without any persistent
state on disk.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: wido

scripts/vm/network/vnet/modifymacip.sh

@@ -24,10 +24,8 @@
 #
 # Both -4 and -6 may be specified multiple times to cover primary and secondary
 # addresses (e.g. link-local + global unicast for IPv6).
-# On add the script persists the NIC's address info so that delete can
-# recover the IPs without them being passed explicitly.
-
-STATE_DIR=/var/run/cloud/macip
+# On delete the bridge neighbour table is queried for all entries matching the
+# MAC address; no separate state file is required.
 
 usage() {
     echo "Usage: $0 -o <add|delete> -b <bridge> -m <mac> [-4 <ipv4>] ... [-6 <ipv6>] ..."
@@ -55,24 +53,7 @@ if [[ -z "$OP" || -z "$BRIDGE" || -z "$MAC" ]]; then
     exit 2
 fi
 
-# Normalise MAC address for use as a filename (replace colons with underscores)
-MAC_NORM="${MAC//:/_}"
-STATE_FILE="${STATE_DIR}/${MAC_NORM}.conf"
-
 add_entries() {
-    mkdir -p "${STATE_DIR}"
-
-    # Persist state so that delete can recover IPs without them being passed in
-    {
-        for addr in "${IPV4_LIST[@]}"; do
-            printf 'IPV4=%s\n' "${addr}"
-        done
-        for addr in "${IPV6_LIST[@]}"; do
-            printf 'IPV6=%s\n' "${addr}"
-        done
-        printf 'BRIDGE=%s\n' "${BRIDGE}"
-    } > "${STATE_FILE}"
-
     for addr in "${IPV4_LIST[@]}"; do
         ip neigh replace "${addr}" lladdr "${MAC}" dev "${BRIDGE}" nud permanent
         ip route replace "${addr}/32" dev "${BRIDGE}"
@@ -89,32 +70,17 @@ add_entries() {
 }
 
 delete_entries() {
-    local -a del_ipv4=()
-    local -a del_ipv6=()
-    local del_bridge="${BRIDGE}"
-
-    # Recover IPs and bridge from the state file written at add time
-    if [[ -f "${STATE_FILE}" ]]; then
-        while IFS='=' read -r key value; do
-            case "$key" in
-                IPV4)   [[ -n "$value" ]] && del_ipv4+=("$value") ;;
-                IPV6)   [[ -n "$value" ]] && del_ipv6+=("$value") ;;
-                BRIDGE) del_bridge="${del_bridge:-$value}" ;;
-            esac
-        done < "${STATE_FILE}"
-    fi
-
-    for addr in "${del_ipv4[@]}"; do
-        ip neigh del "${addr}" dev "${del_bridge}" 2>/dev/null || true
-        ip route del "${addr}/32" dev "${del_bridge}" 2>/dev/null || true
-    done
-
-    for addr in "${del_ipv6[@]}"; do
-        ip -6 neigh del "${addr}" dev "${del_bridge}" 2>/dev/null || true
-        ip -6 route del "${addr}/128" dev "${del_bridge}" 2>/dev/null || true
-    done
-
-    rm -f "${STATE_FILE}"
+    # Find all IPv4 neighbour entries on the bridge matching this MAC and remove them
+    while read -r addr; do
+        ip neigh del "${addr}" dev "${BRIDGE}" 2>/dev/null || true
+        ip route del "${addr}/32" dev "${BRIDGE}" 2>/dev/null || true
+    done < <(ip neigh show dev "${BRIDGE}" | awk -v mac="${MAC}" 'tolower($3) == tolower(mac) {print $1}')
+
+    # Find all IPv6 neighbour entries on the bridge matching this MAC and remove them
+    while read -r addr; do
+        ip -6 neigh del "${addr}" dev "${BRIDGE}" 2>/dev/null || true
+        ip -6 route del "${addr}/128" dev "${BRIDGE}" 2>/dev/null || true
+    done < <(ip -6 neigh show dev "${BRIDGE}" | awk -v mac="${MAC}" 'tolower($3) == tolower(mac) {print $1}')
 }
 
 case "$OP" in