route-update.sh: zero-downtime route reload without flush

router/route-update.sh

@@ -452,10 +452,26 @@ process_routes()
             continue
         fi
 
-        # Flush and load via batch
-        $ipcmd route flush table "$table" 2>/dev/null
+        # Zero-downtime reload: replace all, then remove stale
         sed "s|^|route replace |; s|$| $route_via|" "$resolved_new" | \
             $ipcmd -batch - 2>&1 | grep -v "^$" | head -5
+        local stale=$(mktemp)
+        $ipcmd route show table "$table" 2>/dev/null | awk '{print $1}' | sort | \
+            comm -23 - "$resolved_new" > "$stale"
+        if [ -s "$stale" ] ; then
+            vlog "[$name]$label removing $(wc -l < "$stale") stale routes"
+            sed "s|^|route del |; s|$| table $table|" "$stale" | \
+                $ipcmd -batch - 2>/dev/null
+        fi
+        rm -f "$stale"
+
+        # Verify route count matches expected
+        local actual=$($ipcmd route show table "$table" 2>/dev/null | wc -l)
+        if [ "$actual" != "$count" ] ; then
+            log "[$name]$label WARNING: route count mismatch: expected $count, got $actual"
+        else
+            vlog "[$name]$label route count OK: $actual"
+        fi
 
         # Ensure ip rule exists
         if ! $ipcmd -N rule show | grep -q "lookup $table.*pref $pref" ; then