route-update.sh: add multipath support for multiple gateways

router/route-update.sh

@@ -58,11 +58,14 @@ rule_pref()
 }
 
 # Read gateway and table from a group directory
-# Sets: gw, table
+# Sets: gw, table, route_via
+#   gw        - first gateway (for display and IPv4/v6 detection)
+#   table     - routing table number
+#   route_via - route suffix: "via GW table T" or "table T nexthop via GW1 ... nexthop via GW2 ..."
 read_group_config()
 {
     local dir="$1"
-    gw="" ; table=""
+    gw="" ; table="" ; route_via=""
 
     if [ -f "$dir/gateway" ] ; then
         read -r gw < "$dir/gateway"
@@ -77,6 +80,18 @@ read_group_config()
         echo "[$(basename "$dir")] No table file, skipping" >&2
         return 1
     fi
+
+    # Build route suffix: single vs multipath
+    local gw_count=$(grep -c . "$dir/gateway")
+    if [ "$gw_count" -le 1 ] ; then
+        route_via="via $gw table $table"
+    else
+        route_via="table $table"
+        while read -r g ; do
+            [ -n "$g" ] || continue
+            route_via="$route_via nexthop via $g weight 1"
+        done < "$dir/gateway"
+    fi
 }
 
 # --- Manual add/del ---
@@ -105,11 +120,11 @@ if [ "$ACTION" = "add" ] || [ "$ACTION" = "del" ] ; then
 
     if [ "$ACTION" = "add" ] ; then
         if is_ipv4 "$ADD_DEL_TARGET" || is_ipv6 "$ADD_DEL_TARGET" ; then
-            $ipcmd route replace "$ADD_DEL_TARGET" via "$gw" table "$table"
+            $ipcmd route replace "$ADD_DEL_TARGET" $route_via
         else
             get_ipv4_list "$ADD_DEL_TARGET" | sort -u | while read -r ip ; do
                 [ -n "$ip" ] || continue
-                $ipcmd route replace "$ip" via "$gw" table "$table"
+                $ipcmd route replace "$ip" $route_via
             done
         fi
     else
@@ -221,7 +236,8 @@ process_routes()
         fi
 
         local count=$(wc -l < "$resolved_new")
-        log "[$name]$label Loading $count routes into table $table via $gw"
+        local gw_display=$(paste -sd, < "$gwdir/gateway")
+        log "[$name]$label Loading $count routes into table $table via $gw_display"
 
         if [ -n "$SHOW" ] ; then
             echo "  Would flush table $table and load $count routes"
@@ -233,7 +249,7 @@ process_routes()
 
         # Flush and load via batch
         $ipcmd route flush table "$table" 2>/dev/null
-        sed "s|^|route replace |; s|$| via $gw table $table|" "$resolved_new" | \
+        sed "s|^|route replace |; s|$| $route_via|" "$resolved_new" | \
             $ipcmd -batch - 2>&1 | grep -v "^$" | head -5
 
         # Ensure ip rule exists