Refactor local DNS cache partitioning

route/network_environment_linux.go

@@ -0,0 +1,59 @@
+package route
+
+import (
+	"net"
+	"net/netip"
+	"slices"
+
+	"github.com/sagernet/netlink"
+)
+
+func systemGateways(interfaceIndex int) []netip.Addr {
+	routes, err := netlink.RouteListFiltered(netlink.FAMILY_ALL, &netlink.Route{LinkIndex: interfaceIndex}, netlink.RT_FILTER_OIF)
+	if err != nil {
+		return nil
+	}
+	var gateways []netip.Addr
+	for _, currentRoute := range routes {
+		if currentRoute.Gw == nil {
+			continue
+		}
+		if currentRoute.Dst != nil {
+			ones, _ := currentRoute.Dst.Mask.Size()
+			if ones != 0 {
+				continue
+			}
+		}
+		gateway, valid := netip.AddrFromSlice(currentRoute.Gw)
+		if valid {
+			gateways = append(gateways, gateway.Unmap())
+		}
+	}
+	return gateways
+}
+
+func systemNeighborHardwareAddresses(interfaceIndex int, addresses []netip.Addr) map[netip.Addr]net.HardwareAddr {
+	neighbors, err := netlink.NeighList(interfaceIndex, netlink.FAMILY_ALL)
+	if err != nil {
+		return nil
+	}
+	hardwareAddresses := make(map[netip.Addr]net.HardwareAddr)
+	for _, neighbor := range neighbors {
+		if neighbor.State&(netlink.NUD_INCOMPLETE|netlink.NUD_FAILED) != 0 {
+			continue
+		}
+		if len(neighbor.HardwareAddr) == 0 {
+			continue
+		}
+		neighborAddress, valid := netip.AddrFromSlice(neighbor.IP)
+		if !valid {
+			continue
+		}
+		neighborAddress = neighborAddress.Unmap()
+		if !slices.Contains(addresses, neighborAddress) {
+			continue
+		}
+		hardwareAddresses[neighborAddress] = neighbor.HardwareAddr
+	}
+	return hardwareAddresses
+}