// Copyright 2012 Google, Inc. All rights reserved. // // Use of this source code is governed by a BSD-style license // that can be found in the LICENSE file in the root of the source // tree. //go:build linux // Generate a local routing table structure following the code at // https://github.com/google/gopacket/blob/master/routing/routing.go package netroute import ( "net" "sort" "syscall" "unsafe" "github.com/google/gopacket/routing" ) // Pulled from http://man7.org/linux/man-pages/man7/rtnetlink.7.html // See the section on RTM_NEWROUTE, specifically 'struct rtmsg'. type routeInfoInMemory struct { Family byte DstLen byte SrcLen byte TOS byte Table byte Protocol byte Scope byte Type byte Flags uint32 } func New() (routing.Router, error) { rtr := &router{} rtr.ifaces = make(map[int]net.Interface) rtr.addrs = make(map[int]ipAddrs) tab, err := syscall.NetlinkRIB(syscall.RTM_GETROUTE, syscall.AF_UNSPEC) if err != nil { return nil, err } msgs, err := syscall.ParseNetlinkMessage(tab) if err != nil { return nil, err } loop: for _, m := range msgs { switch m.Header.Type { case syscall.NLMSG_DONE: break loop case syscall.RTM_NEWROUTE: rt := (*routeInfoInMemory)(unsafe.Pointer(&m.Data[0])) routeInfo := rtInfo{} attrs, err := syscall.ParseNetlinkRouteAttr(&m) if err != nil { return nil, err } switch rt.Family { case syscall.AF_INET: rtr.v4 = append(rtr.v4, &routeInfo) case syscall.AF_INET6: rtr.v6 = append(rtr.v6, &routeInfo) default: continue loop } for _, attr := range attrs { switch attr.Attr.Type { case syscall.RTA_DST: routeInfo.Dst = &net.IPNet{ IP: net.IP(attr.Value), Mask: net.CIDRMask(int(rt.DstLen), len(attr.Value)*8), } case syscall.RTA_SRC: routeInfo.Src = &net.IPNet{ IP: net.IP(attr.Value), Mask: net.CIDRMask(int(rt.SrcLen), len(attr.Value)*8), } case syscall.RTA_GATEWAY: routeInfo.Gateway = net.IP(attr.Value) case syscall.RTA_PREFSRC: routeInfo.PrefSrc = net.IP(attr.Value) case syscall.RTA_IIF: routeInfo.InputIface = *(*uint32)(unsafe.Pointer(&attr.Value[0])) case syscall.RTA_OIF: routeInfo.OutputIface = *(*uint32)(unsafe.Pointer(&attr.Value[0])) case syscall.RTA_PRIORITY: routeInfo.Priority = *(*uint32)(unsafe.Pointer(&attr.Value[0])) } } } } sort.Sort(rtr.v4) sort.Sort(rtr.v6) ifaces, err := net.Interfaces() if err != nil { return nil, err } for _, iface := range ifaces { rtr.ifaces[iface.Index] = iface var addrs ipAddrs ifaceAddrs, err := iface.Addrs() if err != nil { return nil, err } for _, addr := range ifaceAddrs { if inet, ok := addr.(*net.IPNet); ok { // Go has a nasty habit of giving you IPv4s as ::ffff:1.2.3.4 instead of 1.2.3.4. // We want to use mapped v4 addresses as v4 preferred addresses, never as v6 // preferred addresses. if v4 := inet.IP.To4(); v4 != nil { if addrs.v4 == nil { addrs.v4 = v4 } } else if addrs.v6 == nil { addrs.v6 = inet.IP } } } rtr.addrs[iface.Index] = addrs } return rtr, nil }