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