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226 lines
5.5 KiB
Go
226 lines
5.5 KiB
Go
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// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package netmon
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import (
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"fmt"
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"net/netip"
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"strings"
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"sync"
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"golang.org/x/net/route"
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"golang.org/x/sys/unix"
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"tailscale.com/net/netaddr"
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"tailscale.com/types/logger"
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)
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const debugRouteMessages = false
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// unspecifiedMessage is a minimal message implementation that should not
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// be ignored. In general, OS-specific implementations should use better
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// types and avoid this if they can.
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type unspecifiedMessage struct{}
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func (unspecifiedMessage) ignore() bool { return false }
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func newOSMon(logf logger.Logf, _ *Monitor) (osMon, error) {
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fd, err := unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, 0)
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if err != nil {
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return nil, err
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}
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return &darwinRouteMon{
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logf: logf,
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fd: fd,
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}, nil
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}
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type darwinRouteMon struct {
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logf logger.Logf
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fd int // AF_ROUTE socket
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buf [2 << 10]byte
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closeOnce sync.Once
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}
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func (m *darwinRouteMon) Close() error {
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var err error
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m.closeOnce.Do(func() {
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err = unix.Close(m.fd)
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})
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return err
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}
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func (m *darwinRouteMon) Receive() (message, error) {
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for {
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n, err := unix.Read(m.fd, m.buf[:])
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if err != nil {
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return nil, err
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}
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msgs, err := route.ParseRIB(route.RIBTypeRoute, m.buf[:n])
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if err != nil {
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if debugRouteMessages {
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m.logf("read %d bytes (% 02x), failed to parse RIB: %v", n, m.buf[:n], err)
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}
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return unspecifiedMessage{}, nil
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}
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if len(msgs) == 0 {
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if debugRouteMessages {
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m.logf("read %d bytes with no messages (% 02x)", n, m.buf[:n])
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}
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continue
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}
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nSkip := 0
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for _, msg := range msgs {
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if m.skipMessage(msg) {
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nSkip++
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}
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}
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if debugRouteMessages {
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m.logf("read %d bytes, %d messages (%d skipped)", n, len(msgs), nSkip)
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if nSkip < len(msgs) {
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m.logMessages(msgs)
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}
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}
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if nSkip == len(msgs) {
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continue
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}
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return unspecifiedMessage{}, nil
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}
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}
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func (m *darwinRouteMon) skipMessage(msg route.Message) bool {
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switch msg := msg.(type) {
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case *route.InterfaceMulticastAddrMessage:
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return true
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case *route.InterfaceAddrMessage:
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return m.skipInterfaceAddrMessage(msg)
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case *route.RouteMessage:
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return m.skipRouteMessage(msg)
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}
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return false
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}
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// addrType returns addrs[rtaxType], if that (the route address type) exists,
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// else it returns nil.
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//
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// The RTAX_* constants at https://github.com/apple/darwin-xnu/blob/main/bsd/net/route.h
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// for what each address index represents.
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func addrType(addrs []route.Addr, rtaxType int) route.Addr {
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if len(addrs) > rtaxType {
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return addrs[rtaxType]
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}
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return nil
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}
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func (m *darwinRouteMon) IsInterestingInterface(iface string) bool {
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baseName := strings.TrimRight(iface, "0123456789")
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switch baseName {
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// TODO(maisem): figure out what this list should actually be.
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case "llw", "awdl", "ipsec":
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return false
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}
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return true
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}
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func (m *darwinRouteMon) skipInterfaceAddrMessage(msg *route.InterfaceAddrMessage) bool {
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if la, ok := addrType(msg.Addrs, unix.RTAX_IFP).(*route.LinkAddr); ok {
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if !m.IsInterestingInterface(la.Name) {
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return true
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}
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}
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return false
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}
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func (m *darwinRouteMon) skipRouteMessage(msg *route.RouteMessage) bool {
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if ip := ipOfAddr(addrType(msg.Addrs, unix.RTAX_DST)); ip.IsLinkLocalUnicast() {
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// Skip those like:
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// dst = fe80::b476:66ff:fe30:c8f6%15
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return true
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}
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return false
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}
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func (m *darwinRouteMon) logMessages(msgs []route.Message) {
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for i, msg := range msgs {
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switch msg := msg.(type) {
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default:
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m.logf(" [%d] %T", i, msg)
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case *route.InterfaceAddrMessage:
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m.logf(" [%d] InterfaceAddrMessage: ver=%d, type=%v, flags=0x%x, idx=%v",
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i, msg.Version, msg.Type, msg.Flags, msg.Index)
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m.logAddrs(msg.Addrs)
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case *route.InterfaceMulticastAddrMessage:
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m.logf(" [%d] InterfaceMulticastAddrMessage: ver=%d, type=%v, flags=0x%x, idx=%v",
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i, msg.Version, msg.Type, msg.Flags, msg.Index)
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m.logAddrs(msg.Addrs)
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case *route.RouteMessage:
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m.logf(" [%d] RouteMessage: ver=%d, type=%v, flags=0x%x, idx=%v, id=%v, seq=%v, err=%v",
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i, msg.Version, msg.Type, msg.Flags, msg.Index, msg.ID, msg.Seq, msg.Err)
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m.logAddrs(msg.Addrs)
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}
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}
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}
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func (m *darwinRouteMon) logAddrs(addrs []route.Addr) {
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for i, a := range addrs {
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if a == nil {
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continue
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}
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m.logf(" %v = %v", rtaxName(i), fmtAddr(a))
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}
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}
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// ipOfAddr returns the route.Addr (possibly nil) as a netip.Addr
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// (possibly zero).
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func ipOfAddr(a route.Addr) netip.Addr {
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switch a := a.(type) {
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case *route.Inet4Addr:
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return netaddr.IPv4(a.IP[0], a.IP[1], a.IP[2], a.IP[3])
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case *route.Inet6Addr:
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ip := netip.AddrFrom16(a.IP)
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if a.ZoneID != 0 {
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ip = ip.WithZone(fmt.Sprint(a.ZoneID)) // TODO: look up net.InterfaceByIndex? but it might be changing?
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}
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return ip
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}
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return netip.Addr{}
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}
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func fmtAddr(a route.Addr) any {
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if a == nil {
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return nil
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}
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if ip := ipOfAddr(a); ip.IsValid() {
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return ip
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}
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switch a := a.(type) {
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case *route.LinkAddr:
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return fmt.Sprintf("[LinkAddr idx=%v name=%q addr=%x]", a.Index, a.Name, a.Addr)
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default:
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return fmt.Sprintf("%T: %+v", a, a)
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}
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}
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// See https://github.com/apple/darwin-xnu/blob/main/bsd/net/route.h
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func rtaxName(i int) string {
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switch i {
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case unix.RTAX_DST:
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return "dst"
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case unix.RTAX_GATEWAY:
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return "gateway"
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case unix.RTAX_NETMASK:
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return "netmask"
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case unix.RTAX_GENMASK:
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return "genmask"
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case unix.RTAX_IFP: // "interface name sockaddr present"
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return "IFP"
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case unix.RTAX_IFA: // "interface addr sockaddr present"
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return "IFA"
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case unix.RTAX_AUTHOR:
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return "author"
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case unix.RTAX_BRD:
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return "BRD"
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}
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return fmt.Sprint(i)
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}
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