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// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package monitor
import (
"fmt"
"strings"
"sync"
"golang.org/x/net/route"
"golang.org/x/sys/unix"
"inet.af/netaddr"
"tailscale.com/types/logger"
)
const debugRouteMessages = false
// unspecifiedMessage is a minimal message implementation that should not
// be ignored. In general, OS-specific implementations should use better
// types and avoid this if they can.
type unspecifiedMessage struct{}
func (unspecifiedMessage) ignore() bool { return false }
func newOSMon(logf logger.Logf, _ *Mon) (osMon, error) {
fd, err := unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, 0)
if err != nil {
return nil, err
}
return &darwinRouteMon{
logf: logf,
fd: fd,
}, nil
}
type darwinRouteMon struct {
logf logger.Logf
fd int // AF_ROUTE socket
buf [2 << 10]byte
closeOnce sync.Once
}
func (m *darwinRouteMon) Close() error {
var err error
m.closeOnce.Do(func() {
err = unix.Close(m.fd)
})
return err
}
func (m *darwinRouteMon) Receive() (message, error) {
for {
n, err := unix.Read(m.fd, m.buf[:])
if err != nil {
return nil, err
}
msgs, err := route.ParseRIB(route.RIBTypeRoute, m.buf[:n])
if err != nil {
if debugRouteMessages {
m.logf("read %d bytes (% 02x), failed to parse RIB: %v", n, m.buf[:n], err)
}
return unspecifiedMessage{}, nil
}
if len(msgs) == 0 {
if debugRouteMessages {
m.logf("read %d bytes with no messages (% 02x)", n, m.buf[:n])
}
continue
}
nSkip := 0
for _, msg := range msgs {
if m.skipMessage(msg) {
nSkip++
}
}
if debugRouteMessages {
m.logf("read %d bytes, %d messages (%d skipped)", n, len(msgs), nSkip)
if nSkip < len(msgs) {
m.logMessages(msgs)
}
}
if nSkip == len(msgs) {
continue
}
return unspecifiedMessage{}, nil
}
}
func (m *darwinRouteMon) skipMessage(msg route.Message) bool {
switch msg := msg.(type) {
case *route.InterfaceMulticastAddrMessage:
return true
case *route.InterfaceAddrMessage:
return m.skipInterfaceAddrMessage(msg)
case *route.RouteMessage:
return m.skipRouteMessage(msg)
}
return false
}
// addrType returns addrs[rtaxType], if that (the route address type) exists,
// else it returns nil.
//
// The RTAX_* constants at https://github.com/apple/darwin-xnu/blob/main/bsd/net/route.h
// for what each address index represents.
func addrType(addrs []route.Addr, rtaxType int) route.Addr {
if len(addrs) > rtaxType {
return addrs[rtaxType]
}
return nil
}
func (m *darwinRouteMon) skipInterfaceAddrMessage(msg *route.InterfaceAddrMessage) bool {
if la, ok := addrType(msg.Addrs, unix.RTAX_IFP).(*route.LinkAddr); ok {
baseName := strings.TrimRight(la.Name, "0123456789")
switch baseName {
case "llw", "awdl", "pdp_ip":
return true
}
}
return false
}
func (m *darwinRouteMon) skipRouteMessage(msg *route.RouteMessage) bool {
if ip := ipOfAddr(addrType(msg.Addrs, unix.RTAX_DST)); ip.IsLinkLocalUnicast() {
// Skip those like:
// dst = fe80::b476:66ff:fe30:c8f6%15
return true
}
return false
}
func (m *darwinRouteMon) logMessages(msgs []route.Message) {
for i, msg := range msgs {
switch msg := msg.(type) {
default:
m.logf(" [%d] %T", i, msg)
case *route.InterfaceAddrMessage:
m.logf(" [%d] InterfaceAddrMessage: ver=%d, type=%v, flags=0x%x, idx=%v",
i, msg.Version, msg.Type, msg.Flags, msg.Index)
m.logAddrs(msg.Addrs)
case *route.InterfaceMulticastAddrMessage:
m.logf(" [%d] InterfaceMulticastAddrMessage: ver=%d, type=%v, flags=0x%x, idx=%v",
i, msg.Version, msg.Type, msg.Flags, msg.Index)
m.logAddrs(msg.Addrs)
case *route.RouteMessage:
m.logf(" [%d] RouteMessage: ver=%d, type=%v, flags=0x%x, idx=%v, id=%v, seq=%v, err=%v",
i, msg.Version, msg.Type, msg.Flags, msg.Index, msg.ID, msg.Seq, msg.Err)
m.logAddrs(msg.Addrs)
}
}
}
func (m *darwinRouteMon) logAddrs(addrs []route.Addr) {
for i, a := range addrs {
if a == nil {
continue
}
m.logf(" %v = %v", rtaxName(i), fmtAddr(a))
}
}
// ipOfAddr returns the route.Addr (possibly nil) as a netaddr.IP
// (possibly zero).
func ipOfAddr(a route.Addr) netaddr.IP {
switch a := a.(type) {
case *route.Inet4Addr:
return netaddr.IPv4(a.IP[0], a.IP[1], a.IP[2], a.IP[3])
case *route.Inet6Addr:
ip := netaddr.IPv6Raw(a.IP)
if a.ZoneID != 0 {
ip = ip.WithZone(fmt.Sprint(a.ZoneID)) // TODO: look up net.InterfaceByIndex? but it might be changing?
}
return ip
}
return netaddr.IP{}
}
func fmtAddr(a route.Addr) interface{} {
if a == nil {
return nil
}
if ip := ipOfAddr(a); !ip.IsZero() {
return ip
}
switch a := a.(type) {
case *route.LinkAddr:
return fmt.Sprintf("[LinkAddr idx=%v name=%q addr=%x]", a.Index, a.Name, a.Addr)
default:
return fmt.Sprintf("%T: %+v", a, a)
}
}
// See https://github.com/apple/darwin-xnu/blob/main/bsd/net/route.h
func rtaxName(i int) string {
switch i {
case unix.RTAX_DST:
return "dst"
case unix.RTAX_GATEWAY:
return "gateway"
case unix.RTAX_NETMASK:
return "netmask"
case unix.RTAX_GENMASK:
return "genmask"
case unix.RTAX_IFP: // "interface name sockaddr present"
return "IFP"
case unix.RTAX_IFA: // "interface addr sockaddr present"
return "IFA"
case unix.RTAX_AUTHOR:
return "author"
case unix.RTAX_BRD:
return "BRD"
}
return fmt.Sprint(i)
}
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