mirror of
https://github.com/tailscale/tailscale.git
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b9adbe2002
In prep for most of the package funcs in net/interfaces to become methods in a long-lived netmon.Monitor that can cache things. (Many of the funcs are very heavy to call regularly, whereas the long-lived netmon.Monitor can subscribe to things from the OS and remember answers to questions it's asked regularly later) Updates tailscale/corp#10910 Updates tailscale/corp#18960 Updates #7967 Updates #3299 Change-Id: Ie4e8dedb70136af2d611b990b865a822cd1797e5 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
154 lines
4.1 KiB
Go
154 lines
4.1 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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// Common code for FreeBSD and Darwin. This might also work on other
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// BSD systems (e.g. OpenBSD) but has not been tested.
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//go:build darwin || freebsd
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package netmon
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import (
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"errors"
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"fmt"
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"log"
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"net/netip"
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"syscall"
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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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)
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// ErrNoGatewayIndexFound is returned by DefaultRouteInterfaceIndex when no
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// default route is found.
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var ErrNoGatewayIndexFound = errors.New("no gateway index found")
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// DefaultRouteInterfaceIndex returns the index of the network interface that
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// owns the default route. It returns the first IPv4 or IPv6 default route it
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// finds (it does not prefer one or the other).
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func DefaultRouteInterfaceIndex() (int, error) {
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// $ netstat -nr
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// Routing tables
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// Internet:
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// Destination Gateway Flags Netif Expire
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// default 10.0.0.1 UGSc en0 <-- want this one
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// default 10.0.0.1 UGScI en1
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// From man netstat:
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// U RTF_UP Route usable
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// G RTF_GATEWAY Destination requires forwarding by intermediary
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// S RTF_STATIC Manually added
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// c RTF_PRCLONING Protocol-specified generate new routes on use
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// I RTF_IFSCOPE Route is associated with an interface scope
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rib, err := fetchRoutingTable()
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if err != nil {
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return 0, fmt.Errorf("route.FetchRIB: %w", err)
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}
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msgs, err := parseRoutingTable(rib)
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if err != nil {
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return 0, fmt.Errorf("route.ParseRIB: %w", err)
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}
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for _, m := range msgs {
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rm, ok := m.(*route.RouteMessage)
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if !ok {
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continue
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}
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if isDefaultGateway(rm) {
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if delegatedIndex, err := getDelegatedInterface(rm.Index); err == nil && delegatedIndex != 0 {
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return delegatedIndex, nil
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} else if err != nil {
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log.Printf("interfaces_bsd: could not get delegated interface: %v", err)
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}
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return rm.Index, nil
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}
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}
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return 0, ErrNoGatewayIndexFound
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}
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func init() {
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likelyHomeRouterIP = likelyHomeRouterIPBSDFetchRIB
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}
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func likelyHomeRouterIPBSDFetchRIB() (ret, myIP netip.Addr, ok bool) {
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rib, err := fetchRoutingTable()
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if err != nil {
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log.Printf("routerIP/FetchRIB: %v", err)
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return ret, myIP, false
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}
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msgs, err := parseRoutingTable(rib)
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if err != nil {
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log.Printf("routerIP/ParseRIB: %v", err)
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return ret, myIP, false
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}
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for _, m := range msgs {
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rm, ok := m.(*route.RouteMessage)
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if !ok {
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continue
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}
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if !isDefaultGateway(rm) {
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continue
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}
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gw, ok := rm.Addrs[unix.RTAX_GATEWAY].(*route.Inet4Addr)
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if !ok {
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continue
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}
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// If the route entry has an interface address associated with
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// it, then parse and return that. This is optional.
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if len(rm.Addrs) >= unix.RTAX_IFA {
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if addr, ok := rm.Addrs[unix.RTAX_IFA].(*route.Inet4Addr); ok {
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myIP = netaddr.IPv4(addr.IP[0], addr.IP[1], addr.IP[2], addr.IP[3])
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}
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}
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return netaddr.IPv4(gw.IP[0], gw.IP[1], gw.IP[2], gw.IP[3]), myIP, true
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}
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return ret, myIP, false
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}
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var v4default = [4]byte{0, 0, 0, 0}
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var v6default = [16]byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
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func isDefaultGateway(rm *route.RouteMessage) bool {
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if rm.Flags&unix.RTF_GATEWAY == 0 {
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return false
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}
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// Defined locally because FreeBSD does not have unix.RTF_IFSCOPE.
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const RTF_IFSCOPE = 0x1000000
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if rm.Flags&RTF_IFSCOPE != 0 {
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return false
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}
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// Addrs is [RTAX_DST, RTAX_GATEWAY, RTAX_NETMASK, ...]
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if len(rm.Addrs) <= unix.RTAX_NETMASK {
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return false
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}
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dst := rm.Addrs[unix.RTAX_DST]
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netmask := rm.Addrs[unix.RTAX_NETMASK]
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if dst == nil || netmask == nil {
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return false
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}
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if dst.Family() == syscall.AF_INET && netmask.Family() == syscall.AF_INET {
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dstAddr, dstOk := dst.(*route.Inet4Addr)
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nmAddr, nmOk := netmask.(*route.Inet4Addr)
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if dstOk && nmOk && dstAddr.IP == v4default && nmAddr.IP == v4default {
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return true
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}
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}
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if dst.Family() == syscall.AF_INET6 && netmask.Family() == syscall.AF_INET6 {
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dstAddr, dstOk := dst.(*route.Inet6Addr)
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nmAddr, nmOk := netmask.(*route.Inet6Addr)
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if dstOk && nmOk && dstAddr.IP == v6default && nmAddr.IP == v6default {
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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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