@ -7,10 +7,11 @@
package netmon
import (
"encoding/json"
"errors"
"fmt"
"net/netip"
"runtime"
"slices"
"sync"
"time"
@ -45,12 +46,15 @@ type osMon interface {
// until the osMon is closed. After a Close, the returned
// error is ignored.
Receive ( ) ( message , error )
// IsInterestingInterface reports whether the provided interface should
// be considered for network change events.
IsInterestingInterface ( iface string ) bool
}
// IsInterestingInterface is the function used to determine whether
// a given interface name is interesting enough to pay attention to
// for network change monitoring purposes.
//
// If nil, all interfaces are considered interesting.
var IsInterestingInterface func ( Interface , [ ] netip . Prefix ) bool
// Monitor represents a monitoring instance.
type Monitor struct {
logf logger . Logf
@ -62,10 +66,6 @@ type Monitor struct {
stop chan struct { } // closed on Stop
static bool // static Monitor that doesn't actually monitor
// Things that must be set early, before use,
// and not change at runtime.
tsIfName string // tailscale interface name, if known/set ("tailscale0", "utun3", ...)
mu syncs . Mutex // guards all following fields
cbs set . HandleSet [ ChangeFunc ]
ifState * State
@ -77,7 +77,8 @@ type Monitor struct {
goroutines sync . WaitGroup
wallTimer * time . Timer // nil until Started; re-armed AfterFunc per tick
lastWall time . Time
timeJumped bool // whether we need to send a changed=true after a big time jump
timeJumped bool // whether we need to send a changed=true after a big time jump
tsIfName string // tailscale interface name, if known/set ("tailscale0", "utun3", ...)
}
// ChangeFunc is a callback function registered with Monitor that's called when the
@ -85,6 +86,8 @@ type Monitor struct {
type ChangeFunc func ( * ChangeDelta )
// ChangeDelta describes the difference between two network states.
//
// Use NewChangeDelta to construct one and compute the cached fields.
type ChangeDelta struct {
// Old is the old interface state, if known.
// It's nil if the old state is unknown.
@ -96,21 +99,182 @@ type ChangeDelta struct {
// Do not mutate it.
New * State
// Major is our legacy boolean of whether the network changed in some major
// way.
//
// Deprecated: do not remove. As of 2023-08-23 we're in a renewed effort to
// remove it and ask specific qustions of ChangeDelta instead. Look at Old
// and New (or add methods to ChangeDelta) instead of using Major.
Major bool
// TimeJumped is whether there was a big jump in wall time since the last
// time we checked. This is a hint that a mobile sleeping device might have
// time we checked. This is a hint that a sleeping device might have
// come out of sleep.
TimeJumped bool
// TODO(bradfitz): add some lazy cached fields here as needed with methods
// on *ChangeDelta to let callers ask specific questions
// The tailscale interface name, e.g. "tailscale0", "utun3", etc. Not all
// platforms know this or set it. Copied from netmon.Monitor.tsIfName.
TailscaleIfaceName string
// Computed Fields
DefaultInterfaceChanged bool // whether default route interface changed
IsLessExpensive bool // whether new state is less expensive than old
HasPACOrProxyConfigChanged bool // whether PAC/HTTP proxy config changed
InterfaceIPsChanged bool // whether any interface IPs changed in a meaningful way
AvailableProtocolsChanged bool // whether we have seen a change in available IPv4/IPv6
DefaultInterfaceMaybeViable bool // whether the default interface is potentially viable (has usable IPs, is up and is not the tunnel itself)
// RebindLikelyRequired combines the various fields above to report whether this change likely requires us
// to rebind sockets. This is a very conservative estimate and covers a number of
// cases where a rebind is not strictly necessary. Consumers of the ChangeDelta should
// use this as a hint only. If in doubt, rebind.
RebindLikelyRequired bool
}
var skipRebindIfNoDefaultRouteChange = true
// NewChangeDelta builds a ChangeDelta and eagerly computes the cached fields.
func NewChangeDelta ( old , new * State , timeJumped bool , tsIfName string ) ChangeDelta {
cd := ChangeDelta {
Old : old ,
New : new ,
TimeJumped : timeJumped ,
TailscaleIfaceName : tsIfName ,
}
if cd . New == nil {
return cd
} else if cd . Old == nil {
cd . DefaultInterfaceChanged = cd . New . DefaultRouteInterface != ""
cd . IsLessExpensive = false
cd . HasPACOrProxyConfigChanged = true
cd . InterfaceIPsChanged = true
} else {
cd . AvailableProtocolsChanged = cd . Old . HaveV4 != cd . New . HaveV4 || cd . Old . HaveV6 != cd . New . HaveV6
cd . DefaultInterfaceChanged = cd . Old . DefaultRouteInterface != cd . New . DefaultRouteInterface
cd . IsLessExpensive = cd . Old . IsExpensive && ! cd . New . IsExpensive
cd . HasPACOrProxyConfigChanged = cd . Old . PAC != cd . New . PAC || cd . Old . HTTPProxy != cd . New . HTTPProxy
cd . InterfaceIPsChanged = cd . isInterestingIntefaceChange ( )
}
// If the default route interface is populated, but it's not up this event signifies that we're in
// the process of tearing it down. Rebinds are going to fail so it's flappy to try.
defIfName := new . DefaultRouteInterface
defIf := new . Interface [ defIfName ]
cd . DefaultInterfaceMaybeViable = true
// The default interface is not viable if is down or is the Tailscale interface itself.
if ! defIf . IsUp ( ) || defIfName == tsIfName {
cd . DefaultInterfaceMaybeViable = false
}
// Compute rebind requirement. A number of these checks are redundant - HaveSomeAddressChanged
// subsumes InterfaceIPsChanged, IsExpensive likely does not change without a new interface
// appearing, but we'll keep them all for clarity and testability.
cd . RebindLikelyRequired = ( cd . New == nil || // Do we need to rebind if there is no current state?
cd . Old == nil ||
cd . TimeJumped ||
cd . DefaultInterfaceChanged ||
cd . InterfaceIPsChanged ||
cd . IsLessExpensive ||
cd . HasPACOrProxyConfigChanged ||
cd . AvailableProtocolsChanged ) &&
cd . DefaultInterfaceMaybeViable
// (barnstar) TODO: There are likely a number of optimizations we can do here to avoid
// rebinding in cases where it is not necessary but we really need to leave that to the
// upstream component. If it's sockets are happy, then it probably doesn't need to rebind,
// but it may want to if any of these fields are true.
return cd
}
// isInterestingIntefaceChange reports whether any interfaces have changed in a meaninful way.
// This excludes interfaces that are not interesting per IsInterestingInterface and
// filters out changes to interface IPs that that are uninteresting (e.g. link-local addresses).
func ( cd * ChangeDelta ) isInterestingIntefaceChange ( ) bool {
// If either side is nil treat as changed.
if cd . Old == nil || cd . New == nil {
return true
}
// Compare interfaces in both directions. Old to new and new to old.
for iname , oldInterface := range cd . Old . Interface {
if iname == cd . TailscaleIfaceName {
// Ignore changes in the Tailscale interface itself.
continue
}
oldIps := filterRoutableIPs ( cd . Old . InterfaceIPs [ iname ] )
if IsInterestingInterface != nil && ! IsInterestingInterface ( oldInterface , oldIps ) {
continue
}
// Old interfaces with no routable addresses are not interesting
if len ( oldIps ) == 0 {
continue
}
// The old interface doesn't exist in the new interface set and it has
// an a global unicast IP. That's considered a change from the perspective
// of anything that may have been bound to it. If it didn't have a global
// unicast IP, it's not interesting.
newInterface , ok := cd . New . Interface [ iname ]
if ! ok {
return true
}
newIps , ok := cd . New . InterfaceIPs [ iname ]
if ! ok {
return true
}
newIps = filterRoutableIPs ( newIps )
if ! oldInterface . Equal ( newInterface ) || ! prefixesEqual ( oldIps , newIps ) {
return true
}
}
for iname , newInterface := range cd . New . Interface {
if iname == cd . TailscaleIfaceName {
continue
}
newIps := filterRoutableIPs ( cd . New . InterfaceIPs [ iname ] )
if IsInterestingInterface != nil && ! IsInterestingInterface ( newInterface , newIps ) {
continue
}
// New interfaces with no routable addresses are not interesting
if len ( newIps ) == 0 {
continue
}
oldInterface , ok := cd . Old . Interface [ iname ]
if ! ok {
return true
}
oldIps , ok := cd . Old . InterfaceIPs [ iname ]
if ! ok {
// Redundant but we can't dig up the "old" IPs for this interface.
return true
}
oldIps = filterRoutableIPs ( oldIps )
// The interface's IPs, Name, MTU, etc have changed. This is definitely interesting.
if ! newInterface . Equal ( oldInterface ) || ! prefixesEqual ( oldIps , newIps ) {
return true
}
}
return false
}
func filterRoutableIPs ( addrs [ ] netip . Prefix ) [ ] netip . Prefix {
var filtered [ ] netip . Prefix
for _ , pfx := range addrs {
a := pfx . Addr ( )
// Skip link-local multicast addresses.
if a . IsLinkLocalMulticast ( ) {
continue
}
if isUsableV4 ( a ) || isUsableV6 ( a ) {
filtered = append ( filtered , pfx )
}
}
fmt . Printf ( "Filtered: %v\n" , filtered )
return filtered
}
// New instantiates and starts a monitoring instance.
@ -174,9 +338,17 @@ func (m *Monitor) interfaceStateUncached() (*State, error) {
// This must be called only early in tailscaled startup before the monitor is
// used.
func ( m * Monitor ) SetTailscaleInterfaceName ( ifName string ) {
m . mu . Lock ( )
defer m . mu . Unlock ( )
m . tsIfName = ifName
}
func ( m * Monitor ) TailscaleInterfaceName ( ) string {
m . mu . Lock ( )
defer m . mu . Unlock ( )
return m . tsIfName
}
// GatewayAndSelfIP returns the current network's default gateway, and
// the machine's default IP for that gateway.
//
@ -344,18 +516,7 @@ func (m *Monitor) pump() {
}
}
// isInterestingInterface reports whether the provided interface should be
// considered when checking for network state changes.
// The ips parameter should be the IPs of the provided interface.
func ( m * Monitor ) isInterestingInterface ( i Interface , ips [ ] netip . Prefix ) bool {
if ! m . om . IsInterestingInterface ( i . Name ) {
return false
}
return true
}
// debounce calls the callback function with a delay between events
// / debounce calls the callback function with a delay between events
// and exits when a stop is issued.
func ( m * Monitor ) debounce ( ) {
defer m . goroutines . Done ( )
@ -376,7 +537,10 @@ func (m *Monitor) debounce() {
select {
case <- m . stop :
return
case <- time . After ( 250 * time . Millisecond ) :
// 1s is reasonable debounce time for network changes. Events such as undocking a laptop
// or roaming onto wifi will often generate multiple events in quick succession as interfaces
// flap. We want to avoid spamming consumers of these events.
case <- time . After ( 1000 * time . Millisecond ) :
}
}
}
@ -403,34 +567,18 @@ func (m *Monitor) handlePotentialChange(newState *State, forceCallbacks bool) {
return
}
delta := ChangeDelta {
Old : oldState ,
New : newState ,
TimeJumped : timeJumped ,
}
delta := NewChangeDelta ( oldState , newState , timeJumped , m . tsIfName )
delta . Major = m . IsMajorChangeFrom ( oldState , newState )
if delta . Major {
if delta . RebindLikelyRequired {
m . gwValid = false
if s1 , s2 := oldState . String ( ) , delta . New . String ( ) ; s1 == s2 {
m . logf ( "[unexpected] network state changed, but stringification didn't: %v" , s1 )
m . logf ( "[unexpected] old: %s" , jsonSummary ( oldState ) )
m . logf ( "[unexpected] new: %s" , jsonSummary ( newState ) )
}
}
m . ifState = newState
// See if we have a queued or new time jump signal.
if timeJumped {
m . resetTimeJumpedLocked ( )
if ! delta . Major {
// Only log if it wasn't an interesting change.
m . logf ( "time jumped (probably wake from sleep); synthesizing major change event" )
delta . Major = true
}
}
metricChange . Add ( 1 )
if delta . Major {
if delta . RebindLikelyRequired {
metricChangeMajor . Add ( 1 )
}
if delta . TimeJumped {
@ -442,107 +590,24 @@ func (m *Monitor) handlePotentialChange(newState *State, forceCallbacks bool) {
}
}
// IsMajorChangeFrom reports whether the transition from s1 to s2 is
// a "major" change, where major roughly means it's worth tearing down
// a bunch of connections and rebinding.
//
// TODO(bradiftz): tigten this definition.
func ( m * Monitor ) IsMajorChangeFrom ( s1 , s2 * State ) bool {
if s1 == nil && s2 == nil {
// reports whether a and b contain the same set of prefixes regardless of order.
func prefixesEqual ( a , b [ ] netip . Prefix ) bool {
if len ( a ) != len ( b ) {
return false
}
if s1 == nil || s2 == nil {
return true
}
if s1 . HaveV6 != s2 . HaveV6 ||
s1 . HaveV4 != s2 . HaveV4 ||
s1 . IsExpensive != s2 . IsExpensive ||
s1 . DefaultRouteInterface != s2 . DefaultRouteInterface ||
s1 . HTTPProxy != s2 . HTTPProxy ||
s1 . PAC != s2 . PAC {
return true
}
for iname , i := range s1 . Interface {
if iname == m . tsIfName {
// Ignore changes in the Tailscale interface itself.
continue
}
ips := s1 . InterfaceIPs [ iname ]
if ! m . isInterestingInterface ( i , ips ) {
continue
}
i2 , ok := s2 . Interface [ iname ]
if ! ok {
return true
}
ips2 , ok := s2 . InterfaceIPs [ iname ]
if ! ok {
return true
}
if ! i . Equal ( i2 ) || ! prefixesMajorEqual ( ips , ips2 ) {
return true
}
}
// Iterate over s2 in case there is a field in s2 that doesn't exist in s1
for iname , i := range s2 . Interface {
if iname == m . tsIfName {
// Ignore changes in the Tailscale interface itself.
continue
}
ips := s2 . InterfaceIPs [ iname ]
if ! m . isInterestingInterface ( i , ips ) {
continue
}
i1 , ok := s1 . Interface [ iname ]
if ! ok {
return true
}
ips1 , ok := s1 . InterfaceIPs [ iname ]
if ! ok {
return true
}
if ! i . Equal ( i1 ) || ! prefixesMajorEqual ( ips , ips1 ) {
return true
}
}
return false
}
// prefixesMajorEqual reports whether a and b are equal after ignoring
// boring things like link-local, loopback, and multicast addresses.
func prefixesMajorEqual ( a , b [ ] netip . Prefix ) bool {
// trim returns a subslice of p with link local unicast,
// loopback, and multicast prefixes removed from the front.
trim := func ( p [ ] netip . Prefix ) [ ] netip . Prefix {
for len ( p ) > 0 {
a := p [ 0 ] . Addr ( )
if a . IsLinkLocalUnicast ( ) || a . IsLoopback ( ) || a . IsMulticast ( ) {
p = p [ 1 : ]
continue
}
break
}
return p
}
for {
a = trim ( a )
b = trim ( b )
if len ( a ) == 0 || len ( b ) == 0 {
return len ( a ) == 0 && len ( b ) == 0
}
if a [ 0 ] != b [ 0 ] {
return false
}
a , b = a [ 1 : ] , b [ 1 : ]
}
}
aa := make ( [ ] netip . Prefix , len ( a ) )
bb := make ( [ ] netip . Prefix , len ( b ) )
copy ( aa , a )
copy ( bb , b )
func jsonSummary ( x any ) any {
j , err := json . Marshal ( x )
if err != nil {
return err
less := func ( x , y netip . Prefix ) int {
return x . Addr ( ) . Compare ( y . Addr ( ) )
}
return j
slices . SortFunc ( aa , less )
slices . SortFunc ( bb , less )
return slices . Equal ( aa , bb )
}
func wallTime ( ) time . Time {
Jonathan Nobels
1 month ago