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MTR enables concurrent detection; PTR_LOOKUP is True does not affect … #4

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95 changes: 56 additions & 39 deletions pkg/mtr/mtr.go
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Original file line number Diff line number Diff line change
Expand Up @@ -87,8 +87,10 @@ func (m *MTR) registerStatistic(ttl int, r icmp.ICMPReturn) *hop.HopStatistic {

s.Targets = addTarget(s.Targets, r.Addr)

s.Packets = s.Packets.Prev()
s.Packets.Value = r
if m.ringBufferSize > 0 {
s.Packets = s.Packets.Prev()
s.Packets.Value = r
}

if !r.Success {
s.Lost++
Expand Down Expand Up @@ -150,7 +152,7 @@ func (m *MTR) Render(offset int) {
}

func (m *MTR) RunWithContext(ctx context.Context, count int) error {
err := m.discover(ctx, count)
err := m.loopDiscover(ctx, count)
close(m.channel)
return err
}
Expand All @@ -161,57 +163,72 @@ func (m *MTR) Run(count int) error {
return err
}

// discover discovers all hops on the route
func (m *MTR) discover(ctx context.Context, count int) error {
// loopDiscover: discovers all hops on the route
func (m *MTR) loopDiscover(ctx context.Context, count int) error {
// Sequences are incrementing as we don't won't to get old replys which might be from a previous run (where we timed out and continued).
// We can't use the process id as unique identifier as there might be multiple runs within a single binary, thus we use a fixed pseudo random number.
rand.Seed(time.Now().UnixNano())
seq := rand.Intn(math.MaxUint16)
id := rand.Intn(math.MaxUint16) & 0xffff

ipAddr := net.IPAddr{IP: net.ParseIP(m.Address)}
wg := new(sync.WaitGroup)

for i := 1; i <= count; i++ {
select {
case <-ctx.Done():
return ErrTimeout
case <-time.After(m.interval):
unknownHopsCount := 0

ttlLoop:
for ttl := 1; ttl < m.maxHops; ttl++ {
seq++
select {
case <-ctx.Done():
return ErrTimeout
case <-time.After(m.hopsleep):
var hopReturn icmp.ICMPReturn
var err error
if ipAddr.IP.To4() != nil {
hopReturn, err = icmp.SendDiscoverICMP(m.SrcAddress, &ipAddr, ttl, id, m.timeout, seq)
} else {
hopReturn, err = icmp.SendDiscoverICMPv6(m.SrcAddress, &ipAddr, ttl, id, m.timeout, seq)
}

m.mutex.Lock()
s := m.registerStatistic(ttl, hopReturn)
s.Dest = &ipAddr
s.PID = id
m.mutex.Unlock()
m.channel <- struct{}{}
if hopReturn.Addr == m.Address {
break ttlLoop
}
if err != nil || !hopReturn.Success {
unknownHopsCount++
if unknownHopsCount >= m.maxUnknownHops {
return ErrMaxUnknownHops
}
continue ttlLoop
}
unknownHopsCount = 0
wg.Add(1)
go func() {
defer wg.Done()

_ = m.discover(seq, id, ipAddr, ctx)
}()
}
}
wg.Wait()
return nil
}

func (m *MTR) discover(seq, id int, ipAddr net.IPAddr, ctx context.Context) error {
unknownHopsCount := 0
ttlLoop:
for ttl := 1; ttl < m.maxHops; ttl++ {
seq++
select {
case <-ctx.Done():
return ErrTimeout
case <-time.After(m.hopsleep):
var hopReturn icmp.ICMPReturn
var err error
if ipAddr.IP.To4() != nil {
hopReturn, err = icmp.SendDiscoverICMP(m.SrcAddress, &ipAddr, ttl, id, m.timeout, seq)
} else {
hopReturn, err = icmp.SendDiscoverICMPv6(m.SrcAddress, &ipAddr, ttl, id, m.timeout, seq)
}

go func(ttl int, hopReturn icmp.ICMPReturn) {
m.mutex.Lock()
defer m.mutex.Unlock()

s := m.registerStatistic(ttl, hopReturn)
s.Dest = &ipAddr
s.PID = id
}(ttl, hopReturn)

m.channel <- struct{}{}
if hopReturn.Addr == m.Address {
break ttlLoop
}
if err != nil || !hopReturn.Success {
unknownHopsCount++
if unknownHopsCount >= m.maxUnknownHops {
return ErrMaxUnknownHops
}
continue ttlLoop
}
unknownHopsCount = 0
}
}
return nil
Expand Down