vendor: only vendor on emitted binaries

Moves the vendor/ directory to cmd/vendor. Vendored binaries are built
from cmd/, which is backed by symlinks pointing back to repo root.

cmd/vendor/github.com/xiang90/probing/status.go

@@ -0,0 +1,96 @@
+package probing
+
+import (
+	"sync"
+	"time"
+)
+
+var (
+	// weight factor
+	α = 0.125
+)
+
+type Status interface {
+	Total() int64
+	Loss() int64
+	Health() bool
+	// Estimated smoothed round trip time
+	SRTT() time.Duration
+	// Estimated clock difference
+	ClockDiff() time.Duration
+	StopNotify() <-chan struct{}
+}
+
+type status struct {
+	mu        sync.Mutex
+	srtt      time.Duration
+	total     int64
+	loss      int64
+	health    bool
+	clockdiff time.Duration
+	stopC     chan struct{}
+}
+
+// SRTT = (1-α) * SRTT + α * RTT
+func (s *status) SRTT() time.Duration {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.srtt
+}
+
+func (s *status) Total() int64 {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.total
+}
+
+func (s *status) Loss() int64 {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.loss
+}
+
+func (s *status) Health() bool {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.health
+}
+
+func (s *status) ClockDiff() time.Duration {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.clockdiff
+}
+
+func (s *status) StopNotify() <-chan struct{} {
+	return s.stopC
+}
+
+func (s *status) record(rtt time.Duration, when time.Time) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.total += 1
+	s.health = true
+	s.srtt = time.Duration((1-α)*float64(s.srtt) + α*float64(rtt))
+	s.clockdiff = time.Now().Sub(when) - s.srtt/2
+}
+
+func (s *status) recordFailure() {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.total++
+	s.health = false
+	s.loss += 1
+}
+
+func (s *status) reset() {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.srtt = 0
+	s.total = 0
+	s.health = false
+	s.clockdiff = 0
+}