add TCPConn Read+Write and ancilliary methods; looks like IP mux is broken

internal/backoff.go

@@ -0,0 +1,59 @@
+package internal
+
+import "time"
+
+type BackoffFlags uint8
+
+const (
+	BackoffHasPriority BackoffFlags = 1 << iota
+	BackoffCriticalPath
+)
+
+func NewBackoff(priority BackoffFlags) Backoff {
+	if priority&BackoffCriticalPath != 0 {
+		return Backoff{
+			maxWait: uint32(1 * time.Millisecond),
+		}
+	}
+	return Backoff{
+		maxWait: uint32(time.Second) >> (priority & BackoffHasPriority),
+	}
+}
+
+// A Backoff with a non-zero MaxWait is ready for use.
+type Backoff struct {
+	// wait defines the amount of time that Miss will wait on next call.
+	wait uint32
+	// Maximum allowable value for Wait.
+	maxWait uint32
+	// startWait is the value that Wait takes after a call to Hit.
+	startWait uint32
+	// expMinusOne is the shift performed on Wait minus one, so the zero value performs a shift of 1.
+	expMinusOne uint32
+}
+
+// Hit sets eb.Wait to the StartWait value.
+func (eb *Backoff) Hit() {
+	if eb.maxWait == 0 {
+		panic("MaxWait cannot be zero")
+	}
+	eb.wait = eb.startWait
+}
+
+// Miss sleeps for eb.Wait and increases eb.Wait exponentially.
+func (eb *Backoff) Miss() {
+	const k = 1
+	wait := eb.wait
+	maxWait := eb.maxWait
+	exp := eb.expMinusOne + 1
+	if maxWait == 0 {
+		panic("MaxWait cannot be zero")
+	}
+	time.Sleep(time.Duration(wait))
+	wait |= k
+	wait <<= exp
+	if wait > maxWait {
+		wait = maxWait
+	}
+	eb.wait = wait
+}