Tcp buffer bug fix (#79)

* start working on tracking down tcp buffer bug

* mtu refactor

* modularize test

* more precise testing

* tests fail, but is it the failure we are looking for?

* fix typo in espradio link (#76)

* implement a new backoff abstraction (#75)

* rewrite backoff api

* rewrite tcp.Conn.Write

* keep fixing small things

* much better Conn.Read implementation

* fix critical overflow bug in internal.ConnRWBackoff

---------

Co-authored-by: Joel Wetzell <jwetzell@yahoo.com>

internal/backoff.go

@@ -1,17 +1,21 @@
 package internal
 
-import "time"
+import (
+	"time"
+)
 
 // ConnRWBackoff implements exponential backoff suitable for TCP connection
 // read/write polling. It starts at 1us and caps at 5ms, doubling on each consecutive backoff.
 func ConnRWBackoff(consecutiveBackoffs int) {
 	const (
-		minWait = time.Microsecond >> 1
-		maxWait = 5 * time.Millisecond
+		minWait        = uint32(time.Microsecond) >> 1
+		maxWait        = 5 * uint32(time.Millisecond)
+		maxShift       = 23
+		_overflowCheck = minWait << maxShift
 	)
-	wait := minWait << consecutiveBackoffs
+	wait := minWait << min(consecutiveBackoffs, maxShift)
 	if wait > maxWait {
 		wait = maxWait
 	}
-	time.Sleep(wait)
+	time.Sleep(time.Duration(wait))
 }