fshttp: Obey bwlimit in http Transport - fixes #4395

This change uses the bwlimit code to apply limits to the receive and
transmit data functions in the HTTP Transport.

This means that all HTTP transactions will have limiting applied -
this includes listings for example.

For HTTP based transorts this makes the limiting in Accounting
redundant and possibly counter productive

fs/accounting/token_bucket.go

@@ -20,6 +20,8 @@ type TokenBucketSlot int
 // Slots for the token bucket
 const (
 	TokenBucketSlotAccounting TokenBucketSlot = iota
+	TokenBucketSlotTransportRx
+	TokenBucketSlotTransportTx
 	TokenBucketSlots
 )
 

fs/fshttp/http.go

@@ -58,26 +58,31 @@ func (c *timeoutConn) nudgeDeadline() (err error) {
 	return c.Conn.SetDeadline(when)
 }
 
-// readOrWrite bytes doing idle timeouts
-func (c *timeoutConn) readOrWrite(f func([]byte) (int, error), b []byte) (n int, err error) {
-	n, err = f(b)
+// Read bytes doing idle timeouts
+func (c *timeoutConn) Read(b []byte) (n int, err error) {
+	// Ideally we would LimitBandwidth(len(b)) here and replace tokens we didn't use
+	n, err = c.Conn.Read(b)
+	accounting.TokenBucket.LimitBandwidth(accounting.TokenBucketSlotTransportRx, n)
 	// Don't nudge if no bytes or an error
 	if n == 0 || err != nil {
 		return
 	}
 	// Nudge the deadline on successful Read or Write
 	err = c.nudgeDeadline()
-	return
-}
-
-// Read bytes doing idle timeouts
-func (c *timeoutConn) Read(b []byte) (n int, err error) {
-	return c.readOrWrite(c.Conn.Read, b)
+	return n, err
 }
 
 // Write bytes doing idle timeouts
 func (c *timeoutConn) Write(b []byte) (n int, err error) {
-	return c.readOrWrite(c.Conn.Write, b)
+	accounting.TokenBucket.LimitBandwidth(accounting.TokenBucketSlotTransportTx, len(b))
+	n, err = c.Conn.Write(b)
+	// Don't nudge if no bytes or an error
+	if n == 0 || err != nil {
+		return
+	}
+	// Nudge the deadline on successful Read or Write
+	err = c.nudgeDeadline()
+	return n, err
 }
 
 // dial with context and timeouts