Eliminate MaxOnionsPending; replace it with MaxOnionQueueDelay

The right way to set "MaxOnionsPending" was to adjust it until the
processing delay was appropriate.  So instead, let's measure how long
it takes to process onionskins (sampling them once we have a big
number), and then limit the queue based on its expected time to
finish.

This change is extra-necessary for ntor, since there is no longer a
reasonable way to set MaxOnionsPending without knowing what mix of
onionskins you'll get.

This patch also reserves 1/3 of the onionskin spots for ntor
handshakes, on the theory that TAP handshakes shouldn't be allowed to
starve their speedier cousins.  We can change this later if need be.

Resolves 7291.

1 files changed, 2 insertions, 3 deletions

diff --git a/src/or/or.h b/src/or/or.h
index 7b8ff705a4..7db5a52f34 100644
--- a/src/or/or.h
+++ b/src/or/or.h
@@ -2579,6 +2579,7 @@ struct ntor_handshake_state_t;
 #define ONION_HANDSHAKE_TYPE_TAP 0x0000
 #define ONION_HANDSHAKE_TYPE_FAST 0x0001
 #define ONION_HANDSHAKE_TYPE_NTOR 0x0002
+#define MAX_ONION_HANDSHAKE_TYPE 0x0002
 typedef struct {
   uint16_t tag;
   union {
@@ -3483,9 +3484,7 @@ typedef struct {
                              * and try a new circuit if the stream has been
                              * waiting for this many seconds. If zero, use
                              * our default internal timeout schedule. */
-  int MaxOnionsPending; /**< How many circuit CREATE requests do we allow
-                         * to wait simultaneously before we start dropping
-                         * them? */
+  int MaxOnionQueueDelay; /**<DOCDOC*/
   int NewCircuitPeriod; /**< How long do we use a circuit before building
                          * a new one? */
   int MaxCircuitDirtiness; /**< Never use circs that were first used more than