Refactor intro machines, stage 2/2: Move histogram code.

The client side had garbage histograms and deadcode here, too. That code has
been removed.

The tests have also been updated to properly test the intro circ by sending
padding from the relay side to the client, and verifying that both shut down
when padding was up. (The tests previously erroneously tested only the client
side of intro circs, which actually were supposed to be doing nothing).

1 files changed, 47 insertions, 49 deletions

diff --git a/src/core/or/circuitpadding_machines.c b/src/core/or/circuitpadding_machines.c
index 4256a7be4a..be02a597dc 100644
--- a/src/core/or/circuitpadding_machines.c
+++ b/src/core/or/circuitpadding_machines.c
@@ -57,48 +57,6 @@
 #include "core/or/circuitpadding_machines.h"
 #include "core/or/circuitpadding.h"
 
-/* Setup the OBFUSCATE_CIRC_SETUP state of the machine that hides client-side
- * intro circuits. */
-static void
-setup_obf_state_for_hiding_intro_circuits(circpad_state_t *obf_state,
-                                            bool is_client)
-{
-  /* Token removal strategy for OBFUSCATE_CIRC_SETUP state. We pick the
-   * simplest one since we rely on the state length sampling and not the
-   * tokens. */
-  obf_state->token_removal = CIRCPAD_TOKEN_REMOVAL_NONE;
-
-  /* Figure out the length of the OBFUSCATE_CIRC_SETUP state so that it's
-   * randomized. We will set the histogram such that we don't send any padding
-   * from the origin-side, so just tune these parameteres for the
-   * relay-side. */
-  obf_state->length_dist.type = CIRCPAD_DIST_UNIFORM;
-  obf_state->length_dist.param1 = INTRO_MACHINE_MINIMUM_PADDING;
-  obf_state->length_dist.param2 = INTRO_MACHINE_MAXIMUM_PADDING;
-
-  /* Configure histogram */
-  obf_state->histogram_len = 2;
-  if (is_client) {
-    /* For the origin-side machine we don't want to send any padding, so setup
-     * infinite delays. */
-    obf_state->histogram_edges[0] = CIRCPAD_DELAY_INFINITE-1;
-    obf_state->histogram_edges[1] = CIRCPAD_DELAY_INFINITE;
-    /* zero tokens */
-    obf_state->histogram[0] = 0;
-  } else {
-    /* For the relay-side machine we want to batch padding instantly to pretend
-     * its an incoming directory download. So set the histogram edges tight:
-     * (1, 10ms, infinity). */
-    obf_state->histogram_edges[0] = 1000;
-    obf_state->histogram_edges[1] = 10000;
-    /* padding is controlled by state length, so this is just a high value */
-    obf_state->histogram[0] = 1000;
-  }
-
-  /* just one bin, so setup the total tokens */
-  obf_state->histogram_total_tokens = obf_state->histogram[0];
-}
-
 /** Create a client-side padding machine that aims to hide IP circuits. In
  *  particular, it keeps intro circuits alive until a bunch of fake traffic has
  *  been pushed through.
@@ -170,11 +128,11 @@ circpad_machine_client_hide_intro_circuits(smartlist_t *machines_sl)
     CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP;
 
   /* origin-side machine has no event reactions while in
-   * CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP, so no more state transitions here). */
+   * CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP, so no more state transitions here. */
 
-  setup_obf_state_for_hiding_intro_circuits(
-                   &client_machine->states[CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP],
-                   true);
+  /* The client side should never send padding, so it does not need
+   * to specify token removal, or a histogram definition or state lengths.
+   * That is all controlled by the middle node. */
 
   /* Register the machine */
   client_machine->machine_num = smartlist_len(machines_sl);
@@ -242,9 +200,49 @@ circpad_machine_relay_hide_intro_circuits(smartlist_t *machines_sl)
     next_state[CIRCPAD_EVENT_NONPADDING_SENT] =
     CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP;
 
-  setup_obf_state_for_hiding_intro_circuits(
-                 &relay_machine->states[CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP],
-                 false);
+  /* Token removal strategy for OBFUSCATE_CIRC_SETUP state: Don't
+   * remove any tokens.
+   *
+   * We rely on the state length sampling and not token removal, to avoid
+   * the mallocs required to copy the histograms for token removal,
+   * and to avoid monotime calls needed to determine histogram
+   * bins for token removal. */
+  relay_machine->states[CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP].
+    token_removal = CIRCPAD_TOKEN_REMOVAL_NONE;
+
+  /* Figure out the length of the OBFUSCATE_CIRC_SETUP state so that it's
+   * randomized. The relay side will send between INTRO_MACHINE_MINIMUM_PADDING
+   * and INTRO_MACHINE_MAXIMUM_PADDING padding cells towards the client. */
+  relay_machine->states[CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP].
+    length_dist.type = CIRCPAD_DIST_UNIFORM;
+  relay_machine->states[CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP].
+    length_dist.param1 = INTRO_MACHINE_MINIMUM_PADDING;
+  relay_machine->states[CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP].
+    length_dist.param2 = INTRO_MACHINE_MAXIMUM_PADDING;
+
+  /* Configure histogram */
+  relay_machine->states[CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP].
+     histogram_len = 2;
+
+  /* For the relay-side machine we want to batch padding instantly to pretend
+   * its an incoming directory download. So set the histogram edges tight:
+   * (1, 10ms, infinity). */
+  relay_machine->states[CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP].
+    histogram_edges[0] = 1000;
+  relay_machine->states[CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP].
+    histogram_edges[1] = 10000;
+
+  /* We put all our tokens in bin 0, which means we want 100% probability
+   * for choosing a inter-packet delay of between 1000 and 10000 microseconds
+   * (1 to 10ms). Since we only have 1 bin, it doesn't matter how many tokens
+   * there are, 1000 out of 1000 is 100% */
+  relay_machine->states[CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP].
+    histogram[0] = 1000;
+
+  /* just one bin, so setup the total tokens */
+  relay_machine->states[CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP].
+    histogram_total_tokens =
+      relay_machine->states[CIRCPAD_STATE_OBFUSCATE_CIRC_SETUP].histogram[0];
 
   /* Register the machine */
   relay_machine->machine_num = smartlist_len(machines_sl);