From 509b52eb1f41a8bfb2bfda1509a2c3b47e3c6bdd Mon Sep 17 00:00:00 2001
From: Christopher Baines <cb15g11@soton.ac.uk>
Date: Wed, 19 Mar 2014 14:28:50 +0000
Subject: Round robin stuff

---
 src/or/config.c  |  1 +
 src/or/or.h      |  5 +++++
 src/or/rendmid.c | 39 +++++++++++++++++++++++++++++++++++----
 3 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/src/or/config.c b/src/or/config.c
index 443ebcac8..b4b9ee9de 100644
--- a/src/or/config.c
+++ b/src/or/config.c
@@ -349,6 +349,7 @@ static config_var_t option_vars_[] = {
   V(PerConnBWRate,               MEMUNIT,  "0"),
   V(PidFile,                     STRING,   NULL),
   V(IntroPointAcceptMutipleConnections, BOOL, "0"),
+  V(IntroPointLoadBalancingAlgorithm, STRING, "random"),
   V(TestingTorNetwork,           BOOL,     "0"),
   V(TestingMinExitFlagThreshold, MEMUNIT,  "0"),
   V(TestingMinFastFlagThreshold, MEMUNIT,  "0"),
diff --git a/src/or/or.h b/src/or/or.h
index 14097da6e..cfbaba469 100644
--- a/src/or/or.h
+++ b/src/or/or.h
@@ -3206,6 +3206,9 @@ typedef struct or_circuit_t {
    * to zero, it is initialized to the default value.
    */
   uint32_t max_middle_cells;
+
+  /** True iff this circuit was the last one used for an introduction. */
+  unsigned int intro_last_used : 1;
 } or_circuit_t;
 
 /** Convert a circuit subtype to a circuit_t. */
@@ -4022,6 +4025,8 @@ typedef struct {
 
   int IntroPointAcceptMutipleConnections;
 
+  char* IntroPointLoadBalancingAlgorithm;
+
   /** Minimum value for the Exit flag threshold on testing networks. */
   uint64_t TestingMinExitFlagThreshold;
 
diff --git a/src/or/rendmid.c b/src/or/rendmid.c
index e7a7849db..81a2f16ec 100644
--- a/src/or/rendmid.c
+++ b/src/or/rendmid.c
@@ -174,6 +174,7 @@ rend_mid_introduce(or_circuit_t *circ, const uint8_t *request,
                 (char*)request, REND_SERVICE_ID_LEN);
 
   /* The first 20 bytes are all we look at: they have a hash of Bob's PK. */
+
   smartlist_t *intro_circuits = circuits_get_intro_point((char*)request);
 
   log_info(LD_REND,
@@ -189,14 +190,44 @@ rend_mid_introduce(or_circuit_t *circ, const uint8_t *request,
   }
 
   // Need to select which circuit to use
-  int circ_selection = crypto_rand_int(smartlist_len(intro_circuits));
+  int circ_selection = -1;
 
-  log_info(LD_REND,
-           "selected circuit %i for service %s",
-           circ_selection, safe_str(serviceid));
+  if (strcasecmp(get_options()->IntroPointLoadBalancingAlgorithm, "random")) {
+    circ_selection = crypto_rand_int(smartlist_len(intro_circuits));
+
+    log_info(LD_REND,
+             "selected circuit %i randomly for service %s",
+             circ_selection, safe_str(serviceid));
+  } else if (strcasecmp(get_options()->IntroPointLoadBalancingAlgorithm,
+                        "roundrobin")) {
+
+    SMARTLIST_FOREACH_BEGIN(intro_circuits, or_circuit_t *, circuit)
+    {
+      circ_selection++;
+      if (circuit->intro_last_used) {
+        circuit->intro_last_used = 0;
+        break;
+      }
+    }
+    SMARTLIST_FOREACH_END(circuit);
+
+    circ_selection++;
+
+    if (circ_selection == smartlist_len(intro_circuits))
+      circ_selection = 0;
+
+    log_info(LD_REND,
+             "selected circuit %i using round robin for service %s",
+             circ_selection, safe_str(serviceid));
+  } else if (strcasecmp(get_options()->IntroPointLoadBalancingAlgorithm,
+                        "weightedroundrobin")) {
+
+  }
 
   intro_circ = smartlist_get(intro_circuits, circ_selection);
 
+  intro_circ->intro_last_used = 1;
+
   log_info(LD_REND,
            "Sending introduction request for service %s "
            "from circ %u to circ %u",
-- 
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