From 3f3f8921f6b7695292592e346bbea24f73a6c941 Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Tue, 16 Sep 2003 20:13:43 +0000
Subject: [PATCH] Make sequential ACI selection logic handle HIGHER/LOWER

svn:r466
---
 src/or/circuit.c | 18 ++++++++++++------
 src/or/or.h      |  3 ++-
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/src/or/circuit.c b/src/or/circuit.c
index ceafed6caf..dbaf7c59c4 100644
--- a/src/or/circuit.c
+++ b/src/or/circuit.c
@@ -123,17 +123,23 @@ static aci_t get_unique_aci_by_addr_port(uint32_t addr, uint16_t port, int aci_t
   connection_t *conn;
 
 #ifdef SEQUENTIAL_ACI
-  /* Right now, this is the only used aci_type.  XXX The others should
-     be removed. */
-  assert(aci_type == ACI_TYPE_BOTH); 
+  uint16_t high_bit;
+  high_bit = (aci_type == ACI_TYPE_HIGHER) ? 1<<15 : 0;
   conn = connection_exact_get_by_addr_port(addr,port);
   if (!conn)
     return 1; /* No connection exists; conflict is impossible. */
+
   do {
-    test_aci = conn->next_aci++; /* This can wrap around to 0; that's okay. */
-    if (test_aci == 0)
-      continue;
+    /* Sequentially iterate over test_aci=1...1<<15-1 until we find an
+     * aci such that (high_bit|test_aci) is not already used. */
+    test_aci = conn->next_aci++;
+    if (test_aci == 0 || test_aci >= 1<<15) {
+      test_aci = 1;
+      conn->next_aci = 2;
+    }
+    test_aci |= high_bit;
   } while(circuit_get_by_aci_conn(test_aci, conn));
+  return test_aci;
 #else
 try_again:
   log_fn(LOG_DEBUG,"trying to get a unique aci");
diff --git a/src/or/or.h b/src/or/or.h
index d9f7cbc089..2bea073025 100644
--- a/src/or/or.h
+++ b/src/or/or.h
@@ -330,7 +330,8 @@ struct connection_t {
   char nonce[8];
 #endif
 #ifdef SEQUENTIAL_ACI
-  uint16_t next_aci; /* Which ACI do we try to use next on this connection? */
+  uint16_t next_aci; /* Which ACI do we try to use next on this connection? 
+                      * This is always in the range 0..1<<15-1.*/
 #endif
 
 /* Used only by edge connections: */