[or-cvs] make sure there"s no conflict when generating stream_ids

[Roger Dingledine]

Update of /home/or/cvsroot/src/or
In directory moria.mit.edu:/home2/arma/work/onion/cvs/src/or

Modified Files:
	connection_edge.c or.h 
Log Message:
make sure there's no conflict when generating stream_ids


Index: connection_edge.c
===================================================================
RCS file: /home/or/cvsroot/src/or/connection_edge.c,v
retrieving revision 1.81
retrieving revision 1.82
diff -u -d -r1.81 -r1.82
--- connection_edge.c	19 Dec 2003 05:09:51 -0000	1.81
+++ connection_edge.c	19 Dec 2003 21:25:43 -0000	1.82
@@ -665,6 +665,29 @@
   return 1;
 }
 
+/* Iterate over the two bytes of stream_id until we get one that is not
+ * already in use. Return 0 if can't get a unique stream_id.
+ */
+static uint16_t get_unique_stream_id_by_circ(circuit_t *circ) {
+  connection_t *tmpconn;
+  uint16_t test_stream_id;
+  uint32_t attempts=0;
+
+again:
+  test_stream_id = circ->next_stream_id++;
+  if(++attempts > 1<<16) {
+    /* Make sure we don't loop forever if all stream_id's are used. */
+    log_fn(LOG_WARN,"No unused stream IDs. Failing.");
+    return 0;
+  }
+  if (test_stream_id == 0)
+    goto again;
+  for(tmpconn = circ->p_streams; tmpconn; tmpconn=tmpconn->next_stream)
+    if(tmpconn->stream_id == test_stream_id)
+      goto again;
+  return test_stream_id;
+}
+
 /* deliver the destaddr:destport in a relay cell */
 static void connection_ap_handshake_send_begin(connection_t *ap_conn, circuit_t *circ)
 {
@@ -677,8 +700,11 @@
   assert(ap_conn->state == AP_CONN_STATE_CIRCUIT_WAIT);
   assert(ap_conn->socks_request);
 
-  crypto_pseudo_rand(sizeof(ap_conn->stream_id), (unsigned char*) &ap_conn->stream_id);
-  /* XXX check for collisions */
+  ap_conn->stream_id = get_unique_stream_id_by_circ(circ);
+  if (ap_conn->stream_id==0) {
+    ap_conn->marked_for_close = 1;
+    return;
+  }
 
   in.s_addr = htonl(client_dns_lookup_entry(ap_conn->socks_request->address));
   string_addr = in.s_addr ? inet_ntoa(in) : NULL;

Index: or.h
===================================================================
RCS file: /home/or/cvsroot/src/or/or.h,v
retrieving revision 1.213
retrieving revision 1.214
diff -u -d -r1.213 -r1.214
--- or.h	19 Dec 2003 19:55:02 -0000	1.213
+++ or.h	19 Dec 2003 21:25:44 -0000	1.214
@@ -445,6 +445,7 @@
   connection_t *n_conn; /* for the OR conn, if there is one */
   connection_t *p_streams;
   connection_t *n_streams;
+  uint16_t next_stream_id;
   int package_window;
   int deliver_window;