Netflow record collapsing defense.

This defense will cause Cisco, Juniper, Fortinet, and other routers operating
in the default configuration to collapse netflow records that would normally
be split due to the 15 second flow idle timeout.

Collapsing these records should greatly reduce the utility of default netflow
data for correlation attacks, since all client-side records should become 30
minute chunks of total bytes sent/received, rather than creating multiple
separate records for every webpage load/ssh command interaction/XMPP chat/whatever
else happens to be inactive for more than 15 seconds.

The defense adds consensus parameters to govern the range of timeout values
for sending padding packets, as well as for keeping connections open.

The defense only sends padding when connections are otherwise inactive, and it
does not pad connections used solely for directory traffic at all. By default
it also doesn't pad inter-relay connections.

Statistics on the total padding in the last 24 hours are exported to the
extra-info descriptors.

1 files changed, 14 insertions, 2 deletions

diff --git a/src/or/connection_or.c b/src/or/connection_or.c
index cefe42c4db..40c28e60e5 100644
--- a/src/or/connection_or.c
+++ b/src/or/connection_or.c
@@ -55,6 +55,7 @@
 #include "ext_orport.h"
 #include "scheduler.h"
 #include "torcert.h"
+#include "channelpadding.h"
 
 static int connection_tls_finish_handshake(or_connection_t *conn);
 static int connection_or_launch_v3_or_handshake(or_connection_t *conn);
@@ -1983,12 +1984,23 @@ connection_or_write_cell_to_buf(const cell_t *cell, or_connection_t *conn)
 
   cell_pack(&networkcell, cell, conn->wide_circ_ids);
 
+  rep_hist_padding_count_write(PADDING_TYPE_TOTAL);
+  if (cell->command == CELL_PADDING)
+    rep_hist_padding_count_write(PADDING_TYPE_CELL);
+
   connection_write_to_buf(networkcell.body, cell_network_size, TO_CONN(conn));
 
   /* Touch the channel's active timestamp if there is one */
-  if (conn->chan)
+  if (conn->chan) {
     channel_timestamp_active(TLS_CHAN_TO_BASE(conn->chan));
 
+    if (conn->chan->base_.currently_padding) {
+      rep_hist_padding_count_write(PADDING_TYPE_ENABLED_TOTAL);
+      if (cell->command == CELL_PADDING)
+        rep_hist_padding_count_write(PADDING_TYPE_ENABLED_CELL);
+    }
+  }
+
   if (conn->base_.state == OR_CONN_STATE_OR_HANDSHAKING_V3)
     or_handshake_state_record_cell(conn, conn->handshake_state, cell, 0);
 }
@@ -2094,7 +2106,7 @@ connection_or_process_cells_from_inbuf(or_connection_t *conn)
 }
 
 /** Array of recognized link protocol versions. */
-static const uint16_t or_protocol_versions[] = { 1, 2, 3, 4 };
+static const uint16_t or_protocol_versions[] = { 1, 2, 3, 4, 5 };
 /** Number of versions in <b>or_protocol_versions</b>. */
 static const int n_or_protocol_versions =
   (int)( sizeof(or_protocol_versions)/sizeof(uint16_t) );