1 files changed, 283 insertions, 0 deletions
diff --git a/src/feature/stats/connstats.c b/src/feature/stats/connstats.c
new file mode 100644
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--- /dev/null
+++ b/src/feature/stats/connstats.c
@@ -0,0 +1,283 @@
+/* Copyright (c) 2001 Matej Pfajfar.
+ * Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2020, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * @file connstats.c
+ * @brief Count bidirectional vs one-way connections.
+ *
+ * Connection statistics, use to track one-way and bidirectional connections.
+ *
+ * Note that this code counts concurrent connections in each
+ * BIDI_INTERVAL-second interval, not total connections.  It can tell you what
+ * fraction of connections are bidirectional at each time, not necessarily
+ * what number are bidirectional.
+ **/
+
+#include "orconfig.h"
+#include "core/or/or.h"
+#include "feature/stats/connstats.h"
+#include "app/config/config.h"
+
+/** Start of the current connection stats interval or 0 if we're not
+ * collecting connection statistics. */
+static time_t start_of_conn_stats_interval;
+
+/** Initialize connection stats. */
+void
+conn_stats_init(time_t now)
+{
+  start_of_conn_stats_interval = now;
+}
+
+/** Count connections on which we read and wrote less than this many bytes
+ * as "below threshold." */
+#define BIDI_THRESHOLD 20480
+
+/** Count connections that we read or wrote at least this factor as many
+ * bytes from/to than we wrote or read to/from as mostly reading or
+ * writing. */
+#define BIDI_FACTOR 10
+
+/** Interval length in seconds for considering read and written bytes for
+ * connection stats. */
+#define BIDI_INTERVAL 10
+
+/** Start of next BIDI_INTERVAL second interval. */
+static time_t bidi_next_interval = 0;
+
+/** A single grouped set of connection type counts. */
+typedef struct conn_counts_t {
+  /** Number of connections that we read and wrote less than BIDI_THRESHOLD
+   * bytes from/to in BIDI_INTERVAL seconds. */
+  uint32_t below_threshold;
+
+  /** Number of connections that we read at least BIDI_FACTOR times more
+   * bytes from than we wrote to in BIDI_INTERVAL seconds. */
+  uint32_t mostly_read;
+
+  /** Number of connections that we wrote at least BIDI_FACTOR times more
+   * bytes to than we read from in BIDI_INTERVAL seconds. */
+  uint32_t mostly_written;
+
+  /** Number of connections that we read and wrote at least BIDI_THRESHOLD
+   * bytes from/to, but not BIDI_FACTOR times more in either direction in
+   * BIDI_INTERVAL seconds. */
+  uint32_t both_read_and_written;
+} conn_counts_t ;
+
+/** A collection of connection counts, over all OR connections. */
+static conn_counts_t counts;
+/** A collection of connection counts, over IPv6 OR connections only. */
+static conn_counts_t counts_ipv6;
+
+/** Entry in a map from connection ID to the number of read and written
+ * bytes on this connection in a BIDI_INTERVAL second interval. */
+typedef struct bidi_map_entry_t {
+  HT_ENTRY(bidi_map_entry_t) node;
+  uint64_t conn_id; /**< Connection ID */
+  size_t read; /**< Number of read bytes */
+  size_t written; /**< Number of written bytes */
+  bool is_ipv6; /**< True if this is an IPv6 connection */
+} bidi_map_entry_t;
+
+/** Map of OR connections together with the number of read and written
+ * bytes in the current BIDI_INTERVAL second interval. */
+static HT_HEAD(bidimap, bidi_map_entry_t) bidi_map =
+     HT_INITIALIZER();
+
+/** Hashtable helper: return true if @a a and @a b have the same key. */
+static int
+bidi_map_ent_eq(const bidi_map_entry_t *a, const bidi_map_entry_t *b)
+{
+  return a->conn_id == b->conn_id;
+}
+
+/** Hashtable helper: compute a digest for the key of @a entry. */
+static unsigned
+bidi_map_ent_hash(const bidi_map_entry_t *entry)
+{
+  return (unsigned) entry->conn_id;
+}
+
+HT_PROTOTYPE(bidimap, bidi_map_entry_t, node, bidi_map_ent_hash,
+             bidi_map_ent_eq);
+HT_GENERATE2(bidimap, bidi_map_entry_t, node, bidi_map_ent_hash,
+             bidi_map_ent_eq, 0.6, tor_reallocarray_, tor_free_);
+
+/** Release all storage held in connstats.c */
+void
+conn_stats_free_all(void)
+{
+  bidi_map_entry_t **ptr, **next, *ent;
+  for (ptr = HT_START(bidimap, &bidi_map); ptr; ptr = next) {
+    ent = *ptr;
+    next = HT_NEXT_RMV(bidimap, &bidi_map, ptr);
+    tor_free(ent);
+  }
+  HT_CLEAR(bidimap, &bidi_map);
+}
+
+/** Reset counters for conn statistics. */
+void
+conn_stats_reset(time_t now)
+{
+  start_of_conn_stats_interval = now;
+  memset(&counts, 0, sizeof(counts));
+  memset(&counts_ipv6, 0, sizeof(counts_ipv6));
+  conn_stats_free_all();
+}
+
+/** Stop collecting connection stats in a way that we can re-start doing
+ * so in conn_stats_init(). */
+void
+conn_stats_terminate(void)
+{
+  conn_stats_reset(0);
+}
+
+/**
+ * Record a single entry @a ent in the counts structure @a cnt.
+ */
+static void
+add_entry_to_count(conn_counts_t *cnt, const bidi_map_entry_t *ent)
+{
+  if (ent->read + ent->written < BIDI_THRESHOLD)
+    cnt->below_threshold++;
+  else if (ent->read >= ent->written * BIDI_FACTOR)
+    cnt->mostly_read++;
+  else if (ent->written >= ent->read * BIDI_FACTOR)
+    cnt->mostly_written++;
+  else
+    cnt->both_read_and_written++;
+}
+
+/**
+ * Count all the connection information we've received during the current
+ * period in 'bidimap', and store that information in the appropriate count
+ * structures.
+ **/
+static void
+collect_period_statistics(void)
+{
+  bidi_map_entry_t **ptr, **next, *ent;
+  for (ptr = HT_START(bidimap, &bidi_map); ptr; ptr = next) {
+    ent = *ptr;
+    add_entry_to_count(&counts, ent);
+    if (ent->is_ipv6)
+      add_entry_to_count(&counts_ipv6, ent);
+    next = HT_NEXT_RMV(bidimap, &bidi_map, ptr);
+    tor_free(ent);
+  }
+  log_info(LD_GENERAL, "%d below threshold, %d mostly read, "
+           "%d mostly written, %d both read and written.",
+           counts.below_threshold, counts.mostly_read, counts.mostly_written,
+           counts.both_read_and_written);
+}
+
+/** We read <b>num_read</b> bytes and wrote <b>num_written</b> from/to OR
+ * connection <b>conn_id</b> in second <b>when</b>. If this is the first
+ * observation in a new interval, sum up the last observations. Add bytes
+ * for this connection. */
+void
+conn_stats_note_or_conn_bytes(uint64_t conn_id, size_t num_read,
+                              size_t num_written, time_t when,
+                              bool is_ipv6)
+{
+  if (!start_of_conn_stats_interval)
+    return;
+  /* Initialize */
+  if (bidi_next_interval == 0)
+    bidi_next_interval = when + BIDI_INTERVAL;
+  /* Sum up last period's statistics */
+  if (when >= bidi_next_interval) {
+    collect_period_statistics();
+    while (when >= bidi_next_interval)
+      bidi_next_interval += BIDI_INTERVAL;
+  }
+  /* Add this connection's bytes. */
+  if (num_read > 0 || num_written > 0) {
+    bidi_map_entry_t *entry, lookup;
+    lookup.conn_id = conn_id;
+    entry = HT_FIND(bidimap, &bidi_map, &lookup);
+    if (entry) {
+      entry->written += num_written;
+      entry->read += num_read;
+      entry->is_ipv6 |= is_ipv6;
+    } else {
+      entry = tor_malloc_zero(sizeof(bidi_map_entry_t));
+      entry->conn_id = conn_id;
+      entry->written = num_written;
+      entry->read = num_read;
+      entry->is_ipv6 = is_ipv6;
+      HT_INSERT(bidimap, &bidi_map, entry);
+    }
+  }
+}
+
+/** Return a newly allocated string containing the connection statistics
+ * until <b>now</b>, or NULL if we're not collecting conn stats. Caller must
+ * ensure start_of_conn_stats_interval is in the past. */
+char *
+conn_stats_format(time_t now)
+{
+  char *result, written_at[ISO_TIME_LEN+1];
+
+  if (!start_of_conn_stats_interval)
+    return NULL; /* Not initialized. */
+
+  tor_assert(now >= start_of_conn_stats_interval);
+
+  format_iso_time(written_at, now);
+  tor_asprintf(&result,
+               "conn-bi-direct %s (%d s) "
+                    "%"PRIu32",%"PRIu32",%"PRIu32",%"PRIu32"\n"
+               "ipv6-conn-bi-direct %s (%d s) "
+                    "%"PRIu32",%"PRIu32",%"PRIu32",%"PRIu32"\n",
+               written_at,
+               (unsigned) (now - start_of_conn_stats_interval),
+               counts.below_threshold,
+               counts.mostly_read,
+               counts.mostly_written,
+               counts.both_read_and_written,
+               written_at,
+               (unsigned) (now - start_of_conn_stats_interval),
+               counts_ipv6.below_threshold,
+               counts_ipv6.mostly_read,
+               counts_ipv6.mostly_written,
+               counts_ipv6.both_read_and_written);
+
+  return result;
+}
+
+/** If 24 hours have passed since the beginning of the current conn stats
+ * period, write conn stats to $DATADIR/stats/conn-stats (possibly
+ * overwriting an existing file) and reset counters.  Return when we would
+ * next want to write conn stats or 0 if we never want to write. */
+time_t
+conn_stats_save(time_t now)
+{
+  char *str = NULL;
+
+  if (!start_of_conn_stats_interval)
+    return 0; /* Not initialized. */
+  if (start_of_conn_stats_interval + WRITE_STATS_INTERVAL > now)
+    goto done; /* Not ready to write */
+
+  /* Generate history string. */
+  str = conn_stats_format(now);
+
+  /* Reset counters. */
+  conn_stats_reset(now);
+
+  /* Try to write to disk. */
+  if (!check_or_create_data_subdir("stats")) {
+    write_to_data_subdir("stats", "conn-stats", str, "connection statistics");
+  }
+
+ done:
+  tor_free(str);
+  return start_of_conn_stats_interval + WRITE_STATS_INTERVAL;
+}