1 files changed, 113 insertions, 0 deletions
diff --git a/src/core/or/congestion_control_common.h b/src/core/or/congestion_control_common.h
new file mode 100644
index 0000000000..01dbc1ceb4
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+++ b/src/core/or/congestion_control_common.h
@@ -0,0 +1,113 @@
+/* Copyright (c) 2019-2021, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file congestion_control_common.h
+ * \brief Public APIs for congestion control
+ **/
+
+#ifndef TOR_CONGESTION_CONTROL_COMMON_H
+#define TOR_CONGESTION_CONTROL_COMMON_H
+
+#include "core/or/crypt_path_st.h"
+#include "core/or/circuit_st.h"
+
+typedef struct congestion_control_t congestion_control_t;
+
+/** Wrapper for the free function, set the CC pointer to NULL after free */
+#define congestion_control_free(cc) \
+    FREE_AND_NULL(congestion_control_t, congestion_control_free_, cc)
+
+void congestion_control_free_(congestion_control_t *cc);
+
+congestion_control_t *congestion_control_new(void);
+
+int congestion_control_dispatch_cc_alg(congestion_control_t *cc,
+                                       const circuit_t *circ,
+                                       const crypt_path_t *layer_hint);
+
+void congestion_control_note_cell_sent(congestion_control_t *cc,
+                                       const circuit_t *circ,
+                                       const crypt_path_t *cpath);
+
+bool congestion_control_update_circuit_estimates(congestion_control_t *,
+                                                 const circuit_t *,
+                                                 const crypt_path_t *);
+
+int congestion_control_get_package_window(const circuit_t *,
+                                          const crypt_path_t *);
+
+int sendme_get_inc_count(const circuit_t *, const crypt_path_t *);
+bool circuit_sent_cell_for_sendme(const circuit_t *, const crypt_path_t *);
+bool is_monotime_clock_reliable(void);
+
+void congestion_control_new_consensus_params(const networkstatus_t *ns);
+
+/* Ugh, C.. these four are private. Use the getter instead, when
+ * external to the congestion control code. */
+extern uint32_t or_conn_highwater;
+extern uint32_t or_conn_lowwater;
+extern int32_t cell_queue_high;
+extern int32_t cell_queue_low;
+
+/** Stop writing on an orconn when its outbuf is this large */
+static inline uint32_t
+or_conn_highwatermark(void)
+{
+  return or_conn_highwater;
+}
+
+/** Resume writing on an orconn when its outbuf is less than this */
+static inline uint32_t
+or_conn_lowwatermark(void)
+{
+  return or_conn_lowwater;
+}
+
+/** Stop reading on edge connections when we have this many cells
+ * waiting on the appropriate queue. */
+static inline int32_t
+cell_queue_highwatermark(void)
+{
+  return cell_queue_high;
+}
+
+/** Start reading from edge connections again when we get down to this many
+ * cells. */
+static inline int32_t
+cell_queue_lowwatermark(void)
+{
+  return cell_queue_low;
+}
+
+/**
+ * Compute an N-count EWMA, aka N-EWMA. N-EWMA is defined as:
+ *  EWMA = alpha*value + (1-alpha)*EWMA_prev
+ * with alpha = 2/(N+1).
+ *
+ * This works out to:
+ *  EWMA = value*2/(N+1) + EMA_prev*(N-1)/(N+1)
+ *       = (value*2 + EWMA_prev*(N-1))/(N+1)
+ */
+static inline uint64_t
+n_count_ewma(uint64_t curr, uint64_t prev, uint64_t N)
+{
+  if (prev == 0)
+    return curr;
+  else
+    return (2*curr + (N-1)*prev)/(N+1);
+}
+
+/* Private section starts. */
+#ifdef TOR_CONGESTION_CONTROL_PRIVATE
+
+/*
+ * Unit tests declaractions.
+ */
+#ifdef TOR_UNIT_TESTS
+
+#endif /* defined(TOR_UNIT_TESTS) */
+
+#endif /* defined(TOR_CONGESTION_CONTROL_PRIVATE) */
+
+#endif /* !defined(TOR_CONGESTION_CONTROL_COMMON_H) */