trace: Add single tracepoint in circuit subsystem

This is the very first tracepoint in tor. It is in the circuit subsystem for
when a new circuit opens.

LTTng instrumentation requires lot more around a tracepoint than USDT thus
this commit only adds one tracepoint in order to outline a base to add more
tracepoints later.

The idea is that we separate subsystem into what LTTng defines as "providers"
so the circuit provider contains the tracepoint definitions for the circuit
subsystem.

Signed-off-by: David Goulet <dgoulet@torproject.org>

Signed-off-by: David Goulet <dgoulet@torproject.org>

scripts/maint/practracker/exceptions.txt

@@ -324,3 +324,4 @@ problem function-size /src/tools/tor-gencert.c:parse_commandline() 111
 problem function-size /src/tools/tor-resolve.c:build_socks5_resolve_request() 102
 problem function-size /src/tools/tor-resolve.c:do_resolve() 171
 problem function-size /src/tools/tor-resolve.c:main() 112
+problem dependency-violation /src/core/or/trace_probes_circuit.c 1

src/core/or/circuituse.c

@@ -39,6 +39,7 @@
 #include "core/or/connection_edge.h"
 #include "core/or/extendinfo.h"
 #include "core/or/policies.h"
+#include "core/or/trace_probes_circuit.h"
 #include "feature/client/addressmap.h"
 #include "feature/client/bridges.h"
 #include "feature/client/circpathbias.h"
@@ -63,6 +64,7 @@
 #include "feature/stats/predict_ports.h"
 #include "lib/math/fp.h"
 #include "lib/time/tvdiff.h"
+#include "lib/trace/events.h"
 
 #include "core/or/cpath_build_state_st.h"
 #include "feature/dircommon/dir_connection_st.h"
@@ -1683,6 +1685,7 @@ circuit_testing_failed(origin_circuit_t *circ, int at_last_hop)
 void
 circuit_has_opened(origin_circuit_t *circ)
 {
+  tor_trace(circuit, opened, circ);
   circuit_event_status(circ, CIRC_EVENT_BUILT, 0);
 
   /* Remember that this circuit has finished building. Now if we start

src/core/or/include.am

@@ -34,6 +34,7 @@ LIBTOR_APP_A_SOURCES += 				\
 	src/core/or/scheduler_vanilla.c		\
 	src/core/or/sendme.c			\
 	src/core/or/status.c			\
+	src/core/or/trace_probes_circuit.c	\
 	src/core/or/versions.c
 
 # ADD_C_FILE: INSERT HEADERS HERE.
@@ -94,5 +95,6 @@ noinst_HEADERS +=					\
 	src/core/or/socks_request_st.h			\
 	src/core/or/status.h				\
 	src/core/or/tor_version_st.h			\
+	src/core/or/trace_probes_circuit.h		\
 	src/core/or/var_cell_st.h			\
 	src/core/or/versions.h

src/core/or/trace_probes_circuit.c

@@ -0,0 +1,27 @@
+/* Copyright (c) 2020, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file trace_probes_circuit.c
+ * \brief Tracepoint provider source file for the circuit subsystem. Probes
+ *        are generated within this C file for LTTng-UST
+ **/
+
+#include "orconfig.h"
+
+/*
+ * Following section is specific to LTTng-UST.
+ */
+#ifdef USE_TRACING_INSTRUMENTATION_LTTNG
+
+/* Header files that the probes need. */
+#include "core/or/circuitlist.h"
+#include "core/or/or.h"
+#include "core/or/origin_circuit_st.h"
+
+#define TRACEPOINT_DEFINE
+#define TRACEPOINT_CREATE_PROBES
+
+#include "trace_probes_circuit.h"
+
+#endif /* USE_TRACING_INSTRUMENTATION_LTTNG */

src/core/or/trace_probes_circuit.h

@@ -0,0 +1,155 @@
+/* Copyright (c) 2020, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file trace_probes_circuit.c
+ * \brief The tracing probes for the circuit subsystem. Currently, only
+ *        LTTng-UST probes are available.
+ **/
+
+#include "orconfig.h"
+
+/* We only build the following if LTTng instrumentation has been enabled. */
+#ifdef USE_TRACING_INSTRUMENTATION_LTTNG
+
+/* The following defines are LTTng-UST specific. */
+#undef TRACEPOINT_PROVIDER
+#define TRACEPOINT_PROVIDER tor_circuit
+
+#undef TRACEPOINT_INCLUDE
+#define TRACEPOINT_INCLUDE "./src/core/or/trace_probes_circuit.h"
+
+#if !defined(TOR_TRACE_PROBES_CIRCUIT_H) || defined(TRACEPOINT_HEADER_MULTI_READ)
+#define TOR_TRACE_PROBES_CIRCUIT_H
+
+#include <lttng/tracepoint.h>
+
+TRACEPOINT_ENUM(tor_circuit, purpose,
+  TP_ENUM_VALUES(
+    /* Initializing. */
+    ctf_enum_value("<UNSET>", 0)
+
+    /* OR Side. */
+    ctf_enum_value("OR", CIRCUIT_PURPOSE_OR)
+    ctf_enum_value("OR_INTRO_POINT", CIRCUIT_PURPOSE_INTRO_POINT)
+    ctf_enum_value("OR_REND_POINT_WAITING",
+                   CIRCUIT_PURPOSE_REND_POINT_WAITING)
+    ctf_enum_value("OR_REND_ESTABLISHED", CIRCUIT_PURPOSE_REND_ESTABLISHED)
+
+    /* Client Side. */
+    ctf_enum_value("C_GENERAL", CIRCUIT_PURPOSE_C_GENERAL)
+    ctf_enum_value("C_INTRODUCING", CIRCUIT_PURPOSE_C_INTRODUCING)
+    ctf_enum_value("C_INTRODUCE_ACK_WAIT",
+                   CIRCUIT_PURPOSE_C_INTRODUCE_ACK_WAIT)
+    ctf_enum_value("C_INTRODUCE_ACKED", CIRCUIT_PURPOSE_C_INTRODUCE_ACKED)
+    ctf_enum_value("C_ESTABLISH_REND", CIRCUIT_PURPOSE_C_ESTABLISH_REND)
+    ctf_enum_value("C_REND_READY", CIRCUIT_PURPOSE_C_REND_READY)
+    ctf_enum_value("C_REND_READY_INTRO_ACKED",
+                   CIRCUIT_PURPOSE_C_REND_READY_INTRO_ACKED)
+    ctf_enum_value("C_REND_JOINED", CIRCUIT_PURPOSE_C_REND_JOINED)
+    ctf_enum_value("C_HSDIR_GET", CIRCUIT_PURPOSE_C_HSDIR_GET)
+
+    /* CBT and Padding. */
+    ctf_enum_value("C_MEASURE_TIMEOUT", CIRCUIT_PURPOSE_C_MEASURE_TIMEOUT)
+    ctf_enum_value("C_CIRCUIT_PADDING", CIRCUIT_PURPOSE_C_CIRCUIT_PADDING)
+
+    /* Service Side. */
+    ctf_enum_value("S_ESTABLISH_INTRO", CIRCUIT_PURPOSE_S_ESTABLISH_INTRO)
+    ctf_enum_value("S_INTRO", CIRCUIT_PURPOSE_S_INTRO)
+    ctf_enum_value("S_CONNECT_REND", CIRCUIT_PURPOSE_S_CONNECT_REND)
+    ctf_enum_value("S_REND_JOINED", CIRCUIT_PURPOSE_S_REND_JOINED)
+    ctf_enum_value("S_HSDIR_POST", CIRCUIT_PURPOSE_S_HSDIR_POST)
+
+    /* Misc. */
+    ctf_enum_value("TESTING", CIRCUIT_PURPOSE_TESTING)
+    ctf_enum_value("CONTROLER", CIRCUIT_PURPOSE_CONTROLLER)
+    ctf_enum_value("PATH_BIAS_TESTING", CIRCUIT_PURPOSE_PATH_BIAS_TESTING)
+
+    /* VanGuard */
+    ctf_enum_value("HS_VANGUARDS", CIRCUIT_PURPOSE_HS_VANGUARDS)
+  )
+)
+
+TRACEPOINT_ENUM(tor_circuit, end_reason,
+  TP_ENUM_VALUES(
+    /* Local reasons. */
+    ctf_enum_value("IP_NOW_REDUNDANT", END_CIRC_REASON_IP_NOW_REDUNDANT)
+    ctf_enum_value("MEASUREMENT_EXPIRED", END_CIRC_REASON_MEASUREMENT_EXPIRED)
+    ctf_enum_value("REASON_NOPATH", END_CIRC_REASON_NOPATH)
+    ctf_enum_value("AT_ORIGIN", END_CIRC_AT_ORIGIN)
+    ctf_enum_value("NONE", END_CIRC_REASON_NONE)
+    ctf_enum_value("TORPROTOCOL", END_CIRC_REASON_TORPROTOCOL)
+    ctf_enum_value("INTERNAL", END_CIRC_REASON_INTERNAL)
+    ctf_enum_value("REQUESTED", END_CIRC_REASON_REQUESTED)
+    ctf_enum_value("HIBERNATING", END_CIRC_REASON_HIBERNATING)
+    ctf_enum_value("RESOURCELIMIT", END_CIRC_REASON_RESOURCELIMIT)
+    ctf_enum_value("CONNECTFAILED", END_CIRC_REASON_CONNECTFAILED)
+    ctf_enum_value("OR_IDENTITY", END_CIRC_REASON_OR_IDENTITY)
+    ctf_enum_value("CHANNEL_CLOSED", END_CIRC_REASON_CHANNEL_CLOSED)
+    ctf_enum_value("FINISHED", END_CIRC_REASON_FINISHED)
+    ctf_enum_value("TIMEOUT", END_CIRC_REASON_TIMEOUT)
+    ctf_enum_value("DESTROYED", END_CIRC_REASON_DESTROYED)
+    ctf_enum_value("NOSUCHSERVICE", END_CIRC_REASON_NOSUCHSERVICE)
+
+    /* Remote reasons. */
+    ctf_enum_value("FLAG_REMOTE", END_CIRC_REASON_FLAG_REMOTE)
+    ctf_enum_value("REMOTE_TORPROTOCOL",
+             END_CIRC_REASON_FLAG_REMOTE | END_CIRC_REASON_TORPROTOCOL)
+    ctf_enum_value("REMOTE_INTERNAL",
+             END_CIRC_REASON_FLAG_REMOTE | END_CIRC_REASON_INTERNAL)
+    ctf_enum_value("REMOTE_REQUESTED",
+             END_CIRC_REASON_FLAG_REMOTE | END_CIRC_REASON_REQUESTED)
+    ctf_enum_value("REMOTE_HIBERNATING",
+             END_CIRC_REASON_FLAG_REMOTE | END_CIRC_REASON_HIBERNATING)
+    ctf_enum_value("REMOTE_RESOURCELIMIT",
+             END_CIRC_REASON_FLAG_REMOTE | END_CIRC_REASON_RESOURCELIMIT)
+    ctf_enum_value("REMOTE_CONNECTFAILED",
+             END_CIRC_REASON_FLAG_REMOTE | END_CIRC_REASON_CONNECTFAILED)
+    ctf_enum_value("REMOTE_OR_IDENTITY",
+             END_CIRC_REASON_FLAG_REMOTE | END_CIRC_REASON_OR_IDENTITY)
+    ctf_enum_value("REMOTE_CHANNEL_CLOSED",
+             END_CIRC_REASON_FLAG_REMOTE | END_CIRC_REASON_CHANNEL_CLOSED)
+    ctf_enum_value("REMOTE_FINISHED",
+             END_CIRC_REASON_FLAG_REMOTE | END_CIRC_REASON_FINISHED)
+    ctf_enum_value("REMOTE_TIMEOUT",
+             END_CIRC_REASON_FLAG_REMOTE | END_CIRC_REASON_TIMEOUT)
+    ctf_enum_value("REMOTE_DESTROYED",
+             END_CIRC_REASON_FLAG_REMOTE | END_CIRC_REASON_DESTROYED)
+    ctf_enum_value("REMOTE_NOSUCHSERVICE",
+             END_CIRC_REASON_FLAG_REMOTE | END_CIRC_REASON_NOSUCHSERVICE)
+  )
+)
+
+TRACEPOINT_ENUM(tor_circuit, state,
+  TP_ENUM_VALUES(
+    ctf_enum_value("BUILDING", CIRCUIT_STATE_BUILDING)
+    ctf_enum_value("ONIONSKIN_PENDING", CIRCUIT_STATE_ONIONSKIN_PENDING)
+    ctf_enum_value("CHAN_WAIT", CIRCUIT_STATE_CHAN_WAIT)
+    ctf_enum_value("GUARD_WAIT", CIRCUIT_STATE_GUARD_WAIT)
+    ctf_enum_value("OPEN", CIRCUIT_STATE_OPEN)
+  )
+)
+
+TRACEPOINT_EVENT_CLASS(tor_circuit, origin_circuit_t_class,
+  TP_ARGS(const origin_circuit_t *, circ),
+  TP_FIELDS(
+    ctf_integer(uint32_t, circ_id, circ->global_identifier)
+    ctf_enum(tor_circuit, purpose, int, purpose, TO_CIRCUIT(circ)->purpose)
+    ctf_enum(tor_circuit, state, int, state, TO_CIRCUIT(circ)->state)
+  )
+)
+
+/*
+ * Origin circuit events.
+ */
+
+TRACEPOINT_EVENT_INSTANCE(tor_circuit, origin_circuit_t_class, opened,
+  TP_ARGS(const origin_circuit_t *, circ)
+)
+
+#endif /* TOR_TRACE_PROBES_CIRCUIT_H */
+
+/* Must be include after the probes declaration. */
+#include <lttng/tracepoint-event.h>
+
+#endif /* USE_TRACING_INSTRUMENTATION_LTTNG */