Merge branch 'tor-gitlab/mr/54'

16 files changed, 168 insertions, 19 deletions

diff --git a/changes/ticket40046 b/changes/ticket40046
new file mode 100644
index 0000000000..68e1ed2544
--- /dev/null
+++ b/changes/ticket40046
@@ -0,0 +1,3 @@
+  o Code simplification and refactoring:
+    - Add and use a set of functions to perform downcasts on constant
+      connection and channel pointers. Closes ticket 40046.
diff --git a/src/core/mainloop/connection.c b/src/core/mainloop/connection.c
index 282d90c2b0..90fd35b527 100644
--- a/src/core/mainloop/connection.c
+++ b/src/core/mainloop/connection.c
@@ -220,8 +220,12 @@ static smartlist_t *outgoing_addrs = NULL;
 
 /**************************************************************/
 
-/** Convert a connection_t* to an listener_connection_t*; assert if the cast
- * is invalid. */
+/**
+ * Cast a `connection_t *` to a `listener_connection_t *`.
+ *
+ * Exit with an assertion failure if the input is not a
+ * `listener_connection_t`.
+ **/
 listener_connection_t *
 TO_LISTENER_CONN(connection_t *c)
 {
@@ -229,6 +233,18 @@ TO_LISTENER_CONN(connection_t *c)
   return DOWNCAST(listener_connection_t, c);
 }
 
+/**
+ * Cast a `const connection_t *` to a `const listener_connection_t *`.
+ *
+ * Exit with an assertion failure if the input is not a
+ * `listener_connection_t`.
+ **/
+const listener_connection_t *
+CONST_TO_LISTENER_CONN(const connection_t *c)
+{
+  return TO_LISTENER_CONN((connection_t *)c);
+}
+
 size_t
 connection_get_inbuf_len(connection_t *conn)
 {
@@ -417,7 +433,7 @@ connection_describe_peer_internal(const connection_t *conn,
     address = conn->address ? conn->address : "unix socket";
   } else if (conn->type == CONN_TYPE_OR) {
     /* For OR connections, we have a lot to do. */
-    const or_connection_t *or_conn = TO_OR_CONN((connection_t *)conn);
+    const or_connection_t *or_conn = CONST_TO_OR_CONN(conn);
     /* we report 'real_addr' as the address we're talking with, if it's set.
      *
      * TODO: Eventually we should have 'addr' always mean the address on the
@@ -2241,7 +2257,7 @@ connection_connect_log_client_use_ip_version(const connection_t *conn)
   /* OR conns keep the original address in real_addr, as addr gets overwritten
    * with the descriptor address */
   if (conn->type == CONN_TYPE_OR) {
-    const or_connection_t *or_conn = TO_OR_CONN((connection_t *)conn);
+    const or_connection_t *or_conn = CONST_TO_OR_CONN(conn);
     tor_addr_copy(&real_addr, &or_conn->real_addr);
   } else if (conn->type == CONN_TYPE_DIR) {
     tor_addr_copy(&real_addr, &conn->addr);
diff --git a/src/core/mainloop/connection.h b/src/core/mainloop/connection.h
index af45007676..ee3dce49f4 100644
--- a/src/core/mainloop/connection.h
+++ b/src/core/mainloop/connection.h
@@ -31,6 +31,8 @@ struct tor_addr_t;
 struct or_options_t;
 
 struct listener_connection_t *TO_LISTENER_CONN(struct connection_t *);
+const struct listener_connection_t *CONST_TO_LISTENER_CONN(
+                                      const struct connection_t *);
 
 struct buf_t;
 
diff --git a/src/core/or/channeltls.c b/src/core/or/channeltls.c
index 082a035c3c..90049a7e5c 100644
--- a/src/core/or/channeltls.c
+++ b/src/core/or/channeltls.c
@@ -389,6 +389,25 @@ channel_tls_from_base(channel_t *chan)
   return (channel_tls_t *)(chan);
 }
 
+/**
+ * Cast a const channel_tls_t to a const channel_t.
+ */
+const channel_t *
+channel_tls_to_base_const(const channel_tls_t *tlschan)
+{
+  return channel_tls_to_base((channel_tls_t*) tlschan);
+}
+
+/**
+ * Cast a const channel_t to a const channel_tls_t, with appropriate
+ * type-checking asserts.
+ */
+const channel_tls_t *
+channel_tls_from_base_const(const channel_t *chan)
+{
+  return channel_tls_from_base((channel_t *)chan);
+}
+
 /********************************************
  * Method implementations for channel_tls_t *
  *******************************************/
@@ -519,7 +538,7 @@ static int
 channel_tls_get_remote_addr_method(const channel_t *chan,
                                    tor_addr_t *addr_out)
 {
-  const channel_tls_t *tlschan = BASE_CHAN_TO_TLS((channel_t*) chan);
+  const channel_tls_t *tlschan = CONST_BASE_CHAN_TO_TLS(chan);
 
   tor_assert(tlschan);
   tor_assert(addr_out);
@@ -574,7 +593,7 @@ channel_tls_get_transport_name_method(channel_t *chan, char **transport_out)
 static const char *
 channel_tls_describe_peer_method(const channel_t *chan)
 {
-  const channel_tls_t *tlschan = BASE_CHAN_TO_TLS((channel_t*)chan);
+  const channel_tls_t *tlschan = CONST_BASE_CHAN_TO_TLS(chan);
   tor_assert(tlschan);
 
   if (tlschan->conn) {
diff --git a/src/core/or/channeltls.h b/src/core/or/channeltls.h
index f04ce0fa9c..e7010a51fc 100644
--- a/src/core/or/channeltls.h
+++ b/src/core/or/channeltls.h
@@ -19,6 +19,8 @@ struct curve25519_public_key_t;
 
 #define BASE_CHAN_TO_TLS(c) (channel_tls_from_base((c)))
 #define TLS_CHAN_TO_BASE(c) (channel_tls_to_base((c)))
+#define CONST_BASE_CHAN_TO_TLS(c) (channel_tls_from_base_const((c)))
+#define CONST_TLS_CHAN_TO_BASE(c) (channel_tls_to_base_const((c)))
 
 #define TLS_CHAN_MAGIC 0x8a192427U
 
@@ -44,6 +46,8 @@ channel_t * channel_tls_handle_incoming(or_connection_t *orconn);
 
 channel_t * channel_tls_to_base(channel_tls_t *tlschan);
 channel_tls_t * channel_tls_from_base(channel_t *chan);
+const channel_t * channel_tls_to_base_const(const channel_tls_t *tlschan);
+const channel_tls_t * channel_tls_from_base_const(const channel_t *chan);
 
 /* Things for connection_or.c to call back into */
 void channel_tls_handle_cell(cell_t *cell, or_connection_t *conn);
diff --git a/src/core/or/connection_edge.c b/src/core/or/connection_edge.c
index 8eb9f8ba0f..ed27fb1b57 100644
--- a/src/core/or/connection_edge.c
+++ b/src/core/or/connection_edge.c
@@ -166,8 +166,12 @@ static int connection_exit_connect_dir(edge_connection_t *exitconn);
 static int consider_plaintext_ports(entry_connection_t *conn, uint16_t port);
 static int connection_ap_supports_optimistic_data(const entry_connection_t *);
 
-/** Convert a connection_t* to an edge_connection_t*; assert if the cast is
- * invalid. */
+/**
+ * Cast a `connection_t *` to an `edge_connection_t *`.
+ *
+ * Exit with an assertion failure if the input is not an
+ * `edge_connection_t`.
+ **/
 edge_connection_t *
 TO_EDGE_CONN(connection_t *c)
 {
@@ -176,6 +180,24 @@ TO_EDGE_CONN(connection_t *c)
   return DOWNCAST(edge_connection_t, c);
 }
 
+/**
+ * Cast a `const connection_t *` to a `const edge_connection_t *`.
+ *
+ * Exit with an assertion failure if the input is not an
+ * `edge_connection_t`.
+ **/
+const edge_connection_t *
+CONST_TO_EDGE_CONN(const connection_t *c)
+{
+  return TO_EDGE_CONN((connection_t *)c);
+}
+
+/**
+ * Cast a `connection_t *` to an `entry_connection_t *`.
+ *
+ * Exit with an assertion failure if the input is not an
+ * `entry_connection_t`.
+ **/
 entry_connection_t *
 TO_ENTRY_CONN(connection_t *c)
 {
@@ -183,6 +205,24 @@ TO_ENTRY_CONN(connection_t *c)
   return (entry_connection_t*) SUBTYPE_P(c, entry_connection_t, edge_.base_);
 }
 
+/**
+ * Cast a `const connection_t *` to a `const entry_connection_t *`.
+ *
+ * Exit with an assertion failure if the input is not an
+ * `entry_connection_t`.
+ **/
+const entry_connection_t *
+CONST_TO_ENTRY_CONN(const connection_t *c)
+{
+  return TO_ENTRY_CONN((connection_t*) c);
+}
+
+/**
+ * Cast an `edge_connection_t *` to an `entry_connection_t *`.
+ *
+ * Exit with an assertion failure if the input is not an
+ * `entry_connection_t`.
+ **/
 entry_connection_t *
 EDGE_TO_ENTRY_CONN(edge_connection_t *c)
 {
@@ -190,6 +230,18 @@ EDGE_TO_ENTRY_CONN(edge_connection_t *c)
   return (entry_connection_t*) SUBTYPE_P(c, entry_connection_t, edge_);
 }
 
+/**
+ * Cast a `const edge_connection_t *` to a `const entry_connection_t *`.
+ *
+ * Exit with an assertion failure if the input is not an
+ * `entry_connection_t`.
+ **/
+const entry_connection_t *
+CONST_EDGE_TO_ENTRY_CONN(const edge_connection_t *c)
+{
+  return EDGE_TO_ENTRY_CONN((edge_connection_t*)c);
+}
+
 /** An AP stream has failed/finished. If it hasn't already sent back
  * a socks reply, send one now (based on endreason). Also set
  * has_sent_end to 1, and mark the conn.
diff --git a/src/core/or/connection_edge.h b/src/core/or/connection_edge.h
index 8c06af5664..9b2cbb8532 100644
--- a/src/core/or/connection_edge.h
+++ b/src/core/or/connection_edge.h
@@ -20,6 +20,10 @@ edge_connection_t *TO_EDGE_CONN(connection_t *);
 entry_connection_t *TO_ENTRY_CONN(connection_t *);
 entry_connection_t *EDGE_TO_ENTRY_CONN(edge_connection_t *);
 
+const edge_connection_t *CONST_TO_EDGE_CONN(const connection_t *);
+const entry_connection_t *CONST_TO_ENTRY_CONN(const connection_t *);
+const entry_connection_t *CONST_EDGE_TO_ENTRY_CONN(const edge_connection_t *);
+
 #define EXIT_CONN_STATE_MIN_ 1
 /** State for an exit connection: waiting for response from DNS farm. */
 #define EXIT_CONN_STATE_RESOLVING 1
diff --git a/src/core/or/connection_or.c b/src/core/or/connection_or.c
index e62c28821a..91dcbe695b 100644
--- a/src/core/or/connection_or.c
+++ b/src/core/or/connection_or.c
@@ -99,8 +99,11 @@ static void connection_or_check_canonicity(or_connection_t *conn,
 
 /**************************************************************/
 
-/** Convert a connection_t* to an or_connection_t*; assert if the cast is
- * invalid. */
+/**
+ * Cast a `connection_t *` to an `or_connection_t *`.
+ *
+ * Exit with an assertion failure if the input is not an `or_connnection_t`.
+ **/
 or_connection_t *
 TO_OR_CONN(connection_t *c)
 {
@@ -108,6 +111,17 @@ TO_OR_CONN(connection_t *c)
   return DOWNCAST(or_connection_t, c);
 }
 
+/**
+ * Cast a `const connection_t *` to a `const or_connection_t *`.
+ *
+ * Exit with an assertion failure if the input is not an `or_connnection_t`.
+ **/
+const or_connection_t *
+CONST_TO_OR_CONN(const connection_t *c)
+{
+  return TO_OR_CONN((connection_t *)c);
+}
+
 /** Clear clear conn->identity_digest and update other data
  * structures as appropriate.*/
 void
diff --git a/src/core/or/connection_or.h b/src/core/or/connection_or.h
index e9ace56ab4..fe81b5c5e1 100644
--- a/src/core/or/connection_or.h
+++ b/src/core/or/connection_or.h
@@ -16,6 +16,7 @@ struct ed25519_public_key_t;
 struct ed25519_keypair_t;
 
 or_connection_t *TO_OR_CONN(connection_t *);
+const or_connection_t *CONST_TO_OR_CONN(const connection_t *);
 
 #include "core/or/orconn_event.h"
 
diff --git a/src/core/or/scheduler.c b/src/core/or/scheduler.c
index 072d78128b..18f11487d9 100644
--- a/src/core/or/scheduler.c
+++ b/src/core/or/scheduler.c
@@ -713,7 +713,7 @@ scheduler_bug_occurred(const channel_t *chan)
 
   if (chan != NULL) {
     const size_t outbuf_len =
-      buf_datalen(TO_CONN(BASE_CHAN_TO_TLS((channel_t *) chan)->conn)->outbuf);
+      buf_datalen(TO_CONN(CONST_BASE_CHAN_TO_TLS(chan)->conn)->outbuf);
     tor_snprintf(buf, sizeof(buf),
                  "Channel %" PRIu64 " in state %s and scheduler state %s."
                  " Num cells on cmux: %d. Connection outbuf len: %lu.",
diff --git a/src/core/or/scheduler_kist.c b/src/core/or/scheduler_kist.c
index 5c1922847e..8c6a7bd1d1 100644
--- a/src/core/or/scheduler_kist.c
+++ b/src/core/or/scheduler_kist.c
@@ -203,7 +203,7 @@ update_socket_info_impl, (socket_table_ent_t *ent))
   tor_assert(ent);
   tor_assert(ent->chan);
   const tor_socket_t sock =
-    TO_CONN(BASE_CHAN_TO_TLS((channel_t *) ent->chan)->conn)->s;
+    TO_CONN(CONST_BASE_CHAN_TO_TLS(ent->chan)->conn)->s;
   struct tcp_info tcp;
   socklen_t tcp_info_len = sizeof(tcp);
 
diff --git a/src/feature/control/control.c b/src/feature/control/control.c
index ee1026359d..ef707319a6 100644
--- a/src/feature/control/control.c
+++ b/src/feature/control/control.c
@@ -61,8 +61,12 @@
 #include <sys/stat.h>
 #endif
 
-/** Convert a connection_t* to an control_connection_t*; assert if the cast is
- * invalid. */
+/**
+ * Cast a `connection_t *` to a `control_connection_t *`.
+ *
+ * Exit with an assertion failure if the input is not a
+ * `control_connection_t`.
+ **/
 control_connection_t *
 TO_CONTROL_CONN(connection_t *c)
 {
@@ -70,6 +74,18 @@ TO_CONTROL_CONN(connection_t *c)
   return DOWNCAST(control_connection_t, c);
 }
 
+/**
+ * Cast a `const connection_t *` to a `const control_connection_t *`.
+ *
+ * Exit with an assertion failure if the input is not a
+ * `control_connection_t`.
+ **/
+const control_connection_t *
+CONST_TO_CONTROL_CONN(const connection_t *c)
+{
+  return TO_CONTROL_CONN((connection_t*)c);
+}
+
 /** Create and add a new controller connection on <b>sock</b>.  If
  * <b>CC_LOCAL_FD_IS_OWNER</b> is set in <b>flags</b>, this Tor process should
  * exit when the connection closes.  If <b>CC_LOCAL_FD_IS_AUTHENTICATED</b>
diff --git a/src/feature/control/control.h b/src/feature/control/control.h
index 7e72b2736b..f884286ec7 100644
--- a/src/feature/control/control.h
+++ b/src/feature/control/control.h
@@ -13,6 +13,7 @@
 #define TOR_CONTROL_H
 
 control_connection_t *TO_CONTROL_CONN(connection_t *);
+const control_connection_t *CONST_TO_CONTROL_CONN(const connection_t *);
 
 #define CONTROL_CONN_STATE_MIN_ 1
 /** State for a control connection: Authenticated and accepting v1 commands. */
diff --git a/src/feature/control/control_bootstrap.c b/src/feature/control/control_bootstrap.c
index fee7612ba2..d4f2adde81 100644
--- a/src/feature/control/control_bootstrap.c
+++ b/src/feature/control/control_bootstrap.c
@@ -274,7 +274,7 @@ control_event_bootstrap_problem(const char *warn, const char *reason,
   const char *recommendation = "ignore";
   int severity;
   char *or_id = NULL, *hostaddr = NULL;
-  or_connection_t *or_conn = NULL;
+  const or_connection_t *or_conn = NULL;
 
   /* bootstrap_percent must not be in "undefined" state here. */
   tor_assert(status >= 0);
@@ -301,7 +301,7 @@ control_event_bootstrap_problem(const char *warn, const char *reason,
 
   if (conn && conn->type == CONN_TYPE_OR) {
     /* XXX TO_OR_CONN can't deal with const */
-    or_conn = TO_OR_CONN((connection_t *)conn);
+    or_conn = CONST_TO_OR_CONN(conn);
     or_id = tor_strdup(hex_str(or_conn->identity_digest, DIGEST_LEN));
   } else {
     or_id = tor_strdup("?");
diff --git a/src/feature/dircommon/directory.c b/src/feature/dircommon/directory.c
index 7f9f157a49..b276ac3441 100644
--- a/src/feature/dircommon/directory.c
+++ b/src/feature/dircommon/directory.c
@@ -79,8 +79,12 @@
  *   connection_finished_connecting() in connection.c
  */
 
-/** Convert a connection_t* to a dir_connection_t*; assert if the cast is
- * invalid. */
+/**
+ * Cast a `connection_t *` to a `dir_connection_t *`.
+ *
+ * Exit with an assertion failure if the input is not a
+ * `dir_connection_t`.
+ **/
 dir_connection_t *
 TO_DIR_CONN(connection_t *c)
 {
@@ -88,6 +92,18 @@ TO_DIR_CONN(connection_t *c)
   return DOWNCAST(dir_connection_t, c);
 }
 
+/**
+ * Cast a `const connection_t *` to a `const dir_connection_t *`.
+ *
+ * Exit with an assertion failure if the input is not a
+ * `dir_connection_t`.
+ **/
+const dir_connection_t *
+CONST_TO_DIR_CONN(const connection_t *c)
+{
+  return TO_DIR_CONN((connection_t *)c);
+}
+
 /** Return false if the directory purpose <b>dir_purpose</b>
  * does not require an anonymous (three-hop) connection.
  *
@@ -217,7 +233,7 @@ connection_dir_is_anonymous(const dir_connection_t *dir_conn)
     return false;
   }
 
-  edge_conn = TO_EDGE_CONN((connection_t *) linked_conn);
+  edge_conn = CONST_TO_EDGE_CONN(linked_conn);
   circ = edge_conn->on_circuit;
 
   /* Can't be a circuit we initiated and without a circuit, no channel. */
diff --git a/src/feature/dircommon/directory.h b/src/feature/dircommon/directory.h
index 0f26cdeff9..0aa2ff53ef 100644
--- a/src/feature/dircommon/directory.h
+++ b/src/feature/dircommon/directory.h
@@ -13,6 +13,7 @@
 #define TOR_DIRECTORY_H
 
 dir_connection_t *TO_DIR_CONN(connection_t *c);
+const dir_connection_t *CONST_TO_DIR_CONN(const connection_t *c);
 
 #define DIR_CONN_STATE_MIN_ 1
 /** State for connection to directory server: waiting for connect(). */