Define new CONST_TO_*_CONN() functions for const-to-const casts

These names are analogous to the CONST_TO_*_CIRC() functions we have
for circuits.

Part of #40046.

src/core/mainloop/connection.c

@@ -233,6 +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)
 {

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;
 

src/core/or/connection_edge.c

@@ -180,6 +180,18 @@ 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 *`.
  *
@@ -193,6 +205,18 @@ 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 *`.
  *
@@ -206,6 +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.

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

src/core/or/connection_or.c

@@ -111,6 +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

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"
 

src/feature/control/control.c

@@ -74,6 +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>

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. */

src/feature/dircommon/directory.c

@@ -92,6 +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.
  *

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(). */