Improve export_hs_client_circuit_id() function.

- Change default values.
- Beautify.
- Documentation.

src/core/or/connection_edge.c

@@ -597,31 +597,34 @@ connected_cell_format_payload(uint8_t *payload_out,
   return connected_payload_len;
 }
 
-/* DOCDOCDOC */
-static void
-send_ha_proxy_header(const edge_connection_t *edge_conn,
-                     connection_t *conn)
+/* This is an onion service client connection: Export the client circuit ID
+ * according to the HAProxy proxy protocol. */
+STATIC void
+export_hs_client_circuit_id_haproxy(const edge_connection_t *edge_conn,
+                                    connection_t *conn)
 {
-  char buf[512];
-  char dst_ipv6[39] = "::1";
+  char *buf;
+  const char dst_ipv6[] = "::1";
   /* See RFC4193 regarding fc00::/7 */
-  char src_ipv6_prefix[34] = "fc00:dead:beef:4dad:";
+  const char src_ipv6_prefix[] = "fc00:dead:beef:4dad:";
   /* TODO: retain virtual port and use as destination port */
   uint16_t dst_port = 443;
-  uint16_t src_port = 0;
-  uint32_t gid = 0;
+  uint16_t src_port = 1; /* default value */
+  uint32_t gid = 0; /* default value */
 
+  /* Generate a GID and source port for this client */
   if (edge_conn->on_circuit != NULL) {
     gid = TO_ORIGIN_CIRCUIT(edge_conn->on_circuit)->global_identifier;
     src_port = gid & 0x0000ffff;
   }
 
-  gid = (gid == 0) ? 1 : gid;
-  src_port = (src_port == 0) ? 1 : src_port;
+  /* Build the string */
+  tor_asprintf(&buf, "PROXY TCP6 %s:%x %s %d %d\r\n",
+               src_ipv6_prefix, gid, dst_ipv6, src_port, dst_port);
 
-  tor_snprintf(buf, sizeof(buf), "PROXY TCP6 %s:%x %s %d %d\r\n",
-	       src_ipv6_prefix, gid, dst_ipv6, src_port, dst_port);
   connection_buf_add(buf, strlen(buf), conn);
+
+  tor_free(buf);
 }
 
 /** Connected handler for exit connections: start writing pending
@@ -649,7 +652,7 @@ connection_edge_finished_connecting(edge_connection_t *edge_conn)
    * protocol header */
   if (edge_conn->hs_ident &&
       hs_service_exports_circuit_id(&edge_conn->hs_ident->identity_pk)) {
-    send_ha_proxy_header(edge_conn, conn);
+    export_hs_client_circuit_id_haproxy(edge_conn, conn);
   }
 
   connection_watch_events(conn, READ_EVENT); /* stop writing, keep reading */

src/core/or/connection_edge.h

@@ -243,6 +243,9 @@ STATIC void connection_ap_handshake_rewrite(entry_connection_t *conn,
                                             rewrite_result_t *out);
 
 STATIC int connection_ap_process_http_connect(entry_connection_t *conn);
+STATIC void
+export_hs_client_circuit_id_haproxy(const edge_connection_t *edge_conn,
+                                    connection_t *conn);
 #endif /* defined(CONNECTION_EDGE_PRIVATE) */
 
 #endif /* !defined(TOR_CONNECTION_EDGE_H) */