Allow overriding stream list implementation

include/srtp_priv.h

@@ -66,6 +66,7 @@ extern "C" {
 
 typedef struct srtp_stream_ctx_t_ srtp_stream_ctx_t;
 typedef srtp_stream_ctx_t *srtp_stream_t;
+typedef struct srtp_stream_list_ctx_t_ *srtp_stream_list_t;
 
 /*
  * the following declarations are libSRTP internal functions
@@ -102,6 +103,9 @@ srtp_err_status_t srtp_steam_init_all_master_keys(
  */
 srtp_err_status_t srtp_stream_init(srtp_stream_t srtp, const srtp_policy_t *p);
 
+srtp_err_status_t srtp_stream_dealloc(srtp_stream_ctx_t *stream,
+                                      const srtp_stream_ctx_t *stream_template);
+
 /*
  * libsrtp internal datatypes
  */
@@ -156,7 +160,7 @@ typedef struct srtp_stream_ctx_t_ {
  * an srtp_ctx_t holds a stream list and a service description
  */
 typedef struct srtp_ctx_t_ {
-    struct srtp_stream_ctx_t_ *stream_list;     /* linked list of streams     */
+    srtp_stream_list_t stream_list;             /* linked list of streams     */
     struct srtp_stream_ctx_t_ *stream_template; /* act as template for other  */
                                                 /* streams                    */
     void *user_data;                            /* user custom data           */

include/stream_list_priv.h

@@ -0,0 +1,118 @@
+/*
+ * stream_list_priv.h
+ *
+ * list of SRTP streams, keyed by SSRC
+ *
+ * Alba Mendez
+ */
+/*
+ *
+ * Copyright (c) 2001-2017, Cisco Systems, Inc.
+ * Copyright (c) 2022, Dolby Laboratories, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *   Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ *   Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ *   Neither the name of the Cisco Systems, Inc. nor the names of its
+ *   contributors may be used to endorse or promote products derived
+ *   from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef SRTP_STREAM_LIST_PRIV_H
+#define SRTP_STREAM_LIST_PRIV_H
+
+#include <srtp_priv.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * srtp_stream_list_t holds a list of srtp_stream_t, each identified
+ * by their SSRC.
+ *
+ * the API was extracted to allow downstreams to override its
+ * implementation by defining the `SRTP_NO_STREAM_LIST` preprocessor
+ * directive, which removes the default implementation of these
+ * functions. if this is done, the `next` field is free for the
+ * implementation to use.
+ *
+ * this is still an internal interface; there is no stability
+ * guarantee--downstreams should watch this file for changes in
+ * signatures or semantics.
+ */
+
+/**
+ * allocate and initialize a stream list instance
+ */
+srtp_err_status_t srtp_stream_list_create(srtp_stream_list_t *list);
+
+/**
+ * insert a stream into the list
+ *
+ * ownership is transferred from caller to the list.
+ *
+ * if another stream with the same SSRC already exists in the list,
+ * behavior is undefined. if the SSRC field is mutated while the
+ * stream is inserted, further operations have undefined behavior
+ */
+void srtp_stream_list_insert(srtp_stream_list_t *list, srtp_stream_t stream);
+
+/*
+ * look up the stream corresponding to the specified SSRC and return it.
+ * if no such SSRC is found, NULL is returned.
+ */
+srtp_stream_t srtp_stream_list_get(srtp_stream_list_t *list, uint32_t ssrc);
+
+/**
+ * delete the stream associated to the specified SSRC.
+ *
+ * if a stream is found and removed, it's returned and ownership is
+ * transferred to the caller. if not found, NULL is returned.
+ */
+srtp_stream_t srtp_stream_list_delete(srtp_stream_list_t *list, uint32_t ssrc);
+
+/**
+ * iterate through all stored streams. while iterating, it is allowed to delete
+ * the current element; any other mutation to the list is undefined behavior.
+ * returning non-zero from callback aborts the iteration.
+ */
+void srtp_stream_list_for_each(srtp_stream_list_t *list,
+                               int (*callback)(srtp_stream_t, void *),
+                               void *data);
+
+/**
+ * deallocate a stream list instance and all streams inserted in it
+ */
+srtp_err_status_t srtp_stream_list_dealloc(srtp_stream_list_t *list,
+                                           srtp_stream_t template_);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SRTP_STREAM_LIST_PRIV_H */