Allow overriding stream list implementation

.github/workflows/stream_list.yml

@@ -0,0 +1,41 @@
+name: Stream List CI
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+
+    runs-on: ${{ matrix.os }}
+
+    env:
+      CTEST_OUTPUT_ON_FAILURE: 1
+
+    steps:
+
+    - uses: actions/checkout@v2
+
+    - name: Create Build Environment
+      run: cmake -E make_directory ${{github.workspace}}/build
+
+    - name: Configure CMake
+      working-directory: ${{github.workspace}}/build
+      shell: bash
+      run: cmake $GITHUB_WORKSPACE -DBUILD_WITH_SANITIZERS=TRUE -DCMAKE_C_FLAGS:STRING="-DSRTP_NO_STREAM_LIST -DSRTP_USE_TEST_STREAM_LIST"
+
+    - name: Build
+      working-directory: ${{github.workspace}}/build
+      shell: bash
+      run: cmake --build . -t srtp_driver
+
+    - name: Test
+      working-directory: ${{github.workspace}}/build
+      shell: bash
+      run: ctest -R srtp_driver

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
@@ -96,12 +97,6 @@ srtp_err_status_t srtp_steam_init_all_master_keys(
     srtp_master_key_t **keys,
     const unsigned int max_master_keys);
 
-/*
- * srtp_stream_init(s, p) initializes the srtp_stream_t s to
- * use the policy at the location p
- */
-srtp_err_status_t srtp_stream_init(srtp_stream_t srtp, const srtp_policy_t *p);
-
 /*
  * libsrtp internal datatypes
  */
@@ -149,14 +144,21 @@ typedef struct srtp_stream_ctx_t_ {
     int *enc_xtn_hdr;
     int enc_xtn_hdr_count;
     uint32_t pending_roc;
-    struct srtp_stream_ctx_t_ *next; /* linked list of streams */
+    /*
+    The next and prev pointers are here to allow for a stream list to be
+    implemented as an intrusive doubly-linked list (the former being the
+    default).  Other stream list implementations can ignore these fields or use
+    them for some other purpose specific to the stream list implementation.
+    */
+    struct srtp_stream_ctx_t_ *next;
+    struct srtp_stream_ctx_t_ *prev;
 } strp_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 +1,122 @@
+/*
+ * 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` & `prev` fields are 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_alloc(srtp_stream_list_t *list_ptr);
+
+/**
+ * deallocate a stream list instance
+ *
+ * the list must be empty or else an error is returned.
+ */
+srtp_err_status_t srtp_stream_list_dealloc(srtp_stream_list_t list);
+
+/**
+ * insert a stream into the list
+ *
+ * returns srtp_err_status_alloc_fail if insertion failed due to unavailable
+ * capacity in the list. if operation succeeds, srtp_err_status_ok is returned
+ *
+ * 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
+ */
+srtp_err_status_t 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);
+
+/**
+ * remove the stream from the list.
+ *
+ * The stream to be removed is referenced "by value", i.e., by the pointer to be
+ * removed from the list. This pointer is obtained using `srtp_stream_list_get`
+ * or as callback parameter in `srtp_stream_list_for_each`.
+ */
+void srtp_stream_list_remove(srtp_stream_list_t list, srtp_stream_t stream);
+
+/**
+ * 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);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SRTP_STREAM_LIST_PRIV_H */