SDP: Ensure SDPs "merge" properly.

The gist of this work ensures that when a remote SDP is received, it is
merged properly with the local capabilities. The remote SDP is converted
into a stream topology. That topology is then merged with the current
local topology on the SDP state. That new merged topology is then used
to create an SDP. Finally, adjustments are made to RTP instances based
on knowledge gained from the remote SDP.

There are also a battery of tests in this commit that ensure that some
basic SDP merges work as expected.

While this may not sound like a big change, it has the property that it
caused lots of ancillary changes.

* The remote SDP is no longer stored on the SDP state. Biggest reason:
  there's no need for it. The remote SDP is used at the time it is being
  set and nowhere else.

* Some new SDP APIs were added in order to find attributes and convert
  generic SDP attributes into rtpmap structures.

* Writing tests made me realize that retrieving a value from an SDP
  options structure, the SDP options needs to be made const.

* The SDP state machine was essentially gutted by a previous commit.
  Initially, I attempted to reinstate it, but I found that as it had
  been defined, it was not all that useful. What was more useful was
  knowing the role we play in SDP negotiation, so the SDP state machine
  has been transformed into an indicator of role.

* Rather than storing separate local and joint stream state
  capabilities, it makes more sense to keep track of current stream
  state and update it as things change.

Change-Id: I5938c2be3c6f0a003aa88a39a59e0880f8b2df3d

4 files changed, 141 insertions, 22 deletions

diff --git a/include/asterisk/codec.h b/include/asterisk/codec.h
index 2ae955181..2f5756cd1 100644
--- a/include/asterisk/codec.h
+++ b/include/asterisk/codec.h
@@ -166,6 +166,17 @@ int ast_codec_get_max(void);
 const char *ast_codec_media_type2str(enum ast_media_type type);
 
 /*!
+ * \brief Conversion function to take a media string and convert it to a media type
+ *
+ * \param media_type_str The media type string
+ *
+ * \retval The ast_media_type that corresponds to the string
+ *
+ * \since 15.0.0
+ */
+enum ast_media_type ast_media_type_from_str(const char *media_type_str);
+
+/*!
  * \brief Get the number of samples contained within a frame
  *
  * \param frame The frame itself
diff --git a/include/asterisk/sdp.h b/include/asterisk/sdp.h
index 3649b4037..d5bf9147b 100644
--- a/include/asterisk/sdp.h
+++ b/include/asterisk/sdp.h
@@ -147,6 +147,22 @@ struct ast_sdp {
 };
 
 /*!
+ * \brief A structure representing an SDP rtpmap attribute
+ */
+struct ast_sdp_rtpmap {
+	/*! The RTP payload number for the rtpmap */
+	int payload;
+	/*! The Name of the codec */
+	char *encoding_name;
+	/*! The clock rate of the codec */
+	int clock_rate;
+	/*! Optional encoding parameters */
+	char *encoding_parameters;
+	/*! Area where strings are stored */
+	char buf[0];
+};
+
+/*!
  * \brief Free an SDP Attribute
  *
  * \param a_line The attribute to free
@@ -545,15 +561,88 @@ struct ast_sdp *ast_sdp_alloc(struct ast_sdp_o_line *o_line,
 	struct ast_sdp_t_line *t_line);
 
 /*!
- * \brief Create an SDP from an existing SDP State local topology
+ * \brief Find an attribute on the top-level SDP
+ *
+ * \note This will not search within streams for the given attribute.
+ *
+ * \param sdp The SDP in which to search
+ * \param attr_name The name of the attribute to search for
+ * \param payload Optional payload number to search for. If irrelevant, set to -1
+ *
+ * \retval NULL Could not find the given attribute
+ * \retval Non-NULL The attribute to find
+ *
+ * \since 15.0.0
+ */
+struct ast_sdp_a_line *ast_sdp_find_attribute(const struct ast_sdp *sdp,
+	const char *attr_name, int payload);
+
+/*!
+ * \brief Find an attribute on an SDP stream (m-line)
  *
- * \param sdp_state SDP State
+ * \param sdp The SDP in which to search
+ * \param attr_name The name of the attribute to search for
+ * \param payload Optional payload number to search for. If irrelevant, set to -1
  *
+ * \retval NULL Could not find the given attribute
+ * \retval Non-NULL The attribute to find
+ *
+ * \since 15.0.0
+ */
+struct ast_sdp_a_line *ast_sdp_m_find_attribute(const struct ast_sdp_m_line *m_line,
+	const char *attr_name, int payload);
+
+/*!
+ * \brief Convert an SDP a_line into an rtpmap
+ *
+ * The returned value is heap-allocated and must be freed with
+ * ast_sdp_rtpmap_free()
+ *
+ * \param a_line The SDP a_line to convert
+ *
+ * \retval NULL Fail
  * \retval non-NULL Success
- * \retval NULL Failure
  *
- * \since 15
+ * \since 15.0.0
  */
-struct ast_sdp *ast_sdp_create_from_state(const struct ast_sdp_state *sdp_state);
+struct ast_sdp_rtpmap *ast_sdp_a_get_rtpmap(const struct ast_sdp_a_line *a_line);
 
+
+/*!
+ * \brief Allocate a new SDP rtpmap
+ *
+ * \param payload The RTP payload number
+ * \param encoding_name The human-readable name for the codec
+ * \param clock_rate The rate of the codec, in cycles per second
+ * \param encoding_parameters Optional codec-specific parameters (such as number of channels)
+ *
+ * \retval NULL Fail
+ * \retval non-NULL Success
+ *
+ * \since 15.0.0
+ */
+struct ast_sdp_rtpmap *ast_sdp_rtpmap_alloc(int payload, const char *encoding_name,
+	int clock_rate, const char *encoding_parameters);
+
+/*!
+ * \brief Free an SDP rtpmap
+ *
+ * \since 15.0.0
+ */
+void ast_sdp_rtpmap_free(struct ast_sdp_rtpmap *rtpmap);
+
+/*!
+ * \brief Turn an SDP into a stream topology
+ *
+ * This traverses the m-lines of the SDP and creates a stream topology, with
+ * each m-line corresponding to a stream in the created topology.
+ *
+ * \param sdp The SDP to convert
+ *
+ * \retval NULL An error occurred when converting
+ * \retval non-NULL The generated stream topology
+ *
+ * \since 15.0.0
+ */
+struct ast_stream_topology *ast_get_topology_from_sdp(const struct ast_sdp *sdp);
 #endif /* _SDP_PRIV_H */
diff --git a/include/asterisk/sdp_options.h b/include/asterisk/sdp_options.h
index 0186eea57..4b411c771 100644
--- a/include/asterisk/sdp_options.h
+++ b/include/asterisk/sdp_options.h
@@ -106,7 +106,7 @@ void ast_sdp_options_set_media_address(struct ast_sdp_options *options,
  *
  * \returns media_address
  */
-const char *ast_sdp_options_get_media_address(struct ast_sdp_options *options);
+const char *ast_sdp_options_get_media_address(const struct ast_sdp_options *options);
 
 /*!
  * \since 15.0.0
@@ -126,7 +126,7 @@ void ast_sdp_options_set_sdpowner(struct ast_sdp_options *options,
  *
  * \returns sdpowner
  */
-const char *ast_sdp_options_get_sdpowner(struct ast_sdp_options *options);
+const char *ast_sdp_options_get_sdpowner(const struct ast_sdp_options *options);
 
 /*!
  * \since 15.0.0
@@ -146,7 +146,7 @@ void ast_sdp_options_set_sdpsession(struct ast_sdp_options *options,
  *
  * \returns sdpsession
  */
-const char *ast_sdp_options_get_sdpsession(struct ast_sdp_options *options);
+const char *ast_sdp_options_get_sdpsession(const struct ast_sdp_options *options);
 
 /*!
  * \since 15.0.0
@@ -166,7 +166,7 @@ void ast_sdp_options_set_rtp_engine(struct ast_sdp_options *options,
  *
  * \returns rtp_engine
  */
-const char *ast_sdp_options_get_rtp_engine(struct ast_sdp_options *options);
+const char *ast_sdp_options_get_rtp_engine(const struct ast_sdp_options *options);
 
 /*!
  * \since 15.0.0
@@ -186,7 +186,7 @@ void ast_sdp_options_set_bind_rtp_to_media_address(struct ast_sdp_options *optio
  *
  * \returns bind_rtp_to_media_address
  */
-unsigned int ast_sdp_options_get_bind_rtp_to_media_address(struct ast_sdp_options *options);
+unsigned int ast_sdp_options_get_bind_rtp_to_media_address(const struct ast_sdp_options *options);
 
 /*!
  * \since 15.0.0
@@ -206,7 +206,7 @@ void ast_sdp_options_set_rtp_symmetric(struct ast_sdp_options *options,
  *
  * \returns rtp_symmetric
  */
-unsigned int ast_sdp_options_get_rtp_symmetric(struct ast_sdp_options *options);
+unsigned int ast_sdp_options_get_rtp_symmetric(const struct ast_sdp_options *options);
 
 /*!
  * \since 15.0.0
@@ -226,7 +226,7 @@ void ast_sdp_options_set_telephone_event(struct ast_sdp_options *options,
  *
  * \returns telephone_event
  */
-unsigned int ast_sdp_options_get_telephone_event(struct ast_sdp_options *options);
+unsigned int ast_sdp_options_get_telephone_event(const struct ast_sdp_options *options);
 
 /*!
  * \since 15.0.0
@@ -246,7 +246,7 @@ void ast_sdp_options_set_rtp_ipv6(struct ast_sdp_options *options,
  *
  * \returns rtp_ipv6
  */
-unsigned int ast_sdp_options_get_rtp_ipv6(struct ast_sdp_options *options);
+unsigned int ast_sdp_options_get_rtp_ipv6(const struct ast_sdp_options *options);
 
 /*!
  * \since 15.0.0
@@ -266,7 +266,7 @@ void ast_sdp_options_set_g726_non_standard(struct ast_sdp_options *options,
  *
  * \returns g726_non_standard
  */
-unsigned int ast_sdp_options_get_g726_non_standard(struct ast_sdp_options *options);
+unsigned int ast_sdp_options_get_g726_non_standard(const struct ast_sdp_options *options);
 
 /*!
  * \since 15.0.0
@@ -286,7 +286,7 @@ void ast_sdp_options_set_tos_audio(struct ast_sdp_options *options,
  *
  * \returns tos_audio
  */
-unsigned int ast_sdp_options_get_tos_audio(struct ast_sdp_options *options);
+unsigned int ast_sdp_options_get_tos_audio(const struct ast_sdp_options *options);
 
 /*!
  * \since 15.0.0
@@ -306,7 +306,7 @@ void ast_sdp_options_set_cos_audio(struct ast_sdp_options *options,
  *
  * \returns cos_audio
  */
-unsigned int ast_sdp_options_get_cos_audio(struct ast_sdp_options *options);
+unsigned int ast_sdp_options_get_cos_audio(const struct ast_sdp_options *options);
 
 /*!
  * \since 15.0.0
@@ -326,7 +326,7 @@ void ast_sdp_options_set_tos_video(struct ast_sdp_options *options,
  *
  * \returns tos_video
  */
-unsigned int ast_sdp_options_get_tos_video(struct ast_sdp_options *options);
+unsigned int ast_sdp_options_get_tos_video(const struct ast_sdp_options *options);
 
 /*!
  * \since 15.0.0
@@ -346,7 +346,7 @@ void ast_sdp_options_set_cos_video(struct ast_sdp_options *options,
  *
  * \returns cos_video
  */
-unsigned int ast_sdp_options_get_cos_video(struct ast_sdp_options *options);
+unsigned int ast_sdp_options_get_cos_video(const struct ast_sdp_options *options);
 
 /*!
  * \since 15.0.0
@@ -366,7 +366,7 @@ void ast_sdp_options_set_ice(struct ast_sdp_options *options,
  *
  * \returns ice
  */
-enum ast_sdp_options_ice ast_sdp_options_get_ice(struct ast_sdp_options *options);
+enum ast_sdp_options_ice ast_sdp_options_get_ice(const struct ast_sdp_options *options);
 
 /*!
  * \since 15.0.0
@@ -386,7 +386,7 @@ void ast_sdp_options_set_impl(struct ast_sdp_options *options,
  *
  * \returns impl
  */
-enum ast_sdp_options_impl ast_sdp_options_get_impl(struct ast_sdp_options *options);
+enum ast_sdp_options_impl ast_sdp_options_get_impl(const struct ast_sdp_options *options);
 
 /*!
  * \since 15.0.0
@@ -406,6 +406,25 @@ void ast_sdp_options_set_encryption(struct ast_sdp_options *options,
  *
  * \returns encryption
  */
-enum ast_sdp_options_encryption ast_sdp_options_get_encryption(struct ast_sdp_options *options);
+enum ast_sdp_options_encryption ast_sdp_options_get_encryption(const struct ast_sdp_options *options);
+
+/*!
+ * \since 15.0.0
+ * \brief Get SDP Options RTCP MUX
+ *
+ * \param options SDP Options
+ *
+ * \returns Boolean indicating if RTCP MUX is enabled.
+ */
+unsigned int ast_sdp_options_get_rtcp_mux(const struct ast_sdp_options *options);
+
+/*!
+ * \since 15.0.0
+ * \brief Set SDP Options RTCP MUX
+ *
+ * \param options SDP Options
+ * \param value Boolean that indicates if RTCP MUX should be enabled.
+ */
+void ast_sdp_options_set_rtcp_mux(struct ast_sdp_options *options, unsigned int value);
 
 #endif /* _ASTERISK_SDP_OPTIONS_H */
diff --git a/include/asterisk/sdp_state.h b/include/asterisk/sdp_state.h
index a186d7eef..7f25c2532 100644
--- a/include/asterisk/sdp_state.h
+++ b/include/asterisk/sdp_state.h
@@ -138,7 +138,7 @@ const void *ast_sdp_state_get_local_sdp_impl(struct ast_sdp_state *sdp_state);
  *
  * \since 15
  */
-void ast_sdp_state_set_remote_sdp(struct ast_sdp_state *sdp_state, struct ast_sdp *sdp);
+void ast_sdp_state_set_remote_sdp(struct ast_sdp_state *sdp_state, const struct ast_sdp *sdp);
 
 /*!
  * \brief Set the remote SDP from an Implementation