MT#56128 RTPEngine: Add options for arbitrary SDP manipulations

New section of option flags has been introduced for SDP body
attributes manipulations.

Three levels of the SDP session are concerned:
- session level (global one)
- media level - audio
- media level - video

Three different actions are supported for now:
- add
- remove

The value of the command has a wildcard matching approach.

Other attributes apart `a=` can not be edited by this functionality.
So such headers as: `c=`, `s=`, `o=` cannot be touched.

Change-Id: I939d4582839096b2399f7ded865e91ff6eb960a4
(cherry picked from commit 3f06c18793)

README.md

@@ -1765,6 +1765,145 @@ The following keys are understood:
 
 	This option is only processed in `offer` messages and ignored otherwise.
 
+**Optionally included SDP attributes manipulations:**
+
+`sdp-attr` contains a dictionary controlling various aspects of attribute lines (or `a=` lines).
+
+An intention of these option flags is to control session (global) and media session level
+attributes (`a=` lines). With help of which, it's possible to add and remove
+specific attribute lines.
+
+This does affect an outgoing SDP offer. So it's meant to manipulate body attributes,
+which RTPEngine generates during the offer processing. In other words, it manipulates
+what has been already prepared by the RTPEngine on its own, taking into account received offer.
+
+Furthermore, it's quite important to remember, that the changes, which have been
+applied to SDP body attributes, will be not quite taken into account by the RTPEngine.
+This means, it's not the same, as if they would be originally given by the session originator.
+It's just a text manipulation.
+
+That's why this kind of flags must be used with a full carefulness, because,
+if not, this can lead sometimes to the unwanted result.
+
+Usage syntax:
+
+		"sdp-attr" :
+		{
+			"<media-type>":
+			{
+				"<command>": ["<value>", "<value>"],
+				"<command>": ["<value>", "<value>"]
+			},
+			"<media-type>":
+			{
+				"<command>": ["<value>", "<value>"],
+				"<command>": ["<value>", "<value>"]
+			}
+		}
+
+Description:
+
+* `<media-type>`
+
+	Defines a level of command application. One media type can be given only once per command.
+	`<media-type>` can have one of the following values:
+
+	- `none` or `global`
+
+		Applies to the session level (global) attributes, but not to any of the
+		media session specific attributes.
+
+	- `audio`
+
+		Applies to all currently present media sessions of audio type.
+
+	- `video`
+
+		Applies to all currently present media sessions of audio type.
+
+* `<command>`
+
+	The command to be applied to the targeted attribute line(s).
+	Each command can be used multiple times within one media session scope.
+
+	- `add`
+
+		Adds a new `a=` line with a given value to the concerned media attributes list.
+		If the attribute with such value already exists within this scope of media session,
+		then no duplication is to be added, therefore the older one remains untouched
+		and nothing extra is being added.
+
+		Can take multiple values (so multiple attributes can added per one command).
+
+	- `remove`
+
+		Removes a specified `a=` line from the concerned media attributes list.
+		If such line has been not found, the attributes list remains untouched.
+
+		Can take multiple values (so multiple attributes can removed per one command).
+
+* `<value>`
+
+	The `value` doesn't take the `a=` lvalue part, only what must go after an equal sign.
+
+	For `remove` and `substitute`, the value of the command has a wildcard matching
+	using a prefix. So that, all values caught by the prefix are affected.
+
+	No wild-cards and regex expressions accepted. Only a prefix or whole value are allowed.
+
+	One should remember that some attributes are allowed to be present multiple times,
+	as for example `a=ssrc:`. Therefore the RTPEngine does not expect specified `a=` lines
+	to be unique within concerned media scope (global, audio or video).
+
+	This leads to the next point — `remove` and `substitute` commands can affect just
+	a single attribute, as well as multiple attributes, depending on the uniqueness
+	of the value in the given command.
+
+	For example, for a removal of SSRC one might want to remove all `a=ssrc:` attributes
+	regardless of their content. On the other hand, one might want to remove all attributes
+	corresponding to one SSRC only — so a removal of all `a=ssrc:123456`, for example.
+
+	Thus, in case of intention to remove multiple attribute lines related to a specific
+	scope of session parameters, one should specify a prefix as a value,
+	which would catch all of them. And vice-versa, in case of intention to remove quite
+	a specific attribute, one should consider tight uniqueness of the value (so full value).
+
+Examples:
+
+* Add a new (single) attribute line to the session (global) level:
+
+		"sdp-attr" :
+		{
+			"none" :
+			{
+				"add" : [ "sendrecv" ]
+			}
+		}
+
+* Add two new attribute lines to audio session and remove one for video session:
+
+		"sdp-attr" :
+		{
+			"audio" :
+			{
+				"add" : [ "ptime:20", "sendrecv" ]
+			},
+			"video":
+			{
+				"remove" : [ "rtpmap:101 telephone-event/8000" ]
+			}
+		}
+
+* Remove all attributes related to SSRC of the audio session:
+
+		"sdp-attr" :
+		{
+			"audio":
+			{
+				"remove": [ "ssrc:" ]
+			}
+		}
+
 An example of a complete `offer` request dictionary could be (SDP body abbreviated):
 
 	{ "command": "offer", "call-id": "cfBXzDSZqhYNcXM", "from-tag": "mS9rSAn0Cr",

daemon/call_interfaces.c

@@ -61,7 +61,8 @@ INLINE int call_ng_flags_prefix(struct sdp_ng_flags *out, str *s_ori, const char
 static void call_ng_flags_str_ht(struct sdp_ng_flags *out, str *s, void *htp);
 static void call_ng_flags_str_q_multi(struct sdp_ng_flags *out, str *s, void *qp);
 static void ng_stats_ssrc(bencode_item_t *dict, struct ssrc_hash *ht);
-
+static str *str_dup_escape(const str *s);
+static void sdp_command_free(void * p);
 
 static int call_stream_address_gstring(GString *o, struct packet_stream *ps, enum stream_address_format format) {
 	int len, ret;
@@ -605,6 +606,84 @@ INLINE void ng_osrtp_option(struct sdp_ng_flags *out, str *s, void *dummy) {
 	}
 }
 
+INLINE void ng_sdp_attr_manipulations(GQueue *sdp_attr_manipulations, bencode_item_t *value) {
+
+	if (!value || value->type != BENCODE_DICTIONARY)
+		ilog(LOG_WARN, "SDP manipulations: Wrong type for this type of command.");
+
+	for (bencode_item_t *it = value->child; it; it = it->sibling)
+	{
+		bencode_item_t *command_action = it->sibling ? it->sibling : NULL;
+		enum media_type media;
+		str media_type;
+
+		if (!command_action) /* if no action, makes no sense to continue */
+			continue;
+
+		/* detect media type */
+		if (!bencode_get_str(it, &media_type))
+			continue;
+
+		media = (!str_cmp(&media_type, "none") || !str_cmp(&media_type, "global")) ?
+				MT_UNKNOWN : codec_get_type(&media_type);
+
+		for (bencode_item_t *it_c = command_action->child; it_c; it_c = it_c->sibling)
+		{
+			bencode_item_t *command_value = it_c->sibling ? it_c->sibling : NULL;
+
+			if (!command_value) /* if no value, makes no sense to continue */
+				continue;
+
+			/* detect command type */
+			str command_type;
+			if (!bencode_get_str(it_c, &command_type))
+				continue;
+
+			struct sdp_command * command_obj;
+			command_obj = g_slice_alloc0(sizeof(*command_obj));
+			command_obj->media_type_id = media;
+
+			switch (__csh_lookup(&command_type)) {
+				case CSH_LOOKUP("add"):
+					command_obj->command_type_id = CMD_ADD;
+					break;
+				case CSH_LOOKUP("remove"):
+					command_obj->command_type_id = CMD_REM;
+					break;
+				default:
+					ilog(LOG_WARN, "SDP manipulations: Unknown SDP manipulation command type.");
+					g_slice_free1(sizeof(*command_obj), command_obj);
+					continue;
+			}
+
+			GHashTable ** ht = &command_obj->command_values;
+			*ht = g_hash_table_new_full(str_case_hash, str_case_equal, free, NULL);
+
+			for (bencode_item_t *it_v = command_value->child; it_v; it_v = it_v->sibling)
+			{
+				/* detect command value */
+				str command_value;
+				if (!bencode_get_str(it_v, &command_value))
+					continue;
+
+				str *s_copy = str_dup_escape(&command_value);
+				g_hash_table_replace(*ht, s_copy, s_copy);
+			}
+
+			/* no values - is a bad command */
+			if (g_hash_table_size(command_obj->command_values) == 0)
+			{
+				ilog(LOG_WARN, "SDP manipulations: An issue with given value(s), can't handle it.");
+				sdp_command_free(command_obj);
+				/* this command had no values, but still continue checking other commands */
+				continue;
+			} else {
+				g_queue_push_tail(sdp_attr_manipulations, command_obj);
+			}
+		}
+	}
+}
+
 INLINE void ng_el_option(struct sdp_ng_flags *out, str *s, void *dummy) {
 	switch (__csh_lookup(s)) {
 		case CSH_LOOKUP("off"):
@@ -1258,6 +1337,12 @@ static void call_ng_main_flags(struct sdp_ng_flags *out, str *key, bencode_item_
 			for (bencode_item_t *it = value->child; it && diridx < 2; it = it->sibling)
 				bencode_get_str(it, &out->direction[diridx++]);
 			break;
+		case CSH_LOOKUP("sdp-attr"):
+		case CSH_LOOKUP("SDP-attr"):
+			if (value->type != BENCODE_DICTIONARY)
+				break;
+			ng_sdp_attr_manipulations(&out->sdp_attr_manipulations, value);
+			break;
 		case CSH_LOOKUP("received from"):
 		case CSH_LOOKUP("received-from"):
 			if (value->type != BENCODE_LIST)
@@ -1611,6 +1696,14 @@ static void call_ng_process_flags(struct sdp_ng_flags *out, bencode_item_t *inpu
 	call_ng_flags_init(out, opmode);
 	call_ng_dict_iter(out, input, call_ng_main_flags);
 }
+
+static void sdp_command_free(void * p)
+{
+	struct sdp_command * attr = p;
+	g_hash_table_destroy(attr->command_values);
+	g_slice_free1(sizeof(*attr), attr);
+}
+
 void call_ng_free_flags(struct sdp_ng_flags *flags) {
 	if (flags->codec_except)
 		g_hash_table_destroy(flags->codec_except);
@@ -1622,6 +1715,8 @@ void call_ng_free_flags(struct sdp_ng_flags *flags) {
 		g_hash_table_destroy(flags->sdes_only);
 	if (flags->frequencies)
 		g_array_free(flags->frequencies, true);
+
+	g_queue_clear_full(&flags->sdp_attr_manipulations, sdp_command_free);
 	g_queue_clear_full(&flags->from_tags, free);
 	g_queue_clear_full(&flags->codec_offer, free);
 	g_queue_clear_full(&flags->codec_transcode, free);

daemon/sdp.c

@@ -283,15 +283,85 @@ struct sdp_attribute {	/* example: a=rtpmap:8 PCMA/8000 */
 static char __id_buf[6*2 + 1]; // 6 hex encoded characters
 const str rtpe_instance_id = STR_CONST_INIT(__id_buf);
 
-
+static void attr_free(void *p);
 static void attr_insert(struct sdp_attributes *attrs, struct sdp_attribute *attr);
 
 
-static void attr_free(void *p);
+INLINE void chopper_append_c(struct sdp_chopper *c, const char *s);
 
-static void append_attr_to_gstring(GString *s, const char * name, const str * value);
-static void append_attr_char_to_gstring(GString *s, const char * name, const char * value);
-static void append_attr_int_to_gstring(GString *s, const char * name, const int * value);
+
+static int sdp_manipulate_command_cmp(gconstpointer a, gconstpointer b) {
+	const struct sdp_command * sc = a;
+	const struct sdp_command_fictitious * sc_lookup = b;
+	if (sc->command_type_id != sc_lookup->command_type_id)
+		return 1;
+	if (sc->media_type_id != sc_lookup->media_type_id)
+		return 1;
+	/* here expected only lookup by one value */
+	if (NULL != sc_lookup->command_value) {
+		if (!g_hash_table_lookup(sc->command_values, sc_lookup->command_value))
+			return 1;
+	}
+	return 0;
+}
+
+/**
+ * Checks whether a given type of SDP manipulation exists for a given session level.
+ */
+static int sdp_manipulate_check(enum command_type command_type, GQueue *sdp_manipulate,
+		enum media_type media_type, str *attr_name) {
+	/* for now we only support session lvl, audio and media streams */
+	if (media_type == MT_OTHER)
+	{
+		ilog(LOG_WARNING, "SDP manipulations: Unsupported media type '%d', can't manipulate these attributes.",
+				media_type);
+		return 0;
+	}
+
+	struct sdp_command_fictitious fictitious = {command_type, media_type, attr_name};
+
+	if (g_queue_find_custom(sdp_manipulate, &fictitious, sdp_manipulate_command_cmp))
+		return 1;
+
+	return 0;
+}
+
+/**
+ * Adds values into a requested session level (global, audio, video)
+ */
+static void sdp_manipulations_add(struct sdp_chopper *chop, GQueue *sdp_manipulate,
+		enum media_type media_type) {
+	for (GList *l = sdp_manipulate->head; l; l = l->next)
+	{
+		struct sdp_command * command = l->data;
+		GList *ll = NULL;
+
+		if (command->command_type_id != CMD_ADD ||
+			command->media_type_id != media_type)
+			continue;
+
+		/* TODO: add lookup if not already in the body */
+
+		ll = g_hash_table_get_values(command->command_values);
+		for (GList *l = ll; l; l = l->next)
+		{
+			str * value = l->data;
+			chopper_append_c(chop, "a=");
+			chopper_append_c(chop, value->s);
+			chopper_append_c(chop, "\r\n");
+		}
+
+		if (ll)
+			g_list_free(ll);
+	}
+}
+
+static void append_attr_to_gstring(GString *s, char * name, const str * value,
+		struct sdp_ng_flags *flags, enum media_type media_type);
+static void append_attr_char_to_gstring(GString *s, char * name, const char * value,
+		struct sdp_ng_flags *flags, enum media_type media_type);
+static void append_attr_int_to_gstring(GString *s, char * name, const int * value,
+		struct sdp_ng_flags *flags, enum media_type media_type);
 
 INLINE struct sdp_attribute *attr_get_by_id(struct sdp_attributes *a, int id) {
 	return g_hash_table_lookup(a->id_hash, &id);
@@ -1123,7 +1193,6 @@ int sdp_parse(str *body, GQueue *sessions, const struct sdp_ng_flags *flags) {
 	struct sdp_attributes *attrs;
 	struct sdp_attribute *attr;
 	str *adj_s;
-	GQueue *attr_queue;
 
 	b = body->s;
 	end = str_end(body);
@@ -2167,8 +2236,9 @@ void sdp_chopper_destroy_ret(struct sdp_chopper *chop, str *ret) {
 	sdp_chopper_destroy(chop);
 }
 
+/* processing existing session attributes (those present in offer/answer) */
 static int process_session_attributes(struct sdp_chopper *chop, struct sdp_attributes *attrs,
-		struct sdp_ng_flags *flags)
+		struct sdp_ng_flags *flags, GQueue *sdp_manipulate)
 {
 	GList *l;
 	struct sdp_attribute *attr;
@@ -2176,6 +2246,10 @@ static int process_session_attributes(struct sdp_chopper *chop, struct sdp_attri
 	for (l = attrs->list.head; l; l = l->next) {
 		attr = l->data;
 
+		/* if attr is supposed to be removed don't add to the chop->output */
+		if (sdp_manipulate_check(CMD_REM, sdp_manipulate, MT_UNKNOWN, &attr->line_value))
+			goto strip;
+
 		switch (attr->attr) {
 			case ATTR_ICE:
 			case ATTR_ICE_UFRAG:
@@ -2239,8 +2313,9 @@ strip:
 	return 0;
 }
 
+/* processing existing media attributes (those present in offer/answer) */
 static int process_media_attributes(struct sdp_chopper *chop, struct sdp_media *sdp,
-		struct sdp_ng_flags *flags, struct call_media *media)
+		struct sdp_ng_flags *flags, struct call_media *media, GQueue *sdp_manipulate)
 {
 	GList *l;
 	struct sdp_attributes *attrs = &sdp->attributes;
@@ -2253,6 +2328,10 @@ static int process_media_attributes(struct sdp_chopper *chop, struct sdp_media *
 		if (MEDIA_ISSET(media, GENERATOR))
 			goto strip;
 
+		/* if attr is supposed to be removed don't add to the chop->output */
+		if (sdp_manipulate_check(CMD_REM, sdp_manipulate, sdp->media_type_id, &attr->line_value))
+			goto strip;
+
 		switch (attr->attr) {
 			case ATTR_ICE:
 			case ATTR_ICE_UFRAG:
@@ -2394,7 +2473,7 @@ out:
 
 static void insert_candidate(GString *s, struct stream_fd *sfd,
 		unsigned int type_pref, unsigned int local_pref, enum ice_candidate_type type,
-		struct sdp_ng_flags *flags)
+		struct sdp_ng_flags *flags, struct sdp_media *sdp_media)
 {
 	unsigned long priority;
 	struct packet_stream *ps = sfd->stream;
@@ -2416,20 +2495,21 @@ static void insert_candidate(GString *s, struct stream_fd *sfd,
 		insert_raddr_rport(s_dst, sfd, flags);
 
 	/* append to the chop->output */
-	append_attr_to_gstring(s, s_dst->str, NULL);
+	append_attr_to_gstring(s, s_dst->str, NULL, flags,
+			(sdp_media ? sdp_media->media_type_id : MT_UNKNOWN));
 	g_string_free(s_dst, TRUE);
 }
 
 static void insert_sfd_candidates(GString *s, struct packet_stream *ps,
 		unsigned int type_pref, unsigned int local_pref, enum ice_candidate_type type,
-		struct sdp_ng_flags *flags)
+		struct sdp_ng_flags *flags, struct sdp_media *sdp_media)
 {
 	GList *l;
 	struct stream_fd *sfd;
 
 	for (l = ps->sfds.head; l; l = l->next) {
 		sfd = l->data;
-		insert_candidate(s, sfd, type_pref, local_pref, type, flags);
+		insert_candidate(s, sfd, type_pref, local_pref, type, flags, sdp_media);
 
 		if (local_pref != -1)
 			local_pref++;
@@ -2463,9 +2543,9 @@ static void insert_candidates(GString *s, struct packet_stream *rtp, struct pack
 
 	if (ag && AGENT_ISSET(ag, COMPLETED)) {
 		ifa = rtp->selected_sfd->local_intf;
-		insert_candidate(s, rtp->selected_sfd, type_pref, ifa->unique_id, cand_type, flags);
+		insert_candidate(s, rtp->selected_sfd, type_pref, ifa->unique_id, cand_type, flags, sdp_media);
 		if (rtcp) /* rtcp-mux only possible in answer */
-			insert_candidate(s, rtcp->selected_sfd, type_pref, ifa->unique_id, cand_type, flags);
+			insert_candidate(s, rtcp->selected_sfd, type_pref, ifa->unique_id, cand_type, flags, sdp_media);
 
 		if (flags->opmode == OP_OFFER && AGENT_ISSET(ag, CONTROLLING)) {
 			GQueue rc;
@@ -2483,7 +2563,7 @@ static void insert_candidates(GString *s, struct packet_stream *rtp, struct pack
 						sockaddr_print_buf(&cand->endpoint.address), cand->endpoint.port);
 			}
 			/* append to the chop->output */
-			append_attr_to_gstring(s, s_dst->str, NULL);
+			append_attr_to_gstring(s, s_dst->str, NULL, flags, (sdp_media ? sdp_media->media_type_id : MT_UNKNOWN));
 			g_string_free(s_dst, TRUE);
 
 			g_queue_clear(&rc);
@@ -2491,13 +2571,14 @@ static void insert_candidates(GString *s, struct packet_stream *rtp, struct pack
 		return;
 	}
 
-	insert_sfd_candidates(s, rtp, type_pref, local_pref, cand_type, flags);
+	insert_sfd_candidates(s, rtp, type_pref, local_pref, cand_type, flags, sdp_media);
 
 	if (rtcp) /* rtcp-mux only possible in answer */
-		insert_sfd_candidates(s, rtcp, type_pref, local_pref, cand_type, flags);
+		insert_sfd_candidates(s, rtcp, type_pref, local_pref, cand_type, flags, sdp_media);
 }
 
-static void insert_dtls(GString *s, struct call_media *media, struct dtls_connection *dtls) {
+static void insert_dtls(GString *s, struct call_media *media, struct dtls_connection *dtls,
+		struct sdp_ng_flags *flags) {
 	unsigned char *p;
 	int i;
 	const struct dtls_hash_func *hf;
@@ -2541,7 +2622,7 @@ static void insert_dtls(GString *s, struct call_media *media, struct dtls_connec
 	else if (MEDIA_ISSET(media, SETUP_ACTIVE))
 		actpass = "active";
 
-	append_attr_char_to_gstring(s, "a=setup:", actpass);
+	append_attr_char_to_gstring(s, "a=setup:", actpass, flags, media->type_id);
 
 	/* prepare fingerprint */
 	g_string_append(s_dst, "a=fingerprint:");
@@ -2554,7 +2635,7 @@ static void insert_dtls(GString *s, struct call_media *media, struct dtls_connec
 	g_string_truncate(s_dst, s_dst->len - 1);
 
 	/* append to the chop->output */
-	append_attr_to_gstring(s, s_dst->str, NULL);
+	append_attr_to_gstring(s, s_dst->str, NULL, flags, media->type_id);
 	g_string_free(s_dst, TRUE);
 
 	if (dtls) {
@@ -2567,7 +2648,7 @@ static void insert_dtls(GString *s, struct call_media *media, struct dtls_connec
 			g_string_append_printf(s_dst, "%02x", *p++);
 
 		/* append to the chop->output */
-		append_attr_to_gstring(s, s_dst->str, NULL);
+		append_attr_to_gstring(s, s_dst->str, NULL, flags, media->type_id);
 		g_string_free(s_dst, TRUE);
 	}
 }
@@ -2623,16 +2704,18 @@ static void insert_crypto1(GString *s, struct call_media *media, struct crypto_p
 		g_string_append(s_dst, " UNAUTHENTICATED_SRTP");
 
 	/* append to the chop->output */
-	append_attr_to_gstring(s, s_dst->str, NULL);
+	append_attr_to_gstring(s, s_dst->str, NULL, flags, media->type_id);
 	g_string_free(s_dst, TRUE);
 }
+
 static void insert_crypto(GString *s, struct call_media *media, struct sdp_ng_flags *flags) {
 	if (!media->protocol || !media->protocol->srtp)
 		return;
 	for (GList *l = media->sdes_out.head; l; l = l->next)
 		insert_crypto1(s, media, l->data, flags);
 }
-static void insert_rtcp_attr(GString *s, struct packet_stream *ps, const struct sdp_ng_flags *flags) {
+static void insert_rtcp_attr(GString *s, struct packet_stream *ps, struct sdp_ng_flags *flags,
+		struct sdp_media *sdp_media) {
 	if (flags && flags->no_rtcp_attr)
 		return;
 	GString * s_dst = g_string_new("");
@@ -2650,7 +2733,7 @@ static void insert_rtcp_attr(GString *s, struct packet_stream *ps, const struct
 		g_string_append_printf(s_dst, " IN %.*s", len, buf);
 	}
 	/* append to the chop->output */
-	append_attr_to_gstring(s, s_dst->str, NULL);
+	append_attr_to_gstring(s, s_dst->str, NULL, flags, (sdp_media ? sdp_media->media_type_id : MT_UNKNOWN));
 	g_string_free(s_dst, TRUE);
 }
 
@@ -2709,8 +2792,19 @@ const char *sdp_get_sendrecv(struct call_media *media) {
 }
 
 /* A function used to append attributes to the output chop */
-static void append_attr_to_gstring(GString *s, const char * name, const str * value)
+static void append_attr_to_gstring(GString *s, char * name, const str * value,
+		struct sdp_ng_flags *flags, enum media_type media_type)
 {
+	str attr;
+	str_init(&attr, name);
+	GQueue *sdp_manipulate = &flags->sdp_attr_manipulations;
+
+	/* take into account SDP arbitary manipulations */
+	if (sdp_manipulate_check(CMD_REM, sdp_manipulate, media_type, &attr)) {
+		ilog(LOG_DEBUG, "Cannot insert: '%s' because prevented by SDP manipulations", name);
+		return;
+	}
+
 	/* attr name */
 	if (name[0] != 'a' && name[1] != '=') {
 		g_string_append(s, "a=");
@@ -2724,8 +2818,19 @@ static void append_attr_to_gstring(GString *s, const char * name, const str * va
 }
 
 /* A function used to append attributes to the output chop */
-static void append_attr_char_to_gstring(GString *s, const char * name, const char * value)
+static void append_attr_char_to_gstring(GString *s, char * name, const char * value,
+		struct sdp_ng_flags *flags, enum media_type media_type)
 {
+	str attr;
+	str_init(&attr, name);
+	GQueue *sdp_manipulate = &flags->sdp_attr_manipulations;
+
+	/* take into account SDP arbitary manipulations */
+	if (sdp_manipulate_check(CMD_REM, sdp_manipulate, media_type, &attr)) {
+		ilog(LOG_DEBUG, "Cannot insert: '%s' because prevented by SDP manipulations", name);
+		return;
+	}
+
 	/* attr name */
 	if (name[0] != 'a' && name[1] != '=') {
 		g_string_append(s, "a=");
@@ -2739,8 +2844,19 @@ static void append_attr_char_to_gstring(GString *s, const char * name, const cha
 }
 
 /* A function used to append attributes to the output chop */
-static void append_attr_int_to_gstring(GString *s, const char * name, const int * value)
+static void append_attr_int_to_gstring(GString *s, char * name, const int * value,
+		struct sdp_ng_flags *flags, enum media_type media_type)
 {
+	str attr;
+	str_init(&attr, name);
+	GQueue *sdp_manipulate = &flags->sdp_attr_manipulations;
+
+	/* take into account SDP arbitary manipulations */
+	if (sdp_manipulate_check(CMD_REM, sdp_manipulate, media_type, &attr)) {
+		ilog(LOG_DEBUG, "Cannot insert: '%s' because prevented by SDP manipulations", name);
+		return;
+	}
+
 	/* attr name */
 	if (name[0] != 'a' && name[1] != '=') {
 		g_string_append(s, "a=");
@@ -2753,12 +2869,8 @@ static void append_attr_int_to_gstring(GString *s, const char * name, const int
 	g_string_append(s, "\r\n");
 }
 
-void print_sendrecv(GString *s, struct call_media *media) {
-	append_attr_to_gstring(s, sdp_get_sendrecv(media), NULL);
-}
-
 struct packet_stream *print_rtcp(GString *s, struct call_media *media, GList *rtp_ps_link,
-		struct sdp_ng_flags *flags)
+		struct sdp_ng_flags *flags, struct sdp_media *sdp_media)
 {
 	struct packet_stream *ps = rtp_ps_link->data;
 	struct packet_stream *ps_rtcp = NULL;
@@ -2778,14 +2890,14 @@ struct packet_stream *print_rtcp(GString *s, struct call_media *media, GList *rt
 					|| ((flags->opmode == OP_OFFER || flags->opmode == OP_REQUEST)
 						&& flags->rtcp_mux_require)))
 		{
-			insert_rtcp_attr(s, ps, flags);
-			append_attr_to_gstring(s, "a=rtcp-mux", NULL);
+			insert_rtcp_attr(s, ps, flags, sdp_media);
+			append_attr_to_gstring(s, "a=rtcp-mux", NULL, flags, media->type_id);
 			ps_rtcp = NULL;
 		}
 		else if (ps_rtcp && (!flags || flags->ice_option != ICE_FORCE_RELAY)) {
-			insert_rtcp_attr(s, ps_rtcp, flags);
+			insert_rtcp_attr(s, ps_rtcp, flags, sdp_media);
 			if (MEDIA_ISSET(media, RTCP_MUX))
-				append_attr_to_gstring(s, "a=rtcp-mux", NULL);
+				append_attr_to_gstring(s, "a=rtcp-mux", NULL, flags, media->type_id);
 		}
 	}
 	else
@@ -2801,9 +2913,9 @@ static void print_sdp_session_section(GString *s, struct sdp_ng_flags *flags,
 	bool media_has_ice_lite_self = MEDIA_ISSET(call_media, ICE_LITE_SELF);
 
 	if (flags->loop_protect)
-		append_attr_to_gstring(s, "a=rtpengine:", &rtpe_instance_id);
+		append_attr_to_gstring(s, "a=rtpengine:", &rtpe_instance_id, flags, MT_UNKNOWN);
 	if (media_has_ice && media_has_ice_lite_self)
-		append_attr_to_gstring(s, "a=ice-lite", NULL);
+		append_attr_to_gstring(s, "a=ice-lite", NULL, flags, MT_UNKNOWN);
 }
 
 static struct packet_stream *print_sdp_media_section(GString *s, struct call_media *media,
@@ -2815,9 +2927,9 @@ static struct packet_stream *print_sdp_media_section(GString *s, struct call_med
 	struct packet_stream *ps_rtcp = NULL;
 
 	if (media->media_id.s)
-		append_attr_to_gstring(s, "a=mid:", &media->media_id);
+		append_attr_to_gstring(s, "a=mid:", &media->media_id, flags, media->type_id);
 	if (media->label.len && flags && flags->siprec)
-		append_attr_to_gstring(s, "a=label:", &media->label);
+		append_attr_to_gstring(s, "a=label:", &media->label, flags, media->type_id);
 
 	if (is_active) {
 		if (proto_is_rtp(media->protocol))
@@ -2825,31 +2937,40 @@ static struct packet_stream *print_sdp_media_section(GString *s, struct call_med
 
 		insert_sdp_attributes(s, media);
 
+		/* print sendrecv */
 		if (!flags || !flags->original_sendrecv)
-			print_sendrecv(s, media);
+			append_attr_to_gstring(s, (char*)sdp_get_sendrecv(media), NULL, flags,
+					media->type_id);
 
-		ps_rtcp = print_rtcp(s, media, rtp_ps_link, flags);
+		ps_rtcp = print_rtcp(s, media, rtp_ps_link, flags, sdp_media);
 
 		insert_crypto(s, media, flags);
-		insert_dtls(s, media, dtls_ptr(rtp_ps->selected_sfd));
+		insert_dtls(s, media, dtls_ptr(rtp_ps->selected_sfd), flags);
 
 		if (proto_is_rtp(media->protocol) && media->ptime) {
-			append_attr_int_to_gstring(s, "a=ptime:", &media->ptime);
+			append_attr_int_to_gstring(s, "a=ptime:", &media->ptime, flags,
+					media->type_id);
 		}
 
 		if (MEDIA_ISSET(media, ICE) && media->ice_agent) {
-			append_attr_to_gstring(s, "a=ice-ufrag:", &media->ice_agent->ufrag[1]);
-			append_attr_to_gstring(s, "a=ice-pwd:", &media->ice_agent->pwd[1]);
+			append_attr_to_gstring(s, "a=ice-ufrag:", &media->ice_agent->ufrag[1], flags,
+					media->type_id);
+			append_attr_to_gstring(s, "a=ice-pwd:", &media->ice_agent->pwd[1], flags,
+					media->type_id);
 		}
 
-		if (MEDIA_ISSET(media, TRICKLE_ICE) && media->ice_agent)
-			append_attr_to_gstring(s, "a=ice-options:trickle", NULL);
-		if (MEDIA_ISSET(media, ICE))
+		if (MEDIA_ISSET(media, TRICKLE_ICE) && media->ice_agent) {
+			append_attr_to_gstring(s, "a=ice-options:trickle", NULL, flags,
+					media->type_id);
+		}
+		if (MEDIA_ISSET(media, ICE)) {
 			insert_candidates(s, rtp_ps, ps_rtcp, flags, sdp_media);
+		}
 	}
 
-	if ((MEDIA_ISSET(media, TRICKLE_ICE) && media->ice_agent) || force_end_of_ice)
-		append_attr_to_gstring(s, "a=end-of-candidates", NULL);
+	if ((MEDIA_ISSET(media, TRICKLE_ICE) && media->ice_agent) || force_end_of_ice) {
+		append_attr_to_gstring(s, "a=end-of-candidates", NULL, flags, media->type_id);
+	}
 
 	return ps_rtcp;
 }
@@ -2864,6 +2985,8 @@ static const char *replace_sdp_media_section(struct sdp_chopper *chop, struct ca
 
 	bool is_active = true;
 
+	GQueue *sdp_manipulate = &flags->sdp_attr_manipulations;
+
 	if (flags->ice_option != ICE_FORCE_RELAY && call_media->type_id != MT_MESSAGE) {
 		err = "failed to replace media type";
 		if (replace_media_type(chop, sdp_media, call_media))
@@ -2899,7 +3022,7 @@ static const char *replace_sdp_media_section(struct sdp_chopper *chop, struct ca
 	}
 
 	err = "failed to process media attributes";
-	if (process_media_attributes(chop, sdp_media, flags, call_media))
+	if (process_media_attributes(chop, sdp_media, flags, call_media, sdp_manipulate))
 		goto error;
 
 	copy_up_to_end_of(chop, &sdp_media->s);
@@ -2932,6 +3055,8 @@ int sdp_replace(struct sdp_chopper *chop, GQueue *sessions, struct call_monologu
 	m = monologue->medias.head;
 	media_index = 1;
 
+	GQueue *sdp_manipulate = &flags->sdp_attr_manipulations;
+
 	for (l = sessions->head; l; l = l->next) {
 		session = l->data;
 		err = "no matching session media";
@@ -3020,7 +3145,7 @@ int sdp_replace(struct sdp_chopper *chop, GQueue *sessions, struct call_monologu
 
 		if (!MEDIA_ISSET(call_media, PASSTHRU)) {
 			err = "failed to process session attributes";
-			if (process_session_attributes(chop, &session->attributes, flags))
+			if (process_session_attributes(chop, &session->attributes, flags, sdp_manipulate))
 				goto error;
 		}
 
@@ -3029,6 +3154,10 @@ int sdp_replace(struct sdp_chopper *chop, GQueue *sessions, struct call_monologu
 		/* add a list of important attrs to the session section */
 		print_sdp_session_section(chop->output, flags, call_media);
 
+		/* ADD arbitary SDP manipulations for a session sessions */
+		if (sdp_manipulate_check(CMD_ADD, sdp_manipulate, MT_UNKNOWN, NULL))
+			sdp_manipulations_add(chop, sdp_manipulate, MT_UNKNOWN);
+
 		for (k = session->media_streams.head; k; k = k->next) {
 			sdp_media = k->data;
 
@@ -3102,6 +3231,10 @@ int sdp_replace(struct sdp_chopper *chop, GQueue *sessions, struct call_monologu
 				chopper_append_c(chop, "\r\n");
 			}
 
+			/* ADD arbitary SDP manipulations for audio/video media sessions */
+			if (sdp_manipulate_check(CMD_ADD, sdp_manipulate, sdp_media->media_type_id, NULL))
+				sdp_manipulations_add(chop, sdp_manipulate, sdp_media->media_type_id);
+
 			media_index++;
 			m = m->next;
 		}

include/call_interfaces.h

@@ -10,7 +10,6 @@
 #include "call.h"
 
 
-
 struct call;
 struct call_stats;
 struct streambuf_stream;
@@ -58,6 +57,7 @@ struct sdp_ng_flags {
 	GQueue sdes_order;		/* the order, in which crypto suites are being added to the SDP */
 	GQueue sdes_offerer_pref;	/* preferred crypto suites to be selected for the offerer */
 	str dtls_fingerprint;
+	GQueue sdp_attr_manipulations;	/* commands to manipulate attr lines in SDP */
 	enum {
 		ICE_DEFAULT = 0,
 		ICE_REMOVE,

include/sdp.h

@@ -1,11 +1,31 @@
 #ifndef _SDP_H_
 #define _SDP_H_
 
+
 #include <glib.h>
 #include "str.h"
 #include "call.h"
 #include "media_socket.h"
 
+enum command_type {
+	CMD_ADD = 0,
+	CMD_REM,
+	CMD_SUBST,
+};
+
+/* command to manipulate attr in SDP body */
+struct sdp_command {
+	enum command_type command_type_id;	/* command to apply */
+	enum media_type media_type_id;		/* scope (session, media audio, media video) */
+	GHashTable * command_values;		/* a list of command values, values in str format */
+};
+
+/* This one is used only for lookups */
+struct sdp_command_fictitious {
+	enum command_type command_type_id;
+	enum media_type media_type_id;
+	str * command_value;
+};
 
 struct ice_candidate;
 

t/auto-daemon-tests.pl

@@ -77,9 +77,6 @@ sub stun_succ {
 	return $packet;
 };
 
-
-
-
 new_call;
 
 offer('legacy OSRTP offer, control',
@@ -15370,6 +15367,314 @@ a=rtcp:PORT
 a=crypto:3 AES_256_CM_HMAC_SHA1_80 inline:CRYPTO256
 SDP
 
+# Arbitary SDP manipulations
+
+new_call;
+
+offer('SDP attr manipulations - remove a= line on media audio', { ICE => 'remove', DTLS => 'off', SDES => [ 'nonew' ], 'sdp-attr' => { audio => { remove => ['test'] } }}, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio 2000 RTP/SAVP 0
+c=IN IP4 198.51.100.1
+a=sendrecv
+a=test
+----------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio PORT RTP/SAVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+answer('SDP attr manipulations - remove a= line on media audio', { ICE => 'remove' }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio 2002 RTP/SAVP 0
+c=IN IP4 198.51.100.3
+a=sendrecv
+--------------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio PORT RTP/SAVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+new_call;
+
+offer('SDP attr manipulations - remove a= line on global session', { ICE => 'remove', DTLS => 'off', SDES => [ 'nonew' ], 'sdp-attr' => { none => { remove => ['test'] } }}, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+a=test
+m=audio 2000 RTP/SAVP 0
+c=IN IP4 198.51.100.1
+a=sendrecv
+----------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio PORT RTP/SAVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+answer('SDP attr manipulations - remove a= line on global session', { ICE => 'remove' }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio 2002 RTP/SAVP 0
+c=IN IP4 198.51.100.3
+a=sendrecv
+--------------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio PORT RTP/SAVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+new_call;
+
+offer('SDP attr manipulations - remove a= line on global session and media audio', { ICE => 'remove', DTLS => 'off', SDES => [ 'nonew' ], 'sdp-attr' => { audio => { remove => ['test2'] }, none => { remove => ['test1'] } }}, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+a=test1
+m=audio 2000 RTP/SAVP 0
+c=IN IP4 198.51.100.1
+a=sendrecv
+a=test2
+----------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio PORT RTP/SAVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+answer('SDP attr manipulations - remove a= line on global session and media audio', { ICE => 'remove' }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio 2002 RTP/SAVP 0
+c=IN IP4 198.51.100.3
+a=sendrecv
+--------------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio PORT RTP/SAVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+new_call;
+
+offer('SDP attr manipulations - add a= line on global session and media audio', { ICE => 'remove', DTLS => 'off', SDES => [ 'nonew' ], 'sdp-attr' => { audio => { add => ['test1'] }, none => { add => ['test2'] } }}, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio 2000 RTP/SAVP 0
+c=IN IP4 198.51.100.1
+a=sendrecv
+----------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+a=test2
+m=audio PORT RTP/SAVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+a=test1
+SDP
+
+answer('SDP attr manipulations - add a= line on global session and media audio', { ICE => 'remove' }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio 2002 RTP/SAVP 0
+c=IN IP4 198.51.100.3
+a=sendrecv
+--------------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio PORT RTP/SAVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+new_call;
+
+offer('SDP attr manipulations - add a= line for media audio, two times', { ICE => 'remove', DTLS => 'off', SDES => [ 'nonew' ], 'sdp-attr' => { audio => { add => ['test1', 'test2'] } }}, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio 2000 RTP/SAVP 0
+c=IN IP4 198.51.100.1
+a=sendrecv
+----------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio PORT RTP/SAVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+a=test1
+a=test2
+SDP
+
+answer('SDP attr manipulations - add a= line for media audio, two times', { ICE => 'remove' }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio 2002 RTP/SAVP 0
+c=IN IP4 198.51.100.3
+a=sendrecv
+--------------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio PORT RTP/SAVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+new_call;
+
+offer('SDP attr manipulations - add a= line for media audio and remove one', { ICE => 'remove', DTLS => 'off', SDES => [ 'nonew' ], 'sdp-attr' => { audio => { add => ['test1'], remove => ['test2'] } }}, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio 2000 RTP/SAVP 0
+c=IN IP4 198.51.100.1
+a=sendrecv
+a=test2
+----------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio PORT RTP/SAVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+a=test1
+SDP
+
+answer('SDP attr manipulations - add a= line for media audio and remove one', { ICE => 'remove' }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio 2002 RTP/SAVP 0
+c=IN IP4 198.51.100.3
+a=sendrecv
+--------------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio PORT RTP/SAVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+new_call;
+
+offer('SDP attr manipulations - remove two a= lines from global session level', { ICE => 'remove', DTLS => 'off', SDES => [ 'nonew' ], 'sdp-attr' => { none => { remove => ['test1', 'test2'] } }}, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+a=test1
+a=test2
+m=audio 2000 RTP/SAVP 0
+c=IN IP4 198.51.100.1
+a=sendrecv
+----------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio PORT RTP/SAVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+answer('SDP attr manipulations - remove two a= lines from global session level', { ICE => 'remove' }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio 2002 RTP/SAVP 0
+c=IN IP4 198.51.100.3
+a=sendrecv
+--------------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio PORT RTP/SAVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
 # codec masking gh#664
 
 new_call;