chan_sip: Add dialplan function SIP_HEADERS

Syntax: SIP_HEADERS([prefix])

If the argument is specified, only the headers matching the given prefix
are returned.

The function returns a comma-separated list of SIP header names from an
incoming INVITE message. Multiple headers with the same name are included
in the list only once. The returned list can be iterated over using the
functions POP() and SIP_HEADER().

For example, '${SIP_HEADERS(Co)}' might return the string
'Contact,Content-Length,Content-Type'.

Practical use is rather '${SIP_HEADERS(X-)}' to enumerate optional
extended headers sent by a peer.

ASTERISK-27163

Change-Id: I2076d3893d03a2f82429f393b5b46db6cf68a267

1 files changed, 120 insertions, 1 deletions

diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index beaa3de0b..941a1e96d 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -380,6 +380,37 @@
 			<para>Please observe that contents of the SDP (an attachment to the
 			SIP request) can't be accessed with this function.</para>
 		</description>
+		<see-also>
+			<ref type="function">SIP_HEADERS</ref>
+		</see-also>
+	</function>
+	<function name="SIP_HEADERS" language="en_US">
+		<synopsis>
+			Gets the list of SIP header names from an incoming INVITE message.
+		</synopsis>
+		<syntax>
+			<parameter name="prefix">
+				<para>If specified, only the headers matching the given prefix are returned.</para>
+			</parameter>
+		</syntax>
+		<description>
+			<para>Returns a comma-separated list of header names (without values) from the
+			INVITE message that originated the current channel. Multiple headers with the
+			same name are included in the list only once. The returned list can be iterated
+			over using the functions POP() and SIP_HEADER().</para>
+			<para>For example, <literal>${SIP_HEADERS(Co)}</literal> might return
+			<literal>Contact,Content-Length,Content-Type</literal>. As a practical example,
+			you may use <literal>${SIP_HEADERS(X-)}</literal> to enumerate optional extended
+			headers.</para>
+			<para>This function does not access headers from the incoming SIP REFER message;
+			see the documentation of the function SIP_HEADER for how to access them.</para>
+			<para>Please observe that contents of the SDP (an attachment to the
+			SIP request) can't be accessed with this function.</para>
+		</description>
+		<see-also>
+			<ref type="function">SIP_HEADER</ref>
+			<ref type="function">POP</ref>
+		</see-also>
 	</function>
 	<function name="SIPPEER" language="en_US">
 		<synopsis>
@@ -22995,6 +23026,7 @@ static int func_header_read(struct ast_channel *chan, const char *function, char
 {
 	struct sip_pvt *p;
 	const char *content = NULL;
+	char *mutable_data = ast_strdupa(data);
 	AST_DECLARE_APP_ARGS(args,
 		AST_APP_ARG(header);
 		AST_APP_ARG(number);
@@ -23018,7 +23050,7 @@ static int func_header_read(struct ast_channel *chan, const char *function, char
 		return -1;
 	}
 
-	AST_STANDARD_APP_ARGS(args, data);
+	AST_STANDARD_APP_ARGS(args, mutable_data);
 	if (!args.number) {
 		number = 1;
 	} else {
@@ -23054,6 +23086,91 @@ static struct ast_custom_function sip_header_function = {
 	.read = func_header_read,
 };
 
+/*! \brief Read unique list of SIP headers (dialplan function) */
+static int func_headers_read2(struct ast_channel *chan, const char *function, char *data, struct ast_str **buf, ssize_t maxlen)
+{
+	int i;
+	struct sip_pvt *pvt;
+	char *mutable_data = ast_strdupa(data);
+	struct ast_str *token = ast_str_alloca(100);
+	AST_DECLARE_APP_ARGS(args,
+		AST_APP_ARG(pattern);
+	);
+
+	if (!chan) {
+		return -1;
+	}
+
+	ast_channel_lock(chan);
+
+	if (!IS_SIP_TECH(ast_channel_tech(chan))) {
+		ast_log(LOG_WARNING, "This function can only be used on SIP channels.\n");
+		ast_channel_unlock(chan);
+		return -1;
+	}
+
+	pvt = ast_channel_tech_pvt(chan);
+	if (!pvt) {
+		ast_channel_unlock(chan);
+		return -1;
+	}
+
+	AST_STANDARD_APP_ARGS(args, mutable_data);
+	if (!args.pattern || strcmp(args.pattern, "*") == 0) {
+		args.pattern = "";
+	}
+
+	for (i = 0; i < pvt->initreq.headers; i++) {
+		const char *header = REQ_OFFSET_TO_STR(&pvt->initreq, header[i]);
+		if (ast_begins_with(header, args.pattern)) {
+			int hdrlen = strcspn(header, " \t:,");  /* Comma will break our logic, and illegal per RFC. */
+			const char *term = ast_skip_blanks(header + hdrlen);
+			if (hdrlen > 0 && *term == ':') {  /* Header is malformed otherwise! */
+				const char *s = NULL;
+
+				/* Return short headers in full form always. */
+				if (hdrlen == 1) {
+					char short_hdr[2] = { header[0], '\0' };
+					s = find_full_alias(short_hdr, NULL);
+				}
+				if (s) {
+					/* Short header was found and expanded. */
+					ast_str_set(&token, -1, "%s,", s);
+				} else {
+					/* Return the header as is, whether 1-character or not. */
+					ast_str_set(&token, -1, "%.*s,", hdrlen, header);
+				}
+
+				/* Has the same header been already added? */
+				s = ast_str_buffer(*buf);
+				while ((s = strstr(s, ast_str_buffer(token))) != NULL) {
+					/* Found suffix, but is it the full token? */
+					if (s == ast_str_buffer(*buf) || s[-1] == ',')
+						break;
+					/* Only suffix matched, go on with the search after the comma. */
+					s += hdrlen + 1;
+				}
+
+				/* s is null iff not broken from the loop, hence header not yet added. */
+				if (s == NULL) {
+					ast_str_append(buf, maxlen, "%s", ast_str_buffer(token));
+				}
+			}
+		}
+	}
+
+	ast_str_truncate(*buf, -1);  /* Trim the last comma. Safe if empty. */
+
+	ast_channel_unlock(chan);
+	return 0;
+}
+
+static struct ast_custom_function sip_headers_function = {
+	.name = "SIP_HEADERS",
+	.read2 = func_headers_read2,
+};
+
+
 /*! \brief  Dial plan function to check if domain is local */
 static int func_check_sipdomain(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
 {
@@ -35201,6 +35318,7 @@ static int load_module(void)
 
 	/* Register dialplan functions */
 	ast_custom_function_register(&sip_header_function);
+	ast_custom_function_register(&sip_headers_function);
 	ast_custom_function_register(&sippeer_function);
 	ast_custom_function_register(&checksipdomain_function);
 
@@ -35301,6 +35419,7 @@ static int unload_module(void)
 
 	/* Unregister dial plan functions */
 	ast_custom_function_unregister(&sippeer_function);
+	ast_custom_function_unregister(&sip_headers_function);
 	ast_custom_function_unregister(&sip_header_function);
 	ast_custom_function_unregister(&checksipdomain_function);