func_curl.c: Support custom http headers

When user wants to send json data, the default Content-Type header
is incorect (application/x-www-form-urlencoded). This patch allows
to set any custom headers so the Content-Type header can be
overriden. User can set multiple headers by multiple calls of
curlopt(). This approach is not consistent with other parameters,
but is more readable in dialplan than one call with multiple
headers.

ASTERISK-28613

Change-Id: I4dd68c3f4e25362ef941d73a3861f58348dcfbf9

doc/CHANGES-staging/func_curl_headers.txt

@@ -0,0 +1,6 @@
+Subject: func_curl
+
+A new parameter, httpheader, has been added to CURLOPT function. This parameter
+allows to set custom http headers for subsequent calls off CURL function.
+Any setting of headers will replace the default curl headers
+(e.g. "Content-type: application/x-www-form-urlencoded")

funcs/func_curl.c

@@ -121,6 +121,11 @@
 						<para>Include header information in the result
 						(boolean)</para>
 					</enum>
+					<enum name="httpheader">
+						<para>Add HTTP header. Multiple calls add multiple headers.
+						Setting of any header will remove the default
+						"Content-Type application/x-www-form-urlencoded"</para>
+					</enum>
 					<enum name="httptimeout">
 						<para>For HTTP(S) URIs, number of seconds to wait for a
 						server response</para>
@@ -181,7 +186,7 @@
 		</syntax>
 		<description>
 			<para>Options may be set globally or per channel.  Per-channel
-			settings will override global settings.</para>
+			settings will override global settings. Only HTTP headers are added instead of overriding</para>
 		</description>
 		<see-also>
 			<ref type="function">CURL</ref>
@@ -243,6 +248,9 @@ static int parse_curlopt_key(const char *name, CURLoption *key, enum optiontype
 	if (!strcasecmp(name, "header")) {
 		*key = CURLOPT_HEADER;
 		*ot = OT_BOOLEAN;
+	} else if (!strcasecmp(name, "httpheader")) {
+		*key = CURLOPT_HTTPHEADER;
+		*ot = OT_STRING;
 	} else if (!strcasecmp(name, "proxy")) {
 		*key = CURLOPT_PROXY;
 		*ot = OT_STRING;
@@ -412,16 +420,18 @@ yuck:
 		return -1;
 	}
 
-	/* Remove any existing entry */
+	/* Remove any existing entry, only http headers are left */
 	AST_LIST_LOCK(list);
-	AST_LIST_TRAVERSE_SAFE_BEGIN(list, cur, list) {
-		if (cur->key == new->key) {
-			AST_LIST_REMOVE_CURRENT(list);
-			ast_free(cur);
-			break;
+	if (new->key != CURLOPT_HTTPHEADER) {
+		AST_LIST_TRAVERSE_SAFE_BEGIN(list, cur, list) {
+			if (cur->key == new->key) {
+				AST_LIST_REMOVE_CURRENT(list);
+				ast_free(cur);
+				break;
+			}
 		}
+		AST_LIST_TRAVERSE_SAFE_END
 	}
-	AST_LIST_TRAVERSE_SAFE_END
 
 	/* Insert new entry */
 	ast_debug(1, "Inserting entry %p with key %d and value %p\n", new, new->key, new->value);
@@ -639,6 +649,7 @@ static int acf_curl_helper(struct ast_channel *chan, struct curl_args *args)
 	int ret = -1;
 	CURL **curl;
 	struct curl_settings *cur;
+	struct curl_slist *headers = NULL;
 	struct ast_datastore *store = NULL;
 	int hashcompat = 0;
 	AST_LIST_HEAD(global_curl_info, curl_settings) *list = NULL;
@@ -666,6 +677,8 @@ static int acf_curl_helper(struct ast_channel *chan, struct curl_args *args)
 	AST_LIST_TRAVERSE(&global_curl_info, cur, list) {
 		if (cur->key == CURLOPT_SPECIAL_HASHCOMPAT) {
 			hashcompat = (long) cur->value;
+		} else if (cur->key == CURLOPT_HTTPHEADER) {
+			headers = curl_slist_append(headers, (char*) cur->value);
 		} else {
 			curl_easy_setopt(*curl, cur->key, cur->value);
 		}
@@ -682,6 +695,8 @@ static int acf_curl_helper(struct ast_channel *chan, struct curl_args *args)
 			AST_LIST_TRAVERSE(list, cur, list) {
 				if (cur->key == CURLOPT_SPECIAL_HASHCOMPAT) {
 					hashcompat = (long) cur->value;
+				} else if (cur->key == CURLOPT_HTTPHEADER) {
+					headers = curl_slist_append(headers, (char*) cur->value);
 				} else {
 					curl_easy_setopt(*curl, cur->key, cur->value);
 				}
@@ -697,6 +712,10 @@ static int acf_curl_helper(struct ast_channel *chan, struct curl_args *args)
 		curl_easy_setopt(*curl, CURLOPT_POSTFIELDS, args->postdata);
 	}
 
+	if (headers) {
+		curl_easy_setopt(*curl, CURLOPT_HTTPHEADER, headers);
+	}
+
 	/* Temporarily assign a buffer for curl to write errors to. */
 	curl_errbuf[0] = curl_errbuf[CURL_ERROR_SIZE] = '\0';
 	curl_easy_setopt(*curl, CURLOPT_ERRORBUFFER, curl_errbuf);
@@ -714,6 +733,7 @@ static int acf_curl_helper(struct ast_channel *chan, struct curl_args *args)
 	if (store) {
 		AST_LIST_UNLOCK(list);
 	}
+	curl_slist_free_all(headers);
 
 	if (args->postdata) {
 		curl_easy_setopt(*curl, CURLOPT_POST, 0);
@@ -841,6 +861,7 @@ static struct ast_custom_function acf_curlopt = {
 "  ftptext        - For FTP, force a text transfer (boolean)\n"
 "  ftptimeout     - For FTP, the server response timeout\n"
 "  header         - Retrieve header information (boolean)\n"
+"  httpheader     - Add new custom http header (string)\n"
 "  httptimeout    - Number of seconds to wait for HTTP response\n"
 "  maxredirs      - Maximum number of redirects to follow\n"
 "  proxy          - Hostname or IP to use as a proxy\n"