ARI/PJSIP: Add the ability to redirect (transfer) a channel in a Stasis app

This patch adds a new feature to ARI to redirect a channel to another server,
and fixes a few bugs in PJSIP's handling of the Transfer dialplan
application/ARI redirect capability.

*New Feature*
A new operation has been added to the ARI channels resource, redirect. With
this, a channel in a Stasis application can be redirected to another endpoint
of the same underlying channel technology.

*Bug fixes*
In the process of writing this new feature, two bugs were fixed in the PJSIP
stack:
(1) The existing .transfer channel callback had the limitation that it could
    only transfer channels to a SIP URI, i.e., you had to pass
    'PJSIP/sip:foo@my_provider.com' to the dialplan application. While this is
    still supported, it is somewhat unintuitive - particularly in a world full
    of endpoints. As such, we now also support specifying the PJSIP endpoint to
    transfer to.
(2) res_pjsip_multihomed was, unfortunately, trying to 'help' a 302 redirect by
    updating its Contact header. Alas, that resulted in the forwarding
    destination set by the dialplan application/ARI resource/whatever being
    rewritten with very incorrect information. Hence, we now don't bother
    updating an outgoing response if it is a 302. Since this took a looong time
    to find, some additional debug statements have been added to those modules
    that update the Contact headers.

Review: https://reviewboard.asterisk.org/r/4316/

ASTERISK-24015 #close
Reported by: Private Name

ASTERISK-24703 #close
Reported by: Matt Jordan
........

Merged revisions 431717 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@431718 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 58 insertions, 0 deletions

diff --git a/res/ari/resource_channels.c b/res/ari/resource_channels.c
index 24aabe588..67498af9f 100644
--- a/res/ari/resource_channels.c
+++ b/res/ari/resource_channels.c
@@ -156,6 +156,64 @@ void ast_ari_channels_continue_in_dialplan(
 	ast_ari_response_no_content(response);
 }
 
+void ast_ari_channels_redirect(struct ast_variable *headers,
+	struct ast_ari_channels_redirect_args *args,
+	struct ast_ari_response *response)
+{
+	RAII_VAR(struct stasis_app_control *, control, NULL, ao2_cleanup);
+	RAII_VAR(struct ast_channel_snapshot *, chan_snapshot, NULL, ao2_cleanup);
+	char *tech;
+	char *resource;
+	int tech_len;
+
+	control = find_control(response, args->channel_id);
+	if (!control) {
+		return;
+	}
+
+	if (ast_strlen_zero(args->endpoint)) {
+		ast_ari_response_error(response, 400, "Not Found",
+			"Required parameter 'endpoint' not provided.");
+		return;
+	}
+
+	tech = ast_strdupa(args->endpoint);
+	if (!(resource = strchr(tech, '/')) || !(tech_len = resource - tech)) {
+		ast_ari_response_error(response, 422, "Unprocessable Entity",
+			"Endpoint parameter '%s' does not contain tech/resource", args->endpoint);
+		return;
+	}
+
+	*resource++ = '\0';
+	if (ast_strlen_zero(resource)) {
+		ast_ari_response_error(response, 422, "Unprocessable Entity",
+			"No resource provided in endpoint parameter '%s'", args->endpoint);
+		return;
+	}
+
+	chan_snapshot = ast_channel_snapshot_get_latest(args->channel_id);
+	if (!chan_snapshot) {
+		ast_ari_response_error(response, 500, "Internal Server Error",
+			"Unable to find channel snapshot for '%s'", args->channel_id);
+		return;
+	}
+
+	if (strncasecmp(chan_snapshot->type, tech, tech_len)) {
+		ast_ari_response_error(response, 422, "Unprocessable Entity",
+			"Endpoint technology '%s' does not match channel technology '%s'",
+			tech, chan_snapshot->type);
+		return;
+	}
+
+	if (stasis_app_control_redirect(control, resource)) {
+		ast_ari_response_error(response, 500, "Internal Server Error",
+			"Failed to redirect channel");
+		return;
+	}
+
+	ast_ari_response_no_content(response);
+}
+
 void ast_ari_channels_answer(struct ast_variable *headers,
 	struct ast_ari_channels_answer_args *args,
 	struct ast_ari_response *response)