ubus: add CORS header support

In order to support cross-domain AJAX requests to the /ubus endpoint
we need to implement the Cross-Origin Resource Sharing (CORS) spec
in the ubus plugin.

- Implement a new option "-X" to enable CORS support in ubus
- Implement rudimentary support for "OPTIONS" HTTP requests
- Implement essential CORS headers the ubus plugin

The current CORS response headers merely reflect the request headers
sent by the client, this way any requesting origin is automatically
allowed. Cross-domain cookies (Access-Control-Allow-Credentials) are
unconditionally enabled.

Restricting permitted origins and toggle the credential accepting can
be made configurable in a future commit to allow more fine grained
control over permitted AJAX clients.

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/client.c b/client.c
index 3a6b09e..9b8fb07 100644
--- a/client.c
+++ b/client.c
@@ -39,6 +39,7 @@ const char * const http_methods[] = {
 	[UH_HTTP_MSG_GET] = "GET",
 	[UH_HTTP_MSG_POST] = "POST",
 	[UH_HTTP_MSG_HEAD] = "HEAD",
+	[UH_HTTP_MSG_OPTIONS] = "OPTIONS",
 };
 
 void uh_http_header(struct client *cl, int code, const char *summary)