Allow remote upload (preflighted requests)

Implement preflighted requests (OPTIONS) to allow remote file upload
(CORS).

-
https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS#Preflighted_requests

- https://www.w3.org/TR/cors/

src/libs/Network/uip/webserver/http-strings

@@ -4,6 +4,7 @@ http_301 "301 "
 http_302 "302 "
 http_get "GET "
 http_post "POST "
+http_options "OPTIONS "
 http_10 "HTTP/1.0"
 http_11 "HTTP/1.1"
 http_content_type "content-type: "

src/libs/Network/uip/webserver/http-strings.c

@@ -16,6 +16,9 @@ const char http_get[5] =
 const char http_post[6] = 
 /* "POST " */
 {0x50, 0x4f, 0x53, 0x54, 0x20, };
+const char http_options[9] = 
+/* "OPTIONS " */
+{0x4f, 0x50, 0x54, 0x49, 0x4f, 0x4e, 0x53, 0x20, };
 const char http_10[9] = 
 /* "HTTP/1.0" */
 {0x48, 0x54, 0x54, 0x50, 0x2f, 0x31, 0x2e, 0x30, };

src/libs/Network/uip/webserver/http-strings.h

@@ -4,6 +4,7 @@ extern const char http_301[5];
 extern const char http_302[5];
 extern const char http_get[5];
 extern const char http_post[6];
+extern const char http_options[9];
 extern const char http_10[9];
 extern const char http_11[9];
 extern const char http_content_type[15];

src/libs/Network/uip/webserver/httpd.c

@@ -83,8 +83,9 @@
 #define STATE_OUTPUT  3
 #define STATE_UPLOAD  4
 
-#define GET  1
-#define POST 2
+#define GET     1
+#define POST    2
+#define OPTIONS 3
 
 #define ISO_nl      0x0a
 #define ISO_space   0x20
@@ -324,7 +325,11 @@ PT_THREAD(handle_output(struct httpd_state *s))
 {
     PT_BEGIN(&s->outputpt);
 
-    if (s->method == POST) {
+    if (s->method == OPTIONS) {
+        PT_WAIT_THREAD(&s->outputpt, send_headers(s, http_header_preflight));
+        PSOCK_SEND_STR(&s->sout, "OK\r\n");
+    }
+    else if (s->method == POST) {
         if (strcmp(s->filename, "/command") == 0) {
             DEBUG_PRINTF("Executed command post\n");
             PT_WAIT_THREAD(&s->outputpt, send_headers(s, http_header_200));
@@ -471,16 +476,18 @@ PT_THREAD(handle_input(struct httpd_state *s))
 
     PSOCK_READTO(&s->sin, ISO_space);
 
-    if (strncmp(s->inputbuf, http_get, 4) == 0) {
+    if (strncmp(s->inputbuf, http_get, 3) == 0) {
         s->method = GET;
     } else if (strncmp(s->inputbuf, http_post, 4) == 0) {
         s->method = POST;
+    } else if (strncmp(s->inputbuf, http_options, 7) == 0) {
+        s->method = OPTIONS;
     } else {
         DEBUG_PRINTF("Unexpected method: %s\n", s->inputbuf);
         PSOCK_CLOSE_EXIT(&s->sin);
     }
 
-    DEBUG_PRINTF("Method: %s\n", s->method == POST ? "POST" : "GET");
+    DEBUG_PRINTF("Method: %s\n", s->method == POST ? "POST" : (s->method == GET ? "GET" : "OPTIONS"));
 
     PSOCK_READTO(&s->sin, ISO_space);
 
@@ -509,7 +516,10 @@ PT_THREAD(handle_input(struct httpd_state *s))
             s->inputbuf[PSOCK_DATALEN(&s->sin) - 1] = 0;
             if (s->inputbuf[0] == '\r') {
                 DEBUG_PRINTF("end of headers\n");
-                if (s->method == GET) {
+                if (s->method == OPTIONS) {
+                   s->state = STATE_OUTPUT;
+                   break;
+                } else if (s->method == GET) {
                     s->state = STATE_OUTPUT;
                     break;
                 } else if (s->method == POST) {