Allow setting size when serving static files

Author: AndreyDodonov-EH

subsys/net/lib/http/Kconfig

@@ -44,6 +44,7 @@ if HTTP_SERVER
 
 config HTTP_SERVER_STACK_SIZE
 	int "HTTP server thread stack size"
+	default 4096 if FILE_SYSTEM
 	default 3072
 	help
 	  HTTP server thread stack size for processing RX/TX events.
@@ -219,6 +220,17 @@ config HTTP_SERVER_COMPRESSION
 	    5. deflate  -> .zz
 	    6. File without compression
 
+config HTTP_SERVER_STATIC_FS_RESPONSE_SIZE
+	int "Size of static file system response buffer"
+	depends on FILE_SYSTEM
+	default 1024
+	help 
+	  The size of a single chunk when serving static files from the file system.
+	  This config value must be large enough to hold the headers in a single chunk.
+	  If set to 0, the server will use the minimal viable buffer size for the response.
+	  Please note that it is allocated on the stack of the HTTP server thread,
+	  so CONFIG_HTTP_SERVER_STACK_SIZE has to be sufficiently large.
+
 endif
 
 # Hidden option to avoid having multiple individual options that are ORed together

subsys/net/lib/http/http_server_http1.c

@@ -482,12 +482,23 @@ int handle_http1_static_fs_resource(struct http_resource_detail_static_fs *stati
 		sizeof("Content-Length: 01234567890123456789\r\n")
 #define CONTENT_ENCODING_HEADER_SIZE                                                               \
 	sizeof(CONTENT_ENCODING_HEADER) + HTTP_COMPRESSION_MAX_STRING_LEN + sizeof("\r\n")
+
+/* Calculate the minimum required size */
 #define STATIC_FS_RESPONSE_SIZE                                                                    \
 	COND_CODE_1(                                                                               \
 		IS_ENABLED(CONFIG_HTTP_SERVER_COMPRESSION),                                        \
 		(STATIC_FS_RESPONSE_BASE_SIZE + CONTENT_ENCODING_HEADER_SIZE),                     \
 		(STATIC_FS_RESPONSE_BASE_SIZE))
 
+// Issue in Zephyr: https://github.com/zephyrproject-rtos/zephyr/issues/92921
+#if CONFIG_HTTP_SERVER_STATIC_FS_RESPONSE_SIZE > 0
+BUILD_ASSERT(CONFIG_HTTP_SERVER_STATIC_FS_RESPONSE_SIZE >= STATIC_FS_RESPONSE_SIZE,
+			"CONFIG_HTTP_SERVER_STATIC_FS_RESPONSE_SIZE must be at least " 
+			"large enough to hold HTTP headers");
+#undef STATIC_FS_RESPONSE_SIZE
+#define STATIC_FS_RESPONSE_SIZE CONFIG_HTTP_SERVER_STATIC_FS_RESPONSE_SIZE
+#endif
+
 	enum http_compression chosen_compression = 0;
 	int len;
 	int remaining;
@@ -919,7 +930,7 @@ int handle_http1_request(struct http_client_ctx *client)
 
 	parsed = http_parser_execute(&client->parser, &client->parser_settings,
 				     client->cursor, client->data_len);
-
+	
 	if (parsed > client->data_len) {
 		LOG_ERR("HTTP/1 parser error, too much data consumed");
 		ret = -EBADMSG;