core: add X-Sequence header supportv1.2.2

Add non-standard HTTP header "X-Sequence" to the header section of
requests (og_send_request) sent to a connected client.

Define a starting sequence number when creating a new instance of struct
og_client inside og_server_accept_cb. This sequence number is
incremented by one for each outgoing request from ogServer.

This sequence number is checked when receiving a response from a
connected client, if they do not match the connection is dropped.

Use sequence 0 for out-of-band commands (reboot, poweroff, stop). Any
client response with header "X-Sequence: 0" bypasses sequence check.

1 files changed, 19 insertions, 3 deletions

diff --git a/src/rest.c b/src/rest.c
index 1f35174..ff51332 100644
--- a/src/rest.c
+++ b/src/rest.c
@@ -296,6 +296,7 @@ int og_send_request(enum og_rest_method method, enum og_cmd_type type,
 	const char *uri;
 	unsigned int i;
 	int client_sd;
+	bool has_seq;
 
 	if (method == OG_METHOD_GET)
 		snprintf(method_str, 5, "GET");
@@ -312,9 +313,17 @@ int og_send_request(enum og_rest_method method, enum og_cmd_type type,
 					    JSON_COMPACT);
 
 	uri = og_cmd_to_uri[type];
-	snprintf(buf, OG_MSG_REQUEST_MAXLEN,
-		 "%s /%s HTTP/1.1\r\nContent-Length: %d\r\n%s\r\n\r\n%s",
-		 method_str, uri, content_length, content_type, content);
+
+	switch (type) {
+		case OG_CMD_POWEROFF:
+		case OG_CMD_REBOOT:
+		case OG_CMD_STOP:
+			has_seq = false;
+			break;
+		default:
+			has_seq = true;
+			break;
+	}
 
 	for (i = 0; i < params->ips_array_len; i++) {
 		cli = og_client_find(params->ips_array[i]);
@@ -331,6 +340,13 @@ int og_send_request(enum og_rest_method method, enum og_cmd_type type,
 			continue;
 		}
 
+		if (++cli->seq == 0)
+			cli->seq++;
+
+		snprintf(buf, OG_MSG_REQUEST_MAXLEN,
+			 "%s /%s HTTP/1.1\r\nContent-Length: %d\r\nX-Sequence: %u\r\n%s\r\n\r\n%s",
+			 method_str, uri, content_length, has_seq ? cli->seq : 0, content_type, content);
+
 		if (send(client_sd, buf, strlen(buf), 0) < 0)
 			continue;