Add FIFO buffer endpoint at /admin/api/ftl/dnsmasq_log. This is a FIFO buffer collecting and returning up to 32 messages from memory (compile-time option). The API endpoint can be continuously polled with the last returned ID to only show new messages that can be appended to a log on the web interface.

Signed-off-by: DL6ER <dl6er@dl6er.de>

src/FTL.h

@@ -139,4 +139,7 @@ extern pthread_t timerthread;
 // Intentionally ignore result of function declared warn_unused_result
 #define igr(x) {__typeof__(x) __attribute__((unused)) d=(x);} 
 
+#define max(a,b) ({ __typeof__ (a) _a = (a); __typeof__ (b) _b = (b); _a > _b ? _a : _b; })
+#define min(a,b) ({ __typeof__ (a) _a = (a); __typeof__ (b) _b = (b); _a < _b ? _a : _b; })
+
 #endif // FTL_H

src/api/ftl.c

@@ -11,12 +11,15 @@
 #include "FTL.h"
 #include "http-common.h"
 #include "routes.h"
+#include "ftl.h"
 #include "json_macros.h"
 #include "datastructure.h"
 // get_FTL_version()
 #include "log.h"
 // git constants
 #include "version.h"
+// config struct
+#include "config.h"
 
 int api_ftl_clientIP(struct mg_connection *conn)
 {
@@ -25,3 +28,95 @@ int api_ftl_clientIP(struct mg_connection *conn)
 	JSON_OBJ_REF_STR(json,"remote_addr", request->remote_addr);
 	JSON_SEND_OBJECT(json);
 }
+
+static char dnsmasq_log_messages[LOG_SIZE][MAX_MESSAGE] = { 0 };
+static time_t dnsmasq_log_stamps[LOG_SIZE] = { 0 };
+static int dnsmasq_next_id = 0;
+
+int api_ftl_dnsmasq_log(struct mg_connection *conn)
+{
+	// Verify requesting client is allowed to see this ressource
+	if(check_client_auth(conn) < 0)
+	{
+		return send_json_unauthorized(conn, NULL);
+	}
+
+	unsigned int start = 0u;
+	const struct mg_request_info *request = mg_get_request_info(conn);
+	if(request->query_string != NULL)
+	{
+		// Does the user request an ID to sent from?
+		int num;
+		if((num = get_int_var(request->query_string, "nextID")) > 0)
+		{
+			if(num >= dnsmasq_next_id)
+			{
+				// Do not return any data
+				start = LOG_SIZE;
+			}
+			else if(num < max(dnsmasq_next_id - LOG_SIZE, 0))
+			{
+				// Requested an ID smaller than the lowest one we have
+				// We return the entire buffer
+				start = 0;
+			}
+			else
+			{
+				// Reply with partial buffer
+				start = LOG_SIZE - (dnsmasq_next_id - num);
+			}
+		}
+	}
+
+	// Process data
+	cJSON *json = JSON_NEW_OBJ();
+	cJSON *log = JSON_NEW_ARRAY();
+	unsigned int idx = 0u;
+	for(unsigned int i = start; i < LOG_SIZE; i++)
+	{
+		// Reconstruct log message identification number
+		if(dnsmasq_next_id < LOG_SIZE)
+		{
+			idx = i;
+		}
+		else
+		{
+			idx = dnsmasq_next_id - LOG_SIZE + i;
+		}
+
+		cJSON *entry = JSON_NEW_OBJ();
+		JSON_OBJ_ADD_NUMBER(entry, "id", idx);
+		JSON_OBJ_ADD_NUMBER(entry, "timestamp", dnsmasq_log_stamps[i]);
+		JSON_OBJ_REF_STR(entry, "message", dnsmasq_log_messages[i]);
+		JSON_ARRAY_ADD_ITEM(log, entry);
+	}
+	JSON_OBJ_ADD_ITEM(json, "log", log);
+	JSON_OBJ_ADD_NUMBER(json, "nextID", dnsmasq_next_id);
+	JSON_SEND_OBJECT(json);
+}
+
+void add_to_dnsmasq_log_fifo_buffer(const char *payload, const int length)
+{
+	unsigned int idx = dnsmasq_next_id++;
+	if(idx >= LOG_SIZE)
+	{
+		// Log is full, move everything one slot forward to make space
+		memmove(dnsmasq_log_messages[0], dnsmasq_log_messages[1], (LOG_SIZE - 1u) * MAX_MESSAGE);
+		idx = LOG_SIZE - 1u;
+	}
+	// Copy relevant string into temporary buffer
+	memcpy(dnsmasq_log_messages[idx], payload, length);
+
+	// Zero-terminate buffer, truncate newline if found
+	if(dnsmasq_log_messages[idx][length - 1u] == '\n')
+	{
+		dnsmasq_log_messages[idx][length - 1u] = '\0';
+	}
+	else
+	{
+		dnsmasq_log_messages[idx][length] = '\0';
+	}
+
+	// Set timestamp
+	dnsmasq_log_stamps[idx] = time(NULL);
+}

src/api/ftl.h

@@ -0,0 +1,23 @@
+/* Pi-hole: A black hole for Internet advertisements
+*  (c) 2019 Pi-hole, LLC (https://pi-hole.net)
+*  Network-wide ad blocking via your own hardware.
+*
+*  FTL Engine
+*  API FTL prototypes
+*
+*  This file is copyright under the latest version of the EUPL.
+*  Please see LICENSE file for your rights under this license. */
+#ifndef API_FTL_H
+#define API_FTL_H
+
+/* From RFC 3164 */
+#define MAX_MESSAGE 1024
+
+// How many messages do we keep in memory (FIFO message buffer)?
+// The memory required is the set number in kilobytes
+// Defaults to 32 [uses 32 KB of memory]
+#define LOG_SIZE 32
+
+void add_to_dnsmasq_log_fifo_buffer(const char *payload, const int length);
+
+#endif // API_FTL_H

src/api/routes.c

@@ -44,6 +44,10 @@ int api_handler(struct mg_connection *conn, void *ignored)
 	{
 		return api_ftl_clientIP(conn);
 	}
+	else if(startsWith("/api/ftl/dnsmasq_log", request->local_uri))
+	{
+		return api_ftl_dnsmasq_log(conn);
+	}
 	/******************************** api/stats **************************/
 	else if(startsWith("/api/stats/summary", request->local_uri))
 	{

src/api/routes.h

@@ -29,8 +29,7 @@ int api_stats_recentblocked(struct mg_connection *conn);
 
 // FTL methods
 int api_ftl_clientIP(struct mg_connection *conn);
-int api_ftl_version(struct mg_connection *conn);
-int api_ftl_db(struct mg_connection *conn);
+int api_ftl_dnsmasq_log(struct mg_connection *conn);
 
 // DNS methods
 int api_dns_status(struct mg_connection *conn);

src/api/stats.c

@@ -27,8 +27,6 @@
 // enum REGEX
 #include "regex_r.h"
 
-#define min(a,b) ({ __typeof__ (a) _a = (a); __typeof__ (b) _b = (b); _a < _b ? _a : _b; })
-
 /* qsort comparision function (count field), sort ASC
 static int __attribute__((pure)) cmpasc(const void *a, const void *b)
 {

src/dnsmasq/log.c

@@ -300,8 +300,8 @@ void my_syslog(int priority, const char *format, ...)
 #endif
 
   /*************************** Pi-hole specific logging **************************/
-  va_start(ap, format);
   char buffer[MAX_MESSAGE + 1u];
+  va_start(ap, format);
   len = vsnprintf(buffer, MAX_MESSAGE, format, ap) + 1u; /* include zero-terminator */
   va_end(ap);
   FTL_dnsmasq_log(buffer, len > MAX_MESSAGE ? MAX_MESSAGE : len);

src/dnsmasq_interface.c

@@ -34,6 +34,8 @@
 #include "args.h"
 // http_init()
 #include "api/http-common.h"
+// add_to_dnsmasq_log_buffer()
+#include "api/ftl.h"
 
 static void print_flags(const unsigned int flags);
 static void save_reply_type(const unsigned int flags, const union all_addr *addr,
@@ -1813,24 +1815,5 @@ void FTL_TCP_worker_terminating(void)
 
 void FTL_dnsmasq_log(const char *payload, const int length)
 {
-	// Get temporary space for dnsmasq's log message
-	char log_str[length + 1u];
-
-	// Copy relevant string into temporary buffer
-	memcpy(log_str, payload, length);
-
-	// Zero-terminate buffer, truncate newline if found
-	if(log_str[length - 1u] == '\n')
-	{
-		log_str[length - 1u] = '\0';
-	}
-	else
-	{
-		log_str[length] = '\0';
-	}
-
-	if(config.debug & DEBUG_API)
-	{
-		logg("DNSMASQ LOG: \"%s\"", log_str);
-	}
-}
+	add_to_dnsmasq_log_fifo_buffer(payload, length);
+}