diff --git a/src/sources/files.c b/src/sources/files.c
index 8604717..44d1cba 100644
--- a/src/sources/files.c
+++ b/src/sources/files.c
@@ -4,14 +4,15 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
-#include "source.h"
-
 #include <limits.h>
 #include <sys/file.h>
 #include <sys/stat.h>
 
 #include <glob.h>
 
+#include "source.h"
+#define MODNAME "files"
+
 typedef struct f2b_file_t {
   struct f2b_file_t *next;
   bool opened;
@@ -22,17 +23,12 @@ typedef struct f2b_file_t {
 
 struct _config {
   char path[256];
-  char error[256];
-  void (*errcb)(const char *errstr);
+  void (*logcb)(enum loglevel lvl, const char *msg);
   f2b_file_t *files;
   f2b_file_t *current;
 };
 
-static void
-errcb_stub(const char *str) {
-  assert(str != NULL);
-  (void)(str);
-}
+#include "source.c"
 
 static bool
 file_open(f2b_file_t *file, const char *path) {
@@ -77,21 +73,24 @@ file_close(f2b_file_t *file) {
 }
 
 static bool
-file_rotated(const f2b_file_t *file) {
+file_rotated(const cfg_t *cfg, const f2b_file_t *file) {
   struct stat st;
-
   assert(file != NULL);
 
   if (!file->opened)
     return true;
 
-  if (stat(file->path, &st) != 0)
+  if (stat(file->path, &st) != 0) {
+    log_msg(cfg, error, "file stat error: %s", strerror(errno));
     return true;
+  }
 
   if (file->st.st_dev  != st.st_dev ||
       file->st.st_ino  != st.st_ino ||
-      file->st.st_size  > st.st_size)
+      file->st.st_size  > st.st_size) {
+    log_msg(cfg, info, "file replaced: %s", file->path);
     return true;
+  }
 
   return false;
 }
@@ -117,7 +116,7 @@ create(const char *init) {
   if ((cfg = calloc(1, sizeof(cfg_t))) == NULL)
     return NULL;
   strlcpy(cfg->path, init, sizeof(cfg->path));
-  cfg->errcb = &errcb_stub;
+  cfg->logcb = &logcb_stub;
   return cfg;
 }
 
@@ -143,21 +142,6 @@ ready(cfg_t *cfg) {
   return true;
 }
 
-char *
-error(cfg_t *cfg) {
-  assert(cfg != NULL);
-
-  return cfg->error;
-}
-
-void
-errcb(cfg_t *cfg, void (*cb)(const char *errstr)) {
-  assert(cfg != NULL);
-  assert(cb  != NULL);
-
-  cfg->errcb = cb;
-}
-
 bool
 start(cfg_t *cfg) {
   f2b_file_t *file = NULL;
@@ -172,11 +156,7 @@ start(cfg_t *cfg) {
     if ((file = calloc(1, sizeof(f2b_file_t))) == NULL)
       continue;
     if (file_open(file, globbuf.gl_pathv[i]) == false) {
-      if (cfg->errcb) {
-        snprintf(cfg->error, sizeof(cfg->error), "can't open file: %s -- %s",
-          globbuf.gl_pathv[i], strerror(errno));
-        cfg->errcb(cfg->error);
-      }
+      log_msg(cfg, error, "can't open file: %s -- %s", globbuf.gl_pathv[i], strerror(errno));
       free(file);
       continue;
     }
@@ -217,13 +197,10 @@ next(cfg_t *cfg, char *buf, size_t bufsize, bool reset) {
     cfg->current = cfg->files;
 
   for (f2b_file_t *file = cfg->current; file != NULL; file = file->next) {
-    if (file_rotated(file))
+    if (file_rotated(cfg, file))
       file_close(file);
     if (!file->opened && !file_open(file, NULL)) {
-      if (cfg->errcb) {
-        snprintf(cfg->error, sizeof(cfg->error), "can't open file: %s", file->path);
-        cfg->errcb(cfg->error);
-      }
+      log_msg(cfg, error, "can't open file: %s", file->path);
       continue;
     }
     if (file_getline(file, buf, bufsize))
diff --git a/src/sources/portknock.c b/src/sources/portknock.c
index 4a23095..d8faafe 100644
--- a/src/sources/portknock.c
+++ b/src/sources/portknock.c
@@ -4,8 +4,6 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
-#include "source.h"
-
 #include <ctype.h>
 #include <fcntl.h>
 #include <sys/socket.h>
@@ -13,6 +11,8 @@
 #include <arpa/inet.h>
 #include <netdb.h>
 
+#include "source.h"
+#define MODNAME "portknock"
 #define HOST_MAX 48
 #define PORT_MAX 6
 
@@ -25,17 +25,12 @@ typedef struct f2b_port_t {
 
 struct _config {
   char name[32];
-  char error[256];
-  void (*errcb)(const char *errstr);
+  void (*logcb)(enum loglevel lvl, const char *msg);
   f2b_port_t *ports;
   f2b_port_t *current;
 };
 
-static void
-errcb_stub(const char *str) {
-  assert(str != NULL);
-  (void)(str);
-}
+#include "source.c"
 
 static bool
 try_parse_listen_opt(f2b_port_t *port, const char *value) {
@@ -79,7 +74,7 @@ create(const char *init) {
   if ((cfg = calloc(1, sizeof(cfg_t))) == NULL)
     return NULL;
   strlcpy(cfg->name, init, sizeof(cfg->name));
-  cfg->errcb = &errcb_stub;
+  cfg->logcb = &logcb_stub;
   return cfg;
 }
 
@@ -92,11 +87,11 @@ config(cfg_t *cfg, const char *key, const char *value) {
   if (strcmp(key, "listen") == 0) {
     f2b_port_t *port = NULL;
     if ((port = calloc(1, sizeof(f2b_port_t))) == NULL) {
-      strlcpy(cfg->error, "out of memory", sizeof(cfg->error));
+      log_msg(cfg, error, "out of memory");
       return false;
     }
     if (try_parse_listen_opt(port, value) == false) {
-      snprintf(cfg->error, sizeof(cfg->error), "can't parse: %s", value);
+      log_msg(cfg, error, "can't parse: %s", value);
       free(port);
       return false;
     }
@@ -116,21 +111,6 @@ ready(cfg_t *cfg) {
   return false;
 }
 
-char *
-error(cfg_t *cfg) {
-  assert(cfg != NULL);
-
-  return cfg->error;
-}
-
-void
-errcb(cfg_t *cfg, void (*cb)(const char *errstr)) {
-  assert(cfg != NULL);
-  assert(cb  != NULL);
-
-  cfg->errcb = cb;
-}
-
 bool
 start(cfg_t *cfg) {
   struct addrinfo hints;
@@ -148,8 +128,7 @@ start(cfg_t *cfg) {
     port->sock = -1;
     int ret = getaddrinfo(port->host, port->port, &hints, &result);
     if (ret != 0) {
-      snprintf(cfg->error, sizeof(cfg->error), "getaddrinfo: %s", gai_strerror(ret));
-      cfg->errcb(cfg->error);
+      log_msg(cfg, error, "getaddrinfo: %s", gai_strerror(ret));
       continue;
     }
     for (struct addrinfo *rp = result; rp != NULL; rp = rp->ai_next) {
@@ -169,10 +148,8 @@ start(cfg_t *cfg) {
       }
     }
     freeaddrinfo(result);
-    if (port->sock < 0) {
-      snprintf(cfg->error, sizeof(cfg->error), "can't bind/listen on %s:%s", port->host, port->port);
-      cfg->errcb(cfg->error);
-    }
+    if (port->sock < 0)
+      log_msg(cfg, error, "can't bind/listen on %s:%s", port->host, port->port);
   }
 
   return true;
@@ -208,8 +185,7 @@ next(cfg_t *cfg, char *buf, size_t bufsize, bool reset) {
     if (sock < 0 && errno == EAGAIN)
       continue;
     if (sock < 0) {
-      snprintf(cfg->error, sizeof(cfg->error), "accept error: %s", strerror(errno));
-      cfg->errcb(cfg->error);
+      log_msg(cfg, error, "accept() error: %s", strerror(errno));
       continue;
     }
     close(sock);
@@ -221,7 +197,7 @@ next(cfg_t *cfg, char *buf, size_t bufsize, bool reset) {
       inet_ntop(AF_INET6, &(((struct sockaddr_in6 *) &addr)->sin6_addr), buf, bufsize);
       return true;
     }
-    cfg->errcb("can't convert sockaddr to string: unknown AF");
+    cfg->logcb(error, "can't convert sockaddr to string: unknown AF");
   }
 
   return false;
diff --git a/src/sources/redis.c b/src/sources/redis.c
index 0383a00..fb0ac0b 100644
--- a/src/sources/redis.c
+++ b/src/sources/redis.c
@@ -4,20 +4,20 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
-#include "source.h"
-
 #include <stdint.h>
 #include <hiredis/hiredis.h>
 
 #include "../strlcpy.h"
 
+#include "source.h"
+
+#define MODNAME "redis"
 #define ID_MAX 32
 
 struct _config {
   char name[ID_MAX + 1];
   char hash[ID_MAX * 2];
-  char error[256];
-  void (*errcb)(const char *errstr);
+  void (*logcb)(enum loglevel lvl, const char *msg);
   time_t timeout;
   uint8_t database;
   char password[32];
@@ -26,11 +26,7 @@ struct _config {
   redisContext *conn;
 };
 
-static void
-errcb_stub(const char *str) {
-  assert(str != NULL);
-  (void)(str);
-}
+#include "source.c"
 
 static bool
 redis_connect(cfg_t *cfg) {
@@ -47,14 +43,14 @@ redis_connect(cfg_t *cfg) {
     if (!conn)
       break;
     if (conn->err) {
-      snprintf(cfg->error, sizeof(cfg->error), "Connection error: %s", conn->errstr);
+      log_msg(cfg, error, "connection error: %s", conn->errstr);
       break;
     }
     if (cfg->password[0]) {
       if ((reply = redisCommand(conn, "AUTH %s", cfg->password)) == NULL)
         break;
       if (reply->type == REDIS_REPLY_ERROR) {
-        snprintf(cfg->error, sizeof(cfg->error), "auth error: %s", reply->str);
+        log_msg(cfg, error, "auth error: %s", reply->str);
         break;
       }
       freeReplyObject(reply);
@@ -63,7 +59,7 @@ redis_connect(cfg_t *cfg) {
       if ((reply = redisCommand(conn, "SELECT %d", cfg->database)) == NULL)
         break;
       if (reply->type == REDIS_REPLY_ERROR) {
-        snprintf(cfg->error, sizeof(cfg->error), "auth error: %s", reply->str);
+        log_msg(cfg, error, "reply error: %s", reply->str);
         break;
       }
       freeReplyObject(reply);
@@ -71,13 +67,13 @@ redis_connect(cfg_t *cfg) {
     timeout.tv_sec  = 0;
     timeout.tv_usec = 10000; /* 0.01s */
     if (redisSetTimeout(conn, timeout) != REDIS_OK) {
-      strlcpy(cfg->error, "can't enable nonblocking mode", sizeof(cfg->error));
+      log_msg(cfg, error, "can't enable nonblocking mode");
       break;
     }
     if ((reply = redisCommand(conn, "SUBSCRIBE %s", cfg->hash)) == NULL)
       break;
     if (reply->type == REDIS_REPLY_ERROR) {
-      snprintf(cfg->error, sizeof(cfg->error), "can't subscribe: %s", reply->str);
+      log_msg(cfg, error, "can't subscribe: %s", reply->str);
       break;
     }
     freeReplyObject(reply);
@@ -118,7 +114,7 @@ create(const char *init) {
   strlcpy(cfg->name, init, sizeof(cfg->name));
   strlcpy(cfg->hash, "f2b-banned-", sizeof(cfg->hash));
   strlcat(cfg->hash, init, sizeof(cfg->hash));
-  cfg->errcb = &errcb_stub;
+  cfg->logcb = &logcb_stub;
 
   return cfg;
 }
@@ -163,21 +159,6 @@ ready(cfg_t *cfg) {
   return true;
 }
 
-char *
-error(cfg_t *cfg) {
-  assert(cfg != NULL);
-
-  return cfg->error;
-}
-
-void
-errcb(cfg_t *cfg, void (*cb)(const char *errstr)) {
-  assert(cfg != NULL);
-  assert(cb  != NULL);
-
-  cfg->errcb = cb;
-}
-
 bool
 start(cfg_t *cfg) {
   assert(cfg != NULL);
@@ -209,7 +190,7 @@ next(cfg_t *cfg, char *buf, size_t bufsize, bool reset) {
     return false; /* reconnect failure */
 
   if (cfg->conn->err) {
-    snprintf(cfg->error, sizeof(cfg->error), "connection error: %s", cfg->conn->errstr);
+    log_msg(cfg, error, "connection error: %s", cfg->conn->errstr);
     return false;
   }
 
@@ -221,18 +202,16 @@ next(cfg_t *cfg, char *buf, size_t bufsize, bool reset) {
         strlcpy(buf, reply->element[2]->str, bufsize);
         gotit = true;
       } else {
-        cfg->errcb(cfg->error);
+        log_msg(cfg, error, "wrong redis message type: %s", reply->element[0]->str);
       }
     } else {
-      strlcpy(cfg->error, "reply is not a array type",  sizeof(cfg->error));
-      cfg->errcb(cfg->error);
+      log_msg(cfg, error, "reply is not a array type");
     }
     freeReplyObject(reply);
   } else if (cfg->conn->err == REDIS_ERR_IO && errno == EAGAIN) {
     cfg->conn->err = 0; /* reset error to prevent reconnecting */
   } else {
-    snprintf(cfg->error, sizeof(cfg->error),  "can't get reply from server %s: %s", cfg->host, cfg->conn->errstr);
-    cfg->errcb(cfg->error);
+    log_msg(cfg, error, "can't get reply from server %s: %s", cfg->host, cfg->conn->errstr);
   }
 
   return gotit;
diff --git a/src/sources/source.c b/src/sources/source.c
new file mode 100644
index 0000000..ce8a370
--- /dev/null
+++ b/src/sources/source.c
@@ -0,0 +1,38 @@
+/* Copyright 2016 Alex 'AdUser' Z (ad_user@runbox.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+/* function shared between modules */
+
+static void
+logcb_stub(enum loglevel lvl, const char *str) {
+  assert(str != NULL);
+  (void)(lvl);
+  (void)(str);
+}
+
+__attribute__ ((format (printf, 3, 4)))
+static void
+log_msg(const cfg_t *cfg, enum loglevel lvl, const char *format, ...) {
+  char buf[4096] = "";
+  va_list args;
+  size_t len;
+
+  len = snprintf(buf, sizeof(buf), "source/%s ", MODNAME);
+  va_start(args, format);
+  vsnprintf(buf + len, sizeof(buf) - len, format, args);
+  va_end(args);
+
+  cfg->logcb(lvl, buf);
+}
+
+void
+logcb(cfg_t *cfg, void (*cb)(enum loglevel lvl, const char *msg)) {
+  assert(cfg != NULL);
+  assert(cb  != NULL);
+
+  cfg->logcb = cb;
+}
diff --git a/src/sources/source.h b/src/sources/source.h
index 566ed16..5bbecb8 100644
--- a/src/sources/source.h
+++ b/src/sources/source.h
@@ -9,11 +9,21 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdarg.h>
 #include <string.h>
 #include <unistd.h>
 
 #include "../strlcpy.h"
 
+enum loglevel {
+  debug  = 0,
+  info   = 1,
+  notice = 2,
+  warn   = 3,
+  error  = 4,
+  fatal  = 5,
+}; /* see log.h */
+
 /**
  * @file
  * This header describes module API of type 'source'
@@ -24,17 +34,15 @@
  *   f2b, source;
  *   f2b =>  source [label="create(init)"];
  *   f2b <<  source [label="module handler, cfg_t *cfg"];
+ *   f2b =>  source [label="logcb(cfg, cb)"];
  *       |||;
  *   f2b =>  source [label="config(cfg, param, value)"];
  *   f2b <<  source [label="true"];
  *   f2b =>  source [label="config(cfg, param, value)"];
  *   f2b <<  source [label="true"];
  *   f2b =>  source [label="config(cfg, param, value)"];
+ *   f2b <<= source [label="logcb(level, char *msg)"];
  *   f2b <<  source [label="false"];
- *   f2b =>  source [label="error(cfg)"];
- *   f2b <<  source [label="const char *error"];
- *       |||;
- *   f2b =>  source [label="errcb(cfg, cb), optional"];
  *       |||;
  *   f2b =>  source [label="ready(cfg)"];
  *   f2b <<  source [label="true"];
@@ -48,7 +56,7 @@
  *   f2b =>  source [label="next(cfg, buf, sizeof(buf), true)"];
  *   f2b <<  source [label="true"];
  *   f2b =>  source [label="next(cfg, buf, sizeof(buf), false)"];
- *   f2b <<= source [label="errcb(char *error)"];
+ *   f2b <<= source [label="logcb(level, char *msg)"];
  *   f2b <<  source [label="true"];
  *   f2b =>  source [label="next(cfg, buf, sizeof(buf), false)"];
  *   f2b <<  source [label="false"];
@@ -81,7 +89,7 @@ extern cfg_t *create(const char *init);
  * @param cfg Module handler
  * @param key Parameter name
  * @param value Parameter value
- * @returns true on success, false on error with setting intenal error buffer
+ * @returns true on success, false on error
  */
 extern bool   config(cfg_t *cfg, const char *key, const char *value);
 /**
@@ -91,24 +99,16 @@ extern bool   config(cfg_t *cfg, const char *key, const char *value);
  */
 extern bool    ready(cfg_t *cfg);
 /**
- * @brief Returns last error description
- * @param cfg Module handler
- * @returns Pointer to string with description of last error
- * @note Returned pointer not marked with const, because libdl complains,
- *       but contents on pointer should not be modified or written in any way
- */
-extern char   *error(cfg_t *cfg);
-/**
- * @brief Sets the error callback for use in processing
+ * @brief Sets the log callback
  * @param cfg Module handler
- * @param cb Error callback
- * @note Optional, if this function is not called, processing errors will be suppressed
+ * @param cb Logging callback
+ * @note Optional, if this function is not called, warnings/errors of module will be suppressed
  */
-extern void    errcb(cfg_t *cfg, void (*cb)(const char *errstr));
+extern void    logcb(cfg_t *cfg, void (*cb)(enum loglevel l, const char *msg));
 /**
  * @brief Allocate resources and start processing
  * @param cfg Module handler
- * @returns true on success, false on error with setting intenal error buffer
+ * @returns true on success, false on error
  */
 extern bool    start(cfg_t *cfg);
 /**