Send host labels via exporting connectors (#7554)

* Add labels to the JSON exporting connector

* Add labels to the Graphite exporting connector

* Add labels to the OpenTSDB telnet exporting connector

* Add labels to the OpenTSDB HTTP exporting connector

* Replace control characters in JSON strings

* Add unit tests

1 files changed, 10 insertions, 4 deletions

diff --git a/libnetdata/inlined.h b/libnetdata/inlined.h
index 330b65648e..6f236b8f47 100644
--- a/libnetdata/inlined.h
+++ b/libnetdata/inlined.h
@@ -246,12 +246,18 @@ static inline char *strncpyz(char *dst, const char *src, size_t n) {
     return p;
 }
 
-static inline void escape_json_string(char *dst, char *src, size_t len) {
+static inline void sanitize_json_string(char *dst, char *src, size_t len) {
     while (*src != '\0' && len > 1) {
         if (*src == '\\' || *src == '\"' || *src < 0x1F) {
-            *dst++ = '\\';
-            *dst++ = *src++;
-            len -= 2;
+            if (*src < 0x1F) {
+                *dst++ = '_';
+                src++;
+                len--;
+            } else {
+                *dst++ = '\\';
+                *dst++ = *src++;
+                len -= 2;
+            }
         } else {
             *dst++ = *src++;
             len--;