added an machine-id file handling for randomly generated uuids in a fallback scenario

Signed-off-by: dietWall <[email protected]>

Author: dietWall

src/flb_utils.c

@@ -2043,13 +2043,39 @@ static int machine_id_read_and_sanitize(char *path,
     return 0;
 }
 
+int write_uuid_to_file(char* filename, char* uuid) {
+    int fd;
+    size_t uuid_len;
+
+    if (filename == NULL || uuid == NULL) {
+        return FLB_FALSE;
+    }
+
+    /* write uuid to file */
+    fd = flb_open(filename, O_CREAT | O_WRONLY | O_TRUNC, 0666);
+    if (fd == -1) {
+        return FLB_FALSE;
+    }
+
+    uuid_len = strlen(uuid);
+
+    if (flb_write(fd, uuid, uuid_len) != uuid_len) {
+        flb_close(fd);
+        return FLB_FALSE;
+    }
+
+    flb_close(fd);
+    return FLB_TRUE;
+}
+
 int flb_utils_get_machine_id(char **out_id, size_t *out_size)
 {
     int ret;
     char *id;
     size_t bytes;
     char *uuid;
     int fallback = FLB_FALSE;
+    char *fallback_id = "machine-id";           //should reside in current working directory
 
 #ifdef __linux__
     char *dbus_var = "/var/lib/dbus/machine-id";
@@ -2084,6 +2110,24 @@ int flb_utils_get_machine_id(char **out_id, size_t *out_size)
             return 0;
         }
     }
+
+    if (access(fallback_id, F_OK) == 0) 
+    {
+        ret = machine_id_read_and_sanitize(fallback_id, &id, &bytes);
+        if(ret == 0)
+        {
+            if (bytes == 0) {
+                /* guid is somewhat corrupted */
+                fallback = FLB_TRUE;
+                goto fallback;
+            }
+        }
+
+        *out_id = id;
+        *out_size = bytes;
+        return 0;
+    }
+
 #elif defined(__FreeBSD__) || defined(__NetBSD__) || \
       defined(__OpenBSD__) || defined(__DragonFly__)
 
@@ -2175,7 +2219,7 @@ int flb_utils_get_machine_id(char **out_id, size_t *out_size)
 #endif
 
 fallback:
-
+    
     flb_warn("falling back on random machine UUID");
 
     /* generate a random uuid */
@@ -2185,15 +2229,22 @@ int flb_utils_get_machine_id(char **out_id, size_t *out_size)
         return -1;
     }
     ret = flb_utils_uuid_v4_gen(uuid);
+    
     if (ret == 0) {
+
+        int write_result = write_uuid_to_file(fallback_id, uuid);
+        if (write_result != 0)
+        {
+            //writing failed, next uuid generation
+            flb_warn("failed to write machine-id to file %s", fallback_id);
+        }
         *out_id = uuid;
         *out_size = strlen(uuid);
         if (fallback == FLB_TRUE) {
             return 2;
         }
         return 0;
     }
-
     return -1;
 }