backup: print the full network hostname in the label file

src/knot/zone/backup.c

@@ -17,6 +17,7 @@
 #include <assert.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <netdb.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -71,18 +72,26 @@ static const char *label_file_head = LABEL_FILE_HEAD;
 
 static int make_label_file(zone_backup_ctx_t *ctx, char *full_path)
 {
-	int ret;
-
 	FILE *file = fopen(full_path, "w");
 	if (file == NULL) {
 		return knot_map_errno();
 	}
 
 	// Prepare the hostname.
 	char hostname[HOSTNAME_MAX];
-	gethostname(hostname, HOSTNAME_MAX);
+	int ret = gethostname(hostname, HOSTNAME_MAX);
 	// When the name doesn't fit, the \0 terminator isn't always guaranteed.
 	hostname[HOSTNAME_MAX - 1] = '\0';
+	char *netname = hostname;
+	if (ret == 0) {
+		struct hostent* h;
+		h = gethostbyname(hostname);
+		if (h != NULL) {
+			netname = h->h_name;
+		}
+	} else {
+		netname = "<unknown>";
+	}
 
 	// Prepare the timestamps.
 	char started_time[64], finished_time[64];
@@ -107,7 +116,7 @@ static int make_label_file(zone_backup_ctx_t *ctx, char *full_path)
 	                  "+backupdir %s\n"
 	              "zone_count: %d\n",
 	              label_file_head,
-	              BACKUP_VERSION, hostname, started_time, finished_time, PACKAGE_VERSION,
+	              BACKUP_VERSION, netname, started_time, finished_time, PACKAGE_VERSION,
 	              ctx->backup_zonefile ? "" : "no",
 	              ctx->backup_journal ? "" : "no",
 	              ctx->backup_timers ? "" : "no",