Description: Fix undefined sprintf usage
Author: Christoph Biedl <debian.axhn@manchmal.in-ulm.de>
Bug: https://bitbucket.org/ripencc/bgpdump/issues/33/
Last-Update: 2016-07-18

    Documentation states appending to a buffer using
        sprintf (buf, "%s.foo", buf);
    results in undefined behaviour. Work around it.

--- a/bgpdump.c
+++ b/bgpdump.c
@@ -261,19 +261,20 @@
 	char time_str_fixed[128];
     char prefix[BGPDUMP_ADDRSTRLEN];
     char *bgp4mp_format;
+    int len;
 	
 	date=gmtime(&entry->time);
 	time2str(date,time_str_fixed);
     
     if (mode == 1) {
         // Timestamp mode
-        sprintf(time_str, "%ld", entry->time);
+        len = sprintf(time_str, "%ld", entry->time);
     } else {
-        time2str(date,time_str);
+        len = time2str(date,time_str);
     }
     // Appending microseconds to time_str if needed
     if (entry->type == BGPDUMP_TYPE_ZEBRA_BGP_ET) {
-        sprintf(time_str, "%s.%06ld", time_str, entry->ms);
+        sprintf(time_str + len, ".%06ld", entry->ms);
     }
     
 	if (mode==0)
--- a/util.c
+++ b/util.c
@@ -66,9 +66,9 @@
 void warn(const char *fmt, ...) { log(WARNING, warn); }
 void debug(const char *fmt, ...) { log(INFO, info); }
 
-void time2str(struct tm* date,char *time_str)
+int time2str(struct tm* date,char *time_str)
 {
-    sprintf(time_str, "%02d/%02d/%02d %02d:%02d:%02d", date->tm_mon+1, date->tm_mday, date->tm_year%100,
+    return sprintf(time_str, "%02d/%02d/%02d %02d:%02d:%02d", date->tm_mon+1, date->tm_mday, date->tm_year%100,
             date->tm_hour, date->tm_min, date->tm_sec);
 }
 
--- a/util.h
+++ b/util.h
@@ -38,7 +38,7 @@
 char *fmt_ipv6(BGPDUMP_IP_ADDRESS addr, char *buffer);
 void test_fmt_ip(void);
 
-void time2str(struct tm* date,char *time_str);
+int time2str(struct tm* date,char *time_str);
 int int2str(uint32_t value, char* str);
 void test_utils(void);