# Re: \[PATCH 2.6\]: IPv6: strcpy -\> strlcpy

- From: YOSHIFUJI Hideaki / 吉藤英明 \<hidden\>
- Date: 2003-11-28 00:40:27 
- List: netdev
- Page: https://ratatoskr.run/netdev/2003/11/597330
- Thread: https://ratatoskr.run/lkml/2003/11/597316/t.md

```text
In article [ref] (at Fri, 28 Nov 2003 09:26:42 +0900 (JST)), YOSHIFUJI Hideaki / 吉藤英明 [ref] says:

> >  3)   if (len)
> >          strncpy(dst, src, len - 1);
> >       dst[len] = 0;

grr, another mistake...:

          if (len) {
             strncpy(dst, src, len - 1);
             dst[len - 1];
          }

----------------
1) use strlcpy0(dst, src, len)

size_t strlcpy0(char *dst, const char *src, size_t maxlen)
{
  size_t len = strlcpy(dst, src, maxlen);
  if (likely(maxlen != 0) && len < maxlen - 1)
    memset(dst + len + 1, 0, maxlen - len - 1);
}

2a) use strncpy0(dst, src, len)

char *strncpy0(char *dst, const char *src, size_t maxlen)
{
  memset(dst, 0, maxlen);
  if (likely(maxlen != 0))
    strncpy(dst, src, maxlen - 1);
}

2b) fix strncpy() to zero-out rest of destination buffer 
    and use strncpy0(dst, src, len)

char *strncpy0(char *dst, const char *src, size_t maxlen)
{
  if (likely(maxlen != 0)) {
    strncpy(dst, src, maxlen - 1);
    dst[maxlen - 1] = 0;
  }
}


I prefer 1 > 2b >> 2a.

--yoshfuji
```