Re: Best way to handle a variable-length NULL-terminated string in a tvb

["Jeremy O'Brien" <obrien654j () gmail com>]

Separated by. tvb_get_stringz is exactly what I was looking for. Thank you!

On Fri, Apr 30, 2010 at 15:42, Guy Harris <guy () alum mit edu> wrote:
> On Apr 30, 2010, at 12:33 PM, Jeremy O'Brien wrote:
>
> > So I have several strings in my protocol, which are separated by
> > NULL's.
>
> Separated by, or terminated by?
>
> I.e., is there a NUL at the end of the *last* string, or just in *between* strings?
>
> > There is no information contained in the packet that gives the
> > length of each string. Is there a better way to add these strings to
> > the protocol dissection besides doing a tvb_get_ephemeral_string() on
> > the section of the tvb in question, searching for the ending NULL's
> > for each string, and manually incrementing the offset for each one?
> > I'm just not sure if wireshark has any convenience functions that
> > would handle this sort of situation.
>
> /**
>  * Given a tvbuff and an offset, with the offset assumed to refer to
>  * a null-terminated string, find the length of that string (and throw
>  * an exception if the tvbuff ends before we find the null), allocate
>  * a buffer big enough to hold the string, copy the string into it,
>  * and return a pointer to the string.  Also return the length of the
>  * string (including the terminating null) through a pointer.
>  *
>  * tvb_get_stringz() returns a string allocated by g_malloc() and therefore
>  *                   MUST be g_free() by the caller in order not to leak
>  *                   memory.
>  *
>  * tvb_get_ephemeral_stringz() returns a string that does not need to be freed,
>  *                   instead it will automatically be freed once the next
>  *                   packet is dissected.
>  *
>  * tvb_get_seasonal_stringz() returns a string that does not need to be freed,
>  *                   instead it will automatically be freed when a new capture
>  *                   or file is opened.
>  */
> extern guint8 *tvb_get_stringz(tvbuff_t *tvb, const gint offset, gint *lengthp);
> extern guint8 *tvb_get_ephemeral_stringz(tvbuff_t *tvb, const gint offset, gint *lengthp);
> extern guint8 *tvb_get_seasonal_stringz(tvbuff_t *tvb, const gint offset, gint *lengthp);
>
> You presumably want tvb_get_ephemeral_stringz().
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