nlmsg: Improve payload printing

It makes more sense to use isprint() than isalnum() because we use non
alphanumeric characters like '%', '_', etc. And, in case of non
printable character, print a space is preferable to print a NULL (0) in
order to keep alignment.

Before:
...
|00012|--|00002|	|len |flags| type|
| 5f 5f 73 65  |	|      data      |	   s e
| 74 25 64 00  |	|      data      |	 t  d
...

After:
...
|00012|--|00002|	|len |flags| type|
| 5f 5f 73 65  |	|      data      |	 _ _ s e
| 74 25 64 00  |	|      data      |	 t % d
...

Signed-off-by: Carlos Falgueras García <carlosfg@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

0 files changed, 0 insertions, 0 deletions