Re: [PATCH] message parsing functions for nfqueue

[Pablo Neira <pablo@netfilter.org>]

Eric Leblond wrote:
> This is a patch against libnfnetlink_queue.
> 
> It adds "high" level functions to access to the data contained in a
> nfqueue message. These are mostly encapsulation of NFA macros.
> 
> -
> -	if (tb[NFQA_PACKET_HDR-1]) {
> -		struct nfqnl_msg_packet_hdr *ph = 
> -					NFA_DATA(tb[NFQA_PACKET_HDR-1]);
> +	struct nfqnl_msg_packet_hdr *ph;
> +	u_int32_t mark,ifi; 
> +	int ret;
> +	unsigned int datalength;
> +	char * data;
> +	
> +	ph = nfqnl_get_msg_packet_hdr(tb);
> +	if (ph){
>  		id = ntohl(ph->packet_id);
>  		printf("hw_protocol=0x%04x hook=%u id=%u ",
>  			ntohs(ph->hw_protocol), ph->hook, id);
>  	}

Instead of adding a function to access every attribute like above, why 
don't we add something more generic in libnfnetlink? Like the following 
macros:

#define nfnl_get_data(tb, attr, type)			\
({	type __ret = 0;					\
  	if (tb[attr-1])					\
  		__ret = *(type *)NFA_DATA(tb[attr-1]);	\
	__ret;						\
})

#define nfnl_get_pointer_to_data(tb, attr, type)	\
({	type *__ret = NULL;				\
  	if (tb[attr-1])					\
  		__ret = NFA_DATA(tb[attr-1]);		\
  	__ret;						\
})

Maybe too generic ?

OTOH, if we add such high level functions we'll have to do the same in 
other libnfnetlink_* libraries to keep homogeneity of the API.

--
Pablo