[PATCH 3/4] nfnetlink: introduce generic netfilter subsystem decoder

[Dmitry V. Levin]

On Thu, Jan 18, 2018 at 10:02:34PM +0800, Chen Jingpiao wrote:
> * defs.h (nl_netfilter_msg_types): New xlat prototype.
> * netlink_netfilter.c: Include "nlattr.h".
> (decode_netlink_netfilter): Call decode_nlattr.
> ---
>  defs.h              |  1 +
>  netlink_netfilter.c | 11 +++++++++--
>  2 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/defs.h b/defs.h
> index 6b51626..cf75802 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -287,6 +287,7 @@ extern const struct xlat inet_protocols[];
>  extern const struct xlat ip_type_of_services[];
>  extern const struct xlat msg_flags[];
>  extern const struct xlat netlink_protocols[];
> +extern const struct xlat nl_netfilter_msg_types[];
>  extern const struct xlat nl_route_types[];
>  extern const struct xlat open_access_modes[];
>  extern const struct xlat open_mode_flags[];
> diff --git a/netlink_netfilter.c b/netlink_netfilter.c
> index a5efeb6..2840301 100644
> --- a/netlink_netfilter.c
> +++ b/netlink_netfilter.c
> @@ -31,6 +31,7 @@
>  #ifdef HAVE_LINUX_NETFILTER_NFNETLINK_H
>  
>  # include "print_fields.h"
> +# include "nlattr.h"
>  
>  # include <netinet/in.h>
>  # include <arpa/inet.h>
> @@ -77,8 +78,14 @@ decode_netlink_netfilter(struct tcb *const tcp,
>  		const size_t offset = NLMSG_ALIGN(sizeof(nfmsg));
>  		if (len > offset) {
>  			tprints(", ");
> -			printstr_ex(tcp, addr + offset,
> -				    len - offset, QUOTE_FORCE_HEX);
> +			if (subsys_id >= NFNL_SUBSYS_COUNT
> +			    || xlookup(nl_netfilter_msg_types,
> +				       nlmsghdr->nlmsg_type))
> +				printstr_ex(tcp, addr + offset,
> +					    len - offset, QUOTE_FORCE_HEX);
> +			else
> +				decode_nlattr(tcp, addr + offset, len - offset,
> +					      NULL, NULL, NULL, 0, NULL);
>  		}
>  	}
>  

Is this xlookup better than an explicit check for
(nlmsghdr->nlmsg_type >= NFNL_MSG_BATCH_BEGIN &&
 nlmsghdr->nlmsg_type <= NFNL_MSG_BATCH_END)

?

-- 
ldv
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