Subject: Re: rfc: netfilter: Unhide FWINV macro arguments ?

From: Pablo Neira Ayuso <[email-masked]>
Date: Fri, 17 Jun 2016 13:59:32 +0200

On Thu, Jun 16, 2016 at 11:20:59AM -0700, Joe Perches wrote:
> There are several FWINV #defines with identical form
> that hide a specific structure variable and dereference
> it with a invflags member.

Right, this macro is obscure indeed.

> $ git grep "define FWINV"
> include/linux/netfilter_bridge/ebtables.h:#define FWINV(bool,invflg) ((bool) ^ !!(info->invflags & invflg))
> net/bridge/netfilter/ebtables.c:#define FWINV2(bool, invflg) ((bool) ^ !!(e->invflags & invflg))
> net/ipv4/netfilter/arp_tables.c:#define FWINV(bool, invflg) ((bool) ^ !!(arpinfo->invflags & (invflg)))
> net/ipv4/netfilter/ip_tables.c:#define FWINV(bool, invflg) ((bool) ^ !!(ipinfo->invflags & (invflg)))
> net/ipv6/netfilter/ip6_tables.c:#define FWINV(bool, invflg) ((bool) ^ !!(ip6info->invflags & (invflg)))
> net/netfilter/xt_tcpudp.c:#define FWINVTCP(bool, invflg) ((bool) ^ !!(tcpinfo->invflags & (invflg)))
> 
> It might make sense to use a new macro like:
> 
> #define INVFLAG(var, test, invflag)			\
> 	((test) ^ !!((var)->invflags & (invflag)))
> 
> and convert all the various FWINV style uses
> 
> $ git grep --name-only "\bFWINV"
> include/linux/netfilter_bridge/ebtables.h
> net/bridge/netfilter/ebt_802_3.c
> net/bridge/netfilter/ebt_arp.c
> net/bridge/netfilter/ebt_ip.c
> net/bridge/netfilter/ebt_ip6.c
> net/bridge/netfilter/ebt_stp.c
> net/bridge/netfilter/ebtables.c
> net/ipv4/netfilter/arp_tables.c
> net/ipv4/netfilter/ip_tables.c
> net/ipv6/netfilter/ip6_tables.c
> net/netfilter/xt_tcpudp.c
> 
> $ git grep "\bFWINV" | grep -v "#" | wc -l
> 65

I'll be taking a patch to sort out this. Thanks.