Re: [PATCH] iptables: cleanup FIXME

[Phil Sutter <phil@nwl.cc>]

Hi Michael,

On Fri, May 24, 2024 at 03:24:51PM +0200, Michael Estner wrote:
> I checked bitmask in the ebt_entry struct in iptables/xshared.h
> Should be compared here since bitmask needs to be the first
> field in the struct ebt_entry.

The reason why 'bitmask' has to be the first field is that in kernel
space, the first bit in it is used to distinguish list element types
between 'struct ebt_entries' and 'struct ebt_entry'. See
EBT_ENTRY_OR_ENTRIES define and the related comment in
include/uapi/linux/netfilter_bridge/ebtables.h for reference.

While it seems sensible to do, I wonder why things seem to work fine
even without it. Do we find a corner-case which makes it necessary to
compare 'bitmask'? Or the other way round, is there a case which breaks
if we do?

Cheers, Phil