Re: [PATCH nft 2/2] netlink: add and use _nftnl_udata_buf_alloc() helper

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Thu, Nov 09, 2023 at 04:19:29PM +0100, Thomas Haller wrote:
> On Thu, 2023-11-09 at 16:14 +0100, Pablo Neira Ayuso wrote:
> > On Wed, Nov 08, 2023 at 07:24:25PM +0100, Thomas Haller wrote:
> > > We don't want to handle allocation errors, but crash via
> > > memory_allocation_error().
> > > Also, we usually just allocate NFT_USERDATA_MAXLEN buffers.
> > > 
> > > Add a helper for that and use it.
> > > 
> > > Signed-off-by: Thomas Haller <thaller@redhat.com>
> > > ---
> > >  include/netlink.h       |  3 +++
> > >  src/mnl.c               | 16 ++++------------
> > >  src/netlink.c           |  7 ++-----
> > >  src/netlink_linearize.c |  4 +---
> > >  4 files changed, 10 insertions(+), 20 deletions(-)
> > > 
> > > diff --git a/include/netlink.h b/include/netlink.h
> > > index 6766d7e8563f..15cbb332c8dd 100644
> > > --- a/include/netlink.h
> > > +++ b/include/netlink.h
> > > @@ -260,4 +260,7 @@ struct nft_expr_loc *nft_expr_loc_find(const
> > > struct nftnl_expr *nle,
> > >  
> > >  struct dl_proto_ctx *dl_proto_ctx(struct rule_pp_ctx *ctx);
> > >  
> > > +#define _nftnl_udata_buf_alloc() \
> > > +	memory_allocation_check(nftnl_udata_buf_alloc(NFT_USERDATA
> > > _MAXLEN))
> > 
> > Add a wrapper function, no macro.
> > 
> 
> Hi,
> 
> memory_allocation_error() is itself a macro, as it uses
> __FILE__,__LINE__

In this case above, __FILE__ and __LINE__ does not provide much
information?

nftnl_expr_alloc() returns NULL when support for an expression is
missing in libnftnl, that provides a hint on that, this is very rare
and it can only happen when developing support for new expressions.

Maybe simply say __func__ instead to know what function has failed
when performing the memory allocation is a hint that is fine enough.

> This is also a macro, to preserve those parameters.
> 
> Thomas
>