Re: [PATCH] Allow to compile for < 3.17 kernel version

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

On Thu, Sep 25, 2014 at 07:12:57PM +0200, Pablo Neira Ayuso wrote:
> On Thu, Sep 25, 2014 at 03:57:04AM +0300, Vadim Kochan wrote:
> > Added declaration checking for NFT_EXPR_LOG_LEVEL enum
> > which was added for 3.17 kernel version.
> > 
[...]
> > diff --git a/src/netlink_delinearize.c b/src/netlink_delinearize.c
> > index 796b632..cf2ec00 100644
> > --- a/src/netlink_delinearize.c
> > +++ b/src/netlink_delinearize.c
> > @@ -447,11 +447,13 @@ static void netlink_parse_log(struct netlink_parse_ctx *ctx,
> >  			nft_rule_expr_get_u16(nle, NFT_EXPR_LOG_QTHRESHOLD);
> >  		stmt->log.flags |= STMT_LOG_QTHRESHOLD;
> >  	}
> > +#if HAVE_DECL_NFT_EXPR_LOG_LEVEL
> >  	if (nft_rule_expr_is_set(nle, NFT_EXPR_LOG_LEVEL)) {
> >  		stmt->log.level =
> >  			nft_rule_expr_get_u32(nle, NFT_EXPR_LOG_LEVEL);
> >  		stmt->log.flags |= STMT_LOG_LEVEL;
> >  	}
> > +#endif
> >  	list_add_tail(&stmt->list, &ctx->rule->stmts);
> >  }
> >  
> 
> I don't want to pollute the source code with many ifdef's, sorry. And
> if I apply this, more similar follow up patches will come in the
> future.
> 
> I'll make a patch to some recommended libnftnl version at configure
> stage using PKG_CHECK_MODULES.

BTW, regarding the patch title, you should be able to compile libnftnl
and nftables with no matter kernel version since we're caching the
header files.

So the subject is innacurate. The real problem is that you cannot
compile new nftables with old library version since
NFT_EXPR_LOG_LEVEL, which is a different thing.