netdev - Re: [PATCH nf 2/2] netfilter: nf_tables: add clone interface to expression operations

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Message-ID: <20151110185804.GG25929@macbook.localdomain>
Date:	Tue, 10 Nov 2015 18:58:05 +0000
From:	Patrick McHardy <kaber@...sh.net>
To:	Pablo Neira Ayuso <pablo@...filter.org>
Cc:	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH nf 2/2] netfilter: nf_tables: add clone interface to
 expression operations

On 10.11, Pablo Neira Ayuso wrote:
> On Tue, Nov 10, 2015 at 06:30:34PM +0000, Patrick McHardy wrote:
> > >  	__module_get(src->ops->type->owner);
> > > -	memcpy(dst, src, src->ops->size);
> > > +	if (src->ops->clone) {
> > > +		memcpy(dst, src, sizeof(*src));
> > 
> > Why copy if we clone? The function should do a full initialization if it is
> > present I would say.
> 
> This is not copying the variable length data area of the expression,
> just the expression head.

Ah right. But that is only ->ops. We can set this directly, should generate
better code and be easier to understand.

> 
> > > +		err = src->ops->clone(dst, src);
> > > +		if (err < 0)
> > > +			return err;
> > > +	} else {
> > > +		memcpy(dst, src, src->ops->size);
> > > +	}
> > > +	return 0;
> > >  }
> > >  
> 
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