Re: [PATCH nft] libnftables: got rid of repeated initialization of netlink_ctx variable in loop.

[Phil Sutter <phil@nwl.cc>]

Hi,

On Thu, Jul 18, 2019 at 10:05:52PM +0100, Jeremy Sowden wrote:
> Most members in the context doesn't change, so there is no need to
> memset it and reassign most of its members on every iteration.  Moved
> that code out of the loop.
> 
> Fixes: 49900d448ac9 ("libnftables: Move library stuff out of main.c")

This commit merely moved the code from src/main.c into the current
location. I would rather point at a72315d2bad47 ("src: add rule batching
support"), which introduced the loop (and already contains some of the
pointless assignments). Note that commit is from 2013. :)

> Reported-by: Pablo Neira Ayuso <pablo@netfilter.org>
> Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
> ---
>  src/libnftables.c | 11 ++++-------
>  1 file changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/src/libnftables.c b/src/libnftables.c
> index 2f77a7709e2c..834ea661a146 100644
> --- a/src/libnftables.c
> +++ b/src/libnftables.c
> @@ -23,7 +23,7 @@ static int nft_netlink(struct nft_ctx *nft,
>  {
>  	uint32_t batch_seqnum, seqnum = 0, num_cmds = 0;
>  	struct nftnl_batch *batch;
> -	struct netlink_ctx ctx;
> +	struct netlink_ctx ctx = { .msgs = msgs, .nft = nft };

Use '.list = LIST_HEAD_INIT(ctx.list),' here. Refer to cache_update() in
src/rule.c for inspiration. :)

>  	struct cmd *cmd;
>  	struct mnl_err *err, *tmp;
>  	LIST_HEAD(err_list);
> @@ -32,16 +32,13 @@ static int nft_netlink(struct nft_ctx *nft,
>  	if (list_empty(cmds))
>  		return 0;
>  
> -	batch = mnl_batch_init();
> +	init_list_head(&ctx.list);

Drop this.

> +
> +	ctx.batch = batch = mnl_batch_init();

Move ctx.batch init into declaration as well. Drop dedicated 'batch'
variable and replace by 'ctx.batch'.

Thanks, Phil