Re: [nft PATCH 3/4] echo: Fix for added delays in rule updates

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

On Tue, Aug 15, 2017 at 01:43:04AM +0200, Phil Sutter wrote:
> The added cache update upon every command dealing with rules was a
> bummer. Instead, perform the needed cache update only if echo option was
> set.
> 
> Initially, I tried to perform the cache update from within
> netlink_echo_callback(), but that turned into a mess since the shared
> socket between cache_init() and mnl_batch_talk() would receive
> unexpected new input. So instead update the cache from do_command_add(),
> netlink_replace_rule_batch() and do_comand_insert() so it completes
> before mnl_batch_talk() starts listening.
> 
> Signed-off-by: Phil Sutter <phil@nwl.cc>
> ---
>  include/netlink.h |  5 +----
>  src/evaluate.c    |  9 ---------
>  src/netlink.c     | 22 +++++++++++++++-------
>  src/rule.c        | 26 ++++++++++++++++++++++----
>  4 files changed, 38 insertions(+), 24 deletions(-)
> 
> diff --git a/include/netlink.h b/include/netlink.h
> index 3726171424c33..e7e4bbcfc0f51 100644
> --- a/include/netlink.h
> +++ b/include/netlink.h
> @@ -119,10 +119,7 @@ extern int netlink_add_rule_batch(struct netlink_ctx *ctx,
>  extern int netlink_del_rule_batch(struct netlink_ctx *ctx,
>  				  const struct handle *h,
>  				  const struct location *loc);
> -extern int netlink_replace_rule_batch(struct netlink_ctx *ctx,
> -				      const struct handle *h,
> -				      const struct rule *rule,
> -				      const struct location *loc);
> +extern int netlink_replace_rule_batch(struct netlink_ctx *ctx, struct cmd *cmd);

This patch comes with an interesting cleanup, that is that you just
pass struct cmd as function parameter.

Probably we can do this everywhere in the netlink.c code? I wonder if
it's better just to fix this without changing the function footprint.
Then, work a cleanup patch to update all netlink_* functions to pass
struct cmd as parameter.

So we leave everything looking consistent.

>  extern int netlink_add_chain(struct netlink_ctx *ctx, const struct handle *h,
>  			     const struct location *loc,
> diff --git a/src/evaluate.c b/src/evaluate.c
> index 64e14b8ba8d98..0fad0913488d0 100644
> --- a/src/evaluate.c
> +++ b/src/evaluate.c
> @@ -2965,10 +2965,6 @@ static int cmd_evaluate_add(struct eval_ctx *ctx, struct cmd *cmd)
>  		handle_merge(&cmd->set->handle, &cmd->handle);
>  		return set_evaluate(ctx, cmd->set);
>  	case CMD_OBJ_RULE:
> -		ret = cache_update(ctx->nf_sock, ctx->cache, cmd->op,
> -				   ctx->msgs);
> -		if (ret < 0)
> -			return ret;
>  		handle_merge(&cmd->rule->handle, &cmd->handle);
>  		return rule_evaluate(ctx, cmd->rule);
>  	case CMD_OBJ_CHAIN:
> @@ -2983,11 +2979,6 @@ static int cmd_evaluate_add(struct eval_ctx *ctx, struct cmd *cmd)
>  	case CMD_OBJ_COUNTER:
>  	case CMD_OBJ_QUOTA:
>  	case CMD_OBJ_CT_HELPER:
> -		ret = cache_update(ctx->nf_sock, ctx->cache, cmd->op,
> -				   ctx->msgs);
> -		if (ret < 0)
> -			return ret;
> -
>  		return 0;
>  	default:
>  		BUG("invalid command object type %u\n", cmd->obj);
> diff --git a/src/netlink.c b/src/netlink.c
> index f631c26b2b9ca..e7fe62b21da6a 100644
> --- a/src/netlink.c
> +++ b/src/netlink.c
> @@ -459,20 +459,28 @@ int netlink_add_rule_batch(struct netlink_ctx *ctx,
>  	return err;
>  }
>  
> -int netlink_replace_rule_batch(struct netlink_ctx *ctx, const struct handle *h,
> -			       const struct rule *rule,
> -			       const struct location *loc)
> +int netlink_replace_rule_batch(struct netlink_ctx *ctx, struct cmd *cmd)
>  {
>  	struct nftnl_rule *nlr;
> -	int err, flags = ctx->octx->echo ? NLM_F_ECHO : 0;
> +	int err, flags = 0;
>  
> -	nlr = alloc_nftnl_rule(&rule->handle);
> -	netlink_linearize_rule(ctx, nlr, rule);
> +	if (ctx->octx->echo) {
> +		err = cache_update(ctx->nf_sock, ctx->cache,
> +				   cmd->obj, ctx->msgs);
> +		if (err < 0)
> +			return err;
> +
> +		flags |= NLM_F_ECHO;
> +	}
> +
> +	nlr = alloc_nftnl_rule(&cmd->rule->handle);
> +	netlink_linearize_rule(ctx, nlr, cmd->rule);
>  	err = mnl_nft_rule_batch_replace(nlr, ctx->batch, flags, ctx->seqnum);
>  	nftnl_rule_free(nlr);
>  
>  	if (err < 0)
> -		netlink_io_error(ctx, loc, "Could not replace rule to batch: %s",
> +		netlink_io_error(ctx, &cmd->location,
> +				 "Could not replace rule to batch: %s",
>  				 strerror(errno));
>  	return err;
>  }
> diff --git a/src/rule.c b/src/rule.c
> index 1bd5c80158b7b..ab19525757fff 100644
> --- a/src/rule.c
> +++ b/src/rule.c
> @@ -1017,8 +1017,16 @@ static int do_command_add(struct netlink_ctx *ctx, struct cmd *cmd, bool excl)
>  {
>  	uint32_t flags = excl ? NLM_F_EXCL : 0;
>  
> -	if (ctx->octx->echo)
> +	if (ctx->octx->echo) {
> +		int rc;

Another nitpick: We seem to use 'int ret' everywhere in the code. So
probably for consistency, use this name here too.

> +
> +		rc = cache_update(ctx->nf_sock, ctx->cache,
> +				  cmd->obj, ctx->msgs);
> +		if (rc < 0)
> +			return rc;
> +
>  		flags |= NLM_F_ECHO;
> +	}
>  
>  	switch (cmd->obj) {
>  	case CMD_OBJ_TABLE:
> @@ -1048,8 +1056,7 @@ static int do_command_replace(struct netlink_ctx *ctx, struct cmd *cmd)
>  {
>  	switch (cmd->obj) {
>  	case CMD_OBJ_RULE:
> -		return netlink_replace_rule_batch(ctx, &cmd->handle, cmd->rule,
> -						  &cmd->location);
> +		return netlink_replace_rule_batch(ctx, cmd);
>  	default:
>  		BUG("invalid command object type %u\n", cmd->obj);
>  	}
> @@ -1058,7 +1065,18 @@ static int do_command_replace(struct netlink_ctx *ctx, struct cmd *cmd)
>  
>  static int do_command_insert(struct netlink_ctx *ctx, struct cmd *cmd)
>  {
> -	uint32_t flags = ctx->octx->echo ? NLM_F_ECHO : 0;
> +	uint32_t flags = 0;
> +
> +	if (ctx->octx->echo) {
> +		int rc;
> +
> +		rc = cache_update(ctx->nf_sock, ctx->cache,
> +				  cmd->obj, ctx->msgs);
> +		if (rc < 0)
> +			return rc;
> +
> +		flags |= NLM_F_ECHO;
> +	}
>  
>  	switch (cmd->obj) {
>  	case CMD_OBJ_RULE:
> -- 
> 2.13.1
>