netdev - Re: [PATCH 2/2] netfilter: ctnetlink: support kernel-space dump filterings

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Date:	Sat, 25 Feb 2012 02:09:09 +0100 (CET)
From:	Jan Engelhardt <jengelh@...ozas.de>
To:	pablo@...filter.org
cc:	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
	davem@...emloft.net
Subject: Re: [PATCH 2/2] netfilter: ctnetlink: support kernel-space dump
 filterings


On Friday 2012-02-24 23:14, pablo@...filter.org wrote:
>@@ -977,9 +992,25 @@ ctnetlink_get_conntrack(struct sock *ctnl, struct sk_buff *skb,
> 	u16 zone;
> 	int err;
> 
>-	if (nlh->nlmsg_flags & NLM_F_DUMP)
>+	if (nlh->nlmsg_flags & NLM_F_DUMP) {
>+		struct ctnetlink_dump_filter *filter = NULL;
>+
>+#if defined(CONFIG_NF_CONNTRACK_MARK)
>+		filter = kzalloc(sizeof(struct ctnetlink_dump_filter),
>+				 GFP_KERNEL);
>+		if (filter == NULL)
>+			return -ENOMEM;
>+
>+		if (cda[CTA_MARK])
>+			filter->mark.value = ntohl(nla_get_be32(cda[CTA_MARK]));
>+		if (cda[CTA_MARK_MASK]) {
>+			filter->mark.mask =
>+				ntohl(nla_get_be32(cda[CTA_MARK_MASK]));
>+		}
>+#endif
> 		return netlink_dump_start(ctnl, skb, nlh, ctnetlink_dump_table,
>-					  ctnetlink_done, NULL, 0);
>+					  ctnetlink_done, filter, 0);
>+	}

I had thought of the following before your patch came up:

ctnl_dump_any(skb,cb)
{
	...loop over CTs...
}
ctnl_dump_foo(skb,cb)
{
	if (cb->args[0] == NULL) {
		cb->args[0] = filter = kzalloc(sizeof(struct ctnl_dump_filter));
		if (cb->nlh has CTA_MARK) /* [1] */
			filter->mark.value = ...
	}
	return ctnl_dump_any(skb,cb);
}
ctnl_dump_bar(skb,cb)
{
	if (cb->args[0] == NULL) {
		cb->args[0] = somethingelse;
	}
	return ctnl_dump_any(skb,cb);
}
ctnetlink_get_foo(ctnl,skb,...)
{
	netlink_dump_start(ctnl,skb,nlh,ctnl_dump_foo,ctnl_done,0);
}
ctnetlink_get_bar(ctnl,skb,...)
{
	netlink_dump_start(ctnl,skb,nlh,ctnl_dump_bar,ctnl_done,0);
}

[1]: Arguably needs a way to put cda into cb.

==

Either way, netlink is gathering up a lot of arguments and has come
to the point where I would suggest to put it all into a struct,
like we have done for struct xt_action_param.
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