Subject: Re: [PATCH net-next v4 1/2] net sched actions: Add support for user cookies

From: Daniel Borkmann <[email-masked]>
Date: Tue, 17 Jan 2017 15:16:39 +0100

On 01/17/2017 12:11 PM, Jamal Hadi Salim wrote:
> From: Jamal Hadi Salim <[email-masked]>
>
> Introduce optional 128-bit action cookie.
> Like all other cookie schemes in the networking world (eg in protocols
> like http or existing kernel fib protocol field, etc) the idea is to save
> user state that when retrieved serves as a correlator. The kernel
> _should not_ intepret it.  The user can store whatever they wish in the
> 128 bits.
[...]

Since it looks like you need a v5 anyway, few comments below.

>   include/net/act_api.h        |  1 +
>   include/net/pkt_cls.h        |  8 ++++++++
>   include/uapi/linux/pkt_cls.h |  3 +++
>   net/sched/act_api.c          | 25 +++++++++++++++++++++++++
>   4 files changed, 37 insertions(+)
>
> diff --git a/include/net/act_api.h b/include/net/act_api.h
> index 1d71644..0692458 100644
> --- a/include/net/act_api.h
> +++ b/include/net/act_api.h
> @@ -41,6 +41,7 @@ struct tc_action {
>   	struct rcu_head			tcfa_rcu;
>   	struct gnet_stats_basic_cpu __percpu *cpu_bstats;
>   	struct gnet_stats_queue __percpu *cpu_qstats;
> +	struct tc_cookie	*act_ck;

Since we know anyway that this is part of struct tc_action, can't
you just give this some real/readable name like ...

   struct tc_cookie cookie;

... and then ...

>   };
>   #define tcf_head	common.tcfa_head
>   #define tcf_index	common.tcfa_index
> diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h
> index f0a0514..e0bc7e8 100644
> --- a/include/net/pkt_cls.h
> +++ b/include/net/pkt_cls.h
> @@ -515,4 +515,12 @@ struct tc_cls_bpf_offload {
>   	u32 gen_flags;
>   };
>
> +
> +/* This structure holds cookie structure that is passed from user
> + * to the kernel for actions and classifiers
> + */
> +struct tc_cookie {
> +	unsigned char ck[TC_COOKIE_MAX_SIZE];
> +	unsigned char ck_len;

... embed and make this ...

struct tc_cookie {
	u8  *data;
	u32  len;
};

as act->act_ck->ck_len is rather funky, compare that to act->cookie->len.

> +};
>   #endif
[...]
> @@ -575,6 +583,23 @@ struct tc_action *tcf_action_init_1(struct net *net, struct nlattr *nla,
>   	if (err < 0)
>   		goto err_mod;
>
> +	if (tb[TCA_ACT_COOKIE]) {
> +		if (nla_len(tb[TCA_ACT_COOKIE]) > TC_COOKIE_MAX_SIZE) {
> +			err = -EINVAL;
> +			goto err_mod;
> +		}
> +
> +		a->act_ck = kzalloc(sizeof(*a->act_ck), GFP_KERNEL);
> +		if (unlikely(!a->act_ck)) {
> +			err = -ENOMEM;
> +			goto err_mod;
> +		}
> +
> +		memcpy(a->act_ck->ck, nla_data(tb[TCA_ACT_COOKIE]),
> +		       nla_len(tb[TCA_ACT_COOKIE]));
> +		a->act_ck->ck_len = nla_len(tb[TCA_ACT_COOKIE]);

Then you can also simplify all this and use nla_memdup() here for
act->cookie->data.

> +	}
> +
>   	/* module count goes up only when brand new policy is created
>   	 * if it exists and is only bound to in a_o->init() then
>   	 * ACT_P_CREATED is not returned (a zero is).
>