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SubjectRe: [net-next,v2,3/5] seg6: add callbacks for customizing the creation/destruction of a behavior
On Sat,  7 Nov 2020 16:31:37 +0100 Andrea Mayer wrote:
> We introduce two callbacks used for customizing the creation/destruction of
> a SRv6 behavior. Such callbacks are defined in the new struct
> seg6_local_lwtunnel_ops and hereafter we provide a brief description of
> them:
>
> - build_state(...): used for calling the custom constructor of the
> behavior during its initialization phase and after all the attributes
> have been parsed successfully;
>
> - destroy_state(...): used for calling the custom destructor of the
> behavior before it is completely destroyed.
>
> Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it>

Looks good, minor nits.

> diff --git a/net/ipv6/seg6_local.c b/net/ipv6/seg6_local.c
> index 63a82e2fdea9..4b0f155d641d 100644
> --- a/net/ipv6/seg6_local.c
> +++ b/net/ipv6/seg6_local.c
> @@ -33,11 +33,23 @@
>
> struct seg6_local_lwt;
>
> +typedef int (*slwt_build_state_t)(struct seg6_local_lwt *slwt, const void *cfg,
> + struct netlink_ext_ack *extack);
> +typedef void (*slwt_destroy_state_t)(struct seg6_local_lwt *slwt);

Let's avoid the typedefs. Instead of taking a pointer to the op take a
pointer to the ops struct in seg6_local_lwtunnel_build_state() etc.

> +/* callbacks used for customizing the creation and destruction of a behavior */
> +struct seg6_local_lwtunnel_ops {
> + slwt_build_state_t build_state;
> + slwt_destroy_state_t destroy_state;
> +};
> +
> struct seg6_action_desc {
> int action;
> unsigned long attrs;
> int (*input)(struct sk_buff *skb, struct seg6_local_lwt *slwt);
> int static_headroom;
> +
> + struct seg6_local_lwtunnel_ops slwt_ops;
> };
>
> struct bpf_lwt_prog {
> @@ -1015,6 +1027,45 @@ static void destroy_attrs(struct seg6_local_lwt *slwt)
> __destroy_attrs(attrs, 0, SEG6_LOCAL_MAX + 1, slwt);
> }
>
> +/* call the custom constructor of the behavior during its initialization phase
> + * and after that all its attributes have been parsed successfully.
> + */
> +static int
> +seg6_local_lwtunnel_build_state(struct seg6_local_lwt *slwt, const void *cfg,
> + struct netlink_ext_ack *extack)
> +{
> + slwt_build_state_t build_func;
> + struct seg6_action_desc *desc;
> + int err = 0;
> +
> + desc = slwt->desc;
> + if (!desc)
> + return -EINVAL;

This is impossible, right?

> +
> + build_func = desc->slwt_ops.build_state;
> + if (build_func)
> + err = build_func(slwt, cfg, extack);
> +
> + return err;

no need for err, just use return directly.

if (!ops->build_state)
return 0;
return ops->build_state(...);

> +}
> +
> +/* call the custom destructor of the behavior which is invoked before the
> + * tunnel is going to be destroyed.
> + */
> +static void seg6_local_lwtunnel_destroy_state(struct seg6_local_lwt *slwt)
> +{
> + slwt_destroy_state_t destroy_func;
> + struct seg6_action_desc *desc;
> +
> + desc = slwt->desc;
> + if (!desc)
> + return;
> +
> + destroy_func = desc->slwt_ops.destroy_state;
> + if (destroy_func)
> + destroy_func(slwt);
> +}
> +
> static int parse_nla_action(struct nlattr **attrs, struct seg6_local_lwt *slwt)
> {
> struct seg6_action_param *param;
> @@ -1090,8 +1141,16 @@ static int seg6_local_build_state(struct net *net, struct nlattr *nla,
>
> err = parse_nla_action(tb, slwt);
> if (err < 0)
> + /* In case of error, the parse_nla_action() takes care of
> + * releasing resources which have been acquired during the
> + * processing of attributes.
> + */

that's the normal behavior for a kernel function, comment is
unnecessary IMO

> goto out_free;
>
> + err = seg6_local_lwtunnel_build_state(slwt, cfg, extack);
> + if (err < 0)
> + goto free_attrs;

The function is called destroy_attrs, call the label out_destroy_attrs,
or err_destroy_attrs.

> newts->type = LWTUNNEL_ENCAP_SEG6_LOCAL;
> newts->flags = LWTUNNEL_STATE_INPUT_REDIRECT;
> newts->headroom = slwt->headroom;
> @@ -1100,6 +1159,9 @@ static int seg6_local_build_state(struct net *net, struct nlattr *nla,
>
> return 0;
>
> +free_attrs:
> + destroy_attrs(slwt);
> +

no need for empty lines on error paths

> out_free:
> kfree(newts);
> return err;
> @@ -1109,6 +1171,8 @@ static void seg6_local_destroy_state(struct lwtunnel_state *lwt)
> {
> struct seg6_local_lwt *slwt = seg6_local_lwtunnel(lwt);
>
> + seg6_local_lwtunnel_destroy_state(slwt);
> +
> destroy_attrs(slwt);
>
> return;

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