Re: [PATCH net-next v5 01/10] devlink: Add permanent config parameter get/set operations

[Jiri Pirko <jiri@resnulli.us>]

Mon, Oct 30, 2017 at 03:46:07PM CET, steven.lin1@broadcom.com wrote:
>Add support for permanent config parameter get/set commands. Used
>for persistent device configuration parameters.
>
>Signed-off-by: Steve Lin <steven.lin1@broadcom.com>
>Acked-by: Andy Gospodarek <gospo@broadcom.com>

In general, I don't like how you use netlink. Please see the rest of
this code. We should do things in the common way. More info inlined.


[...]

> 
>+/* Permanent config parameters */
>+enum devlink_perm_config_param {
>+	__DEVLINK_PERM_CONFIG_MAX,
>+	DEVLINK_PERM_CONFIG_MAX = __DEVLINK_PERM_CONFIG_MAX - 1
>+};
>+
>+/* Permanent config types */
>+enum devlink_perm_config_type {
>+	DEVLINK_PERM_CONFIG_TYPE_UNSPEC,

You should not need this. Type should be always specified.


>+	DEVLINK_PERM_CONFIG_TYPE_U8,
>+	DEVLINK_PERM_CONFIG_TYPE_U16,
>+	DEVLINK_PERM_CONFIG_TYPE_U32,
>+};

This definitelly should not be in uapi header.

	
>+
>+/* Permanent config value */
>+union devlink_perm_config_value {
>+	__u8	value8;
>+	__u16	value16;
>+	__u32	value32;
>+};

This definitelly should not be in uapi header.



>+
> #endif /* _UAPI_LINUX_DEVLINK_H_ */

[...]


>+static int devlink_nl_config_get_fill(struct sk_buff *msg,
>+				      struct devlink *devlink,
>+				      enum devlink_command cmd,
>+				      struct genl_info *info)
>+{
>+	struct nlattr *tb[DEVLINK_ATTR_MAX + 1];
>+	enum devlink_perm_config_param param;
>+	enum devlink_perm_config_type type;
>+	struct nlattr *cfgparam_attr;
>+	struct nlattr *attr;
>+	void *hdr;
>+	int err;
>+	int rem;
>+
>+	hdr = genlmsg_put(msg, info->snd_portid, info->snd_seq,
>+			  &devlink_nl_family, 0, cmd);
>+	if (!hdr)
>+		return -EMSGSIZE;
>+
>+	err = devlink_nl_put_handle(msg, devlink);
>+	if (err)
>+		goto nla_put_failure;
>+
>+	if (!info->attrs[DEVLINK_ATTR_PERM_CONFIGS]) {
>+		err = -EINVAL;
>+		goto nla_put_failure;
>+	}
>+
>+	cfgparam_attr = nla_nest_start(msg, DEVLINK_ATTR_PERM_CONFIGS);
>+
>+	nla_for_each_nested(attr, info->attrs[DEVLINK_ATTR_PERM_CONFIGS],


Okay. So I have to know what is in kernel in order to get the value.

We need a dump operation. In fact, why can't we just have dump operation?



>+			    rem) {
>+		err = nla_parse_nested(tb, DEVLINK_ATTR_MAX, attr,
>+				       devlink_nl_policy, NULL);
>+		if (err)
>+			goto nla_nest_failure;
>+		if (!tb[DEVLINK_ATTR_PERM_CONFIG_PARAMETER] ||
>+		    !tb[DEVLINK_ATTR_PERM_CONFIG_TYPE])
>+			continue;
>+
>+		param = nla_get_u32(tb[DEVLINK_ATTR_PERM_CONFIG_PARAMETER]);
>+		type = nla_get_u8(tb[DEVLINK_ATTR_PERM_CONFIG_TYPE]);

So to get parameter, I have to specify a type? What if I specify wrong
type? That is wrong. The type should be read attr for get.

You should have a param -> type table and always use that.


>+		if (param > DEVLINK_PERM_CONFIG_MAX ||
>+		    type > NLA_TYPE_MAX) {
>+			continue;
>+		}
>+		/* Note if single_param_get fails, that param won't be in
>+		 * response msg, so caller will know which param(s) failed to
>+		 * get.
>+		 */
>+		devlink_nl_single_param_get(msg, devlink, param, type);
>+	}
>+
>+	nla_nest_end(msg, cfgparam_attr);
>+
>+	genlmsg_end(msg, hdr);
>+	return 0;
>+
>+nla_nest_failure:
>+	nla_nest_cancel(msg, cfgparam_attr);
>+nla_put_failure:


You should make this multipart aware. If config parameters won't fit
into a single skb, you have to allocate another one. See devlink_dpipe_tables_fill
as an example how to do it. It is important to have this from the
beginning as the userspace knows to expect multipart message.



>+	genlmsg_cancel(msg, hdr);
>+	return err;
>+}
>+
>+static int devlink_nl_cmd_perm_config_get_doit(struct sk_buff *skb,
>+					       struct genl_info *info)
>+{
>+	struct devlink *devlink = info->user_ptr[0];
>+	struct sk_buff *msg;
>+	int err;
>+
>+	if (!devlink->ops || !devlink->ops->perm_config_get)
>+		return -EOPNOTSUPP;
>+
>+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
>+	if (!msg)
>+		return -ENOMEM;
>+
>+	err = devlink_nl_config_get_fill(msg, devlink,
>+					 DEVLINK_CMD_PERM_CONFIG_GET, info);
>+
>+	if (err) {
>+		nlmsg_free(msg);
>+		return err;
>+	}
>+
>+	return genlmsg_reply(msg, info);
>+}
>+
>+static int devlink_nl_single_param_set(struct sk_buff *msg,
>+				       struct devlink *devlink,
>+				       enum devlink_perm_config_param param,
>+				       enum devlink_perm_config_type type,
>+				       union devlink_perm_config_value *value)
>+{
>+	const struct devlink_ops *ops = devlink->ops;
>+	struct nlattr *cfgparam_attr;
>+	bool need_restart;
>+	int err;
>+
>+	/* Now set parameter */
>+	err = ops->perm_config_set(devlink, param, type, value, &need_restart);
>+	if (err)
>+		return err;
>+
>+	cfgparam_attr = nla_nest_start(msg, DEVLINK_ATTR_PERM_CONFIG);
>+	/* Update restart reqd - if any param needs restart, should be set */
>+	if (need_restart) {

You should propagate this out so the caller would fill it to the
message. This is a global thing, not per-param, shoult not be nested.



>+		err = nla_put_flag(msg,
>+				 DEVLINK_ATTR_PERM_CONFIG_RESTART_REQUIRED);
>+		if (err)
>+			goto nest_fail;
>+	}
>+
>+	/* Since set was successful, write attr back to msg */
>+	err = nla_put_u32(msg, DEVLINK_ATTR_PERM_CONFIG_PARAMETER, param);
>+	if (err)
>+		goto nest_fail;
>+
>+	nla_nest_end(msg, cfgparam_attr);
>+
>+	return 0;
>+
>+nest_fail:
>+	nla_nest_cancel(msg, cfgparam_attr);
>+	return err;
>+}
>+
>+static int devlink_nl_cmd_perm_config_set_doit(struct sk_buff *skb,
>+					       struct genl_info *info)
>+{
>+	struct devlink *devlink = info->user_ptr[0];
>+	struct nlattr *tb[DEVLINK_ATTR_MAX + 1];
>+	union devlink_perm_config_value value;
>+	enum devlink_perm_config_param param;
>+	enum devlink_perm_config_type type;
>+	struct nlattr *cfgparam_attr;
>+	struct sk_buff *msg;
>+	struct nlattr *attr;
>+	void *hdr;
>+	int rem;
>+	int err;
>+
>+	if (!devlink->ops || !devlink->ops->perm_config_get ||
>+	    !devlink->ops->perm_config_set)
>+		return -EOPNOTSUPP;
>+
>+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
>+	if (!msg)
>+		return -ENOMEM;
>+
>+	hdr = genlmsg_put(msg, info->snd_portid, info->snd_seq,
>+			  &devlink_nl_family, 0, DEVLINK_CMD_PERM_CONFIG_SET);
>+	if (!hdr) {
>+		err = -EMSGSIZE;
>+		goto nla_msg_failure;
>+	}
>+
>+	err = devlink_nl_put_handle(msg, devlink);
>+	if (err)
>+		goto nla_put_failure;
>+
>+	cfgparam_attr = nla_nest_start(msg, DEVLINK_ATTR_PERM_CONFIGS);
>+
>+	nla_for_each_nested(attr, info->attrs[DEVLINK_ATTR_PERM_CONFIGS], rem) {
>+		err = nla_parse_nested(tb, DEVLINK_ATTR_MAX, attr,
>+				       devlink_nl_policy, NULL);
>+		if (err)
>+			goto nla_nest_failure;
>+
>+		if (!tb[DEVLINK_ATTR_PERM_CONFIG_PARAMETER] ||
>+		    !tb[DEVLINK_ATTR_PERM_CONFIG_TYPE] ||
>+		    !tb[DEVLINK_ATTR_PERM_CONFIG_VALUE])
>+			continue;
>+
>+		param = nla_get_u32(tb[DEVLINK_ATTR_PERM_CONFIG_PARAMETER]);
>+		type = nla_get_u8(tb[DEVLINK_ATTR_PERM_CONFIG_TYPE]);
>+		if (param > DEVLINK_PERM_CONFIG_MAX ||
>+		    type > NLA_TYPE_MAX) {
>+			continue;
>+		}
>+
>+		switch (type) {
>+		case DEVLINK_PERM_CONFIG_TYPE_U8:
>+			value.value8 =
>+				nla_get_u8(tb[DEVLINK_ATTR_PERM_CONFIG_VALUE]);
>+			break;
>+		case DEVLINK_PERM_CONFIG_TYPE_U16:
>+			value.value16 =
>+				nla_get_u16(tb[DEVLINK_ATTR_PERM_CONFIG_VALUE]);
>+			break;
>+		case DEVLINK_PERM_CONFIG_TYPE_U32:
>+			value.value32 =
>+				nla_get_u32(tb[DEVLINK_ATTR_PERM_CONFIG_VALUE]);
>+			break;
>+		default:
>+			continue;
>+		}
>+
>+		/* Note if single_param_set fails, that param won't be in
>+		 * response msg, so caller will know which param(s) failed to
>+		 * set.

No. You should not send the params back on set operation. That is wrong.
You should use extact in order to tell anything useful to the user.


>+		 */
>+		devlink_nl_single_param_set(msg, devlink, param, type, &value);
>+	}
>+
>+	nla_nest_end(msg, cfgparam_attr);
>+
>+	genlmsg_end(msg, hdr);
>+	return genlmsg_reply(msg, info);
>+
>+nla_nest_failure:
>+	nla_nest_cancel(msg, cfgparam_attr);
>+nla_put_failure:
>+	genlmsg_cancel(msg, hdr);
>+nla_msg_failure:
>+	return err;
>+}
>+
> int devlink_dpipe_match_put(struct sk_buff *skb,
> 			    struct devlink_dpipe_match *match)
> {
>@@ -2291,6 +2568,8 @@ static const struct nla_policy devlink_nl_policy[DEVLINK_ATTR_MAX + 1] = {
> 	[DEVLINK_ATTR_ESWITCH_ENCAP_MODE] = { .type = NLA_U8 },
> 	[DEVLINK_ATTR_DPIPE_TABLE_NAME] = { .type = NLA_NUL_STRING },
> 	[DEVLINK_ATTR_DPIPE_TABLE_COUNTERS_ENABLED] = { .type = NLA_U8 },
>+	[DEVLINK_ATTR_PERM_CONFIG_PARAMETER] = { .type = NLA_U32 },
>+	[DEVLINK_ATTR_PERM_CONFIG_TYPE] = { .type = NLA_U8 },
> };
> 
> static const struct genl_ops devlink_nl_ops[] = {
>@@ -2451,6 +2730,20 @@ static const struct genl_ops devlink_nl_ops[] = {
> 		.flags = GENL_ADMIN_PERM,
> 		.internal_flags = DEVLINK_NL_FLAG_NEED_DEVLINK,
> 	},
>+	{
>+		.cmd = DEVLINK_CMD_PERM_CONFIG_GET,
>+		.doit = devlink_nl_cmd_perm_config_get_doit,

As I said, you need dumpit.



>+		.policy = devlink_nl_policy,
>+		.flags = GENL_ADMIN_PERM,
>+		.internal_flags = DEVLINK_NL_FLAG_NEED_DEVLINK,
>+	},
>+	{
>+		.cmd = DEVLINK_CMD_PERM_CONFIG_SET,
>+		.doit = devlink_nl_cmd_perm_config_set_doit,
>+		.policy = devlink_nl_policy,
>+		.flags = GENL_ADMIN_PERM,
>+		.internal_flags = DEVLINK_NL_FLAG_NEED_DEVLINK,
>+	},
> };
> 
> static struct genl_family devlink_nl_family __ro_after_init = {
>-- 
>2.7.4
>