Subject: Re: [RFC PATCH v2 net-next 2/2] net: dcb: add new apptrust attribute

From: Petr Machata <[email-masked]>
Date: Mon, 19 Sep 2022 09:30:21 +0200

Daniel Machon <[email-masked]> writes:

> Add new apptrust extension attributes to the 8021Qaz APP managed
> object.
>
> Two new attributes, DCB_ATTR_DCB_APP_TRUST_TABLE and
> DCB_ATTR_DCB_APP_TRUST, has been added. Trusted selectors are passed in
> the nested attribute (TRUST_TABLE), in order of precedence.
>
> The new attributes are meant to allow drivers, whose hw supports the
> notion of trust, to be able to set whether a particular app selector is
> to be trusted - and also the order of precedence of selectors.
>
> Signed-off-by: Daniel Machon <[email-masked]>
> ---
>  include/net/dcbnl.h        |  4 +++
>  include/uapi/linux/dcbnl.h |  4 +++
>  net/dcb/dcbnl.c            | 64 ++++++++++++++++++++++++++++++++++++--
>  3 files changed, 69 insertions(+), 3 deletions(-)
>
> diff --git a/include/net/dcbnl.h b/include/net/dcbnl.h
> index 2b2d86fb3131..8841ab6c2de7 100644
> --- a/include/net/dcbnl.h
> +++ b/include/net/dcbnl.h
> @@ -109,6 +109,10 @@ struct dcbnl_rtnl_ops {
>  	/* buffer settings */
>  	int (*dcbnl_getbuffer)(struct net_device *, struct dcbnl_buffer *);
>  	int (*dcbnl_setbuffer)(struct net_device *, struct dcbnl_buffer *);
> +
> +	/* apptrust */
> +	int (*dcbnl_setapptrust)(struct net_device *, u8 *, int);
> +	int (*dcbnl_getapptrust)(struct net_device *, u8 *, int *);
>  };
>  
>  #endif /* __NET_DCBNL_H__ */
> diff --git a/include/uapi/linux/dcbnl.h b/include/uapi/linux/dcbnl.h
> index 8eab16e5bc13..ede72aefd88f 100644
> --- a/include/uapi/linux/dcbnl.h
> +++ b/include/uapi/linux/dcbnl.h
> @@ -248,6 +248,8 @@ struct dcb_app {
>  	__u16	protocol;
>  };
>  
> +#define IEEE_8021QAZ_APP_SEL_MAX 255
> +
>  /**
>   * struct dcb_peer_app_info - APP feature information sent by the peer
>   *
> @@ -419,6 +421,8 @@ enum ieee_attrs {
>  	DCB_ATTR_IEEE_QCN,
>  	DCB_ATTR_IEEE_QCN_STATS,
>  	DCB_ATTR_DCB_BUFFER,
> +	DCB_ATTR_DCB_APP_TRUST_TABLE,
> +	DCB_ATTR_DCB_APP_TRUST,
>  	__DCB_ATTR_IEEE_MAX
>  };

I find it odd that APP_TRUST is at the same level as APP_TRUST_TABLE. I
think it would be better to have a separate enum ala what APP_TABLE has
with enum ieee_attr_app.

>  #define DCB_ATTR_IEEE_MAX (__DCB_ATTR_IEEE_MAX - 1)
> diff --git a/net/dcb/dcbnl.c b/net/dcb/dcbnl.c
> index dc4fb699b56c..6f5d2b295d09 100644
> --- a/net/dcb/dcbnl.c
> +++ b/net/dcb/dcbnl.c
> @@ -166,6 +166,7 @@ static const struct nla_policy dcbnl_ieee_policy[DCB_ATTR_IEEE_MAX + 1] = {
>  	[DCB_ATTR_IEEE_QCN]         = {.len = sizeof(struct ieee_qcn)},
>  	[DCB_ATTR_IEEE_QCN_STATS]   = {.len = sizeof(struct ieee_qcn_stats)},
>  	[DCB_ATTR_DCB_BUFFER]       = {.len = sizeof(struct dcbnl_buffer)},
> +	[DCB_ATTR_DCB_APP_TRUST_TABLE] = {.type = NLA_NESTED},
>  };
>  
>  /* DCB number of traffic classes nested attributes. */
> @@ -1030,11 +1031,11 @@ static int dcbnl_build_peer_app(struct net_device *netdev, struct sk_buff* skb,
>  /* Handle IEEE 802.1Qaz/802.1Qau/802.1Qbb GET commands. */
>  static int dcbnl_ieee_fill(struct sk_buff *skb, struct net_device *netdev)
>  {
> -	struct nlattr *ieee, *app;
> +	struct nlattr *ieee, *app, *apptrust;
>  	struct dcb_app_type *itr;
>  	const struct dcbnl_rtnl_ops *ops = netdev->dcbnl_ops;
>  	int dcbx;
> -	int err;
> +	int err, i;

Move "err, i" up before dcbx so that it observes the reverse xmass tree
principle, please.

>  
>  	if (nla_put_string(skb, DCB_ATTR_IFNAME, netdev->name))
>  		return -EMSGSIZE;
> @@ -1133,6 +1134,24 @@ static int dcbnl_ieee_fill(struct sk_buff *skb, struct net_device *netdev)
>  	spin_unlock_bh(&dcb_lock);
>  	nla_nest_end(skb, app);
>  
> +	if (ops->dcbnl_getapptrust) {
> +		u8 selectors[IEEE_8021QAZ_APP_SEL_MAX + 1] = {0};
> +		int nselectors;
> +
> +		apptrust = nla_nest_start_noflag(skb,
> +						 DCB_ATTR_DCB_APP_TRUST_TABLE);
> +		if (!app)
> +			return -EMSGSIZE;

I agree with Vladimir that this should not be _noflag.

> +
> +		err = ops->dcbnl_getapptrust(netdev, selectors, &nselectors);
> +		if (err)
> +			return -EMSGSIZE;
> +
> +		for (i = 0; i < nselectors; i++)
> +			nla_put_u8(skb, DCB_ATTR_DCB_APP_TRUST, selectors[i]);
> +		nla_nest_end(skb, apptrust);
> +	}
> +
>  	/* get peer info if available */
>  	if (ops->ieee_peer_getets) {
>  		struct ieee_ets ets;
> @@ -1427,7 +1446,7 @@ static int dcbnl_ieee_set(struct net_device *netdev, struct nlmsghdr *nlh,
>  	const struct dcbnl_rtnl_ops *ops = netdev->dcbnl_ops;
>  	struct nlattr *ieee[DCB_ATTR_IEEE_MAX + 1];
>  	int prio;
> -	int err;
> +	int err, i;

RXT this as well, please.

>  
>  	if (!ops)
>  		return -EOPNOTSUPP;
> @@ -1513,6 +1532,45 @@ static int dcbnl_ieee_set(struct net_device *netdev, struct nlmsghdr *nlh,
>  		}
>  	}
>  
> +	if (ieee[DCB_ATTR_DCB_APP_TRUST_TABLE]) {
> +		u8 selectors[IEEE_8021QAZ_APP_SEL_MAX + 1] = {0};
> +		struct nlattr *attr;
> +		int nselectors = 0;
> +		u8 selector;
> +
> +		int rem;
> +
> +		if (!ops->dcbnl_setapptrust) {
> +			err = -EOPNOTSUPP;
> +			goto err;
> +		}
> +
> +		nla_for_each_nested(attr, ieee[DCB_ATTR_DCB_APP_TRUST_TABLE],
> +				    rem) {
> +			if (nla_type(attr) != DCB_ATTR_DCB_APP_TRUST ||
> +			    nla_len(attr) != 1 ||
> +			    nselectors >= sizeof(selectors)) {
> +				err = -EINVAL;
> +				goto err;
> +			}

I'm assuming you tested this code, I just wrote it into the email
client, so all guarantees are off :)

> +
> +			selector = nla_get_u8(attr);
> +			/* Duplicate selector ? */
> +			for (i = 0; i < nselectors; i++) {
> +				if (selectors[i] == selector) {
> +					err = -EINVAL;
> +					goto err;
> +				}
> +			}

This should validate the selector values as well IMHO. Maybe something
like this?

			switch (selector) {
			...
			case IEEE_8021QAZ_APP_SEL_DGRAM:
			case IEEE_8021QAZ_APP_SEL_ANY:
			case IEEE_8021QAZ_APP_SEL_DSCP:
			case IEEE_8021QAZ_APP_SEL_PCP:
				break;
			default:
				err = -EINVAL;
				goto err;
			}

> +
> +			selectors[nselectors++] = selector;
> +		}
> +
> +		err = ops->dcbnl_setapptrust(netdev, selectors, nselectors);
> +		if (err)
> +			goto err;
> +	}
> +
>  err:
>  	err = nla_put_u8(skb, DCB_ATTR_IEEE, err);
>  	dcbnl_ieee_notify(netdev, RTM_SETDCB, DCB_CMD_IEEE_SET, seq, 0);