net/dcb: Add an optional max rate attribute

Although not specified in 8021Qaz spec, it could be useful to enable drivers
whose HW supports setting a rate limit for an ETS TC. This patch adds this
optional attribute to DCB netlink. To use it, drivers should implement and
register the callbacks ieee_setmaxrate and ieee_getmaxrate. The units are 64
bits long and specified in Kbps to enable usage over both slow and very fast
networks.

Signed-off-by: Amir Vadai <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/dcbnl.h

···
 	__u8	reco_prio_tc[IEEE_8021QAZ_MAX_TCS];
 };
 
+/* This structure contains rate limit extension to the IEEE 802.1Qaz ETS
+ * managed object.
+ * Values are 64 bits long and specified in Kbps to enable usage over both
+ * slow and very fast networks.
+ *
+ * @tc_maxrate: maximal tc tx bandwidth indexed by traffic class
+ */
+struct ieee_maxrate {
+	__u64	tc_maxrate[IEEE_8021QAZ_MAX_TCS];
+};
+
 /* This structure contains the IEEE 802.1Qaz PFC managed object
  *
  * @pfc_cap: Indicates the number of traffic classes on the local device
···
 	DCB_ATTR_IEEE_PEER_ETS,
 	DCB_ATTR_IEEE_PEER_PFC,
 	DCB_ATTR_IEEE_PEER_APP,
+	DCB_ATTR_IEEE_MAXRATE,
 	__DCB_ATTR_IEEE_MAX
 };
 #define DCB_ATTR_IEEE_MAX (__DCB_ATTR_IEEE_MAX - 1)

include/net/dcbnl.h

···
 	/* IEEE 802.1Qaz std */
 	int (*ieee_getets) (struct net_device *, struct ieee_ets *);
 	int (*ieee_setets) (struct net_device *, struct ieee_ets *);
+	int (*ieee_getmaxrate) (struct net_device *, struct ieee_maxrate *);
+	int (*ieee_setmaxrate) (struct net_device *, struct ieee_maxrate *);
 	int (*ieee_getpfc) (struct net_device *, struct ieee_pfc *);
 	int (*ieee_setpfc) (struct net_device *, struct ieee_pfc *);
 	int (*ieee_getapp) (struct net_device *, struct dcb_app *);

net/dcb/dcbnl.c

···
 	[DCB_ATTR_IEEE_ETS]	    = {.len = sizeof(struct ieee_ets)},
 	[DCB_ATTR_IEEE_PFC]	    = {.len = sizeof(struct ieee_pfc)},
 	[DCB_ATTR_IEEE_APP_TABLE]   = {.type = NLA_NESTED},
+	[DCB_ATTR_IEEE_MAXRATE]   = {.len = sizeof(struct ieee_maxrate)},
 };
 
 static const struct nla_policy dcbnl_ieee_app[DCB_ATTR_IEEE_APP_MAX + 1] = {
···
 			goto nla_put_failure;
 	}
 
+	if (ops->ieee_getmaxrate) {
+		struct ieee_maxrate maxrate;
+		err = ops->ieee_getmaxrate(netdev, &maxrate);
+		if (!err) {
+			err = nla_put(skb, DCB_ATTR_IEEE_MAXRATE,
+				      sizeof(maxrate), &maxrate);
+			if (err)
+				goto nla_put_failure;
+		}
+	}
+
 	if (ops->ieee_getpfc) {
 		struct ieee_pfc pfc;
 		err = ops->ieee_getpfc(netdev, &pfc);
···
 	if (ieee[DCB_ATTR_IEEE_ETS] && ops->ieee_setets) {
 		struct ieee_ets *ets = nla_data(ieee[DCB_ATTR_IEEE_ETS]);
 		err = ops->ieee_setets(netdev, ets);
+		if (err)
+			goto err;
+	}
+
+	if (ieee[DCB_ATTR_IEEE_MAXRATE] && ops->ieee_setmaxrate) {
+		struct ieee_maxrate *maxrate =
+			nla_data(ieee[DCB_ATTR_IEEE_MAXRATE]);
+		err = ops->ieee_setmaxrate(netdev, maxrate);
 		if (err)
 			goto err;
 	}