Merge branch 'ethtool-set_channels-add-a-few-more-checks'

Jakub Kicinski says:

====================
ethtool: set_channels: add a few more checks

There seems to be a few more things we can check in the core before
we call drivers' ethtool_ops->set_channels. Adding the checks to
the core simplifies the drivers. This set only includes changes
to the NFP driver as an example.

There is a small risk in the first patch that someone actually
purposefully accepts a strange configuration without RX or TX
channels, but I couldn't find such a driver in the tree.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/nfp_net_ethtool.c

@@ -1438,8 +1438,7 @@ static int nfp_net_set_channels(struct net_device *netdev,
 	unsigned int total_rx, total_tx;
 
 	/* Reject unsupported */
-	if (!channel->combined_count ||
-	    channel->other_count != NFP_NET_NON_Q_VECTORS ||
+	if (channel->other_count != NFP_NET_NON_Q_VECTORS ||
 	    (channel->rx_count && channel->tx_count))
 		return -EINVAL;
 

net/ethtool/channels.c

@@ -129,13 +129,13 @@ int ethnl_set_channels(struct sk_buff *skb, struct genl_info *info)
 {
 	struct nlattr *tb[ETHTOOL_A_CHANNELS_MAX + 1];
 	unsigned int from_channel, old_total, i;
+	bool mod = false, mod_combined = false;
 	struct ethtool_channels channels = {};
 	struct ethnl_req_info req_info = {};
 	const struct nlattr *err_attr;
 	const struct ethtool_ops *ops;
 	struct net_device *dev;
 	u32 max_rx_in_use = 0;
-	bool mod = false;
 	int ret;
 
 	ret = nlmsg_parse(info->nlhdr, GENL_HDRLEN, tb,
@@ -170,7 +170,8 @@ int ethnl_set_channels(struct sk_buff *skb, struct genl_info *info)
 	ethnl_update_u32(&channels.other_count,
 			 tb[ETHTOOL_A_CHANNELS_OTHER_COUNT], &mod);
 	ethnl_update_u32(&channels.combined_count,
-			 tb[ETHTOOL_A_CHANNELS_COMBINED_COUNT], &mod);
+			 tb[ETHTOOL_A_CHANNELS_COMBINED_COUNT], &mod_combined);
+	mod |= mod_combined;
 	ret = 0;
 	if (!mod)
 		goto out_ops;
@@ -193,6 +194,21 @@ int ethnl_set_channels(struct sk_buff *skb, struct genl_info *info)
 		goto out_ops;
 	}
 
+	/* ensure there is at least one RX and one TX channel */
+	if (!channels.combined_count && !channels.rx_count)
+		err_attr = tb[ETHTOOL_A_CHANNELS_RX_COUNT];
+	else if (!channels.combined_count && !channels.tx_count)
+		err_attr = tb[ETHTOOL_A_CHANNELS_TX_COUNT];
+	else
+		err_attr = NULL;
+	if (err_attr) {
+		if (mod_combined)
+			err_attr = tb[ETHTOOL_A_CHANNELS_COMBINED_COUNT];
+		ret = -EINVAL;
+		NL_SET_ERR_MSG_ATTR(info->extack, err_attr, "requested channel counts would result in no RX or TX channel being configured");
+		goto out_ops;
+	}
+
 	/* ensure the new Rx count fits within the configured Rx flow
 	 * indirection table settings
 	 */

net/ethtool/ioctl.c

@@ -1669,6 +1669,12 @@ static noinline_for_stack int ethtool_set_channels(struct net_device *dev,
 
 	dev->ethtool_ops->get_channels(dev, &curr);
 
+	if (channels.rx_count == curr.rx_count &&
+	    channels.tx_count == curr.tx_count &&
+	    channels.combined_count == curr.combined_count &&
+	    channels.other_count == curr.other_count)
+		return 0;
+
 	/* ensure new counts are within the maximums */
 	if (channels.rx_count > curr.max_rx ||
 	    channels.tx_count > curr.max_tx ||
@@ -1676,6 +1682,11 @@ static noinline_for_stack int ethtool_set_channels(struct net_device *dev,
 	    channels.other_count > curr.max_other)
 		return -EINVAL;
 
+	/* ensure there is at least one RX and one TX channel */
+	if (!channels.combined_count &&
+	    (!channels.rx_count || !channels.tx_count))
+		return -EINVAL;
+
 	/* ensure the new Rx count fits within the configured Rx flow
 	 * indirection table settings */
 	if (netif_is_rxfh_configured(dev) &&