[PATCH net-next v3 1/3] net: rss: Require indir table size or hash key size to support RSS

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

A point can be made that devices that report a 0-size indirection table
and 0-length key size don't really support RSS. Let's return -EOPNOTSUPP
in that case, and skip these devices during DUMP requests.

This however also reports -ENOTSUPP for devices that only supports flow
hash fields ops now.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 net/ethtool/ioctl.c | 6 ++++++
 net/ethtool/rss.c   | 7 +++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 27b0e2e275dc..d32b403c8d3a 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -1444,6 +1444,9 @@ static noinline_for_stack int ethtool_get_rxfh(struct net_device *dev,
 	if (ops->get_rxfh_key_size)
 		rxfh_dev.key_size = ops->get_rxfh_key_size(dev);
 
+	if (!rxfh_dev.indir_size && !rxfh_dev.key_size)
+		return -EOPNOTSUPP;
+
 	if (copy_from_user(&rxfh, useraddr, sizeof(rxfh)))
 		return -EFAULT;
 	user_indir_size = rxfh.indir_size;
@@ -1554,6 +1557,9 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 	if (ops->get_rxfh_key_size)
 		dev_key_size = ops->get_rxfh_key_size(dev);
 
+	if (!dev_indir_size && !dev_key_size)
+		return -EOPNOTSUPP;
+
 	if (copy_from_user(&rxfh, useraddr, sizeof(rxfh)))
 		return -EFAULT;
 
diff --git a/net/ethtool/rss.c b/net/ethtool/rss.c
index d4a1a4724b67..cb9bead0cedd 100644
--- a/net/ethtool/rss.c
+++ b/net/ethtool/rss.c
@@ -129,6 +129,9 @@ rss_get_data_alloc(struct net_device *dev, struct rss_reply_data *data)
 	if (ops->get_rxfh_key_size)
 		data->hkey_size = ops->get_rxfh_key_size(dev);
 
+	if (!data->indir_size && !data->hkey_size)
+		return -EOPNOTSUPP;
+
 	indir_bytes = data->indir_size * sizeof(u32);
 	total_size = indir_bytes + data->hkey_size;
 	rss_config = kzalloc(total_size, GFP_KERNEL);
@@ -449,7 +452,7 @@ rss_dump_one_dev(struct sk_buff *skb, struct netlink_callback *cb,
 
 	if (!ctx->ctx_idx) {
 		ret = rss_dump_one_ctx(skb, cb, dev, 0);
-		if (ret)
+		if (ret && ret != -EOPNOTSUPP)
 			return ret;
 		ctx->ctx_idx++;
 	}
@@ -457,7 +460,7 @@ rss_dump_one_dev(struct sk_buff *skb, struct netlink_callback *cb,
 	for (; xa_find(&dev->ethtool->rss_ctx, &ctx->ctx_idx,
 		       ULONG_MAX, XA_PRESENT); ctx->ctx_idx++) {
 		ret = rss_dump_one_ctx(skb, cb, dev, ctx->ctx_idx);
-		if (ret)
+		if (ret && ret != -EOPNOTSUPP)
 			return ret;
 	}
 	ctx->ctx_idx = ctx->start_ctx;
-- 
2.55.0