ethtool: rss: support setting hkey via Netlink

Support setting RSS hashing key via ethtool Netlink.
Use the Netlink policy to make sure user doesn't pass
an empty key, "resetting" the key is not a thing.

Reviewed-by: Gal Pressman <gal@nvidia.com>
Link: https://patch.msgid.link/20250716000331.1378807-7-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 42 insertions, 1 deletions

diff --git a/Documentation/netlink/specs/ethtool.yaml b/Documentation/netlink/specs/ethtool.yaml
index 0d02d8342e4c..aa55fc9068e1 100644
--- a/Documentation/netlink/specs/ethtool.yaml
+++ b/Documentation/netlink/specs/ethtool.yaml
@@ -2656,6 +2656,7 @@ operations:
             - context
             - hfunc
             - indir
+            - hkey
     -
       name: rss-ntf
       doc: |
diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation/networking/ethtool-netlink.rst
index f6e4439caa94..1830354495ae 100644
--- a/Documentation/networking/ethtool-netlink.rst
+++ b/Documentation/networking/ethtool-netlink.rst
@@ -2001,6 +2001,7 @@ Request contents:
   ``ETHTOOL_A_RSS_CONTEXT``            u32     context number
   ``ETHTOOL_A_RSS_HFUNC``              u32     RSS hash func
   ``ETHTOOL_A_RSS_INDIR``              binary  Indir table bytes
+  ``ETHTOOL_A_RSS_HKEY``               binary  Hash key bytes
 =====================================  ======  ==============================
 
 ``ETHTOOL_A_RSS_INDIR`` is the minimal RSS table the user expects. Kernel and
diff --git a/net/ethtool/rss.c b/net/ethtool/rss.c
index bc9025cfcf1c..55260830639f 100644
--- a/net/ethtool/rss.c
+++ b/net/ethtool/rss.c
@@ -477,6 +477,7 @@ const struct nla_policy ethnl_rss_set_policy[ETHTOOL_A_RSS_START_CONTEXT + 1] =
 	[ETHTOOL_A_RSS_CONTEXT] = { .type = NLA_U32, },
 	[ETHTOOL_A_RSS_HFUNC] = NLA_POLICY_MIN(NLA_U32, 1),
 	[ETHTOOL_A_RSS_INDIR] = { .type = NLA_BINARY, },
+	[ETHTOOL_A_RSS_HKEY] = NLA_POLICY_MIN(NLA_BINARY, 1),
 };
 
 static int
@@ -490,8 +491,10 @@ ethnl_rss_set_validate(struct ethnl_req_info *req_info, struct genl_info *info)
 	if (request->rss_context && !ops->create_rxfh_context)
 		bad_attr = bad_attr ?: tb[ETHTOOL_A_RSS_CONTEXT];
 
-	if (request->rss_context && !ops->rxfh_per_ctx_key)
+	if (request->rss_context && !ops->rxfh_per_ctx_key) {
 		bad_attr = bad_attr ?: tb[ETHTOOL_A_RSS_HFUNC];
+		bad_attr = bad_attr ?: tb[ETHTOOL_A_RSS_HKEY];
+	}
 
 	if (bad_attr) {
 		NL_SET_BAD_ATTR(info->extack, bad_attr);
@@ -581,6 +584,31 @@ err_free:
 	return err;
 }
 
+static int
+rss_set_prep_hkey(struct net_device *dev, struct genl_info *info,
+		  struct rss_reply_data *data, struct ethtool_rxfh_param *rxfh,
+		  bool *mod)
+{
+	struct nlattr **tb = info->attrs;
+
+	if (!tb[ETHTOOL_A_RSS_HKEY])
+		return 0;
+
+	if (nla_len(tb[ETHTOOL_A_RSS_HKEY]) != data->hkey_size) {
+		NL_SET_BAD_ATTR(info->extack, tb[ETHTOOL_A_RSS_HKEY]);
+		return -EINVAL;
+	}
+
+	rxfh->key_size = data->hkey_size;
+	rxfh->key = kmemdup(data->hkey, data->hkey_size, GFP_KERNEL);
+	if (!rxfh->key)
+		return -ENOMEM;
+
+	ethnl_update_binary(rxfh->key, rxfh->key_size, tb[ETHTOOL_A_RSS_HKEY],
+			    mod);
+	return 0;
+}
+
 static void
 rss_set_ctx_update(struct ethtool_rxfh_context *ctx, struct nlattr **tb,
 		   struct rss_reply_data *data, struct ethtool_rxfh_param *rxfh)
@@ -592,6 +620,11 @@ rss_set_ctx_update(struct ethtool_rxfh_context *ctx, struct nlattr **tb,
 			ethtool_rxfh_context_indir(ctx)[i] = rxfh->indir[i];
 		ctx->indir_configured = !!nla_len(tb[ETHTOOL_A_RSS_INDIR]);
 	}
+	if (rxfh->key) {
+		memcpy(ethtool_rxfh_context_key(ctx), rxfh->key,
+		       data->hkey_size);
+		ctx->key_configured = !!rxfh->key_size;
+	}
 	if (rxfh->hfunc != ETH_RSS_HASH_NO_CHANGE)
 		ctx->hfunc = rxfh->hfunc;
 }
@@ -629,6 +662,10 @@ ethnl_rss_set(struct ethnl_req_info *req_info, struct genl_info *info)
 	if (rxfh.hfunc == data.hfunc)
 		rxfh.hfunc = ETH_RSS_HASH_NO_CHANGE;
 
+	ret = rss_set_prep_hkey(dev, info, &data, &rxfh, &mod);
+	if (ret)
+		goto exit_free_indir;
+
 	rxfh.input_xfrm = RXH_XFRM_NO_CHANGE;
 
 	mutex_lock(&dev->ethtool->rss_lock);
@@ -660,6 +697,8 @@ ethnl_rss_set(struct ethnl_req_info *req_info, struct genl_info *info)
 
 exit_unlock:
 	mutex_unlock(&dev->ethtool->rss_lock);
+	kfree(rxfh.key);
+exit_free_indir:
 	kfree(rxfh.indir);
 exit_clean_data:
 	rss_cleanup_data(&data.base);