Subject: [PATCH net-next v3 1/5] ethtool: Symmetric OR-XOR RSS hash

From: Gal Pressman <[email-masked]>
Date: Sun, 16 Feb 2025 20:24:49 +0200

Add an additional type of symmetric RSS hash type: OR-XOR.
The "Symmetric-OR-XOR" algorithm transforms the input as follows:

(SRC_IP | DST_IP, SRC_IP ^ DST_IP, SRC_PORT | DST_PORT, SRC_PORT ^ DST_PORT)

Change 'cap_rss_sym_xor_supported' to 'supported_input_xfrm', a bitmap
of supported RXH_XFRM_* types.

Reviewed-by: Cosmin Ratiu <[email-masked]>
Reviewed-by: Tariq Toukan <[email-masked]>
Signed-off-by: Gal Pressman <[email-masked]>
Reviewed-by: Edward Cree <[email-masked]>
---
 Documentation/networking/ethtool-netlink.rst   |  2 +-
 Documentation/networking/scaling.rst           | 14 ++++++++++----
 drivers/net/ethernet/intel/iavf/iavf_ethtool.c |  2 +-
 drivers/net/ethernet/intel/ice/ice_ethtool.c   |  2 +-
 include/linux/ethtool.h                        |  5 ++---
 include/uapi/linux/ethtool.h                   |  4 ++++
 net/ethtool/ioctl.c                            |  8 ++++----
 7 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation/networking/ethtool-netlink.rst
index 3770a2294509..b6e9af4d0f1b 100644
--- a/Documentation/networking/ethtool-netlink.rst
+++ b/Documentation/networking/ethtool-netlink.rst
@@ -1934,7 +1934,7 @@ ETHTOOL_A_RSS_INDIR attribute returns RSS indirection table where each byte
 indicates queue number.
 ETHTOOL_A_RSS_INPUT_XFRM attribute is a bitmap indicating the type of
 transformation applied to the input protocol fields before given to the RSS
-hfunc. Current supported option is symmetric-xor.
+hfunc. Current supported options are symmetric-xor and symmetric-or-xor.
 
 PLCA_GET_CFG
 ============
diff --git a/Documentation/networking/scaling.rst b/Documentation/networking/scaling.rst
index 4eb50bcb9d42..d8971ce07628 100644
--- a/Documentation/networking/scaling.rst
+++ b/Documentation/networking/scaling.rst
@@ -49,14 +49,20 @@ destination address) and TCP/UDP (source port, destination port) tuples
 are swapped, the computed hash is the same. This is beneficial in some
 applications that monitor TCP/IP flows (IDS, firewalls, ...etc) and need
 both directions of the flow to land on the same Rx queue (and CPU). The
-"Symmetric-XOR" is a type of RSS algorithms that achieves this hash
-symmetry by XORing the input source and destination fields of the IP
-and/or L4 protocols. This, however, results in reduced input entropy and
-could potentially be exploited. Specifically, the algorithm XORs the input
+"Symmetric-XOR" and "Symmetric-OR-XOR" are types of RSS algorithms that
+achieve this hash symmetry by XOR/ORing the input source and destination
+fields of the IP and/or L4 protocols. This, however, results in reduced
+input entropy and could potentially be exploited.
+
+Specifically, the "Symmetric-XOR" algorithm XORs the input
 as follows::
 
     # (SRC_IP ^ DST_IP, SRC_IP ^ DST_IP, SRC_PORT ^ DST_PORT, SRC_PORT ^ DST_PORT)
 
+The "Symmetric-OR-XOR" algorithm transforms the input as follows::
+
+    # (SRC_IP | DST_IP, SRC_IP ^ DST_IP, SRC_PORT | DST_PORT, SRC_PORT ^ DST_PORT)
+
 The result is then fed to the underlying RSS algorithm.
 
 Some advanced NICs allow steering packets to queues based on
diff --git a/drivers/net/ethernet/intel/iavf/iavf_ethtool.c b/drivers/net/ethernet/intel/iavf/iavf_ethtool.c
index 74a1e9fe1821..288bb5b2e72e 100644
--- a/drivers/net/ethernet/intel/iavf/iavf_ethtool.c
+++ b/drivers/net/ethernet/intel/iavf/iavf_ethtool.c
@@ -1808,7 +1808,7 @@ static int iavf_set_rxfh(struct net_device *netdev,
 static const struct ethtool_ops iavf_ethtool_ops = {
 	.supported_coalesce_params = ETHTOOL_COALESCE_USECS |
 				     ETHTOOL_COALESCE_USE_ADAPTIVE,
-	.cap_rss_sym_xor_supported = true,
+	.supported_input_xfrm	= RXH_XFRM_SYM_XOR,
 	.get_drvinfo		= iavf_get_drvinfo,
 	.get_link		= ethtool_op_get_link,
 	.get_ringparam		= iavf_get_ringparam,
diff --git a/drivers/net/ethernet/intel/ice/ice_ethtool.c b/drivers/net/ethernet/intel/ice/ice_ethtool.c
index 3072634bf049..a02ce2cea852 100644
--- a/drivers/net/ethernet/intel/ice/ice_ethtool.c
+++ b/drivers/net/ethernet/intel/ice/ice_ethtool.c
@@ -4774,7 +4774,7 @@ static const struct ethtool_ops ice_ethtool_ops = {
 	.supported_coalesce_params = ETHTOOL_COALESCE_USECS |
 				     ETHTOOL_COALESCE_USE_ADAPTIVE |
 				     ETHTOOL_COALESCE_RX_USECS_HIGH,
-	.cap_rss_sym_xor_supported = true,
+	.supported_input_xfrm	= RXH_XFRM_SYM_XOR,
 	.rxfh_per_ctx_key	= true,
 	.get_link_ksettings	= ice_get_link_ksettings,
 	.set_link_ksettings	= ice_set_link_ksettings,
diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index 870994cc3ef7..7f222dccc7d1 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -763,13 +763,12 @@ struct kernel_ethtool_ts_info {
 
 /**
  * struct ethtool_ops - optional netdev operations
+ * @supported_input_xfrm: supported types of input xfrm from %RXH_XFRM_*.
  * @cap_link_lanes_supported: indicates if the driver supports lanes
  *	parameter.
  * @cap_rss_ctx_supported: indicates if the driver supports RSS
  *	contexts via legacy API, drivers implementing @create_rxfh_context
  *	do not have to set this bit.
- * @cap_rss_sym_xor_supported: indicates if the driver supports symmetric-xor
- *	RSS.
  * @rxfh_per_ctx_key: device supports setting different RSS key for each
  *	additional context. Netlink API should report hfunc, key, and input_xfrm
  *	for every context, not just context 0.
@@ -995,9 +994,9 @@ struct kernel_ethtool_ts_info {
  * of the generic netdev features interface.
  */
 struct ethtool_ops {
+	u32     supported_input_xfrm:8;
 	u32     cap_link_lanes_supported:1;
 	u32     cap_rss_ctx_supported:1;
-	u32	cap_rss_sym_xor_supported:1;
 	u32	rxfh_per_ctx_key:1;
 	u32	cap_rss_rxnfc_adds:1;
 	u32	rxfh_indir_space;
diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
index d1089b88efc7..2909ac3a3357 100644
--- a/include/uapi/linux/ethtool.h
+++ b/include/uapi/linux/ethtool.h
@@ -2269,6 +2269,10 @@ static inline int ethtool_validate_duplex(__u8 duplex)
  * be exploited to reduce the RSS queue spread.
  */
 #define	RXH_XFRM_SYM_XOR	(1 << 0)
+/* Similar to SYM_XOR, except that one copy of the XOR'ed fields is replaced by
+ * an OR of the same fields
+ */
+#define	RXH_XFRM_SYM_OR_XOR	(1 << 1)
 #define	RXH_XFRM_NO_CHANGE	0xff
 
 /* L2-L4 network traffic flow types */
diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 7bb94875a7ec..3829e24f9c4c 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -1005,11 +1005,11 @@ static noinline_for_stack int ethtool_set_rxnfc(struct net_device *dev,
 		if (rc)
 			return rc;
 
-		/* Sanity check: if symmetric-xor is set, then:
+		/* Sanity check: if symmetric-xor/symmetric-or-xor is set, then:
 		 * 1 - no other fields besides IP src/dst and/or L4 src/dst
 		 * 2 - If src is set, dst must also be set
 		 */
-		if ((rxfh.input_xfrm & RXH_XFRM_SYM_XOR) &&
+		if ((rxfh.input_xfrm & (RXH_XFRM_SYM_XOR | RXH_XFRM_SYM_OR_XOR)) &&
 		    ((info.data & ~(RXH_IP_SRC | RXH_IP_DST |
 				    RXH_L4_B_0_1 | RXH_L4_B_2_3)) ||
 		     (!!(info.data & RXH_IP_SRC) ^ !!(info.data & RXH_IP_DST)) ||
@@ -1382,11 +1382,11 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 		return -EOPNOTSUPP;
 	/* Check input data transformation capabilities */
 	if (rxfh.input_xfrm && rxfh.input_xfrm != RXH_XFRM_SYM_XOR &&
+	    rxfh.input_xfrm != RXH_XFRM_SYM_OR_XOR &&
 	    rxfh.input_xfrm != RXH_XFRM_NO_CHANGE)
 		return -EINVAL;
 	if (rxfh.input_xfrm != RXH_XFRM_NO_CHANGE &&
-	    (rxfh.input_xfrm & RXH_XFRM_SYM_XOR) &&
-	    !ops->cap_rss_sym_xor_supported)
+	    rxfh.input_xfrm & ~ops->supported_input_xfrm)
 		return -EOPNOTSUPP;
 	create = rxfh.rss_context == ETH_RXFH_CONTEXT_ALLOC;
 
-- 
2.40.1