Symmetric RSS hash functions are beneficial in applications that monitor
both Tx and Rx packets of the same flow (IDS, software firewalls, ..etc).
Getting all traffic of the same flow on the same RX queue results in
higher CPU cache efficiency.
A NIC that supports "symmetric-xor" can achieve this RSS hash symmetry
by XORing the source and destination fields and pass the values to the
RSS hash algorithm.
The user may request RSS hash symmetry for a specific algorithm, via:
# ethtool -X eth0 hfunc <hash_alg> symmetric-xor
or turn symmetry off (asymmetric) by:
# ethtool -X eth0 hfunc <hash_alg>
The specific fields for each flow type should then be specified as usual
via:
# ethtool -N|-U eth0 rx-flow-hash <flow_type> s|d|f|n
Reviewed-by: Wojciech Drewek <wojciech.drewek@xxxxxxxxx>
CC: linux-doc@xxxxxxxxxxxxxxx
Signed-off-by: Ahmed Zaki <ahmed.zaki@xxxxxxxxx>
---
Documentation/netlink/specs/ethtool.yaml | 4 +++
Documentation/networking/ethtool-netlink.rst | 6 +++-
Documentation/networking/scaling.rst | 15 ++++++++++
include/linux/ethtool.h | 6 ++++
include/uapi/linux/ethtool.h | 13 ++++++++-
include/uapi/linux/ethtool_netlink.h | 1 +
net/ethtool/ioctl.c | 30 +++++++++++++++++---
net/ethtool/rss.c | 5 ++++
8 files changed, 74 insertions(+), 6 deletions(-)
diff --git a/Documentation/netlink/specs/ethtool.yaml b/Documentation/netlink/specs/ethtool.yaml
index 5c7a65b009b4..197208f419dc 100644
--- a/Documentation/netlink/specs/ethtool.yaml
+++ b/Documentation/netlink/specs/ethtool.yaml
@@ -908,6 +908,9 @@ attribute-sets:
-
name: hkey
type: binary
+ -
+ name: input_xfrm
+ type: u32
-
name: plca
attributes:
@@ -1598,6 +1601,7 @@ operations:
- hfunc
- indir
- hkey
+ - input_xfrm
dump: *rss-get-op
-
name: plca-get-cfg
diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation/networking/ethtool-netlink.rst
index 6a49624a9cbf..d583d9abf2f8 100644
--- a/Documentation/networking/ethtool-netlink.rst
+++ b/Documentation/networking/ethtool-netlink.rst
@@ -1774,12 +1774,16 @@ Kernel response contents:
``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_INPUT_XFRM`` u32 RSS input data transformation
===================================== ====== ==========================
ETHTOOL_A_RSS_HFUNC attribute is bitmap indicating the hash function
being used. Current supported options are toeplitz, xor or crc32.
-ETHTOOL_A_RSS_INDIR attribute returns RSS indrection table where each byte
+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.
PLCA_GET_CFG
============
diff --git a/Documentation/networking/scaling.rst b/Documentation/networking/scaling.rst
index 03ae19a689fc..4eb50bcb9d42 100644
--- a/Documentation/networking/scaling.rst
+++ b/Documentation/networking/scaling.rst
@@ -44,6 +44,21 @@ by masking out the low order seven bits of the computed hash for the
packet (usually a Toeplitz hash), taking this number as a key into the
indirection table and reading the corresponding value.
+Some NICs support symmetric RSS hashing where, if the IP (source address,
+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
+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
programmable filters. For example, webserver bound TCP port 80 packets
can be directed to their own receive queue. Such “n-tuple” filters can
diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index 78d65ff0cd64..8d00c013ade4 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -613,6 +613,8 @@ struct ethtool_mm_stats {
* to allocate a new RSS context; on return this field will
* contain the ID of the newly allocated context.
* @rss_delete: Set to non-ZERO to remove the @rss_context context.
+ * @input_xfrm: Defines how the input data is transformed. Valid values are one
+ * of %RXH_XFRM_*.
*/
struct ethtool_rxfh_param {
u8 hfunc;
@@ -622,6 +624,7 @@ struct ethtool_rxfh_param {
u8 *key;
u32 rss_context;
u8 rss_delete;
+ u8 input_xfrm;
};
/**
@@ -630,6 +633,8 @@ struct ethtool_rxfh_param {
* parameter.
* @cap_rss_ctx_supported: indicates if the driver supports RSS
* contexts.
+ * @cap_rss_sym_xor_supported: indicates if the driver supports symmetric-xor
+ * RSS.
* @supported_coalesce_params: supported types of interrupt coalescing.
* @supported_ring_params: supported ring params.
* @get_drvinfo: Report driver/device information. Modern drivers no
@@ -809,6 +814,7 @@ struct ethtool_rxfh_param {
struct ethtool_ops {
u32 cap_link_lanes_supported:1;
u32 cap_rss_ctx_supported:1;
+ u32 cap_rss_sym_xor_supported:1;
u32 supported_coalesce_params;
u32 supported_ring_params;
void (*get_drvinfo)(struct net_device *, struct ethtool_drvinfo *);
diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
index f7fba0dc87e5..0787d561ace0 100644
--- a/include/uapi/linux/ethtool.h
+++ b/include/uapi/linux/ethtool.h
@@ -1266,6 +1266,8 @@ struct ethtool_rxfh_indir {
* hardware hash key.
* @hfunc: Defines the current RSS hash function used by HW (or to be set to).
* Valid values are one of the %ETH_RSS_HASH_*.
+ * @input_xfrm: Defines how the input data is transformed. Valid values are one
+ * of %RXH_XFRM_*.
* @rsvd8: Reserved for future use; see the note on reserved space.
* @rsvd32: Reserved for future use; see the note on reserved space.
* @rss_config: RX ring/queue index for each hash value i.e., indirection table
@@ -1285,7 +1287,8 @@ struct ethtool_rxfh {
__u32 indir_size;
__u32 key_size;
__u8 hfunc;
- __u8 rsvd8[3];
+ __u8 input_xfrm;
+ __u8 rsvd8[2];
__u32 rsvd32;
__u32 rss_config[];
};
@@ -1992,6 +1995,14 @@ static inline int ethtool_validate_duplex(__u8 duplex)
#define WOL_MODE_COUNT 8
+/* RSS hash function data
+ * XOR the corresponding source and destination fields of each specified
+ * protocol. Both copies of the XOR'ed fields are fed into the RSS and RXHASH
+ * calculation. Note that this XORing reduces the input set entropy and could
+ * be exploited to reduce the RSS queue spread.
+ */
+#define RXH_XFRM_SYM_XOR (1 << 0)
+
/* L2-L4 network traffic flow types */
#define TCP_V4_FLOW 0x01 /* hash or spec (tcp_ip4_spec) */
#define UDP_V4_FLOW 0x02 /* hash or spec (udp_ip4_spec) */
diff --git a/include/uapi/linux/ethtool_netlink.h b/include/uapi/linux/ethtool_netlink.h
index 73e2c10dc2cc..3f89074aa06c 100644
--- a/include/uapi/linux/ethtool_netlink.h
+++ b/include/uapi/linux/ethtool_netlink.h
@@ -908,6 +908,7 @@ enum {
ETHTOOL_A_RSS_HFUNC, /* u32 */
ETHTOOL_A_RSS_INDIR, /* binary */
ETHTOOL_A_RSS_HKEY, /* binary */
+ ETHTOOL_A_RSS_INPUT_XFRM, /* u32 */
__ETHTOOL_A_RSS_CNT,
ETHTOOL_A_RSS_MAX = (__ETHTOOL_A_RSS_CNT - 1),
diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 86e5fc64b711..86d47425038b 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -972,18 +972,35 @@ static int ethtool_rxnfc_copy_to_user(void __user *useraddr,
static noinline_for_stack int ethtool_set_rxnfc(struct net_device *dev,
u32 cmd, void __user *useraddr)
{
+ const struct ethtool_ops *ops = dev->ethtool_ops;
+ struct ethtool_rxfh_param rxfh = {};
struct ethtool_rxnfc info;
size_t info_size = sizeof(info);
int rc;
- if (!dev->ethtool_ops->set_rxnfc)
+ if (!ops->set_rxnfc || !ops->get_rxfh)
return -EOPNOTSUPP;
rc = ethtool_rxnfc_copy_struct(cmd, &info, &info_size, useraddr);
if (rc)
return rc;
- rc = dev->ethtool_ops->set_rxnfc(dev, &info);
+ rc = ops->get_rxfh(dev, &rxfh);
+ if (rc)
+ return rc;
+
+ /* Sanity check: if symmetric-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) &&
+ ((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)) ||
+ (!!(info.data & RXH_L4_B_0_1) ^ !!(info.data & RXH_L4_B_2_3))))
+ return -EINVAL;
+
+ rc = ops->set_rxnfc(dev, &info);
if (rc)
return rc;
@@ -1198,7 +1215,7 @@ static noinline_for_stack int ethtool_get_rxfh(struct net_device *dev,
user_key_size = rxfh.key_size;
/* Check that reserved fields are 0 for now */
- if (rxfh.rsvd8[0] || rxfh.rsvd8[1] || rxfh.rsvd8[2] || rxfh.rsvd32)
+ if (rxfh.rsvd8[0] || rxfh.rsvd8[1] || rxfh.rsvd32)
return -EINVAL;
/* Most drivers don't handle rss_context, check it's 0 as well */
if (rxfh.rss_context && !ops->cap_rss_ctx_supported)
@@ -1271,11 +1288,15 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
return -EFAULT;
/* Check that reserved fields are 0 for now */
- if (rxfh.rsvd8[0] || rxfh.rsvd8[1] || rxfh.rsvd8[2] || rxfh.rsvd32)
+ if (rxfh.rsvd8[0] || rxfh.rsvd8[1] || rxfh.rsvd32)
return -EINVAL;
/* Most drivers don't handle rss_context, check it's 0 as well */
if (rxfh.rss_context && !ops->cap_rss_ctx_supported)
return -EOPNOTSUPP;
+ /* Check input data transformation capabilities */
+ if ((rxfh.input_xfrm & RXH_XFRM_SYM_XOR) &&
+ !ops->cap_rss_sym_xor_supported)
+ return -EOPNOTSUPP;
/* If either indir, hash key or function is valid, proceed further.
* Must request at least one change: indir size, hash key or function.
@@ -1341,6 +1362,7 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
rxfh_dev.hfunc = rxfh.hfunc;
rxfh_dev.rss_context = rxfh.rss_context;
+ rxfh_dev.input_xfrm = rxfh.input_xfrm;
ret = ops->set_rxfh(dev, &rxfh_dev, extack);
if (ret)
diff --git a/net/ethtool/rss.c b/net/ethtool/rss.c
index efc9f4409e40..71679137eff2 100644
--- a/net/ethtool/rss.c
+++ b/net/ethtool/rss.c
@@ -13,6 +13,7 @@ struct rss_reply_data {
u32 indir_size;
u32 hkey_size;
u32 hfunc;
+ u32 input_xfrm;
u32 *indir_table;
u8 *hkey;
};
@@ -97,6 +98,7 @@ rss_prepare_data(const struct ethnl_req_info *req_base,
goto out_ops;
data->hfunc = rxfh.hfunc;
+ data->input_xfrm = rxfh.input_xfrm;
out_ops:
ethnl_ops_complete(dev);
return ret;
@@ -110,6 +112,7 @@ rss_reply_size(const struct ethnl_req_info *req_base,
int len;
len = nla_total_size(sizeof(u32)) + /* _RSS_HFUNC */
+ nla_total_size(sizeof(u32)) + /* _RSS_INPUT_XFRM */
nla_total_size(sizeof(u32) * data->indir_size) + /* _RSS_INDIR */
nla_total_size(data->hkey_size); /* _RSS_HKEY */
@@ -124,6 +127,8 @@ rss_fill_reply(struct sk_buff *skb, const struct ethnl_req_info *req_base,
if ((data->hfunc &&
nla_put_u32(skb, ETHTOOL_A_RSS_HFUNC, data->hfunc)) ||
+ (data->input_xfrm &&
+ nla_put_u32(skb, ETHTOOL_A_RSS_INPUT_XFRM, data->input_xfrm)) ||
(data->indir_size &&
nla_put(skb, ETHTOOL_A_RSS_INDIR,
sizeof(u32) * data->indir_size, data->indir_table)) ||
--
2.34.1
