net: provide a per host RSS key generic infrastructure

RSS (Receive Side Scaling) typically uses Toeplitz hash and a 40 or 52 bytes
RSS key.

Some drivers use a constant (and well known key), some drivers use a random
key per port, making bonding setups hard to tune. Well known keys increase
attack surface, considering that number of queues is usually a power of two.

This patch provides infrastructure to help drivers doing the right thing.

netdev_rss_key_fill() should be used by drivers to initialize their RSS key,
even if they provide ethtool -X support to let user redefine the key later.

A new /proc/sys/net/core/netdev_rss_key file can be used to get the host
RSS key even for drivers not providing ethtool -x support, in case some
applications want to precisely setup flows to match some RX queues.

Tested:

myhost:~# cat /proc/sys/net/core/netdev_rss_key
11:63:99:bb:79:fb:a5:a7:07:45:b2:20:bf:02:42:2d:08:1a:dd:19:2b:6b:23:ac:56:28:9d:70:c3:ac:e8:16:4b:b7:c1:10:53:a4:78:41:36:40:74:b6:15:ca:27:44:aa:b3:4d:72

myhost:~# ethtool -x eth0
RX flow hash indirection table for eth0 with 8 RX ring(s):
    0:      0     1     2     3     4     5     6     7
RSS hash key:
11:63:99:bb:79:fb:a5:a7:07:45:b2:20:bf:02:42:2d:08:1a:dd:19:2b:6b:23:ac:56:28:9d:70:c3:ac:e8:16:4b:b7:c1:10:53:a4:78:41

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/Documentation/sysctl/net.txt b/Documentation/sysctl/net.txt
index e26c607468a6f2f884d26d179028951ba8601c17..666594b43cfff9f7a50678e3d74bd29c116d3648 100644 (file)
--- a/Documentation/sysctl/net.txt
+++ b/Documentation/sysctl/net.txt
@@ -142,6 +142,28 @@ netdev_max_backlog
 Maximum number  of  packets,  queued  on  the  INPUT  side, when the interface
 receives packets faster than kernel can process them.
 
 Maximum number  of  packets,  queued  on  the  INPUT  side, when the interface
 receives packets faster than kernel can process them.
 

+netdev_rss_key
+--------------
+
+RSS (Receive Side Scaling) enabled drivers use a 40 bytes host key that is
+randomly generated.
+Some user space might need to gather its content even if drivers do not
+provide ethtool -x support yet.
+
+myhost:~# cat /proc/sys/net/core/netdev_rss_key
+84:50:f4:00:a8:15:d1:a7:e9:7f:1d:60:35:c7:47:25:42:97:74:ca:56:bb:b6:a1:d8: ... (52 bytes total)
+
+File contains nul bytes if no driver ever called netdev_rss_key_fill() function.
+Note:
+/proc/sys/net/core/netdev_rss_key contains 52 bytes of key,
+but most drivers only use 40 bytes of it.
+
+myhost:~# ethtool -x eth0
+RX flow hash indirection table for eth0 with 8 RX ring(s):
+    0:    0     1     2     3     4     5     6     7
+RSS hash key:
+84:50:f4:00:a8:15:d1:a7:e9:7f:1d:60:35:c7:47:25:42:97:74:ca:56:bb:b6:a1:d8:43:e3:c9:0c:fd:17:55:c2:3a:4d:69:ed:f1:42:89
+

 netdev_tstamp_prequeue
 ----------------------
 
 netdev_tstamp_prequeue
 ----------------------
 

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 4a6f770377d3c067250ab46f171e2d4d062c154c..db63cf459ba14184b6c1582e333174d13658ca7e 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3422,6 +3422,12 @@ void netdev_upper_dev_unlink(struct net_device *dev,
 void netdev_adjacent_rename_links(struct net_device *dev, char *oldname);
 void *netdev_lower_dev_get_private(struct net_device *dev,
                                   struct net_device *lower_dev);
 void netdev_adjacent_rename_links(struct net_device *dev, char *oldname);
 void *netdev_lower_dev_get_private(struct net_device *dev,
                                   struct net_device *lower_dev);

+
+/* RSS keys are 40 or 52 bytes long */
+#define NETDEV_RSS_KEY_LEN 52
+extern u8 netdev_rss_key[NETDEV_RSS_KEY_LEN];
+void netdev_rss_key_fill(void *buffer, size_t len);
+

 int dev_get_nest_level(struct net_device *dev,
                       bool (*type_check)(struct net_device *dev));
 int skb_checksum_help(struct sk_buff *skb);
 int dev_get_nest_level(struct net_device *dev,
                       bool (*type_check)(struct net_device *dev));
 int skb_checksum_help(struct sk_buff *skb);

diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index b0f84f5ddda8456ff8f69442d453e112340a6bfa..715f51f321e9ccd97c6c2d661c9e4c288f48a2a9 100644 (file)
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -25,6 +25,7 @@
 #include <linux/slab.h>
 #include <linux/rtnetlink.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/rtnetlink.h>
 #include <linux/sched.h>

+#include <linux/net.h>

 
 /*
  * Some useful ethtool_ops methods that're device independent.
 
 /*
  * Some useful ethtool_ops methods that're device independent.


@@ -573,6 +574,16 @@ static int ethtool_copy_validate_indir(u32 *indir, void __user *useraddr,
        return 0;
 }
 
        return 0;
 }
 

+u8 netdev_rss_key[NETDEV_RSS_KEY_LEN];
+
+void netdev_rss_key_fill(void *buffer, size_t len)
+{
+       BUG_ON(len > sizeof(netdev_rss_key));
+       net_get_random_once(netdev_rss_key, sizeof(netdev_rss_key));
+       memcpy(buffer, netdev_rss_key, len);
+}
+EXPORT_SYMBOL(netdev_rss_key_fill);
+

 static noinline_for_stack int ethtool_get_rxfh_indir(struct net_device *dev,
                                                     void __user *useraddr)
 {
 static noinline_for_stack int ethtool_get_rxfh_indir(struct net_device *dev,
                                                     void __user *useraddr)
 {

diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index f93f092fe226088e9eb9b22f5ea762af9464fe36..31baba2a71ce15e49450f69dae81e7d3be1ff3f2 100644 (file)
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -217,6 +217,18 @@ static int set_default_qdisc(struct ctl_table *table, int write,
 }
 #endif
 
 }
 #endif
 

+static int proc_do_rss_key(struct ctl_table *table, int write,
+                          void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+       struct ctl_table fake_table;
+       char buf[NETDEV_RSS_KEY_LEN * 3];
+
+       snprintf(buf, sizeof(buf), "%*phC", NETDEV_RSS_KEY_LEN, netdev_rss_key);
+       fake_table.data = buf;
+       fake_table.maxlen = sizeof(buf);
+       return proc_dostring(&fake_table, write, buffer, lenp, ppos);
+}
+

 static struct ctl_table net_core_table[] = {
 #ifdef CONFIG_NET
        {
 static struct ctl_table net_core_table[] = {
 #ifdef CONFIG_NET
        {


@@ -265,6 +277,13 @@ static struct ctl_table net_core_table[] = {
                .mode           = 0644,
                .proc_handler   = proc_dointvec
        },
                .mode           = 0644,
                .proc_handler   = proc_dointvec
        },

+       {
+               .procname       = "netdev_rss_key",
+               .data           = &netdev_rss_key,
+               .maxlen         = sizeof(int),
+               .mode           = 0444,
+               .proc_handler   = proc_do_rss_key,
+       },

 #ifdef CONFIG_BPF_JIT
        {
                .procname       = "bpf_jit_enable",
 #ifdef CONFIG_BPF_JIT
        {
                .procname       = "bpf_jit_enable",