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net: provide a per host RSS key generic infrastructure

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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>
This commit is contained in:
Eric Dumazet 2014-11-16 06:23:05 -08:00 committed by David S. Miller
parent ca24502434
commit 960fb622f8
4 changed files with 58 additions and 0 deletions
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22
Documentation/sysctl/net.txt
View File

@ -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.
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
----------------------

6
include/linux/netdevice.h
View File

@ -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);
/* 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);

11
net/core/ethtool.c
View File

@ -25,6 +25,7 @@
#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.
@ -573,6 +574,16 @@ static int ethtool_copy_validate_indir(u32 *indir, void __user *useraddr,
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)
{

19
net/core/sysctl_net_core.c
View File

@ -217,6 +217,18 @@ static int set_default_qdisc(struct ctl_table *table, int write,
}
#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
{
@ -265,6 +277,13 @@ static struct ctl_table net_core_table[] = {
.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",