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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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11
net/core/ethtool.c
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@@ -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)
{