netdev - [PATCH net-next] macvlan: add a salt to mc

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <1360291262.28557.89.camel@edumazet-glaptop>
Date:	Thu, 07 Feb 2013 18:41:02 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>,
	Maciej Żenczykowski <maze@...gle.com>
Subject: [PATCH net-next] macvlan: add a salt to mc_hash()

From: Eric Dumazet <edumazet@...gle.com>

Some multicast addresses are common to all macvlans,
so if a multicast message has a hash value collision, we
have to deliver a copy to all macvlans, adding significant
latency and possible packet drops if netdev_max_backlog
limit is hit.

Having a per macvlan hash function permits to reduce the
impact of hash collisions.

Suggested-by: Maciej Żenczykowski <maze@...gle.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
Should be applied after 
  "macvlan: broadcast addr should be part of mc_filter"

 drivers/net/macvlan.c |   17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index ce7c926..e4b8078 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -127,10 +127,18 @@ static int macvlan_broadcast_one(struct sk_buff *skb,
 	return vlan->receive(skb);
 }
 
-static unsigned int mc_hash(const unsigned char *addr)
+static u32 macvlan_hash_mix(const struct macvlan_dev *vlan)
+{
+	return (u32)(((unsigned long)vlan) >> L1_CACHE_SHIFT);
+}
+
+
+static unsigned int mc_hash(const struct macvlan_dev *vlan,
+			    const unsigned char *addr)
 {
 	u32 val = __get_unaligned_cpu32(addr + 2);
 
+	val ^= macvlan_hash_mix(vlan);
 	return hash_32(val, MACVLAN_MC_FILTER_BITS);
 }
 
@@ -145,7 +153,7 @@ static void macvlan_broadcast(struct sk_buff *skb,
 	struct sk_buff *nskb;
 	unsigned int i;
 	int err;
-	unsigned int hash = mc_hash(eth->h_dest);
+	unsigned int hash;
 
 	if (skb->protocol == htons(ETH_P_PAUSE))
 		return;
@@ -155,6 +163,7 @@ static void macvlan_broadcast(struct sk_buff *skb,
 			if (vlan->dev == src || !(vlan->mode & mode))
 				continue;
 
+			hash = mc_hash(vlan, eth->h_dest);
 			if (!test_bit(hash, vlan->mc_filter))
 				continue;
 			nskb = skb_clone(skb, GFP_ATOMIC);
@@ -424,10 +433,10 @@ static void macvlan_set_mac_lists(struct net_device *dev)
 
 		bitmap_zero(filter, MACVLAN_MC_FILTER_SZ);
 		netdev_for_each_mc_addr(ha, dev) {
-			__set_bit(mc_hash(ha->addr), filter);
+			__set_bit(mc_hash(vlan, ha->addr), filter);
 		}
 
-		__set_bit(mc_hash(dev->broadcast), filter);
+		__set_bit(mc_hash(vlan, dev->broadcast), filter);
 
 		bitmap_copy(vlan->mc_filter, filter, MACVLAN_MC_FILTER_SZ);
 	}


--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html