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net: better IFF_XMIT_DST_RELEASE support

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Testing xmit_more support with netperf and connected UDP sockets,
I found strange dst refcount false sharing.

Current handling of IFF_XMIT_DST_RELEASE is not optimal.

Dropping dst in validate_xmit_skb() is certainly too late in case
packet was queued by cpu X but dequeued by cpu Y

The logical point to take care of drop/force is in __dev_queue_xmit()
before even taking qdisc lock.

As Julian Anastasov pointed out, need for skb_dst() might come from some
packet schedulers or classifiers.

This patch adds new helper to cleanly express needs of various drivers
or qdiscs/classifiers.

Drivers that need skb_dst() in their ndo_start_xmit() should call
following helper in their setup instead of the prior :

	dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
->
	netif_keep_dst(dev);

Instead of using a single bit, we use two bits, one being
eventually rebuilt in bonding/team drivers.

The other one, is permanent and blocks IFF_XMIT_DST_RELEASE being
rebuilt in bonding/team. Eventually, we could add something
smarter later.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2014-10-05 18:38:35 -07:00
committed by David S. Miller
parent fe971b95c2
commit 0287587884
27 changed files with 54 additions and 39 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
net/ipv6/ip6_gre.c
View File

@@ -1242,7 +1242,7 @@ static void ip6gre_tunnel_setup(struct net_device *dev)
dev->flags |= IFF_NOARP;
dev->iflink = 0;
dev->addr_len = sizeof(struct in6_addr);
dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
netif_keep_dst(dev);
}
static int ip6gre_tunnel_init(struct net_device *dev)

2
net/ipv6/ip6_tunnel.c
View File

@@ -1493,7 +1493,7 @@ static void ip6_tnl_dev_setup(struct net_device *dev)
dev->mtu -= 8;
dev->flags |= IFF_NOARP;
dev->addr_len = sizeof(struct in6_addr);
dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
netif_keep_dst(dev);
/* This perm addr will be used as interface identifier by IPv6 */
dev->addr_assign_type = NET_ADDR_RANDOM;
eth_random_addr(dev->perm_addr);

2
net/ipv6/ip6_vti.c
View File

@@ -807,7 +807,7 @@ static void vti6_dev_setup(struct net_device *dev)
dev->mtu = ETH_DATA_LEN;
dev->flags |= IFF_NOARP;
dev->addr_len = sizeof(struct in6_addr);
dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
netif_keep_dst(dev);
}
/**

2
net/ipv6/sit.c
View File

@@ -1364,7 +1364,7 @@ static void ipip6_tunnel_setup(struct net_device *dev)
dev->hard_header_len = LL_MAX_HEADER + t_hlen;
dev->mtu = ETH_DATA_LEN - t_hlen;
dev->flags = IFF_NOARP;
dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
netif_keep_dst(dev);
dev->iflink = 0;
dev->addr_len = 4;
dev->features |= NETIF_F_LLTX;