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net: consolidate netif_needs_gso() checks 

netif_needs_gso() is checked twice in the TX path once,
before submitting the skb to the qdisc and once after
it is dequeued from the qdisc just before calling
ndo_hard_start().  This opens a window for a user to
change the gso/tso or tx checksum settings that can
cause netif_needs_gso to be true in one check and false
in the other.

Specifically, changing TX checksum setting may cause
the warning in skb_gso_segment() to be triggered if
the checksum is calculated earlier.

This consolidates the netif_needs_gso() calls so that
the stack only checks if gso is needed in
dev_hard_start_xmit().

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
John Fastabend 2010-06-16 14:18:12 +00:00 committed by David S. Miller
parent 1dc8d8c06d
commit 6afff0caa7
1 changed files with 32 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

68
net/core/dev.c
View File

@ -1895,6 +1895,22 @@ static inline void skb_orphan_try(struct sk_buff *skb)
skb_orphan(skb);
}
/*
* Returns true if either:
* 1. skb has frag_list and the device doesn't support FRAGLIST, or
* 2. skb is fragmented and the device does not support SG, or if
* at least one of fragments is in highmem and device does not
* support DMA from it.
*/
static inline int skb_needs_linearize(struct sk_buff *skb,
struct net_device *dev)
{
return skb_is_nonlinear(skb) &&
((skb_has_frags(skb) && !(dev->features & NETIF_F_FRAGLIST)) ||
(skb_shinfo(skb)->nr_frags && (!(dev->features & NETIF_F_SG) ||
illegal_highdma(dev, skb))));
}
int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
struct netdev_queue *txq)
{
@ -1919,6 +1935,22 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
goto out_kfree_skb;
if (skb->next)
goto gso;
} else {
if (skb_needs_linearize(skb, dev) &&
__skb_linearize(skb))
goto out_kfree_skb;
/* If packet is not checksummed and device does not
* support checksumming for this protocol, complete
* checksumming here.
*/
if (skb->ip_summed == CHECKSUM_PARTIAL) {
skb_set_transport_header(skb, skb->csum_start -
skb_headroom(skb));
if (!dev_can_checksum(dev, skb) &&
skb_checksum_help(skb))
goto out_kfree_skb;
}
}
rc = ops->ndo_start_xmit(skb, dev);
@ -2089,22 +2121,6 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
return rc;
}
/*
* Returns true if either:
* 1. skb has frag_list and the device doesn't support FRAGLIST, or
* 2. skb is fragmented and the device does not support SG, or if
* at least one of fragments is in highmem and device does not
* support DMA from it.
*/
static inline int skb_needs_linearize(struct sk_buff *skb,
struct net_device *dev)
{
return skb_is_nonlinear(skb) &&
((skb_has_frags(skb) && !(dev->features & NETIF_F_FRAGLIST)) ||
(skb_shinfo(skb)->nr_frags && (!(dev->features & NETIF_F_SG) ||
illegal_highdma(dev, skb))));
}
/**
* dev_queue_xmit - transmit a buffer
* @skb: buffer to transmit
@ -2137,25 +2153,6 @@ int dev_queue_xmit(struct sk_buff *skb)
struct Qdisc *q;
int rc = -ENOMEM;
/* GSO will handle the following emulations directly. */
if (netif_needs_gso(dev, skb))
goto gso;
/* Convert a paged skb to linear, if required */
if (skb_needs_linearize(skb, dev) && __skb_linearize(skb))
goto out_kfree_skb;
/* If packet is not checksummed and device does not support
* checksumming for this protocol, complete checksumming here.
*/
if (skb->ip_summed == CHECKSUM_PARTIAL) {
skb_set_transport_header(skb, skb->csum_start -
skb_headroom(skb));
if (!dev_can_checksum(dev, skb) && skb_checksum_help(skb))
goto out_kfree_skb;
}
gso:
/* Disable soft irqs for various locks below. Also
* stops preemption for RCU.
*/
@ -2214,7 +2211,6 @@ int dev_queue_xmit(struct sk_buff *skb)
rc = -ENETDOWN;
rcu_read_unlock_bh();
out_kfree_skb:
kfree_skb(skb);
return rc;
out: