Commit 6afff0ca authored by John Fastabend's avatar John Fastabend Committed by David S. Miller
Browse files

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: default avatarJohn Fastabend <john.r.fastabend@intel.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarJeff Kirsher <jeffrey.t.kirsher@intel.com>
Acked-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1dc8d8c0

net/core/dev.c

+32 −36
Original line number Diff line number Diff line
@@ -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 @@ gso: 
	rc = -ENETDOWN;

	rcu_read_unlock_bh();



out_kfree_skb:

	kfree_skb(skb);

	return rc;

out:

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