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>

diff --git a/net/core/dev.c b/net/core/dev.c
index 5902426..7f390b5 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -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: