[NET]: Add generic segmentation offload

This patch adds the infrastructure for generic segmentation offload.
The idea is to tap into the potential savings of TSO without hardware
support by postponing the allocation of segmented skb's until just
before the entry point into the NIC driver.

The same structure can be used to support software IPv6 TSO, as well as
UFO and segmentation offload for other relevant protocols, e.g., DCCP.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 5 deletions

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 7aad0121232c..74d4a1dceeec 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -96,8 +96,11 @@ static inline int qdisc_restart(struct net_device *dev)
         struct sk_buff *skb;
 
         /* Dequeue packet */
-        if ((skb = q->dequeue(q)) != NULL) {
+        if (((skb = dev->gso_skb)) || ((skb = q->dequeue(q)))) {
                 unsigned nolock = (dev->features & NETIF_F_LLTX);
+
+                dev->gso_skb = NULL;
+
                 /*
                  * When the driver has LLTX set it does its own locking
                  * in start_xmit. No need to add additional overhead by
@@ -134,10 +137,8 @@ static inline int qdisc_restart(struct net_device *dev)
 
                         if (!netif_queue_stopped(dev)) {
                                 int ret;
-                                if (netdev_nit)
-                                        dev_queue_xmit_nit(skb, dev);
 
-                                ret = dev->hard_start_xmit(skb, dev);
+                                ret = dev_hard_start_xmit(skb, dev);
                                 if (ret == NETDEV_TX_OK) { 
                                         if (!nolock) {
                                                 netif_tx_unlock(dev);
@@ -171,7 +172,10 @@ static inline int qdisc_restart(struct net_device *dev)
                  */
 
 requeue:
-                q->ops->requeue(skb, q);
+                if (skb->next)
+                        dev->gso_skb = skb;
+                else
+                        q->ops->requeue(skb, q);
                 netif_schedule(dev);
                 return 1;
         }
@@ -593,6 +597,11 @@ void dev_deactivate(struct net_device *dev)
         /* Wait for outstanding qdisc_run calls. */
         while (test_bit(__LINK_STATE_QDISC_RUNNING, &dev->state))
                 yield();
+
+        if (dev->gso_skb) {
+                kfree_skb(dev->gso_skb);
+                dev->gso_skb = NULL;
+        }
 }
 
 void dev_init_scheduler(struct net_device *dev)