net: TX_RING and packet mmap

New packet socket feature that makes packet socket more efficient for
transmission.

- It reduces number of system call through a PACKET_TX_RING mechanism,
  based on PACKET_RX_RING (Circular buffer allocated in kernel space
  which is mmapped from user space).

- It minimizes CPU copy using fragmented SKB (almost zero copy).

Signed-off-by: Johann Baudy <johann.baudy@gnu-log.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 1b5c3d298f43..aff494ba6a31 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -203,6 +203,9 @@ struct skb_shared_info {
 #ifdef CONFIG_HAS_DMA
         dma_addr_t      dma_maps[MAX_SKB_FRAGS + 1];
 #endif
+        /* Intermediate layers must ensure that destructor_arg
+         * remains valid until skb destructor */
+        void *          destructor_arg;
 };
 
 /* We divide dataref into two halves.  The higher 16 bits hold references