Socket buffers and other network related information.

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+%Network Subsystem
+%Thadeu Cascardo
+
+# Socket Buffers
+
+* include linux/skbuff.h
+* struct sk\\_buff
+       - struct net\\_device *dev
+* alloc\\_skb(len, gfp)
+* dev\\_alloc\\_skb(len) - uses ATOMIC, reserves PAD
+* netdev\\_alloc\\_skb(netdev, len) - uses ATOMIC, since 2.6.18
+
+# Diagram
+
+* head - start of allocated buffer
+* end - end of allocated buffer
+* data - start of data, giving space after headroom
+* tail - end of used space
+* headroom - space between head and data
+* tailroom - space between tail and end
+
+# Socket Buffers operations
+
+* skb\\_put(skb, len) - adds data to end of skb
+* skb\\_push(skb, len) - adds data to start of skb
+* skb\\_pull(skb, len) - allocates headroom
+* skb\\_headroom and skb\\_tailroom
+* skb\\_reserve - only allowed for empty buffer, reserves headroom
+* skb\\_orphan - release it from its socket holder
+       
+
+# Changes in net device
+
+* Use netdev\\_priv, no priv anymore
+* struct net\\_device\\_ops introduced in 2.6.29, with compatibility provided
+  for drivers
+* Compatibility removed in 2.6.31
+* netdev\\_tx\\_t: NETDEV\\_TX\\_OK, NETDEV\\_TX\\_BUSY, NETDEV\\_TX\\_LOCKED
+
+# Other recent changes
+
+* Some members moved to netdev\\_queue to increase cache-line usage
+* GRO/GSO
+* Multi-queue support
+* RPS - Packet Steering