From: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Date: Mon, 24 May 2010 05:21:31 +0000 (-0400)
Subject: Socket buffers and other network related information.
X-Git-Url: http://git.cascardo.eti.br/?p=cascardo%2Fkernel%2Fslides%2F.git;a=commitdiff_plain;h=ca9630fd6c5da2f223f2086318e6aac0ac00f22a

Socket buffers and other network related information.
---

diff --git a/15net/net b/15net/net
new file mode 100644
index 0000000..88907c9
--- /dev/null
+++ b/15net/net
@@ -0,0 +1,45 @@
+%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