Understanding Linux Network Internals

Christian Benvenuti
O'Reilly, 1st Edition, 2005
ISBN 0-596-00255-6

This book gives a great overview of the linux networking internals. In particular, it describes what happens during frame transmission and reception in great detail. I like this book because it gives the big picture along and ties it with the actual code.

What can you learn? (among other things)

What is an sk_buff and how to manipulate it.
How NAPI and non-NAPI drivers process packets in 2.6.x kernels.
How netif_rx, netif_rx_schedule, netif_rx_action, and netif_receive_skb work.
Where are the IP netfilter hooks.
How the bridging code works and where it puts netfilter hooks.

Kernel Versions and Reviews

Covers linux kernel 2.6.
O'Reilly page
See LWN.net review and Amazon.com reviews.