X-Git-Url: http://v3vee.org/palacios/gitweb/gitweb.cgi?a=blobdiff_plain;f=manual%2Fmanual.tex;h=74c8fd6229f5d32826d295377a09e67f91434fa0;hb=cfcc5717f659b3ed2954f41cf363d3bceae8dc84;hp=0e23630de6309dbe618633f68d01c487ad29cf8d;hpb=c7577d6f74e9b6daf0aa9ba08e6d03b81b673cf5;p=palacios.git

diff --git a/manual/manual.tex b/manual/manual.tex
index 0e23630..74c8fd6 100755
--- a/manual/manual.tex
+++ b/manual/manual.tex
@@ -19,7 +19,10 @@
 %\setlength{\rightmargin}{-2.9in}
 \setlength{\oddsidemargin}{0in}
 \setlength{\parindent}{0.5in}
+\setlength\parindent{0in}
+\setlength\parskip{0.1in} 
 
+\newcommand{\note}[1]{{$\rightarrow$ \bf Note: \emph{#1}}}
 
 \begin{document}
 
@@ -29,17 +32,17 @@
 \vspace{0.5in} 
 Palacios Internal Developer Manual
 }
-\author{Jack Lange}
+
 
 \maketitle
 
 
-This manual is written for Internal Palacios developers. It contains
-information on how to obtain the palacios code base, how to go about
+This manual is written for internal Palacios developers. It contains
+information on how to obtain the Palacios code base, how to go about
 the development process, and how to commit those changes to the
-mainline source tree. For in depth information on the palacios code
-structure please see {\em An Introduction to the Palacios Virtual
-Machine Monitor -- Release 1.0}.
+mainline source tree.  This assumes that the reader has read {\em An
+Introduction to the Palacios Virtual Machine Monitor -- Release 1.0}
+and also has a slight working knowledge of {\em git}.
 
 
 \section{Overview}
@@ -50,9 +53,9 @@ uses both the centralized repository and distributed development
 models. A central repository exists that holds the master version of
 the code base. This central repository is cloned by multiple people
 and in multiple places to support various development efforts. A
-feature of git is that every developer actually has a fully copy of
+feature of \texttt{git} is that every developer actually has a fully copy of
 the entire repository, and so can function independently until such
-time as they need to resync with the master version. 
+time as they need to re-sync with the master version. 
 
 There are typically multiple levels of access to the central
 repository, that are granted based on the type of developer being
@@ -60,15 +63,15 @@ granted access. The three basic developer types and their access
 privileges are:
 
 \begin{itemize}
-\item Core Developers: These are the lead developers and are in
+\item Core developers: These are the lead developers and are in
 charge of managing the master repository. They have full read/write
 access permissions to the central repository.
 
-\item Internal Developers: Formal members of the development
+\item Internal developers: Formal members of the development
 team. These people are capable of pulling directly from the central
 repository, but lack the ability to write directly to it. 
 
-\item External Developers: People who are not actual members of the
+\item External developers: People who are not actual members of the
 development team. These people can only access the public repository
 which is only updated to contain the release versions. 
 \end{itemize}
@@ -79,119 +82,638 @@ developer before they can be added to the mainline. We will discuss
 that process in Section~\ref{sec:submission}.
 
 
-\subsection{Palacios}
+\section{Checking out Palacios}
+The central Palacios repository is located on {\em
+newskysaw.cs.northwestern.edu} in {\em /home/palacios/palacios}. All
+internal developers have read access to the directory. Each developer
+must create their own local version of the repository, this is done
+with {\em git clone}.
 
-The central palacios repository 
+\begin{verbatim}
+git clone /home/palacios/palacios
+\end{verbatim}
 
-\includegraphics[height=3.5in]{dev_chart.pdf}
+This creates a local copy of the repository at {\em ./palacios/}.
 
-\subsection{Kitten}
 
-\section{Checking out Palacios}
+All development work is done in the {\em devel} branch of the
+repository. The developer can access this branch via:
+
+\begin{verbatim}
+git checkout --track -b devel origin/devel
+\end{verbatim}
+
+or 
+
+\begin{verbatim}
+/opt/vmm-tools/bin/checkout_branch devel
+\end{verbatim}
+
+{\em Important:}
+Note that Palacios is very actively developed so the contents of the
+{\em devel} branch are frequently changing. In order to keep up to
+date with the latest version, it is necessary to periodically pull the
+latest changes from the master repository by running \verb.git pull..
 
-Checkout or clone the devel branch of Palacios from the master
-repository. You should have the read permission to these branches.
 
 
 \section{Checking out Kitten}
 
-hg clone /home/palacios/kitten
+Kitten is available from Sandia National Labs, and is the main host OS
+we are targeting with Palacios. Loosely speaking, core Palacios
+developers are internal Kitten developers, and internal Palacios
+developers are external Kitten developers. Because we have limited
+access to the Kitten repository, we are maintaining a local mirror
+copy in {\em /home/palacios/kitten}. 
 
-git clone /home/palacios/palacios
+Kitten uses Mercurial for their source management, so you will have to
+make sure the local mercurial version is configured correctly.
+Specifically you should add the following Python path to your shell environment.
+
+\begin{verbatim}
+export PYTHONPATH=/usr/local/lib64/python2.4/site-packages/
+\end{verbatim}
+
+You can then clone Kitten from the local mirror:
+\begin{verbatim}
+hg clone /home/palacios/kitten
+\end{verbatim}
 
-/opt/vmm-tools/bin/checkout\_branch devel
+Both the Kitten and Palacios clone commands should be run from the
+same directory. This means that both repositories should be located at
+the same directory level. The Kitten build process depends on this.
 
+{\em Important:} Like Palacios, Kitten is under active development,
+and its source tree is frequently changing. In order to keep up to
+date with the latest version, it is necessary to periodically pull the
+latest changes from the mirror repository by running \verb.hg.
+pull. followed by \verb.hg update..
 
 \section{Compiling Palacios}
-cd palacios/build/
+Palacios is capable of targeting 32-bit and 64-bit operating systems,
+and includes a build process that supports both these
+architectures. Furthermore, Palacios has multiple build locations,
+with multiple Makefiles: a top level build directory and a
+Palacios-specific build directory. The Palacios build process first
+generates a static library that includes the Palacios VMM. This static
+library is then linked into a host operating system. Palacios
+internally supports GeekOS and can generate a complete OS image via a
+unified build process. 
+
+To combine Palacios with Kitten, it is necessary to first compile
+Palacios and then to compile Kitten externally link it with
+Palacios. The output of the compilation process is a bit more complex
+and generates multiple binaries, and the specifics can be found in the
+Makefiles.
+
+The top level build directory provides a number of high level make
+targets, and is located in {\em palacios/build/}. It supports building
+32-bit and 64-bit versions of the Palacios library independently as well
+as building an integrated version of GeekOS.   The basic targets are:
+\begin{itemize}
+\item \verb.make palacios-full32. -- Generates a 32 bit version of the Palacios static library 
+\item \verb.make palacios-full64. -- Generates a 64 bit version of the
+Palacios static library
+\item \verb.make geekos. -- Compiles the GeekOS kernel, and link it with the
+Palacios static library 
+\item \verb.make geekos-iso. -- Generate an ISO boot disk image from the
+GeekOS kernel that has been compiled
+\end{itemize}
 
+The second build directory is located at {\em palacios/palacios/build}
+and handles only the Palacios compilation process. It supports a
+different set of targets and arguments:
+\begin{itemize}
+\item \verb.make ARCH=32. -- iteratively compiles a 32 bit version of Palacios
+\item \verb.make ARCH=64. -- iteratively compiles a 64 bit version of
+Palacios
+\item \verb.make ARCH=32 world. -- fully recompiles a 32 bit version of
+Palacios
+\item \verb.make ARCH=64 world. -- fully recompiles a 64 bit version of
+Palacios
+\end{itemize}
+
+Both build levels support compilation directives that control the
+debugging messages that are generated by Palacios. These are specified
+by appending a \verb.DEBUG_<COMPONENT>=1. to the end of the
+\verb.make. command. The components that are currently supported are:
+\begin{itemize}
+\item \verb.DEBUG_ALL=1. -- enables debugging for all the VMM components
+({\em Warning:} this generates a {\em lot} of debug information.
+\item \verb.DEBUG_SHADOW_PAGING=1.
+\item \verb.DEBUG_CTRL_REGS=1.
+\item \verb.DEBUG_INTERRUPTS=1.
+\item \verb.DEBUG_IO=1.
+\item \verb.DEBUG_KEYBOARD=1.
+\item \verb.DEBUG_PIC=1.
+\item \verb.DEBUG_PIT=1.
+\item \verb.DEBUG_NVRAM=1.
+\item \verb.DEBUG_GENERIC=1.
+\item \verb.DEBUG_EMULATOR=1.
+\item \verb.DEBUG_RAMDISK=1.
+\item \verb.DEBUG_XED=1.
+\item \verb.DEBUG_HALT=1.
+\item \verb.DEBUG_DEV_MGR=1.
+\item \verb.DEBUG_APIC=1.
+\end{itemize}
 
-This will build Palacios as a library, libv3vee.a in the palacios/palacios/build/.
 
 
 \section{Compiling Kitten}
+Kitten requires a 64-bit version of Palacios, so make sure that
+Palacios has been correctly compiled before compiling Kitten.
+
 \subsection{Configuration}
-Kitten building can be configured by either text or graph configure interface, which is similar to the Linux kernel configure, By one of the following commands:
+Kitten borrows a lot of concepts from Linux, including the Linux build
+process. As such it must be configured before it is actually compiled.
+The Kitten configuration process is the same as Linux, and can be
+accessed via any of these make targets.
+\begin{itemize}
+\item \verb.make xconfig.
+\item \verb.make config.
+\item \verb.make menuconfig.
+\end{itemize}
 
-make xconfig
-make config
-make menuconfig
+There are some specific configuration options that should be disabled
+to work with Palacios. Because Palacios is configured by default to
+provide a guest with direct access to the VGA console, the {\em VGA
+console} device driver should be disabled in the Kitten
+configuration. Similarly the {\em VM console} driver should be
+disabled as well.
 
-Make sure turn on the network device driver, networking, and input kernel command 'console=serial net=rtl8139'
-\subsection{Compilation}
+Furthermore, because the VGA console is not being used the {\em Kernel
+Command Line Arguments} must be modified to remove the {\em VGA}
+device from the console list.
+
+The guest OS that is booted as a VM is included as an ISO image in raw
+binary format inside Kitten's {\em init\_task}. To change the guest
+ISO, you must change the Makefile for the init\_task. This is located
+in {\em user/hello\_world/Makefile} and the syntax is well commented.
+On {\em newskysaw} a collection of guest ISO images are located in
+{\em /opt/vmm-tools/isos/}. 
 
-Build Palacios as a module for Kitten
-In the first time, make sure to build Kitten before you building the Palacios as the module to kitten. 
-Palacios now is built as a module of the Kitten. You can find the palacios.c and palacios.h in the kitten/palacios/. Enter the directory, build the palacios module.
 
-cd kitten/palacios
+\subsection{Compilation}
+After Kitten has been configured it can be compiled. The
+general process is to compile a reference build of Kitten, followed by
+compiling Palacios support as a kernel module, and then doing a new
+full recompilation of Kitten.
+
+The specific compilation steps are run from the top level Kitten directory:
+\begin{verbatim}
+make
+cd palacios
 make -C .. M=`pwd`
 cp built-in.o ../modules/palacios-mod.o
-Build Kitten
-Go back to kitten root directory, and build the Kitten again.
+cd ..
+make
+make isoimage
+\end{verbatim}
+
+\note{This should probably explain how to change the iso (helloworld,etc)}
+
+This generates an ISO boot image containing Kitten, Palacios, and the
+guest that will be run as a VM. The ISO image is located at {\em
+./arch/x86\_64/boot/image.iso}.
 
-make  isoimage
 
 \section{Running Palacios/Kitten}
-Run the whole stuff built above in Qemu using following command: 
+Kitten and Palacios are capable of running under QEMU, which makes
+debugging much simpler.
+
+The basic form of the command to start the Emu emulator is:
+\begin{verbatim}
+/usr/local/qemu/bin/qemu-system-x86_64 -smp 1 -m 1024 \
+        -serial file:./serial.out \
+        -cdrom ./arch/x86_64/boot/image.iso  \
+        < /dev/null
+\end{verbatim}
+
+The command starts up a single processor emulated machine, with 1GB of
+RAM and a CD-ROM drive loaded with the Kitten ISO image.  All output
+to the serial port is written directly to a file called {\em
+  serial.out}. This command can be copied into a shell script for easy
+access.
+
+\section{Development Guidelines}
+
+There are standard requirements we have for code entering the mainline. 
+
+First and foremost, Palacios is designed to be OS independent and
+support 32-bit and 64-bit architectures. This means that developers should
+not include any external OS specific dependencies in any Palacios
+component. Also all changes need to be tested on both 32-bit and 64-bit
+architectures to make sure that they compile as well as run correctly.
+
+\paragraph*{Coding Style}
+
+"The use of equal negative space, as a balance to positive space, in a
+composition is considered by many as good design. This basic and often
+overlooked principle of design gives the eye a "place to rest,"
+increasing the appeal of a composition through subtle means."
+\newline\newline
+Translation: Use the space bar, newlines, and parentheses. 
+
+Curly-brackets are not optional, even for single line conditionals. 
+
+Tabs should be 4 characters in width.
+
+{\em Special:} If you are using XEmacs add the following to your \verb.init\.el. file:
+\begin{verbatim}
+(setq c-basic-offset 4)
+(c-set-offset 'case-label 4)
+\end{verbatim}
+
+{\em Bad}
+\begin{verbatim}
+if(a&&b==5||c!=0) return;
+\end{verbatim}
+
+
+{\em Good}
+\begin{verbatim}
+if (((a) && (b == 5)) || 
+    (c != 0)) {
+       	return;
+}
+\end{verbatim}
 
-/usr/local/qemu/bin/qemu-system-x86\_64 -smp 1 -m 1024 -serial file:./serial.out -cdrom ./arch/x86\_64/boot/image.iso  -net tap, ifname=tap0  < /dev/null
 
 
-\section{Networking}
+\paragraph*{Fail Stop}
+Because booting a basic Linux kernel results in over 1 million VM exits
+catching silent errors is next to impossible. For this reason
+ANY time your code has an error it should return -1, and expect the
+execution to halt. 
 
-\section{Configuring the development host's Qemu network}
-Set up Tap interfaces:
+This includes unimplemented features and unhandled cases. These cases
+should ALWAYS return -1. 
 
-/root/util/tap\_create tapX
 
-Bridging tapX with eth1 will only work (work = send packet and also make packet visible on localhost) if the IP address is set correctly (correctly = match network it is connected to  e.g., network of eth1)  so bring up the network inside of the VM / QEMU as 10-net, and it should route through the eth1 rule and be visible both on the host and in the physical network
+\paragraph*{Function names}
+Externally visible function names should be used rarely and have
+unique names. Currently we have several techniques for achieving this:
 
+\begin{enumerate}
+\item \verb.#ifdefs. in the header file
+\newline
+When the V3 Hypervisor is compiled it defines the symbol
+\verb.__V3VEE__. Any function that is not needed outside the Hypervisor
+context should be inside an \verb.#ifdef __V3VEE__. block, this will make it
+invisible to the host environment.
 
-\subsection{Configuring Kitten}
+\item Static Functions
+\newline
+Any utility functions that are only needed in the .c file where they
+are defined should be declared as static and not included in the
+header file. You should make an effort to use static functions
+whenever possible. 
 
-How to set ip address in kitten:
+\item \verb.v3_. prefix \newline Major interface functions should be
+  named with the prefix \verb.v3_. This allows easy understanding of
+  how to interact with the subsystems.  In the case that they need to
+  be externally visible to the host OS, make them unlikely to collide
+  with other functions.
+\end{enumerate}
 
-Kitten ip address setting is in file drivers/net/ne2k/rtl8139.c, in the code below which is located in function rtl8139\_init.
+\paragraph*{Debugging Output}
+Debugging output is sent through the host OS via functions in the
+\verb.os_hooks. structure. These functions have various wrappers of the form
+\verb.Print*., with \texttt{printf}-style semantics. 
 
-  struct ip\_addr ipaddr = { htonl(0 | 10 << 24 | 0 << 16 | 2 << 8 | 16 << 0) }; 
-  struct ip\_addr netmask = { htonl(0xffffff00) }; 
-  struct ip\_addr gw = { htonl(0 | 10 << 24 | 0 << 16 | 2 << 8 | 2 << 0) };
+Two functions of note are \verb.PrintDebug. and \verb.PrintError..
 
-This sets the ip address as 10.0.2.16, netmask 255.255.255.0 and gateway address 10.0.2.2, change it as you need.
+\begin{itemize}
 
+\item PrintDebug:
+\newline
+Should be used for debugging output that will often be turned off
+selectively by the VMM configuration.
 
+\item PrintError
+\newline
+Should be used when an error occurs, this will never be optimized out
+and will always print. 
+\end{itemize}
 
-\subsection{Running with networking}
 
-\paragraph*{Tap Interface}
-In which, the command line: 
+\section{Code Submission}
+\label{sec:submission}
 
--net tap, ifname=tap2
+To commit changes to the central repository they need to be exported
+as a patch set that can be applied directly to a mainline. Both Git
+and Mercurial contain functionality to allow developers to maintain
+changes as a patch set. There are also a few options that make dealing
+with patches easier.
 
-specifies Qemu to use the host's tap0 as its network interface, then Qemu can access the host's physical network.
+\subsection{Palacios}
 
-\paragraph*{Redirection}
+Git includes support for directly exporting local repository commits
+as a patch set. The basic operation is for a developer to commit a
+change to a local repository, and then export that change as a patch
+that can be applied to another git repository. While this is
+functionally possible, there are a number of issues. The main problem
+is that it is difficult to fully encapsulate a new feature in a single
+commit, and dealing with multiple patches that often overwrite each
+other is not a viable option either. Furthermore, once a patch is
+applied to the mainline, it will generate a conflicting commit that
+will become present when the developer next pulls from the central
+repository. This can result in both repositories getting out of
+sync. It is possible to deal with this by manually re-basing the local
+repository, but it is difficult and error-prone. 
+
+This approach also does not map well when patches are being revised. A
+normal patch will go through multiple revisions as it is reviewed and
+modified by others. This often leads to synchronization issues as well
+as errors with patch revisions. Ultimately it is the responsibility of
+the developer to generate a patch that will apply cleanly to the
+mainline.
+
+For this reason most internal developers should seriously consider
+{\em stacked git}. Stacked git is designed to make patch development
+easier and less of a headache. The basic mode of operation is for a
+developer to initialize a patch for a new feature and then continuously
+apply changes to the patch. Stacked Git allows a developer to layer a
+series of patches on top of a local git repository, without causing
+the repository to unsync due to local commits. Basically, the
+developer never commits changes to the repository itself but instead
+commits the changes to a specific patch. The local patches are managed
+using stack operations (push/pop) which allows a developer to apply
+and unapply patches as needed. Stacked git also manages new changes to
+the underlying git repository as a result of a pull operation and
+prevents collisions as changes are propagated upstream. For instance
+if you have a local patch that is applied to the mainline as a commit,
+when the commit is pulled down the patch becomes empty because it is
+effectively identical to the mainline. It also makes incorporating
+external revisions to a patch easier. Stacked git is installed on {\em
+newskysaw} in \verb./opt/vmm-tools/bin/. 
+
+Brief command overview:
+\begin{itemize}
+\item \verb.stg init. -- Initialize stacked git in a given branch
+\item \verb.stg new. -- create a new patch set, an editor will open
+asking for a commit message that will be used when the patch is
+ultimately committed.
+\item \verb.stg pop. -- pops a patch off of the source tree.
+\item \verb.stg push. -- pushes a patch back on to a source tree.
+\item \verb.stg export. -- exports a patch to a directory as a file
+that can then be emailed.
+\item \verb.stg refresh. -- commits local changes to the patch set at
+the top of the applied stack.
+\item \verb.stg fold. -- Apply a patch file to the current
+patch. (This is how you can manage revisions that are made by other developers).
+\end{itemize}
 
-Also you can use the following command instead to redirect host's 9555 port to Qemu's 80 port.
+You should definitely look at the online documentation to better
+understand how stacked git works. It is not required of course, but if
+you want your changes to be applied its up to you to generate a patch
+that is acceptable to a core developer. Ultimately using Stacked git
+should be easier than going it alone.
 
--net user -net nic,model=rtl8139  -redir tcp:9555::80
 
-In this case, you can access Qemu's 80 port in the host like:
+All patches should be emailed to Jack for inclusion in the
+mainline. An overview of the organization is given in
+Figure~\ref{fig:process}. You should assume that the first revision of
+a patch will not be accepted, and that you will have to make
+changes. Furthermore, the final form of the patch most likely will not
+be exactly what you submitted. 
 
-telnet localhost 9555
+ 
+\begin{figure}[t]
+\begin{center}
+\includegraphics[height=3.5in]{dev_chart.pdf}
+\end{center}
+\caption{Development organization}
+\label{fig:process}
+\end{figure}
 
-Qemu has many options to build up a virtual or real networking. See http://www.h7.dion.ne.jp/~qemu-win/HowToNetwork-en.html for more information.
 
+\subsection{Kitten}
 
+Writing code for Kitten follows essentially the same process as
+Palacios. The difference is that the patches need to be emailed to the
+Kitten developers. To send in a patch, you can just email it to the
+V3Vee development list.
+
+
+Also, instead of Stacked git you should use Mercurial patch
+queues. This feature is enabled in your .hgrc file.
+\begin{verbatim}
+[extensions]
+hgext.mq=
+\end{verbatim}
+
+Mercurial queues use the same stack operations as stacked git, however
+it does not automatically handle the synchronization with pull
+operations. Before you update from the central version of Kitten you
+need to pop all of the patches, and then push them once the update is
+complete.
+
+Basically:
+\begin{verbatim}
+hg qpop -a
+hg pull
+hg update
+hg qpush -a
+\end{verbatim}
+
+
+%Also, remember that Kitten is not a Northwestern project and is being
+%developed by professional developers at Sandia National Labs. So keep
+%in mind that you are representing Northwestern and the rest of the
+%Palacios development group. We are collaborating with them because
+%Kitten and the resources they have are very important for our research
+%efforts. They are collaborating with us because they believe that
+%Palacios might be able to help them. Therefore it is important that we
+%continue to ensure that they see value in our collaboration. In plain
+%terms, we need to make sure they think we're smart and know what we're
+%doing. So please keep that in mind when dealing with the Kitten group.
 
 
-\section{Code Submission}
-\label{sec:submission}
-\subsection{Palacios}
+\section{Networking}
+
+Both the Kitten and GeekOS substrates on which Palacios can run
+currently include drivers for two simple network cards, the NE2000,
+and the RTL8139.  The Kitten substrate is acquiring an ever increasing
+set of drivers for specialized network systems.   A lightweight
+networking stack is included so that TCP/IP networking is possible
+from within the host OS kernel and in Palacios.  
+
+When debugging Palacios on QEMU, it is very convenient to add an
+RTL8139 card to your QEMU configuration, and then drive it from within
+Palacios.  QEMU can be configured to provide local connectivity to the
+QEMU emulated machine, including bridging the emulated machine with a
+physical network.  Local connectivity can be done with redirection, or
+with a TAP interface.  For global connectivity, a TAP interface must
+be used; it is bridged to a physical interface.
+
+\section{Configuring the development host's QEMU network}
+
+To get local connectivity with redirection, no networking changes on
+the host are needed.  However, people usually want to use TAP-based
+networking, which does require changes.  For one thing, TAP interfaces
+can be inspected with tools like wireshark, which makes for much
+easier debugging of network code.
+
+In order to get QEMU networking to function, it is necessary to create
+TAP interfaces, and, optionally, to bridge them to real networks.  A
+development machine typically will have several TAP interfaces, and
+more can be created.  Generally, each developer should have a TAP
+interface of his or her own.  In the following, we will use our
+development machine, newskysaw, as an example.
+
+To set up a TAP interface on newskysaw, the following command is used:
+\begin{verbatim}
+/root/util/tap_create tapX
+\end{verbatim}
+
+When QEMU runs with a tap interface, it will use /etc/qemu-ifup to
+bring up the interface.  On newskysaw, /etc/qemu-ifup looks like this:
+
+\begin{verbatim}
+#!/bin/bash
+echo "Executing /etc/qemu-ifup - no external bridging"
+echo "Bringing up $1 for bridged mode..."
+NET=`echo $1 | cut -dp -f2` 
+sudo /sbin/ifconfig $1 172.2${NET}.0.1 up
+sleep 2
+\end{verbatim}
+
+The interface tap$N$ is brought up with the IP address 172.2$N$.0.1.
+ifconfig will also create a routing rule that sends 172.2$N$.0.1/16
+traffic to tap$N$.  The upshot is that if the code running in QEMU
+uses an IP address in this network (for example: 172.2$N$.0.2), you
+will be able to talk to it from newskysaw.  For example, from
+newskysaw, if you ping 172.21.0.2, the packet (and ARP) will go out via
+tap1.  The source address will appear to be 172.21.0.1.  The QEMU
+machine will see these packets on its interface, and the software
+controlling its interface can respond to 172.21.0.1.  
+
+This form of networking is local to the machine.  You can also bridge
+a TAP interface with a physical interface.  The result of this is that
+a packet sent on it will be sent on the physical interface.  To do
+this requires more effort (and is not set up by default on newskysaw).
+As an example, consider that on newskysaw, the physical interface eth1
+is connected to a private network switch to which the lab test
+computers (v-test-amd, v-test-amd2, etc.) are connected.  To bridge,
+for example, tap10, to this interface, you would do the following
+(with root's help):
+\begin{enumerate}
+\item You need to bring up eth1 (ifconfig eth1 up {\em address}
+netmask {\em mask}).  It is important that the address and mask you
+choose are appropriate for the network eth1 is connected to.
+\item You would bring up tap10 without an address:  /sbin/ifconfig
+tap10 up
+\item You would bridge tap10 and eth1:  /usr/sbin/brctl addif br0
+tap10; /usr/sbin/brctl addif eth1.  This assumes that br0 was
+previously created. 
+\end{enumerate}
+
+Bridging tap$N$ with eth1 will only work (where ``work'' means sending
+a packet on the network and making the packet visible on localhost) if
+the IP address in the code running in QEMU is set correctly.  This
+means that it needs to be set to correspond to the network of eth1).  
+For the newskysaw configuration, this is a 10-net address.
+
+
+\subsection{Configuring Kitten}
+
+Kitten needs to be explicitly configured to use networking. Currently
+only a subset of the networking configurations are supported. To
+enable an Ethernet network you should enable the following options:
+
+\begin{itemize}
+\item Enable TCP Support
+\item Enable UDP Support
+\item Enable socket API
+\item Enable ARP support
+\end{itemize}
+
+The other options are not supported, and enabling them will probably
+break the kernel compilation.
+
+To allow Kitten to communicate with the QEMU network card you also
+need to enable the appropriate device driver: \newline
+\verb.NE2K Device Driver (rtl8139).
+
+The driver then needs to be listed as a Kernel Command Line argument
+in the {\em ISOIMAGE configuration}. To do this add
+\verb.net=rtl819. to the end of the argument string.
+
+Kitten currently does not support the dynamic assignment or IP
+addresses at runtime. Because of this it is necessary to hardcode the
+IP address into the device driver. For the rtl8139 network driver look
+in the file {\em drivers/net/ne2k/rtl8139.c} for the function
+\verb.rtl8139_init..
+
+There should be a block of code that looks like the following:
+\begin{verbatim}
+  struct ip_addr ipaddr = { htonl(0 | 10 << 24 | 0 << 16 | 2 << 8 | 16 << 0) }; 
+  struct ip_addr netmask = { htonl(0xffffff00) }; 
+  struct ip_addr gw = { htonl(0 | 10 << 24 | 0 << 16 | 2 << 8 | 2 << 0) };
+\end{verbatim}
+
+This sets the IP address as 10.0.2.16, netmask 255.255.255.0 and
+gateway address 10.0.2.2. Change these assignments to match your configuration.
+
+
+\paragraph*{Kitten as the Guest OS}
+
+When running Kitten as a VM, the above applies except that you will
+want to enable the {\em VMNET} device driver instead of the {\em rtl8139}.
+
+
+\subsection{Running with networking}
+
+\paragraph*{TAP Interface}
+Running with a TAP interface provides either local or global
+connectivity (depending on how the TAP interface is configured and/or
+bridged).  From the perspective of the QEMU command line, both look
+the same, however.  You simply add something like this to the command
+line:
+\begin{verbatim}
+-net tap,ifname=tap2 -net nic,model=rtl8139
+\end{verbatim}
+The first \verb.-net. option indicates that you want to use a tap
+interface, specifically \verb.tap2..   The second \verb.-net. option
+specifies that this interface will appear to code in the QEMU machine
+to be a network interface card of the specific model RTL8139.  Note
+that this is a model for which we have a driver.  If tap2 were
+bridged, we'd get global connectivity.  If not, we would just get
+local connectivity.  
+
+
+\paragraph*{Redirection}
+It is also possible to achieve limited local connectivity even if you
+have no TAP support on your development machine.  In redirection, QEMU
+essentially acts as a proxy, translating TCP or other connections and
+low-level packet operations on the network interface in the QEMU
+machine.  For example, the following options will redirect the host's
+9555 port to the QEMU machine's 80 port:
+\begin{verbatim}
+-net user -net nic,model=rtl8139  -redir tcp:9555:10.10.10.33:80
+\end{verbatim}
+The first \verb.-net. option indicates that we are using user-level
+networking (proxying).  The second \verb.-net. option indicates that
+this user-level network will appear in the QEMU machine as an RTL8139
+network card.   The \verb.-redir. option indicates that connections on
+localhost:9555 will be translated into equivalent packet exchanges on
+the RTL8139 card in the QEMU machine.  However, we have to tell QEMU
+which IP address and port to use on the QEMU machine's side.  This is
+what the 10.10.10.33 address, and port 80 are.  In the example, if you
+access port 9555 on localhost, say with:
+\begin{verbatim}
+telnet localhost 9555
+\end{verbatim}
+The packets that appear in the QEMU machine will be bound for
+10.10.10.33, port 80.  Within the QEMU machine, your RTL8139 interface
+had better then be up on that address. 
+
+QEMU has many options to build up virtual or real networking. See
+http://www.h7.dion.ne.jp/$\sim$qemu-win/HowToNetwork-en.html for more
+information.
 
-\subsection{Kitten}
 
-For more questions, talk to Jack or Lei.
+For more questions, talk to Jack, Lei, or Peter.
 
 \end{document}