typo

git-svn-id: https://map66.svn.sourceforge.net/svnroot/map66@11 3484d885-4da6-438d-b19d-107d078dd756

2 files changed, 171 insertions, 104 deletions

diff --git a/README.dbk b/README.dbk
index 80887ab..153d50a 100644
--- a/README.dbk
+++ b/README.dbk
@@ -18,12 +18,15 @@
     <pubdate>06-OCT-2010</pubdate>
   </articleinfo>
 
-  <para>These files implement a Linux netfilter target that changes the IPv6 address of packets. The address change is done
-  checksum neutral, thus no checksum re-calculation for the packet is necessary. You can change the IPv6 source address of
-  outgoing packets as well as the IPv6 destination address of incoming packets. This allows you to map an internal IPv6 address
-  range to a second, externally used IPv6 address range. IPv6 address mapping is not very similar to IPv4 network address
-  translation, but one can describe it as some sort of stateless NAT. The implementation is based on the expired IETF discussion
-  paper published here:</para>
+  <para>These files implement a Linux netfilter target that changes the IPv6
+  address of packets. The address change is done checksum neutral, thus no
+  checksum re-calculation for the packet is necessary. You can change the IPv6
+  source address of outgoing packets as well as the IPv6 destination address
+  of incoming packets. This allows you to map an internal IPv6 address range
+  to a second, externally used IPv6 address range. IPv6 address mapping is not
+  very similar to IPv4 network address translation, but one can describe it as
+  some sort of stateless NAT. The implementation is based on the expired IETF
+  discussion paper published here:</para>
 
   <para><ulink
   url="http://tools.ietf.org/html/draft-mrw-behave-nat66-02">http://tools.ietf.org/html/draft-mrw-behave-nat66-02</ulink></para>
@@ -31,37 +34,47 @@
   <section>
     <title>Installation</title>
 
-    <para>MAP66 implements two pieces of software: a shared library that extends the ip6tables command and a Linux kernel
-    module. The shared library file adds the '-j MAP66' target to the ip6tables command. To build and install, you need
-    ip6tables installed as well as the necessary headers. The Linux kernel module requires the Linux source file tree and kernel
-    configuration files to compile. On a Debian/(EKU)buntu, the following command prepares the build environment:</para>
+    <para>MAP66 implements two pieces of software: a shared library that
+    extends the ip6tables command and a Linux kernel module. The shared
+    library file adds the '-j MAP66' target to the ip6tables command. To build
+    and install, you need ip6tables installed as well as the necessary
+    headers. The Linux kernel module requires the Linux source file tree and
+    kernel configuration files to compile. On a Debian/(EKU)buntu, the
+    following command prepares the build environment:</para>
 
     <programlisting>sudo apt-get install build-essential linux-headers iptables-dev</programlisting>
 
-    <para>Unpack the source tgz archive below <filename>/usr/src</filename>, change to the new sub-directory and issue "make" to
-    build. If this compiles without errors, install the ip6tables extension with the following command:</para>
+    <para>Unpack the source tgz archive below <filename>/usr/src</filename>,
+    change to the new sub-directory and issue "make" to build. If this
+    compiles without errors, install the ip6tables extension with the
+    following command:</para>
 
     <programlisting>sudo make install</programlisting>
 
     <note>
-      <para>The kernel module (<filename>ip6t_MAP66.ko</filename> for Linux-2.6 or <filename>ip6t_MAP66.o</filename> for
-      Linux-2.4) is not automatically installed nor loaded into the kernel. You can copy the kernel module file manually, e.g.
-      with <userinput>sudo cp ip6t_MAP66.ko /lib/modules/$(uname -r)/</userinput>.</para>
+      <para>The kernel module (<filename>ip6t_MAP66.ko</filename> for
+      Linux-2.6 or <filename>ip6t_MAP66.o</filename> for Linux-2.4) is not
+      automatically installed nor loaded into the kernel. You can copy the
+      kernel module file manually, e.g. with <userinput>sudo cp ip6t_MAP66.ko
+      /lib/modules/$(uname -r)/</userinput>.</para>
     </note>
   </section>
 
   <section>
     <title>DKMS Integration</title>
 
-    <para>If the next system update needs to install a new kernel version, you also need to re-compile/re-install the MAP66
-    kernel module. With Debian/(EKU)buntu, this can be automated with the Dynamic Kernel Module Support Framework (DKMS). For
-    this, the <filename>dkms.conf</filename> file is included with the MAP66 source file package. Install DKMS with the
+    <para>If the next system update needs to install a new kernel version, you
+    also need to re-compile/re-install the MAP66 kernel module. With
+    Debian/(EKU)buntu, this can be automated with the Dynamic Kernel Module
+    Support Framework (DKMS). For this, the <filename>dkms.conf</filename>
+    file is included with the MAP66 source file package. Install DKMS with the
     following command:</para>
 
     <programlisting>sudo apt-get install dkms</programlisting>
 
-    <para>If not already in place, move/unpack the MAP66 source file archive below <filename>/usr/src/</filename>. To register
-    the MAP66 source to DKMS and compile/install, issue these commands:</para>
+    <para>If not already in place, move/unpack the MAP66 source file archive
+    below <filename>/usr/src/</filename>. To register the MAP66 source to DKMS
+    and compile/install, issue these commands:</para>
 
     <programlisting>sudo dkms add -m ip6t_MAP66 -v 0.3
 sudo dkms build -m ip6t_MAP66 -v 0.3
@@ -77,37 +90,53 @@ sudo dkms install -m ip6t_MAP66 -v 0.3</programlisting>
     <section>
       <title>Brief Version</title>
 
-      <para>You always need to add two ip6tables-rules to your netfilter configuration. One rule matches outgoing packets and
-      changes their IPv6 source address. The second rule matches incoming packets and reverts the address change by altering
-      their IPv6 destination address. To following commands correspond to the <quote>Address Mapping Example</quote> given in
-      the IETF discussion paper:</para>
+      <para>You always need to add two ip6tables-rules to your netfilter
+      configuration. One rule matches outgoing packets and changes their IPv6
+      source address. The second rule matches incoming packets and reverts the
+      address change by altering their IPv6 destination address. To following
+      commands correspond to the <quote>Address Mapping Example</quote> given
+      in the IETF discussion paper:</para>
 
       <programlisting>ip6tables -t mangle -I POSTROUTING -o eth0 -s FD01:0203:0405::/48 -j MAP66 --to 2001:0DB8:0001::/48
 ip6tables -t mangle -I PREROUTING  -i eth0 -d 2001:0DB8:0001::/48 -j MAP66 --to FD01:0203:0405::/48</programlisting>
 
-      <para>This example is also printed to the screen if you issue <userinput>ip6tables -j MAP66 --help</userinput>. By design,
-      you cannot use an arbitrary prefix length. Only /112, /96 .. /16 are supported.</para>
-
-      <para>For each packet, the Linux kernel module also compares the packet's source address to all IPv6 addresses assigned to
-      the outgoing interface. If a match is found, the packet's source address is not mapped. The same comparison happens on the
-      incoming packet's destination address. The comparison requires some CPU resources, especially if the interface has a large
-      number of assigned IPv6 addresses. If you are sure that the mapping cannot match the IPv6 address of the interface (e.g.
-      the mapping rule defines a mapping prefix that cannot result in the interface address) you can switch off the comparison.
-      Add the <userinput>--nocheck</userinput> parameter to the ip6tables command for this.</para>
+      <para>This example is also printed to the screen if you issue
+      <userinput>ip6tables -j MAP66 --help</userinput>. By design, you cannot
+      use an arbitrary prefix length. Only /112, /96 .. /16 are
+      supported.</para>
+
+      <para>For each packet, the Linux kernel module also compares the
+      packet's source address to all IPv6 addresses assigned to the outgoing
+      interface. If a match is found, the packet's source address is not
+      mapped. The same comparison happens on the incoming packet's destination
+      address. The comparison requires some CPU resources, especially if the
+      interface has a large number of assigned IPv6 addresses. If you are sure
+      that the mapping cannot match the IPv6 address of the interface (e.g.
+      the mapping rule defines a mapping prefix that cannot result in the
+      interface address) you can switch off the comparison. Add the
+      <userinput>--nocheck</userinput> parameter to the ip6tables command for
+      this.</para>
     </section>
 
     <section>
       <title>Detailed Version</title>
 
-      <para>The following explanation details a living example from the wireless mesh network that is mentioned under <xref
-      endterm="motivation-title" linkend="motivation"/> (see below). Throughout the mesh network, a private IP address range is
-      used. The ULA prefix is fdca:ffee:babe::/64. All mesh nodes derive their IPv6 interface addresses by correlating the ULA
-      prefix with the EUI48 (<quote>MAC address</quote>) of the respective network adapter.</para>
-
-      <para>There is a Debian based virtual machine that should act as one IPv6 Internet gateway for the mesh. You can reach the
-      virtual machine's web service via IPv4 under <ulink url="http://bbb-vpn.freifunk.net">http://bbb-vpn.freifunk.net</ulink>.
-      To experiment with IPv6, a <ulink url="http://www.sixxs.net/">SIXXS</ulink> static tunnel setup has been added and there
-      is also an experimental 6-to-4 configuration. The following <filename>/etc/network/interfaces</filename> file provides the
+      <para>The following explanation details a living example from the
+      wireless mesh network that is mentioned under <xref
+      endterm="motivation-title" linkend="motivation" /> (see below).
+      Throughout the mesh network, a private IP address range is used. The ULA
+      prefix is fdca:ffee:babe::/64. All mesh nodes derive their IPv6
+      interface addresses by correlating the ULA prefix with the EUI48
+      (<quote>MAC address</quote>) of the respective network adapter.</para>
+
+      <para>There is a Debian based virtual machine that should act as one
+      IPv6 Internet gateway for the mesh. You can reach the virtual machine's
+      web service via IPv4 under <ulink
+      url="http://bbb-vpn.freifunk.net">http://bbb-vpn.freifunk.net</ulink>.
+      To experiment with IPv6, a <ulink
+      url="http://www.sixxs.net/">SIXXS</ulink> static tunnel setup has been
+      added and there is also an experimental 6-to-4 configuration. The
+      following <filename>/etc/network/interfaces</filename> file provides the
       configuration for IPv6:</para>
 
       <programlisting>auto sixxs
@@ -131,10 +160,13 @@ iface tun6to4 inet6 v4tunnel
         ttl 64
         gateway ::192.88.99.1</programlisting>
 
-      <para>As you can see, the virtual machine has an IPv6 prefix of 2001:4dd0:fe77::/48 and is reachable via <ulink
-      url="http://[2001:4dd0:fe77::1]/">http://[2001:4dd0:fe77::1]/</ulink>. For experimental purposes, the 6-to-4 tunnel can be
-      activated by issuing <userinput>ifup tun6to4</userinput>. The netfilter setup of this machine includes the following
-      command sequence to realize mapping from the private fdca:ffee:babe::/64 prefix to the globally valid IPv6
+      <para>As you can see, the virtual machine has an IPv6 prefix of
+      2001:4dd0:fe77::/48 and is reachable via <ulink
+      url="http://[2001:4dd0:fe77::1]/">http://[2001:4dd0:fe77::1]/</ulink>.
+      For experimental purposes, the 6-to-4 tunnel can be activated by issuing
+      <userinput>ifup tun6to4</userinput>. The netfilter setup of this machine
+      includes the following command sequence to realize mapping from the
+      private fdca:ffee:babe::/64 prefix to the globally valid IPv6
       addresses:</para>
 
       <programlisting>ip6tables -t mangle -F POSTROUTING
@@ -150,26 +182,35 @@ ip6tables -t mangle -A POSTROUTING -o tun6to4 -s fdca:ffee:babe::/64 -j MAP66 --
 ip6tables -t mangle -A PREROUTING  -i tun6to4 -d 2002:4d57:3007:1::/64 -j MAP66 --to fdca:ffee:babe::/64 --nocheck
 ip6tables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu</programlisting>
 
-      <para>Because for both IPv6 networks the external prefix length is smaller than the internal prefix length, we can make
-      sure that the mapped addresses cannot match the interface addresses. For example: 2001:4dd0:fe77:1::/64 cannot be
-      converted to 2001:4dd0:fe77:0::1/128 in this context. For this reason, we can use the <userinput>--nocheck</userinput>
-      speedup here.</para>
+      <para>Because for both IPv6 networks the external prefix length is
+      smaller than the internal prefix length, we can make sure that the
+      mapped addresses cannot match the interface addresses. For example:
+      2001:4dd0:fe77:1::/64 cannot be converted to 2001:4dd0:fe77:0::1/128 in
+      this context. For this reason, we can use the
+      <userinput>--nocheck</userinput> speedup here.</para>
 
-      <para>You may stumble over the MSS-clamping rule. While IPv6 defines, that path MTU detection via ICMPv6 must be supported
-      by any host, sometimes path MTU detection does not work. The SIXXS tunnel uses an MTU of 1280 byte. To get the following
-      command working on my PC, I needed to add the above MSS-clamping rule on the gateway:</para>
+      <para>You may stumble over the MSS-clamping rule. While IPv6 defines,
+      that path MTU detection via ICMPv6 must be supported by any host,
+      sometimes path MTU detection does not work. The SIXXS tunnel uses an MTU
+      of 1280 byte. To get the following command working on my PC, I needed to
+      add the above MSS-clamping rule on the gateway:</para>
 
       <programlisting>wget --prefer-family=IPv6 -O - http://6to4.nro.net/</programlisting>
 
       <note>
-        <para>The tun6to4 tunnel interface is disabled normally, because of the implicit 2002::/16 network route configured for
-        that interface. This network route ensures, that traffic between one 2002::/16 to another 2002::/16 travels directly
-        between the IPv4 hosts. Without this network route, any IPv6 traffic will be routed via the 6-to-4 gateways which may
-        not work and place a higher load on those 6-to-4 gateways.</para>
-
-        <para>However, if you ping the SIXXS IP address from another host that has a 6-to-4 address, you will get the answer
-        packet back via the 6-to-4 interface. If the above address mapping is configured, you ping one IPv6 address and get the
-        answer from another IPv6 address...</para>
+        <para>The tun6to4 tunnel interface is disabled normally, because of
+        the implicit 2002::/16 network route configured for that interface.
+        This network route ensures, that traffic between one 2002::/16 to
+        another 2002::/16 travels directly between the IPv4 hosts. Without
+        this network route, any IPv6 traffic will be routed via the 6-to-4
+        gateways which may not work and place a higher load on those 6-to-4
+        gateways.</para>
+
+        <para>However, if you ping the SIXXS IP address from another host that
+        has a 6-to-4 address, you will get the answer packet back via the
+        6-to-4 interface. If the above address mapping is configured, you ping
+        one IPv6 address and get the answer from another IPv6
+        address...</para>
       </note>
     </section>
   </section>
@@ -177,37 +218,48 @@ ip6tables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-
   <section>
     <title>IPv6/IPv4 Precedence</title>
 
-    <para>With (EKU)buntu and eventually with RedHat, you will notice that your browser does not show the IPv6 version of a web
-    site that is multi-homed when using ULA addresses for your IPv6 Internet connection. The reason for this is an add on to the
-    RFC 3484 rules that is compiled into the (EKU)buntu libc. The pre-installed <filename>/etc/gai.conf</filename> file will
-    give you a hint on this.</para>
+    <para>With (EKU)buntu and eventually with RedHat, you will notice that
+    your browser does not show the IPv6 version of a web site that is
+    multi-homed when using ULA addresses for your IPv6 Internet connection.
+    The reason for this is an add on to the RFC 3484 rules that is compiled
+    into the (EKU)buntu libc. The pre-installed
+    <filename>/etc/gai.conf</filename> file will give you a hint on
+    this.</para>
 
-    <para>In short: the getaddrinfo() library function rates a private IPv4 address higher than the ULA IPv6 address when
-    choosing the transport protocol for a new Internet connection if this add on to the RFC 3484 rules is compiled in. For this
-    reason, you may want to change the precedence rules within <filename>/etc/gai.conf</filename>.</para>
+    <para>In short: the getaddrinfo() library function rates a private IPv4
+    address higher than the ULA IPv6 address when choosing the transport
+    protocol for a new Internet connection if this add on to the RFC 3484
+    rules is compiled in. For this reason, you may want to change the
+    precedence rules within <filename>/etc/gai.conf</filename>.</para>
 
     <note>
-      <para>The getaddrinfo() library function manages lists of label, precedence, and scope4 type entries. If the
-      <filename>/etc/gai.conf</filename> file does not provide a single entry for a particular type, the compiled-in list is
-      used. For this reason, you cannot uncomment a single entry to overwrite the default. You need to uncomment all entries of
-      a particular type for this. The <quote>label</quote> lines compare source addresses, the precedence lines compare
-      <quote>destination</quote> addresses.</para>
+      <para>The getaddrinfo() library function manages lists of label,
+      precedence, and scope4 type entries. If the
+      <filename>/etc/gai.conf</filename> file does not provide a single entry
+      for a particular type, the compiled-in list is used. For this reason,
+      you cannot uncomment a single entry to overwrite the default. You need
+      to uncomment all entries of a particular type for this. The
+      <quote>label</quote> lines compare source addresses, the
+      <quote>precedence</quote> lines compare destination addresses.</para>
     </note>
 
     <procedure>
       <title>Change IPv6 Precedence</title>
 
       <step>
-        <para>Open the <filename>/etc/gai.conf</filename> file as root user, e.g. by executing <userinput>sudo nano
+        <para>Open the <filename>/etc/gai.conf</filename> file as root user,
+        e.g. by executing <userinput>sudo nano
         /etc/gai.conf</userinput>.</para>
       </step>
 
       <step>
-        <para>Remove the leading hash character from the 8 lines starting with <quote>#label</quote>.</para>
+        <para>Remove the leading hash character from the 8 lines starting with
+        <quote>#label</quote>.</para>
       </step>
 
       <step>
-        <para>Re-add the hash character to the line stating <quote>#label fc00::/7 6</quote>.</para>
+        <para>Re-add the hash character to the line stating <quote>#label
+        fc00::/7 6</quote>.</para>
       </step>
 
       <step>
@@ -215,53 +267,68 @@ ip6tables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-
       </step>
 
       <step>
-        <para>Restart your browser and re-try to browse to a multi-homed web site.</para>
+        <para>Restart your browser and re-try to browse to a multi-homed web
+        site.</para>
       </step>
     </procedure>
 
-    <para>The above procedure removes the difference between standard IPv6 source addresses and ULA type private IPv6 source
-    addresses. Anything else is unchanged.</para>
+    <para>The above procedure removes the difference between standard IPv6
+    source addresses and ULA type private IPv6 source addresses. Anything else
+    is unchanged.</para>
   </section>
 
   <section id="motivation">
     <title id="motivation-title">Motivation</title>
 
-    <para>My Internet access at home is realized by a wireless community mesh network not owned by me. The mesh is operated with
-    small embedded devices (nodes aka. WLAN routers) that are interconnected via radio links (WLAN IBSS / AdHoc). Routing is
-    done with a specialized protocol such as Batman or OLSR. The routing protocol selects the nearest out of a dozen Internet
-    gateways and configures a default route or an IPIP tunnel accordingly. Each Internet gateway is connected to a different ISP
-    and provides the service with the help of IPv4 network address translation (NAT). Using NAT has the following
-    effects:</para>
+    <para>My Internet access at home is realized by a wireless community mesh
+    network not owned by me. The mesh is operated with small embedded devices
+    (nodes aka. WLAN routers) that are interconnected via radio links (WLAN
+    IBSS / AdHoc). Routing is done with a specialized protocol such as Batman
+    or OLSR. The routing protocol selects the nearest out of a dozen Internet
+    gateways and configures a default route or an IPIP tunnel accordingly.
+    Each Internet gateway is connected to a different ISP and provides the
+    service with the help of IPv4 network address translation (NAT). Using NAT
+    has the following effects:</para>
 
     <itemizedlist>
       <listitem>
-        <para>Address amplification - something not necessary with IPv6 any more</para>
+        <para>Address amplification - something not necessary with IPv6 any
+        more</para>
       </listitem>
 
       <listitem>
-        <para>Anonymization - nice to have as an option but not mission critical</para>
+        <para>Anonymization - nice to have as an option but not mission
+        critical</para>
       </listitem>
 
       <listitem>
-        <para>ISP independence - no reverse routing, no "buy-a-number-range"</para>
+        <para>ISP independence - no reverse routing, no
+        "buy-a-number-range"</para>
       </listitem>
     </itemizedlist>
 
-    <para>The last point <emphasis role="bold">is</emphasis> mission critical. One can obtain a provider independent IPv6
-    address range, but you need the cooperation of an ISP to use that address range for Internet connectivity. If you e.g. move
-    to another ISP you need your address range to be re-routed to your new location.</para>
-
-    <para>ISP independence is also possible with some tunneling technique, such as VPN or mobile IP. Tunneling can be
-    implemented on client PCs and Internet gateways/servers one day. But there is no need to implement the same tunneling
-    technique on every mesh node. Why? Because the mesh nodes can use private IP addresses (or "ULA") to transport the tunnel
-    data between the client PC and the gateway/server. Each tunneling technique typically needs a single instance (the "server")
-    which forms a single point of failure. Rule-of-thumb1: avoid a SPOF for the infrastructure. Rule-of-thumb2: KISS (keep it
-    simple stupid).</para>
-
-    <para>Using private IP addresses on the mesh nodes has a drawback: mesh node software updates e.g. a download via HTTP from
-    an Internet server is not possible. This is where I start to think: <quote>hey, some kind of address mapping may be nice to
-    have</quote>. While opening Pandora's NAT66 box, I discovered that IPv6 nerds do not like the acronym. It is always a good
-    tactic in info wars to rename, hence the name "MAP66".</para>
+    <para>The last point <emphasis role="bold">is</emphasis> mission critical.
+    One can obtain a provider independent IPv6 address range, but you need the
+    cooperation of an ISP to use that address range for Internet connectivity.
+    If you e.g. move to another ISP you need your address range to be
+    re-routed to your new location.</para>
+
+    <para>ISP independence is also possible with some tunneling technique,
+    such as VPN or mobile IP. Tunneling can be implemented on client PCs and
+    Internet gateways/servers one day. But there is no need to implement the
+    same tunneling technique on every mesh node. Why? Because the mesh nodes
+    can use private IP addresses (or "ULA") to transport the tunnel data
+    between the client PC and the gateway/server. Each tunneling technique
+    typically needs a single instance (the "server") which forms a single
+    point of failure. Rule-of-thumb1: avoid a SPOF for the infrastructure.
+    Rule-of-thumb2: KISS (keep it simple stupid).</para>
+
+    <para>Using private IP addresses on the mesh nodes has a drawback: mesh
+    node software updates e.g. a download via HTTP from an Internet server is
+    not possible. This is where I start to think: <quote>hey, some kind of
+    address mapping may be nice to have</quote>. While opening Pandora's NAT66
+    box, I discovered that IPv6 nerds do not like the acronym. It is always a
+    good tactic in info wars to rename, hence the name "MAP66".</para>
 
     <para>// Sven-Ola</para>
   </section>
diff --git a/README.txt b/README.txt
index f2af2d4..4e53698 100644
--- a/README.txt
+++ b/README.txt
@@ -206,7 +206,7 @@ scope4 type entries. If the /etc/gai.conf file does not provide a single entry
 for a particular type, the compiled-in list is used. For this reason, you
 cannot uncomment a single entry to overwrite the default. You need to uncomment
 all entries of a particular type for this. The “label” lines compare source
-addresses, the precedence lines compare “destination” addresses.
+addresses, the “precedence” lines compare destination addresses.
 
 Procedure 1. Change IPv6 Precedence