small doc changes

git-svn-id: https://map66.svn.sourceforge.net/svnroot/map66@7 3484d885-4da6-438d-b19d-107d078dd756

3 files changed, 138 insertions, 195 deletions

diff --git a/Makefile b/Makefile
index a9415e1..f7704aa 100644
--- a/Makefile
+++ b/Makefile
@@ -28,3 +28,7 @@ install: /lib/xtables/libip6t_MAP66.so
 
 README.txt: README.dbk
 	xmlto text README.dbk
+
+README.html: README.dbk
+	xmlto xhtml README.dbk
+
diff --git a/README.dbk b/README.dbk
index 1241b1b..7fc6aff 100644
--- a/README.dbk
+++ b/README.dbk
@@ -8,7 +8,7 @@
     <author>
       <firstname>Sven-Ola</firstname>
 
-      <surname>Tücke</surname>
+      <surname>Tuecke</surname>
 
       <affiliation>
         <orgname>Freifunk</orgname>
@@ -18,15 +18,12 @@
     <pubdate>06-OCT-2010</pubdate>
   </articleinfo>
 
-  <para>These files implement a Linux netfilter target to change the IPv6
-  address of packets. The address change is done checksum neutral, thus no
-  checksum re-calculation for the IPv6 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 the 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 the 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>
@@ -34,48 +31,37 @@
   <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
-    Linux 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, change to the 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 to <filename>/usr/src</filename>, change to the archive's 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>Move/unpack the MAP66 source files below /usr/src and adapt the
-    directory name to the version mentioned in the dkms.conf file. For
-    example, issue <userinput>mkdir /usr/src/ip6t_MAP66-0.3</userinput> and
-    <userinput>cp * /usr/src/ip6t_MAP66-0.3/</userinput>. 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
@@ -91,53 +77,37 @@ 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 the outgoing packet and changes the IPv6
-      source address. The second rule matches the incoming packet and revert
-      the address change by altering the 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 revert 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. It 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 require 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 match 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. It 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 require 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). The mesh
-      network uses a private IP range, the ULA prefix 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
-      Internet gateway for the mesh. You can reach this 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
@@ -161,14 +131,11 @@ 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 reasons, 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 ensure mapping from the
-      private fdca:ffee:babe::/64 prefix to the globally valid IPv6
-      address:</para>
+      <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
 ip6tables -t mangle -F PREROUTING
@@ -183,34 +150,26 @@ 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 interfaces address. For example:
-      2001:4dd0:fe77:1::/64 cannot match 2001:4dd0:fe77:0::1/128. For this
-      reason, we can use the <userinput>--nocheck</userinput> speedup flag
+      <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 interfaces address. 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, 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
-        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 6-to-4.
-        If the above network 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>
@@ -218,68 +177,50 @@ ip6tables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-
   <section>
     <title>Hints (Chapter is To-do)</title>
 
-    <para>Note for me: svn propedit svn:ignore.</para>
-
-    <para>Note on ubuntu. One needs to enable prefer-family in /etc/wgetrc.
-    after this e.g. "wget -O /dev/null http://ftp.se.debian.org" should
-    connect to the IPv6 addrs of that server. Alternative: change presedence
-    of ULAs in /etc/gai.conf </para>
+    <para>Note on ubuntu. One needs to enable prefer-family in /etc/wgetrc. after this e.g. "wget -O /dev/null
+    http://ftp.se.debian.org" should connect to the IPv6 addrs of that server. Alternative: change presedence of ULAs in
+    /etc/gai.conf</para>
 
-    <para>Idea to think about: --salt 3b5b91c5a2 XOR client addresses for some
-    more privacy</para>
+    <para>Idea to think about: --salt 3b5b91c5a2 XOR client addresses for some more privacy</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 _is_ mission critical. One can use 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 that 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.</para>
-
-    <para>Using private IP addresses on the mesh nodes has a drawback: mesh
-    node software updates e.g. via HTTP downloads from an Internet server is
-    not possible. This is where I start to think: "hey, some kind of address
-    mapping may be nice to have". While opening Pandora's NAT66 box, I
-    discovered that IPv6 nerds do not like the acronym. It is always a good
+    <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.</para>
+
+    <para>Using private IP addresses on the mesh nodes has a drawback: mesh node software updates e.g. via HTTP downloads 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>
diff --git a/README.txt b/README.txt
index eaf36f2..2e2eaf0 100644
--- a/README.txt
+++ b/README.txt
@@ -1,6 +1,6 @@
 MAP66 (NAT from IPv6 to IPv6, NAT66) for Linux
 
-Sven-Ola T cke
+Sven-Ola Tuecke
 
 Freifunk
 
@@ -20,9 +20,9 @@ Configuration
 Hints (Chapter is To-do)
 Motivation
 
-These files implement a Linux netfilter target to change the IPv6 address of
+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 IPv6 packet is necessary. You can change the IPv6 source
+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
@@ -38,14 +38,14 @@ 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 Linux configuration files to compile.
+requires the Linux source file tree and kernel configuration files to compile.
 On a Debian/(EKU)buntu, the following command prepares the build environment:
 
 sudo apt-get install build-essential linux-headers iptables-dev
 
-Unpack the source tgz archive, change to the directory and issue "make" to
-build. If this compiles without errors, install the ip6tables extension with
-the following command:
+Unpack the source tgz archive to /usr/src, change to the archive's
+sub-directory and issue "make" to build. If this compiles without errors,
+install the ip6tables extension with the following command:
 
 sudo make install
 
@@ -66,10 +66,9 @@ Install DKMS with the following command:
 
 sudo apt-get install dkms
 
-Move/unpack the MAP66 source files below /usr/src and adapt the directory name
-to the version mentioned in the dkms.conf file. For example, issue mkdir /usr/
-src/ip6t_MAP66-0.3 and cp * /usr/src/ip6t_MAP66-0.3/. To register the MAP66
-source to DKMS and compile/install, issue these commands:
+If not already in place, move/unpack the MAP66 source file archive below /usr/
+src/. To register the MAP66 source to DKMS and compile/install, issue these
+commands:
 
 sudo dkms add -m ip6t_MAP66 -v 0.3
 sudo dkms build -m ip6t_MAP66 -v 0.3
@@ -82,10 +81,10 @@ Configuration
 Brief Version
 
 You always need to add two ip6tables-rules to your netfilter configuration. One
-rule matches the outgoing packet and changes the IPv6 source address. The
-second rule matches the incoming packet and revert the address change by
-altering the IPv6 destination address. To following commands correspond to the
-“Address Mapping Example” given in the IETF discussion paper:
+rule matches outgoing packets and changes their IPv6 source address. The second
+rule matches incoming packets and revert the address change by altering their
+IPv6 destination address. To following commands correspond to the “Address
+Mapping Example” given in the IETF discussion paper:
 
 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
@@ -99,24 +98,25 @@ address to all IPv6 addresses assigned to the outgoing interface. It 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 require 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 match
-the interface address) you can switch off the comparison. Add the --nocheck
-parameter to the ip6tables command for this.
+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
+--nocheck parameter to the ip6tables command for this.
 
 Detailed Version
 
 The following explanation details a living example from the wireless mesh
-network that is mentioned under Motivation (see below). The mesh network uses a
-private IP range, the ULA prefix fdca:ffee:babe::/64. All mesh nodes derive
-their IPv6 interface addresses by correlating the ULA prefix with the EUI48
-(“MAC address”) of the respective network adapter.
-
-There is a Debian based virtual machine that should act as one Internet gateway
-for the mesh. You can reach this virtual machine's web service via IPv4 under
-http://bbb-vpn.freifunk.net. To experiment with IPv6, a SIXXS static tunnel
-setup has been added and there is also an experimental 6-to-4 configuration.
-The following /etc/network/interfaces file provides the configuration for IPv6:
+network that is mentioned under 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 (“MAC address”) of the respective network adapter.
+
+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 http://bbb-vpn.freifunk.net. To experiment with IPv6, a SIXXS static
+tunnel setup has been added and there is also an experimental 6-to-4
+configuration. The following /etc/network/interfaces file provides the
+configuration for IPv6:
 
 auto sixxs
 iface sixxs inet6 v4tunnel
@@ -140,10 +140,10 @@ iface tun6to4 inet6 v4tunnel
         gateway ::192.88.99.1
 
 As you can see, the virtual machine has an IPv6 prefix of 2001:4dd0:fe77::/48
-and is reachable via http://[2001:4dd0:fe77::1]/. For experimental reasons, the
-6-to-4 tunnel can be activated by issuing ifup tun6to4. The netfilter setup of
-this machine includes the following command sequence to ensure mapping from the
-private fdca:ffee:babe::/64 prefix to the globally valid IPv6 address:
+and is reachable via http://[2001:4dd0:fe77::1]/. For experimental purposes,
+the 6-to-4 tunnel can be activated by issuing ifup tun6to4. 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:
 
 ip6tables -t mangle -F POSTROUTING
 ip6tables -t mangle -F PREROUTING
@@ -160,15 +160,15 @@ ip6tables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-
 
 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 interfaces address. For example: 2001:4dd0:fe77:1::/64 cannot match
-2001:4dd0:fe77:0::1/128. For this reason, we can use the --nocheck speedup flag
-here.
+the interfaces address. 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
+--nocheck speedup here.
 
 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, I needed to add the above MSS-clamping rule on the
-gateway:
+following command working on my PC, I needed to add the above MSS-clamping rule
+on the gateway:
 
 wget --prefer-family=IPv6 -O - http://6to4.nro.net/
 
@@ -179,17 +179,15 @@ The tun6to4 tunnel interface is disabled normally, because of the implicit
 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 gateways.
+load on those 6-to-4 gateways.
 
 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 6-to-4. If the above network
-mapping is configured, you ping one IPv6 address and get the answer from
-another IPv6 address...
+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...
 
 Hints (Chapter is To-do)
 
-Note for me: svn propedit svn:ignore.
-
 Note on ubuntu. One needs to enable prefer-family in /etc/wgetrc. after this
 e.g. "wget -O /dev/null http://ftp.se.debian.org" should connect to the IPv6
 addrs of that server. Alternative: change presedence of ULAs in /etc/gai.conf
@@ -214,9 +212,9 @@ address translation (NAT). Using NAT has the following effects:
 
   ● ISP independence - no reverse routing, no "buy-a-number-range"
 
-The last point _is_ mission critical. One can use a provider independent IPv6
+The last point is 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 that
+for Internet connectivity. If you e.g. move to another ISP you need your
 address range to be re-routed to your new location.
 
 ISP independence is also possible with some tunneling technique, such as VPN or
@@ -230,8 +228,8 @@ for the infrastructure. Rule-of-thumb2: KISS.
 
 Using private IP addresses on the mesh nodes has a drawback: mesh node software
 updates e.g. via HTTP downloads from an Internet server is not possible. This
-is where I start to think: "hey, some kind of address mapping may be nice to
-have". While opening Pandora's NAT66 box, I discovered that IPv6 nerds do not
+is where I start to think: “hey, some kind of address mapping may be nice to
+have”. 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".