Updated specification and wrapped all lines at 80 chars.

1 files changed, 191 insertions, 128 deletions

diff --git a/README.IPv6 b/README.IPv6
index 71a1537..420b6cb 100644
--- a/README.IPv6
+++ b/README.IPv6
@@ -3,160 +3,223 @@ IPv6 for Slackware
 
 Features
 --------
-* Dual stack.  Interfaces can be configured with an IPv4 address or an IPv6 address, or both.
-* Each interface can have single or multiple v4 and/or v6 alias IPs.  v6 IPs can be aliases of an IPv4 interface and/or
-  an IPv6 interface, and v4 IPs can be aliases of v6 interfaces.
-* Optional StateLess Address Auto Configuration (SLAAC) of v6 IP addresses (disabled by default).
+* Dual stack.  Interfaces can be configured with an IPv4 address or an IPv6
+  address, or both.
+* Each interface can have single or multiple v4 and/or v6 IPs.  Additional
+  v4 IPs are added as 'alias' interfaces, whereas v6 IPs are simply added
+  to the interface.
+* Optional StateLess Address Auto Configuration (SLAAC) of v6 IP addresses
+  (disabled by default).
 * DHCPv6 support for server controlled address configuration.
-* Fixed IP configuration of IPv6 interfaces and alias addresses.
+* Fixed IP configuration of IPv6 interfaces.
 
 
 Implementation
 --------------
-* Slackware needs to add a /lib/modprobe.d/ipv6.conf file (perhaps /etc/modprobe.d/ipv6.conf?) to a package (which
-  package I'm unsure), with content:
+[This section can be removed from the final README.IPv6 as it relates to
+ implimentation by Pat rather than user level configuration]
+
+Pat should add a /lib/modprobe.d/ipv6.conf (preferred) or
+/etc/modprobe.d/ipv6.conf file to a package (probably network-scripts), with
+content:
     options ipv6 autoconf=0
     options net-pf-10 autoconf=0
-  in order to disable IPv6 auto configuration (SLAAC) by default.
-
-  Rationale: Should (possibly unknown to the end user) the network the host is connecting to employ SLAAC via Router
-  Advertisement (RA), when the ipv6 module is loaded into the kernel the default is to accept RA packets and do auto
-  configuration.  This would result in any interface (whether being configured for any IP networking or not) coming up
-  with a globally routable IPv6 address.
-  We considered this to be a bad idea since Slackware does not employ any firewalling by default, and most daemons will
-  bind to an IPv6 address if it exists - possibly exposing services to the global internet where none is expected.
-  It is not possible to disable SLAAC or RA via sysctl at boot time - when sysctl is invoked in the Slackware boot
-  process, the interfaces have not yet established their /proc/sys/net/ipv6/conf entries for configuration, so the
-  setting would fail.
-
-  Effects: Previous versions of Slackware followed the default behaviour when loading the ipv6 module, so would obtain a
-  globally routable IP address via SLAAC should the network support it.  This behaviour would now change to the more
-  secure default of not configuring network interfaces that the end user does not know about.
-
-  Effects if not used: Although the USE_SLAAC[x] option in rc.inet1.conf can be used to disable stateless address auto
-  configuration by RA for an interface via /proc/sys/net/ipv6/conf/$interface/autoconf, there is a chance that auto
-  configuration will happen anyway because of a race condition between when the ipv6 kernel module is loaded and when
-  USE_SLAAC[x] is applied by rc.inet1 - if a RA packet arrives during that time, the interface will be auto configured
-  regardless of the USE_SLAAC[x] option.
-  Once that auto configured IP is attached to the interface, even disabling auto configuration via the /proc/sys/net
-  interface will not automatically remove the IP from the interface.  A manual 'ip -6 addr del' would need to be applied
-  to remove that address.
-  This can lead to the situation where the user thinks they have disabled stateless auto configuration using the
-  USE_SLAAC[x] option in rc.inet1.conf, but an IP is still assigned in the brief time between module load and setting
-  autconf off via /proc.
-
-* v6 IPs can be configured via SLAAC, DHCP6 or statically using the following new options for rc.inet1.conf:
-  USE_SLAAC[x]=""		Allow StateLess Address Auto Configuration of a (potentially) globally routable v6 IP.
-				With this option set to "yes", the interface's v6 IP will ONLY be configured via SLAAC,
-				even if	RA indicates DHCP6 is available on the network - if SLAAC is not available on
-				the network, no IPv6 address will be assigned.
-				Since dhcpcd is capable of handling SLAAC as well as DHCP, it may be better practice to
-				set USE_DHCP6[x]="yes" to perform full auto configuration instead.
-  USE_DHCP6[x]=""		Use dhcpcd to configure the interface.  This will bring up the interface using DHCP6 if
-				RA indicates DHCP6 support is available on the network, falling back to SLAAC (if
-				configured on the network), or will leave the interface unconfigured after a timeout.
-				When this option is set to "yes", the USE_SLAAC[x] option is ignored.
-				This is the preferred option to configure an interface dynamically - whether the
-				network is setup for DHCP6 or SLAAC, dhcpcd will be able to configure the interface.
-  IP6ADDR[x]=""			Set the static v6 address for the interface.
-				When either the USE_DHCP6[x] or USE_SLAAC[x] options are set to "yes", this setting is
-				ignored - dynamic configuration takes precedence over fixed IPs in Slackware.
-  PREFIXLEN[x]=""		The prefix length for the v6 address set in IP6ADDR[x].  This should be in CIDR format
-				with an optional leading /, eg: 64 or /48.  If this option is not set. a prefix length of
-				64 will be assumed, and a warning emitted about the unset option.
-				This is the equilavant of the v4 NETMASK[x] option, but is named more appropriately for
-				IPv6 terminology.
-  GATEWAY6=""			The default IPv6 gateway for the network.
-
-* Interfaces configured for IPv4 and/or IPv6 can be assigned aliases.  IPv4 interfaces may have IPv6 aliases assigned to
-  them; and, likewise, IPv6 interfaces may have IPv4 aliases.  Both IPv4 and IPv6 interfaces can have a number of v4 or
-  v6 IP alias addresses assigned to them.  IPv4 aliases may be configured in the usual way using the IPv4 IPALIASES[x]
-  option in rc.inet1.conf.  IPv6 aliases are configured using the following new option for rc.inet1.conf:
-  IP6ALIASES[x]=""		A space delimited list of IPv6 address and prefix combinations which should be added to
-				the interface.  Addresses should be listed in the format: ipaddr/prefix -- If no prefix
-				is set, 64 is assumed.
-
-* The following new misc options have been added for use in rc.inet1.conf:
-  USE_RA[x]=""			Normally, unless USE_SLAAC[x]="yes" is set, Router Advertisment (RA) is	disabled for the
-				interface as it can result in extraneous routes being added to the routing table.  With
-				this option set to "yes", RA packets will be accepted on the interface even when DHCP or
-				fixed IP addressing is used, and the routes advertised by the Router will be added to
-				the table.  Conversely, if this option is explicitly set to "no", RA will be disabled
-				at all times - meaning SLAAC cannot be performed even when USE_SLAAC[x]="yes" is set.
-				The default (unset) is to enable RA when SLAAC is in use, and to disable it otherwise.
-				The use of this option should rarely be required as rc.inet1 will do the right thing.
-  SLAAC_TIMEOUT[x]=""		The time to wait (in seconds) for an interface to be configured by SLAAC.  When unset,
-				the default is 15.  Some networks may require a longer period for the router to
-				broadcast an advertisement packet on the network.
+in order to disable IPv6 auto configuration (SLAAC) by default.
+
+Rationale: Should (possibly unknown to the end user) the network the host is
+connecting to employ SLAAC via Router Advertisement (RA), when the ipv6 module
+is loaded into the kernel the default is to accept RA packets and do auto
+configuration.  This would result in any interface (whether being configured for
+any IP networking or not) coming up with a globally routable IPv6 address.
+
+We considered this to be a bad idea since Slackware does not employ any
+firewalling by default, and most daemons will bind to an IPv6 address if it
+exists - possibly exposing services to the global internet where none is
+expected.  It is not possible to disable SLAAC or RA via sysctl at boot time -
+when sysctl is invoked in the Slackware boot process, the interfaces have not
+yet established their /proc/sys/net/ipv6/conf entries for configuration, so the
+setting would fail.
+
+Effects: Previous versions of Slackware followed the default behaviour when
+loading the ipv6 module, so would obtain a globally routable IP address via
+SLAAC should the network support it.  This behaviour would now change to the
+more secure default of not configuring network interfaces that the end user does
+not know about.
+
+Effects if not used: Although the USE_SLAAC[x] option in rc.inet1.conf can be
+used to disable stateless address auto configuration by RA for an interface via
+/proc/sys/net/ipv6/conf/$interface/autoconf, there is a chance that auto
+configuration will happen anyway because of a race condition between when the
+ipv6 kernel module is loaded and when USE_SLAAC[x] is applied by rc.inet1 - if a
+RA packet arrives during that time, the interface will be auto configured
+regardless of the USE_SLAAC[x] option.  Once that auto configured IP is attached
+to the interface, even disabling auto configuration via the /proc/sys/net
+interface will not automatically remove the IP from the interface.  A manual 'ip
+-6 addr del' would need to be applied to remove that address.
+
+This can lead to the situation where the user thinks they have disabled
+stateless auto configuration using the USE_SLAAC[x] option in rc.inet1.conf, but
+an IP is still assigned in the brief time between module load and setting
+autconf off via /proc.
+
+
+Configuration
+-------------
+v6 IPs can be configured via SLAAC, DHCP6 or statically using the following new
+options for rc.inet1.conf:
+  USE_SLAAC[x]=""	Allow StateLess Address Auto Configuration of a
+			(potentially) globally routable v6 IP. With this option
+			set to "yes", the interface's v6 IP will ONLY be
+			configured via SLAAC, even if RA indicates DHCP6 is
+			available on the network - if SLAAC is not available on
+			the network, no IPv6 address will be assigned.
+
+			Since dhcpcd is capable of handling SLAAC as well as
+			DHCP, it is better practice to set USE_DHCP6[x]="yes" to
+			perform full auto configuration instead.
+
+  USE_DHCP6[x]=""	Use dhcpcd to configure the interface.  This will bring
+			up the interface using DHCP6, falling back to SLAAC (if
+			configured on the network), or will leave the interface
+			unconfigured after a timeout.  When this option is set
+			to "yes", the USE_SLAAC[x] option is ignored.
+
+			This is the preferred option to configure an interface
+			dynamically - whether the network is setup for DHCP6 or
+			SLAAC, dhcpcd will be able to configure the interface.
+
+  IP6ADDRS[x]=""	The static v6 IP addresses for the interface.  This
+			option takes a list of v6 IP addresses and prefix
+			lengths in CIDR notation, in a space delimited list.
+			For example: IP6ADDRS[x]="a:b:c:d:e::1/48 1:2:3:4::5/64"
+
+			If a prefix length is not given (separated from the IP
+			address with a /), a length of 64 will be assumed, and
+			a warning emitted about the unset value.
+
+			When either the USE_DHCP6[x] or USE_SLAAC[x] options are
+			set to "yes", this setting is ignored - dynamic
+			configuration takes precedence over fixed IPs in
+			Slackware.
+
+  GATEWAY6=""		The default IPv6 gateway for the network.  This is a
+			IPv6 address in standard format.
+
+The following kesser used misc options have been added for use in rc.inet1.conf:
+  USE_RA[x]=""		Normally, unless USE_SLAAC[x]="yes" is set, Router
+			Advertisment (RA) is disabled for the interface as it
+			can result in extraneous routes being added to the
+			routing table.  With this option set to "yes", RA
+			packets will be accepted on the interface even when DHCP
+			or fixed IP addressing is used, and the routes
+			advertised by the Router will be added to the table.
+
+			Conversely, if this option is explicitly set to "no", RA
+			will be disabled at all times - meaning SLAAC cannot be
+			performed even when USE_SLAAC[x]="yes" is set. The
+			default (unset) is to enable RA when SLAAC is in use,
+			and to disable it otherwise.
+
+			The use of this option should rarely be required as
+			rc.inet1 will do the right thing.
+
+  SLAAC_TIMEOUT[x]=""	The time to wait (in seconds) for an interface to be
+			configured by SLAAC.  When unset, the default is 15.
+			Some networks may require a longer period for the router
+			to broadcast an advertisement packet on the network.
 
 
 Disabling IPv6
 --------------
-For some use cases, where IPv6 support is not required at all, disabling IPv6 may be a better option than leaving the
-interface unconfigured.
+For some use cases, where IPv6 support is not required at all, disabling IPv6
+may be a better option than leaving the interface unconfigured.
 
-There are two similar methods which can be used to disable IPv6.  Both of the options involve creating the file
-/etc/modprobe.d/ipv6.conf (which overrides the /lib/modprobe.d/ipv6.conf file), and adding the following content:
+There are two similar methods which can be used to disable IPv6.  Both of the
+options involve creating (or replacing the content if it already exists) the
+file /etc/modprobe.d/ipv6.conf (which overrides any configuration in the
+/lib/modprobe.d/ipv6.conf file), and making the content as follows:
   alias ipv6 off
   alias net-pf-10 off
 Or:
   install ipv6 /bin/true
   install net-pf-10 /bin/true
 
-It is important to disable both the 'ipv6' and 'net-pf-10' modules since the module can be automatically loaded by each
-name.
+It is important to disable both the 'ipv6' and 'net-pf-10' modules since the
+module can be automatically loaded by each name.
 
 
 Changes from previous Slackware versions
 ----------------------------------------
-* Previously, if the network the host is connecting to is configured for StateLess Address Auto Configuration (SLAAC),
-  the host would bring up an interface with a (potentially) globally routable IPv6 address with no configuration by the
-  user.  This has been changed so that all network configuration must be explicitly enabled.  Thus, interfaces will no
-  longer automatically come up with a valid IPv6 address on networks which support auto configuration, without enabling
-  the USE_SLAAC[x]="yes" option for the interface.  This change is detailed above in the 'Implementation' section and is
-  a security enhancement.
-* Unless RA is explicitly enabled using the USE_RA[x]="yes" option, rc.inet1 now disables RA (via the accept_ra tunable
-  in /proc) for an interface before trying to add any IPs configured for it.  This prevents RA on the network
-  from automatically adding any routes to the table.  When USE_SLAAC[x]="yes" is set, RA is implicitly re-enabled
-  for the interface (since SLAAC and RA are usually used together on a network), unless explicitly disabled with
-  USE_RA[x]="no".  This is a change from previous versions of Slackware, which would auto configure routes.
-  This is a security fix in the same vein as the above.
-* Interfaces will no longer be brought into the 'up' state unless they are actually configured with an IP address.  In
-  previous versions, no matter whether the interface was assigned an IP (either via DHCP or a fixed IP) or not, the
-  interface would be left in the 'up' state after executing 'rc.inet1 start'.  This will no longer happen, and is
-  considered a clean-up of the current odd behaviour.
-* If no NETMASK[x] is set for an interface, rc.inet1 will now assume a prefix/netmask of 24 (and will emit a warning).
-  CIDR notation netmasks are now recommended (with the leading / as optional), but the old style dotted-quad notation is
-  still accepted for IPv4.  This is a configuration enhancement.
-* In previous versions, the IP aliases configuration for IPv4 assumed a netmask of /32, making the interface only
-  addressable by itself.  Now, a netmask of /24 is assumed where none is provided in the configuration.  This is a
-  bugfix.
-* Sometime during this -current cycle, the call to dhcpcd gained a hard coded -L (disable use of IPv4LL addresses as
-  last resort) parameter which effectively rendered the DHCP_NOIPV4LL[x] option redundant - the use of -L was not
-  contingent upon the value of DHCP_NOIPV4LL[x].  The hard coded -L has been removed from the dhcpcd command line,
-  restoring the behaviour of 14.2 and the usefulness of the DHCP_NOIPV4LL[x] option.  If there was a specific reason
-  for the hard coded -L, this can be re-factored to make the -L option the default but still allowing the user to turn
-  IPv4LL off (see comment in rc.inet1 itself).
+* Previously, if the network the host is connecting to is configured for
+  StateLess Address Auto Configuration (SLAAC), the host would bring up an
+  interface with a (potentially) globally routable IPv6 address with no
+  configuration by the user.  This has been changed so that all network
+  configuration must be explicitly enabled.  Thus, interfaces will no longer
+  automatically come up with a valid IPv6 address on networks which support auto
+  configuration, without enabling the USE_SLAAC[x]="yes" option for the
+  interface.  This is a security enhancement.
+
+* Unless RA is explicitly enabled using the USE_RA[x]="yes" option, rc.inet1 now
+  disables RA (via the accept_ra tunable in /proc) for an interface before
+  trying to add any IPs configured for it.  This prevents RA on the network from
+  automatically adding any routes to the table.  When USE_SLAAC[x]="yes" is set,
+  RA is implicitly re-enabled for the interface (since SLAAC and RA are usually
+  used together on a network), unless explicitly disabled with USE_RA[x]="no".
+  This is a change from previous versions of Slackware, which would auto
+  configure routes. This is a security fix in the same vein as the above.
+
+* Interfaces will no longer be brought into the 'up' state unless they are
+  actually configured with an IP address.  In previous versions, no matter
+  whether the interface was assigned an IP (either via DHCP or a fixed IP) or
+  not, the interface would be left in the 'up' state after executing 'rc.inet1
+  start'.  This will no longer happen, and is considered a clean-up of the
+  current, odd, behaviour.
+
+* If no NETMASK[x] is set for an interface, rc.inet1 will now assume a
+  prefix/netmask of 24 (and will emit a warning). CIDR notation netmasks are now
+  recommended (with the leading / as optional), but the old style dotted-quad
+  notation is still accepted for IPv4.  This is a configuration enhancement.
+
+* In previous versions, the IP aliases configuration for IPv4 assumed a netmask
+  of /32, making the interface only addressable by itself.  Now, a netmask of
+  /24 is assumed where none is provided in the configuration.  This is a bugfix.
+
+* Sometime during this -current cycle, the call to dhcpcd gained a hard coded -L
+  (disable use of IPv4LL addresses as last resort) parameter which effectively
+  rendered the DHCP_NOIPV4LL[x] option redundant - the use of -L was not
+  contingent upon the value of DHCP_NOIPV4LL[x].  The hard coded -L has been
+  removed from the dhcpcd command line, restoring the behaviour of 14.2 and the
+  usefulness of the DHCP_NOIPV4LL[x] option.
 
 
 Known issues
 ------------
-* When being invoked without the -4 or -6 option (that is, when both USE_DHCP[x] and USE_DHCP6[x] are set), dhcpcd will
-  only wait until one type of IP is obtained before backgrounding - it will not wait for both a v4 AND v6 to be
-  configured.  This means there is no way to know if the interface has been configured for both types of IP, as one type
-  will continue to be sought in the background; but may ultimately fail.  This is an issue with the way dhcpcd operates
-  and not an issue with rc.inet1.
-* Changes in interface configuration type from DHCP to fixed IP or stateless will cause an issue where the dhcpcd daemon
-  fails to be stopped during a restart or stop/start operation because rc.inet1 is unaware of how an interface was
-  previously configured - it can only stop the interface based upon its current configuration.  This is a by-product of
-  the way the rc.inet1 script is coded (there is no record kept of the previous configuration type of an interface) and
-  is present (but doesn't seem to be documented anywhere) on previous versions of Slackware.  This particular issue is
-  not specifically related to IPv6, but is documented here for completeness.
-* When being killed in if_down(), dhcpcd requires some command line options to match those which were used to invoke it
-  - not only does the interface name need to match, but also the use of -4/-6.  This can cause a problem during a
-  restart or stop/start of the interface if the configuration for DHCP has changed.  This manifests itself in the same
-  way as the issue detailed above and is no more serious.  In both cases, the end user must kill the dhcpcd daemon
-  manually.  This issue is caused by the new way dhcpcd is invoked when using/not using IPv6.
+* When being invoked without the -4 or -6 option (that is, when both USE_DHCP[x]
+  and USE_DHCP6[x] are set), dhcpcd will only wait until one type of IP is
+  obtained before backgrounding - it will not wait for both a v4 AND v6 to be
+  configured.  This means there is no way to know if the interface has been
+  configured for both types of IP, as one type will continue to be sought in the
+  background; but may ultimately fail.  This is an issue with the way dhcpcd
+  operates and not an issue with rc.inet1.
+
+* Changes in interface configuration type from DHCP to fixed IP or stateless
+  will cause an issue where the dhcpcd daemon fails to be stopped during a
+  restart or stop/start operation because rc.inet1 is unaware of how an
+  interface was previously configured - it can only stop the interface based
+  upon its current configuration.  This is a by-product of the way the rc.inet1
+  script is coded (there is no record kept of the previous configuration type of
+  an interface) and is present (but doesn't seem to be documented anywhere) on
+  previous versions of Slackware.  This particular issue is not specifically
+  related to IPv6, but is documented here for completeness.
+
+* When being killed in if_down(), dhcpcd requires some command line options to
+  match those which were used to invoke it - not only does the interface name
+  need to match, but also the use of -4/-6.  This can cause a problem during a
+  restart or stop/start of the interface if the configuration for DHCP has
+  changed.  This manifests itself in the same way as the issue detailed above
+  and is no more serious.  In both cases, the end user must kill the dhcpcd
+  daemon manually.  This issue is caused by the new way dhcpcd is invoked when
+  using/not using IPv6.
 
 
 Thanks