diff options
| -rw-r--r-- | README.IPv6 | 169 | ||||
| -rw-r--r-- | rc.inet1 | 23 |
2 files changed, 183 insertions, 9 deletions
diff --git a/README.IPv6 b/README.IPv6 new file mode 100644 index 0000000..71a1537 --- /dev/null +++ b/README.IPv6 @@ -0,0 +1,169 @@ +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). +* DHCPv6 support for server controlled address configuration. +* Fixed IP configuration of IPv6 interfaces and alias addresses. + + +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: + 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. + + +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. + +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: + 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. + + +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). + + +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. + + +Thanks +------ +* Robby Workman, for the original 'ip' version of rc.inet1 and advice. +* David Spencer, for advice, debating, and testing the SLAAC implementation. + +-- +Darren 'Tadgy' Austin. +<darren (at) afterdark.org.uk> @@ -187,10 +187,11 @@ if_up() { if [ -e /proc/sys/net/ipv6 ]; then # ipv6 networking is available # Disable v6 IP auto configuration before trying to bring up the interface: echo "0" >/proc/sys/net/ipv6/conf/$1/autoconf - # Disable Router Advertisment for this interface until it's needed: if [ "${USE_RA[$i]}" = "yes" ]; then + # Unconditionally accept router advertisements on this interface: echo "1" >/proc/sys/net/ipv6/conf/$1/accept_ra else + # Disable router advertisments on this interface until SLAAC is enabled: echo "0" >/proc/sys/net/ipv6/conf/$1/accept_ra fi fi @@ -214,13 +215,16 @@ if_up() { [ "${DHCP_KEEPNTP[$i]}" = "yes" ] && DHCP_OPTIONS+=("-C" "ntp.conf") [ "${DHCP_KEEPGW[$i]}" = "yes" ] && DHCP_OPTIONS+=("-G") [ "${DHCP_DEBUG[$i]}" = "yes" ] && DHCP_OPTIONS+=("-d") + # The -L option used to be hard coded into the dhcpcd command line in -current. Previous versions did not have + # this hard coded. The code here keeps the 14.2 behaviour, but can be altered to make the use of -L default as + # in -current. To change the behaviour, alter the test to be: [ "${DHCP_NOIPV4LL[$i]}" != "no" ] [ "${DHCP_NOIPV4LL[$i]}" = "yes" ] && DHCP_OPTIONS+=("-L") [ -n "${DHCP_IPADDR[$i]}" ] && DHCP_OPTIONS+=("-r" "${DHCP_IPADDR[$i]}") - echo "Polling for DHCP server on interface ${1}:" + echo "${1}: polling for DHCP server" # 15 seconds should be a reasonable default DHCP timeout. 30 was too much. echo "/etc/rc.d/rc.inet1: /sbin/dhcpcd -t ${DHCP_TIMEOUT[$i]:-15} ${DHCP_OPTIONS[@]} ${1}" | $LOGGER if /sbin/dhcpcd -t "${DHCP_TIMEOUT[$i]:-15}" "${DHCP_OPTIONS[@]}" ${1}; then - # Enable accepting of RA packets if explicitly told to. + # Enable accepting of RA packets if explicitly told to: if [ -e /proc/sys/net/ipv6 ] && [ "${USE_RA[$i]}" = "yes" ]; then echo "1" >/proc/sys/net/ipv6/conf/$1/accept_ra fi @@ -232,24 +236,25 @@ if_up() { fi fi if [ -e /proc/sys/net/ipv6 ] && [ "${USE_DHCP6[$i]}" != "yes" ] && [ "${USE_SLAAC[$i]}" = "yes" ]; then # configure via SLAAC - echo "/etc/rc.d/rc.inet1: using Router Advertisement stateless auto configuration for ${1}" | $LOGGER - # Enable accepting of RA packets, unless explicitly configured not to. + # Enable accepting of RA packets, unless explicitly configured not to: if [ "${USE_RA[$i]}" = "no" ]; then echo "0" >/proc/sys/net/ipv6/conf/$1/accept_ra else + echo "/etc/rc.d/rc.inet1: enabling RA for ${1}" | $LOGGER echo "1" >/proc/sys/net/ipv6/conf/$1/accept_ra fi # Enable auto configuration of interfaces: + echo "/etc/rc.d/rc.inet1: enabling SLAAC for ${1}" | $LOGGER echo "1" >/proc/sys/net/ipv6/conf/$1/autoconf # Bring the interface up: /sbin/ip link set dev ${1} up - echo "Waiting for router announcement on ${1}..." + echo "${1}: waiting for router announcement" for ((j = ${SLAAC_TIMEOUT[$i]:=15} * 2; j--;)); do # by default, wait a max of 15 seconds for the interface to configure /sbin/ip -6 address show dynamic dev ${1} 2>/dev/null | grep -Ewq 'inet6' && { IF_UP=1; break; } sleep 0.5 done if (($IF_UP != 1)); then - echo "Timed out!" + echo "${1}: timed out" echo "/etc/rc.d/rc.inet1: failed to auto configure ${1} after ${SLAAC_TIMEOUT[$i]} seconds" | $LOGGER /sbin/ip address flush dev ${1} /sbin/ip link set dev ${1} down @@ -265,7 +270,7 @@ if_up() { /sbin/ip link set dev ${1} up; then IF_UP=1 else - echo "/etc/rc.d/rc.inet1: failed to a set IP ${IPADDR[$i]} for ${1}" | $LOGGER + echo "/etc/rc.d/rc.inet1: failed to set IP ${IPADDR[$i]} for ${1}" | $LOGGER /sbin/ip address flush dev ${1} /sbin/ip link set dev ${1} down fi @@ -290,7 +295,7 @@ if_up() { fi IF_UP=1 else - echo "/etc/rc.d/rc.inet1: failed to a set IP ${IP6ADDR[$i]} for ${1}" | $LOGGER + echo "/etc/rc.d/rc.inet1: failed to set IP ${IP6ADDR[$i]} for ${1}" | $LOGGER if (($IF_UP != 1)); then # a v4 address was configured, don't flush it /sbin/ip address flush dev ${1} /sbin/ip link set dev ${1} down |