ipv6: generation of stable privacy addresses for link-local and autoconf

This patch implements the stable privacy address generation for link-local and autoconf addresses as specified in RFC7217. RID = F(Prefix, Net_Iface, Network_ID, DAD_Counter, secret_key) is the RID (random identifier). As the hash function F we chose one round of sha1. Prefix will be either the link-local prefix or the router advertised one. As Net_Iface we use the MAC address of the device. DAD_Counter and secret_key are implemented as specified. We don't use Network_ID, as it couples the code too closely to other subsystems. It is specified as optional in the RFC. As Net_Iface we only use the MAC address: we simply have no stable identifier in the kernel we could possibly use: because this code might run very early, we cannot depend on names, as they might be changed by user space early on during the boot process. A new address generation mode is introduced, IN6_ADDR_GEN_MODE_STABLE_PRIVACY. With iproute2 one can switch back to none or eui64 address configuration mode although the stable_secret is already set. We refuse writes to ipv6/conf/all/stable_secret but only allow ipv6/conf/default/stable_secret and the interface specific file to be written to. The default stable_secret is used as the parameter for the namespace, the interface specific can overwrite the secret, e.g. when switching a network configuration from one system to another while inheriting the secret.

HFHannes Frederic Sowa committed 11 years ago