net: ipv6: add tokenized interface identifier support

This patch adds support for IPv6 tokenized IIDs, that allow
for administrators to assign well-known host-part addresses
to nodes whilst still obtaining global network prefix from
Router Advertisements. It is currently in draft status.

The primary target for such support is server platforms
where addresses are usually manually configured, rather
than using DHCPv6 or SLAAC. By using tokenised identifiers,
hosts can still determine their network prefix by use of
SLAAC, but more readily be automatically renumbered should
their network prefix change. [...]

The disadvantage with static addresses is that they are
likely to require manual editing should the network prefix
in use change. If instead there were a method to only
manually configure the static identifier part of the IPv6
address, then the address could be automatically updated
when a new prefix was introduced, as described in [RFC4192]
for example. In such cases a DNS server might be
configured with such a tokenised interface identifier of
::53, and SLAAC would use the token in constructing the
interface address, using the advertised prefix. [...]

http://tools.ietf.org/html/draft-chown-6man-tokenised-ipv6-identifiers-02

The implementation is partially based on top of Mark K.
Thompson's proof of concept. However, it uses the Netlink
interface for configuration resp. data retrival, so that
it can be easily extended in future. Successfully tested
by myself.

Cc: Hannes Frederic Sowa <[e-mail]>
Cc: YOSHIFUJI Hideaki <[e-mail]>
Cc: Thomas Graf <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/if_inet6.h

···
 	struct list_head	tempaddr_list;
 #endif
 
+	struct in6_addr		token;
+
 	struct neigh_parms	*nd_parms;
 	struct inet6_dev	*next;
 	struct ipv6_devconf	cnf;

include/uapi/linux/if_link.h

···
 	IFLA_INET6_MCAST,	/* MC things. What of them?	*/
 	IFLA_INET6_CACHEINFO,	/* time values and max reasm size */
 	IFLA_INET6_ICMP6STATS,	/* statistics (icmpv6)		*/
+	IFLA_INET6_TOKEN,	/* device token			*/
 	__IFLA_INET6_MAX
 };
 

net/ipv6/addrconf.c

···
 		ipv6_regen_rndid((unsigned long) ndev);
 	}
 #endif
+	memset(ndev->token.s6_addr, 0, sizeof(ndev->token.s6_addr));
 
 	if (netif_running(dev) && addrconf_qdisc_ok(dev))
 		ndev->if_flags |= IF_READY;
···
 
 		if (pinfo->prefix_len == 64) {
 			memcpy(&addr, &pinfo->prefix, 8);
-			if (ipv6_generate_eui64(addr.s6_addr + 8, dev) &&
-			    ipv6_inherit_eui64(addr.s6_addr + 8, in6_dev)) {
+
+			if (!ipv6_addr_any(&in6_dev->token)) {
+				read_lock_bh(&in6_dev->lock);
+				memcpy(addr.s6_addr + 8,
+				       in6_dev->token.s6_addr + 8, 8);
+				read_unlock_bh(&in6_dev->lock);
+			} else if (ipv6_generate_eui64(addr.s6_addr + 8, dev) &&
+				   ipv6_inherit_eui64(addr.s6_addr + 8, in6_dev)) {
 				in6_dev_put(in6_dev);
 				return;
 			}
···
 	     + nla_total_size(sizeof(struct ifla_cacheinfo))
 	     + nla_total_size(DEVCONF_MAX * 4) /* IFLA_INET6_CONF */
 	     + nla_total_size(IPSTATS_MIB_MAX * 8) /* IFLA_INET6_STATS */
-	     + nla_total_size(ICMP6_MIB_MAX * 8); /* IFLA_INET6_ICMP6STATS */
+	     + nla_total_size(ICMP6_MIB_MAX * 8) /* IFLA_INET6_ICMP6STATS */
+	     + nla_total_size(sizeof(struct in6_addr)); /* IFLA_INET6_TOKEN */
 }
 
 static inline size_t inet6_if_nlmsg_size(void)
···
 		goto nla_put_failure;
 	snmp6_fill_stats(nla_data(nla), idev, IFLA_INET6_ICMP6STATS, nla_len(nla));
 
+	nla = nla_reserve(skb, IFLA_INET6_TOKEN, sizeof(struct in6_addr));
+	if (nla == NULL)
+		goto nla_put_failure;
+	read_lock_bh(&idev->lock);
+	memcpy(nla_data(nla), idev->token.s6_addr, nla_len(nla));
+	read_unlock_bh(&idev->lock);
+
 	return 0;
 
 nla_put_failure:
···
 		return -EMSGSIZE;
 
 	return 0;
+}
+
+static int inet6_set_iftoken(struct inet6_dev *idev, struct in6_addr *token)
+{
+	struct in6_addr ll_addr;
+	struct inet6_ifaddr *ifp;
+	struct net_device *dev = idev->dev;
+
+	if (token == NULL)
+		return -EINVAL;
+	if (ipv6_addr_any(token))
+		return -EINVAL;
+	if (dev->flags & (IFF_LOOPBACK | IFF_NOARP))
+		return -EINVAL;
+	if (idev->dead || !(idev->if_flags & IF_READY))
+		return -EINVAL;
+	if (!ipv6_accept_ra(idev))
+		return -EINVAL;
+	if (idev->cnf.rtr_solicits <= 0)
+		return -EINVAL;
+
+	write_lock_bh(&idev->lock);
+
+	BUILD_BUG_ON(sizeof(token->s6_addr) != 16);
+	memcpy(idev->token.s6_addr + 8, token->s6_addr + 8, 8);
+
+	write_unlock_bh(&idev->lock);
+
+	ipv6_get_lladdr(dev, &ll_addr, IFA_F_TENTATIVE | IFA_F_OPTIMISTIC);
+	ndisc_send_rs(dev, &ll_addr, &in6addr_linklocal_allrouters);
+
+	write_lock_bh(&idev->lock);
+	idev->if_flags |= IF_RS_SENT;
+
+	/* Well, that's kinda nasty ... */
+	list_for_each_entry(ifp, &idev->addr_list, if_list) {
+		spin_lock(&ifp->lock);
+		if (ipv6_addr_src_scope(&ifp->addr) ==
+		    IPV6_ADDR_SCOPE_GLOBAL) {
+			ifp->valid_lft = 0;
+			ifp->prefered_lft = 0;
+		}
+		spin_unlock(&ifp->lock);
+	}
+
+	write_unlock_bh(&idev->lock);
+	return 0;
+}
+
+static int inet6_set_link_af(struct net_device *dev, const struct nlattr *nla)
+{
+	int err = -EINVAL;
+	struct inet6_dev *idev = __in6_dev_get(dev);
+	struct nlattr *tb[IFLA_INET6_MAX + 1];
+
+	if (!idev)
+		return -EAFNOSUPPORT;
+
+	if (nla_parse_nested(tb, IFLA_INET6_MAX, nla, NULL) < 0)
+		BUG();
+
+	if (tb[IFLA_INET6_TOKEN])
+		err = inet6_set_iftoken(idev, nla_data(tb[IFLA_INET6_TOKEN]));
+
+	return err;
 }
 
 static int inet6_fill_ifinfo(struct sk_buff *skb, struct inet6_dev *idev,
···
 	.family		  = AF_INET6,
 	.fill_link_af	  = inet6_fill_link_af,
 	.get_link_af_size = inet6_get_link_af_size,
+	.set_link_af	  = inet6_set_link_af,
 };
 
 /*