net: Identifier Locator Addressing module

Adding new module name ila. This implements ILA translation. Light
weight tunnel redirection is used to perform the translation in
the data path. This is configured by the "ip -6 route" command
using the "encap ila <locator>" option, where <locator> is the
value to set in destination locator of the packet. e.g.

ip -6 route add 3333:0:0:1:5555:0:1:0/128 \
      encap ila 2001:0:0:1 via 2401:db00:20:911a:face:0:25:0

Sets a route where 3333:0:0:1 will be overwritten by
2001:0:0:1 on output.

Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 236 insertions, 0 deletions

diff --git a/net/ipv6/Kconfig b/net/ipv6/Kconfig
index 643f61339e7b..983bb999738c 100644
--- a/net/ipv6/Kconfig
+++ b/net/ipv6/Kconfig
@@ -92,6 +92,25 @@ config IPV6_MIP6
 
 	  If unsure, say N.
 
+config IPV6_ILA
+	tristate "IPv6: Identifier Locator Addressing (ILA)"
+	select LWTUNNEL
+	---help---
+	  Support for IPv6 Identifier Locator Addressing (ILA).
+
+	  ILA is a mechanism to do network virtualization without
+	  encapsulation. The basic concept of ILA is that we split an
+	  IPv6 address into a 64 bit locator and 64 bit identifier. The
+	  identifier is the identity of an entity in communication
+	  ("who") and the locator expresses the location of the
+	  entity ("where").
+
+	  ILA can be configured using the "encap ila" option with
+	  "ip -6 route" command. ILA is described in
+	  https://tools.ietf.org/html/draft-herbert-nvo3-ila-00.
+
+	  If unsure, say N.
+
 config INET6_XFRM_TUNNEL
 	tristate
 	select INET6_TUNNEL
diff --git a/net/ipv6/Makefile b/net/ipv6/Makefile
index 0f3f1999719a..2c900c7b7eb1 100644
--- a/net/ipv6/Makefile
+++ b/net/ipv6/Makefile
@@ -34,6 +34,7 @@ obj-$(CONFIG_INET6_XFRM_MODE_TUNNEL) += xfrm6_mode_tunnel.o
 obj-$(CONFIG_INET6_XFRM_MODE_ROUTEOPTIMIZATION) += xfrm6_mode_ro.o
 obj-$(CONFIG_INET6_XFRM_MODE_BEET) += xfrm6_mode_beet.o
 obj-$(CONFIG_IPV6_MIP6) += mip6.o
+obj-$(CONFIG_IPV6_ILA) += ila.o
 obj-$(CONFIG_NETFILTER)	+= netfilter/
 
 obj-$(CONFIG_IPV6_VTI) += ip6_vti.o
diff --git a/net/ipv6/ila.c b/net/ipv6/ila.c
new file mode 100644
index 000000000000..2540ab4b76d1
--- /dev/null
+++ b/net/ipv6/ila.c
@@ -0,0 +1,216 @@
+#include <linux/errno.h>
+#include <linux/ip.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/socket.h>
+#include <linux/types.h>
+#include <net/checksum.h>
+#include <net/ip.h>
+#include <net/ip6_fib.h>
+#include <net/lwtunnel.h>
+#include <net/protocol.h>
+#include <uapi/linux/ila.h>
+
+struct ila_params {
+	__be64 locator;
+};
+
+static inline struct ila_params *ila_params_lwtunnel(
+	struct lwtunnel_state *lwstate)
+{
+	return (struct ila_params *)lwstate->data;
+}
+
+static inline __wsum compute_csum_diff8(const __be32 *from, const __be32 *to)
+{
+	__be32 diff[] = {
+		~from[0], ~from[1], to[0], to[1],
+	};
+
+	return csum_partial(diff, sizeof(diff), 0);
+}
+
+static inline __wsum get_csum_diff(struct ipv6hdr *ip6h, struct ila_params *p)
+{
+		return compute_csum_diff8((__be32 *)&ip6h->daddr,
+					  (__be32 *)&p->locator);
+}
+
+static void update_ipv6_locator(struct sk_buff *skb, struct ila_params *p)
+{
+	__wsum diff;
+	struct ipv6hdr *ip6h = ipv6_hdr(skb);
+	size_t nhoff = sizeof(struct ipv6hdr);
+
+	/* First update checksum */
+	switch (ip6h->nexthdr) {
+	case NEXTHDR_TCP:
+		if (likely(pskb_may_pull(skb, nhoff + sizeof(struct tcphdr)))) {
+			struct tcphdr *th = (struct tcphdr *)
+					(skb_network_header(skb) + nhoff);
+
+			diff = get_csum_diff(ip6h, p);
+			inet_proto_csum_replace_by_diff(&th->check, skb,
+							diff, true);
+		}
+		break;
+	case NEXTHDR_UDP:
+		if (likely(pskb_may_pull(skb, nhoff + sizeof(struct udphdr)))) {
+			struct udphdr *uh = (struct udphdr *)
+					(skb_network_header(skb) + nhoff);
+
+			if (uh->check || skb->ip_summed == CHECKSUM_PARTIAL) {
+				diff = get_csum_diff(ip6h, p);
+				inet_proto_csum_replace_by_diff(&uh->check, skb,
+								diff, true);
+				if (!uh->check)
+					uh->check = CSUM_MANGLED_0;
+			}
+		}
+		break;
+	case NEXTHDR_ICMP:
+		if (likely(pskb_may_pull(skb,
+					 nhoff + sizeof(struct icmp6hdr)))) {
+			struct icmp6hdr *ih = (struct icmp6hdr *)
+					(skb_network_header(skb) + nhoff);
+
+			diff = get_csum_diff(ip6h, p);
+			inet_proto_csum_replace_by_diff(&ih->icmp6_cksum, skb,
+							diff, true);
+		}
+		break;
+	}
+
+	/* Now change destination address */
+	*(__be64 *)&ip6h->daddr = p->locator;
+}
+
+static int ila_output(struct sock *sk, struct sk_buff *skb)
+{
+	struct dst_entry *dst = skb_dst(skb);
+	struct rt6_info *rt6 = NULL;
+
+	if (skb->protocol != htons(ETH_P_IPV6))
+		goto drop;
+
+	rt6 = (struct rt6_info *)dst;
+
+	update_ipv6_locator(skb, ila_params_lwtunnel(rt6->rt6i_lwtstate));
+
+	return rt6->rt6i_lwtstate->orig_output(sk, skb);
+
+drop:
+	kfree_skb(skb);
+	return -EINVAL;
+}
+
+static int ila_input(struct sk_buff *skb)
+{
+	struct dst_entry *dst = skb_dst(skb);
+	struct rt6_info *rt6 = NULL;
+
+	if (skb->protocol != htons(ETH_P_IPV6))
+		goto drop;
+
+	rt6 = (struct rt6_info *)dst;
+
+	update_ipv6_locator(skb, ila_params_lwtunnel(rt6->rt6i_lwtstate));
+
+	return rt6->rt6i_lwtstate->orig_input(skb);
+
+drop:
+	kfree_skb(skb);
+	return -EINVAL;
+}
+
+static struct nla_policy ila_nl_policy[ILA_ATTR_MAX + 1] = {
+	[ILA_ATTR_LOCATOR] = { .type = NLA_U64, },
+};
+
+static int ila_build_state(struct net_device *dev, struct nlattr *nla,
+			   struct lwtunnel_state **ts)
+{
+	struct ila_params *p;
+	struct nlattr *tb[ILA_ATTR_MAX + 1];
+	size_t encap_len = sizeof(*p);
+	struct lwtunnel_state *newts;
+	int ret;
+
+	ret = nla_parse_nested(tb, ILA_ATTR_MAX, nla,
+			       ila_nl_policy);
+	if (ret < 0)
+		return ret;
+
+	if (!tb[ILA_ATTR_LOCATOR])
+		return -EINVAL;
+
+	newts = lwtunnel_state_alloc(encap_len);
+	if (!newts)
+		return -ENOMEM;
+
+	newts->len = encap_len;
+	p = ila_params_lwtunnel(newts);
+
+	p->locator = (__force __be64)nla_get_u64(tb[ILA_ATTR_LOCATOR]);
+
+	newts->type = LWTUNNEL_ENCAP_ILA;
+	newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT |
+			LWTUNNEL_STATE_INPUT_REDIRECT;
+
+	*ts = newts;
+
+	return 0;
+}
+
+static int ila_fill_encap_info(struct sk_buff *skb,
+			       struct lwtunnel_state *lwtstate)
+{
+	struct ila_params *p = ila_params_lwtunnel(lwtstate);
+
+	if (nla_put_u64(skb, ILA_ATTR_LOCATOR, (__force u64)p->locator))
+		goto nla_put_failure;
+
+	return 0;
+
+nla_put_failure:
+	return -EMSGSIZE;
+}
+
+static int ila_encap_nlsize(struct lwtunnel_state *lwtstate)
+{
+	/* No encapsulation overhead */
+	return 0;
+}
+
+static int ila_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
+{
+	struct ila_params *a_p = ila_params_lwtunnel(a);
+	struct ila_params *b_p = ila_params_lwtunnel(b);
+
+	return (a_p->locator != b_p->locator);
+}
+
+static const struct lwtunnel_encap_ops ila_encap_ops = {
+	.build_state = ila_build_state,
+	.output = ila_output,
+	.input = ila_input,
+	.fill_encap = ila_fill_encap_info,
+	.get_encap_size = ila_encap_nlsize,
+	.cmp_encap = ila_encap_cmp,
+};
+
+static int __init ila_init(void)
+{
+	return lwtunnel_encap_add_ops(&ila_encap_ops, LWTUNNEL_ENCAP_ILA);
+}
+
+static void __exit ila_fini(void)
+{
+	lwtunnel_encap_del_ops(&ila_encap_ops, LWTUNNEL_ENCAP_ILA);
+}
+
+module_init(ila_init);
+module_exit(ila_fini);
+MODULE_AUTHOR("Tom Herbert <tom@herbertland.com>");
+MODULE_LICENSE("GPL");