net: ipv6: add rpl sr tunnel

This patch adds functionality to configure routes for RPL source routing
functionality. There is no IPIP functionality yet implemented which can
be added later when the cases when to use IPv6 encapuslation comes more
clear.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 398 insertions, 0 deletions

diff --git a/net/ipv6/Kconfig b/net/ipv6/Kconfig
index ae1344e4cec5..2ccaee98fddb 100644
--- a/net/ipv6/Kconfig
+++ b/net/ipv6/Kconfig
@@ -303,4 +303,14 @@ config IPV6_SEG6_BPF
 	depends on IPV6_SEG6_LWTUNNEL
 	depends on IPV6 = y
 
+config IPV6_RPL_LWTUNNEL
+	bool "IPv6: RPL Source Routing Header support"
+	depends on IPV6
+	select LWTUNNEL
+	---help---
+	  Support for RFC6554 RPL Source Routing Header using the lightweight
+	  tunnels mechanism.
+
+	  If unsure, say N.
+
 endif # IPV6
diff --git a/net/ipv6/Makefile b/net/ipv6/Makefile
index 9d3e9bd2334f..cf7b47bdb9b3 100644
--- a/net/ipv6/Makefile
+++ b/net/ipv6/Makefile
@@ -26,6 +26,7 @@ ipv6-$(CONFIG_SYN_COOKIES) += syncookies.o
 ipv6-$(CONFIG_NETLABEL) += calipso.o
 ipv6-$(CONFIG_IPV6_SEG6_LWTUNNEL) += seg6_iptunnel.o seg6_local.o
 ipv6-$(CONFIG_IPV6_SEG6_HMAC) += seg6_hmac.o
+ipv6-$(CONFIG_IPV6_RPL_LWTUNNEL) += rpl_iptunnel.o
 
 ipv6-objs += $(ipv6-y)
 
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index d727c3b41495..345baa0a754f 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -59,6 +59,7 @@
 #endif
 #include <net/calipso.h>
 #include <net/seg6.h>
+#include <net/rpl.h>
 
 #include <linux/uaccess.h>
 #include <linux/mroute6.h>
@@ -1114,6 +1115,10 @@ static int __init inet6_init(void)
 	if (err)
 		goto seg6_fail;
 
+	err = rpl_init();
+	if (err)
+		goto rpl_fail;
+
 	err = igmp6_late_init();
 	if (err)
 		goto igmp6_late_err;
@@ -1136,6 +1141,8 @@ sysctl_fail:
 	igmp6_late_cleanup();
 #endif
 igmp6_late_err:
+	rpl_exit();
+rpl_fail:
 	seg6_exit();
 seg6_fail:
 	calipso_exit();
diff --git a/net/ipv6/rpl_iptunnel.c b/net/ipv6/rpl_iptunnel.c
new file mode 100644
index 000000000000..203037afe001
--- /dev/null
+++ b/net/ipv6/rpl_iptunnel.c
@@ -0,0 +1,380 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/**
+ * Authors:
+ * (C) 2020 Alexander Aring <alex.aring@gmail.com>
+ */
+
+#include <linux/rpl_iptunnel.h>
+
+#include <net/dst_cache.h>
+#include <net/ip6_route.h>
+#include <net/lwtunnel.h>
+#include <net/ipv6.h>
+#include <net/rpl.h>
+
+struct rpl_iptunnel_encap {
+	struct ipv6_rpl_sr_hdr srh[0];
+};
+
+struct rpl_lwt {
+	struct dst_cache cache;
+	struct rpl_iptunnel_encap tuninfo;
+};
+
+static inline struct rpl_lwt *rpl_lwt_lwtunnel(struct lwtunnel_state *lwt)
+{
+	return (struct rpl_lwt *)lwt->data;
+}
+
+static inline struct rpl_iptunnel_encap *
+rpl_encap_lwtunnel(struct lwtunnel_state *lwt)
+{
+	return &rpl_lwt_lwtunnel(lwt)->tuninfo;
+}
+
+static const struct nla_policy rpl_iptunnel_policy[RPL_IPTUNNEL_MAX + 1] = {
+	[RPL_IPTUNNEL_SRH]	= { .type = NLA_BINARY },
+};
+
+static bool rpl_validate_srh(struct net *net, struct ipv6_rpl_sr_hdr *srh,
+			     size_t seglen)
+{
+	int err;
+
+	if ((srh->hdrlen << 3) != seglen)
+		return false;
+
+	/* check at least one segment and seglen fit with segments_left */
+	if (!srh->segments_left ||
+	    (srh->segments_left * sizeof(struct in6_addr)) != seglen)
+		return false;
+
+	if (srh->cmpri || srh->cmpre)
+		return false;
+
+	err = ipv6_chk_rpl_srh_loop(net, srh->rpl_segaddr,
+				    srh->segments_left);
+	if (err)
+		return false;
+
+	if (ipv6_addr_type(&srh->rpl_segaddr[srh->segments_left - 1]) &
+	    IPV6_ADDR_MULTICAST)
+		return false;
+
+	return true;
+}
+
+static int rpl_build_state(struct net *net, struct nlattr *nla,
+			   unsigned int family, const void *cfg,
+			   struct lwtunnel_state **ts,
+			   struct netlink_ext_ack *extack)
+{
+	struct nlattr *tb[RPL_IPTUNNEL_MAX + 1];
+	struct lwtunnel_state *newts;
+	struct ipv6_rpl_sr_hdr *srh;
+	struct rpl_lwt *rlwt;
+	int err, srh_len;
+
+	if (family != AF_INET6)
+		return -EINVAL;
+
+	err = nla_parse_nested(tb, RPL_IPTUNNEL_MAX, nla,
+			       rpl_iptunnel_policy, extack);
+	if (err < 0)
+		return err;
+
+	if (!tb[RPL_IPTUNNEL_SRH])
+		return -EINVAL;
+
+	srh = nla_data(tb[RPL_IPTUNNEL_SRH]);
+	srh_len = nla_len(tb[RPL_IPTUNNEL_SRH]);
+
+	if (srh_len < sizeof(*srh))
+		return -EINVAL;
+
+	/* verify that SRH is consistent */
+	if (!rpl_validate_srh(net, srh, srh_len - sizeof(*srh)))
+		return -EINVAL;
+
+	newts = lwtunnel_state_alloc(srh_len + sizeof(*rlwt));
+	if (!newts)
+		return -ENOMEM;
+
+	rlwt = rpl_lwt_lwtunnel(newts);
+
+	err = dst_cache_init(&rlwt->cache, GFP_ATOMIC);
+	if (err) {
+		kfree(newts);
+		return err;
+	}
+
+	memcpy(&rlwt->tuninfo.srh, srh, srh_len);
+
+	newts->type = LWTUNNEL_ENCAP_RPL;
+	newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
+	newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
+
+	*ts = newts;
+
+	return 0;
+}
+
+static void rpl_destroy_state(struct lwtunnel_state *lwt)
+{
+	dst_cache_destroy(&rpl_lwt_lwtunnel(lwt)->cache);
+}
+
+static int rpl_do_srh_inline(struct sk_buff *skb, const struct rpl_lwt *rlwt,
+			     const struct ipv6_rpl_sr_hdr *srh)
+{
+	struct ipv6_rpl_sr_hdr *isrh, *csrh;
+	const struct ipv6hdr *oldhdr;
+	struct ipv6hdr *hdr;
+	unsigned char *buf;
+	size_t hdrlen;
+	int err;
+
+	oldhdr = ipv6_hdr(skb);
+
+	buf = kzalloc(ipv6_rpl_srh_alloc_size(srh->segments_left - 1) * 2,
+		      GFP_ATOMIC);
+	if (!buf)
+		return -ENOMEM;
+
+	isrh = (struct ipv6_rpl_sr_hdr *)buf;
+	csrh = (struct ipv6_rpl_sr_hdr *)(buf + ((srh->hdrlen + 1) << 3));
+
+	memcpy(isrh, srh, sizeof(*isrh));
+	memcpy(isrh->rpl_segaddr, &srh->rpl_segaddr[1],
+	       (srh->segments_left - 1) * 16);
+	isrh->rpl_segaddr[srh->segments_left - 1] = oldhdr->daddr;
+
+	ipv6_rpl_srh_compress(csrh, isrh, &srh->rpl_segaddr[0],
+			      isrh->segments_left - 1);
+
+	hdrlen = ((csrh->hdrlen + 1) << 3);
+
+	err = skb_cow_head(skb, hdrlen + skb->mac_len);
+	if (unlikely(err))
+		return err;
+
+	skb_pull(skb, sizeof(struct ipv6hdr));
+	skb_postpull_rcsum(skb, skb_network_header(skb),
+			   sizeof(struct ipv6hdr));
+
+	skb_push(skb, sizeof(struct ipv6hdr) + hdrlen);
+	skb_reset_network_header(skb);
+	skb_mac_header_rebuild(skb);
+
+	hdr = ipv6_hdr(skb);
+	memmove(hdr, oldhdr, sizeof(*hdr));
+	isrh = (void *)hdr + sizeof(*hdr);
+	memcpy(isrh, csrh, hdrlen);
+
+	isrh->nexthdr = hdr->nexthdr;
+	hdr->nexthdr = NEXTHDR_ROUTING;
+	hdr->daddr = srh->rpl_segaddr[0];
+
+	ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
+	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
+
+	skb_postpush_rcsum(skb, hdr, sizeof(struct ipv6hdr) + hdrlen);
+
+	kfree(buf);
+
+	return 0;
+}
+
+static int rpl_do_srh(struct sk_buff *skb, const struct rpl_lwt *rlwt)
+{
+	struct dst_entry *dst = skb_dst(skb);
+	struct rpl_iptunnel_encap *tinfo;
+	int err = 0;
+
+	if (skb->protocol != htons(ETH_P_IPV6))
+		return -EINVAL;
+
+	tinfo = rpl_encap_lwtunnel(dst->lwtstate);
+
+	err = rpl_do_srh_inline(skb, rlwt, tinfo->srh);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static int rpl_output(struct net *net, struct sock *sk, struct sk_buff *skb)
+{
+	struct dst_entry *orig_dst = skb_dst(skb);
+	struct dst_entry *dst = NULL;
+	struct rpl_lwt *rlwt;
+	int err = -EINVAL;
+
+	rlwt = rpl_lwt_lwtunnel(orig_dst->lwtstate);
+
+	err = rpl_do_srh(skb, rlwt);
+	if (unlikely(err))
+		goto drop;
+
+	preempt_disable();
+	dst = dst_cache_get(&rlwt->cache);
+	preempt_enable();
+
+	if (unlikely(!dst)) {
+		struct ipv6hdr *hdr = ipv6_hdr(skb);
+		struct flowi6 fl6;
+
+		memset(&fl6, 0, sizeof(fl6));
+		fl6.daddr = hdr->daddr;
+		fl6.saddr = hdr->saddr;
+		fl6.flowlabel = ip6_flowinfo(hdr);
+		fl6.flowi6_mark = skb->mark;
+		fl6.flowi6_proto = hdr->nexthdr;
+
+		dst = ip6_route_output(net, NULL, &fl6);
+		if (dst->error) {
+			err = dst->error;
+			dst_release(dst);
+			goto drop;
+		}
+
+		preempt_disable();
+		dst_cache_set_ip6(&rlwt->cache, dst, &fl6.saddr);
+		preempt_enable();
+	}
+
+	skb_dst_drop(skb);
+	skb_dst_set(skb, dst);
+
+	err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
+	if (unlikely(err))
+		goto drop;
+
+	return dst_output(net, sk, skb);
+
+drop:
+	kfree_skb(skb);
+	return err;
+}
+
+static int rpl_input(struct sk_buff *skb)
+{
+	struct dst_entry *orig_dst = skb_dst(skb);
+	struct dst_entry *dst = NULL;
+	struct rpl_lwt *rlwt;
+	int err;
+
+	rlwt = rpl_lwt_lwtunnel(orig_dst->lwtstate);
+
+	err = rpl_do_srh(skb, rlwt);
+	if (unlikely(err)) {
+		kfree_skb(skb);
+		return err;
+	}
+
+	preempt_disable();
+	dst = dst_cache_get(&rlwt->cache);
+	preempt_enable();
+
+	skb_dst_drop(skb);
+
+	if (!dst) {
+		ip6_route_input(skb);
+		dst = skb_dst(skb);
+		if (!dst->error) {
+			preempt_disable();
+			dst_cache_set_ip6(&rlwt->cache, dst,
+					  &ipv6_hdr(skb)->saddr);
+			preempt_enable();
+		}
+	} else {
+		skb_dst_set(skb, dst);
+	}
+
+	err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
+	if (unlikely(err))
+		return err;
+
+	return dst_input(skb);
+}
+
+static int nla_put_rpl_srh(struct sk_buff *skb, int attrtype,
+			   struct rpl_iptunnel_encap *tuninfo)
+{
+	struct rpl_iptunnel_encap *data;
+	struct nlattr *nla;
+	int len;
+
+	len = RPL_IPTUNNEL_SRH_SIZE(tuninfo->srh);
+
+	nla = nla_reserve(skb, attrtype, len);
+	if (!nla)
+		return -EMSGSIZE;
+
+	data = nla_data(nla);
+	memcpy(data, tuninfo->srh, len);
+
+	return 0;
+}
+
+static int rpl_fill_encap_info(struct sk_buff *skb,
+			       struct lwtunnel_state *lwtstate)
+{
+	struct rpl_iptunnel_encap *tuninfo = rpl_encap_lwtunnel(lwtstate);
+
+	if (nla_put_rpl_srh(skb, RPL_IPTUNNEL_SRH, tuninfo))
+		return -EMSGSIZE;
+
+	return 0;
+}
+
+static int rpl_encap_nlsize(struct lwtunnel_state *lwtstate)
+{
+	struct rpl_iptunnel_encap *tuninfo = rpl_encap_lwtunnel(lwtstate);
+
+	return nla_total_size(RPL_IPTUNNEL_SRH_SIZE(tuninfo->srh));
+}
+
+static int rpl_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
+{
+	struct rpl_iptunnel_encap *a_hdr = rpl_encap_lwtunnel(a);
+	struct rpl_iptunnel_encap *b_hdr = rpl_encap_lwtunnel(b);
+	int len = RPL_IPTUNNEL_SRH_SIZE(a_hdr->srh);
+
+	if (len != RPL_IPTUNNEL_SRH_SIZE(b_hdr->srh))
+		return 1;
+
+	return memcmp(a_hdr, b_hdr, len);
+}
+
+static const struct lwtunnel_encap_ops rpl_ops = {
+	.build_state	= rpl_build_state,
+	.destroy_state	= rpl_destroy_state,
+	.output		= rpl_output,
+	.input		= rpl_input,
+	.fill_encap	= rpl_fill_encap_info,
+	.get_encap_size	= rpl_encap_nlsize,
+	.cmp_encap	= rpl_encap_cmp,
+	.owner		= THIS_MODULE,
+};
+
+int __init rpl_init(void)
+{
+	int err;
+
+	err = lwtunnel_encap_add_ops(&rpl_ops, LWTUNNEL_ENCAP_RPL);
+	if (err)
+		goto out;
+
+	pr_info("RPL Segment Routing with IPv6\n");
+
+	return 0;
+
+out:
+	return err;
+}
+
+void rpl_exit(void)
+{
+	lwtunnel_encap_del_ops(&rpl_ops, LWTUNNEL_ENCAP_RPL);
+}