mpls: ip tunnel support

This implementation uses lwtunnel infrastructure to register
hooks for mpls tunnel encaps.

It picks cues from iptunnel_encaps infrastructure and previous
mpls iptunnel RFC patches from Eric W. Biederman and Robert Shearman

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 241 insertions, 1 deletions

diff --git a/net/mpls/Kconfig b/net/mpls/Kconfig
index 17bde799c854..5c467ef97311 100644
--- a/net/mpls/Kconfig
+++ b/net/mpls/Kconfig
@@ -24,7 +24,13 @@ config NET_MPLS_GSO
 
 config MPLS_ROUTING
         tristate "MPLS: routing support"
-        help
+        ---help---
          Add support for forwarding of mpls packets.
 
+config MPLS_IPTUNNEL
+        tristate "MPLS: IP over MPLS tunnel support"
+        depends on LWTUNNEL && MPLS_ROUTING
+        ---help---
+         mpls ip tunnel support.
+
 endif # MPLS
diff --git a/net/mpls/Makefile b/net/mpls/Makefile
index 65bbe68c72e6..9ca923625016 100644
--- a/net/mpls/Makefile
+++ b/net/mpls/Makefile
@@ -3,5 +3,6 @@
 #
 obj-$(CONFIG_NET_MPLS_GSO) += mpls_gso.o
 obj-$(CONFIG_MPLS_ROUTING) += mpls_router.o
+obj-$(CONFIG_MPLS_IPTUNNEL) += mpls_iptunnel.o
 
 mpls_router-y := af_mpls.o
diff --git a/net/mpls/mpls_iptunnel.c b/net/mpls/mpls_iptunnel.c
new file mode 100644
index 000000000000..eea096f21ba5
--- /dev/null
+++ b/net/mpls/mpls_iptunnel.c
@@ -0,0 +1,233 @@
+/*
+ * mpls tunnels An implementation mpls tunnels using the light weight tunnel
+ *              infrastructure
+ *
+ * Authors:     Roopa Prabhu, <roopa@cumulusnetworks.com>
+ *
+ *              This program is free software; you can redistribute it and/or
+ *              modify it under the terms of the GNU General Public License
+ *              as published by the Free Software Foundation; either version
+ *              2 of the License, or (at your option) any later version.
+ *
+ */
+#include <linux/types.h>
+#include <linux/skbuff.h>
+#include <linux/net.h>
+#include <linux/module.h>
+#include <linux/mpls.h>
+#include <linux/vmalloc.h>
+#include <net/ip.h>
+#include <net/dst.h>
+#include <net/lwtunnel.h>
+#include <net/netevent.h>
+#include <net/netns/generic.h>
+#include <net/ip6_fib.h>
+#include <net/route.h>
+#include <net/mpls_iptunnel.h>
+#include <linux/mpls_iptunnel.h>
+#include "internal.h"
+
+static const struct nla_policy mpls_iptunnel_policy[MPLS_IPTUNNEL_MAX + 1] = {
+        [MPLS_IPTUNNEL_DST]     = { .type = NLA_U32 },
+};
+
+static unsigned int mpls_encap_size(struct mpls_iptunnel_encap *en)
+{
+        /* The size of the layer 2.5 labels to be added for this route */
+        return en->labels * sizeof(struct mpls_shim_hdr);
+}
+
+int mpls_output(struct sock *sk, struct sk_buff *skb)
+{
+        struct mpls_iptunnel_encap *tun_encap_info;
+        struct mpls_shim_hdr *hdr;
+        struct net_device *out_dev;
+        unsigned int hh_len;
+        unsigned int new_header_size;
+        unsigned int mtu;
+        struct dst_entry *dst = skb_dst(skb);
+        struct rtable *rt = NULL;
+        struct rt6_info *rt6 = NULL;
+        struct lwtunnel_state *lwtstate = NULL;
+        int err = 0;
+        bool bos;
+        int i;
+        unsigned int ttl;
+
+        /* Obtain the ttl */
+        if (skb->protocol == htons(ETH_P_IP)) {
+                ttl = ip_hdr(skb)->ttl;
+                rt = (struct rtable *)dst;
+                lwtstate = rt->rt_lwtstate;
+        } else if (skb->protocol == htons(ETH_P_IPV6)) {
+                ttl = ipv6_hdr(skb)->hop_limit;
+                rt6 = (struct rt6_info *)dst;
+                lwtstate = rt6->rt6i_lwtstate;
+        } else {
+                goto drop;
+        }
+
+        skb_orphan(skb);
+
+        /* Find the output device */
+        out_dev = rcu_dereference(dst->dev);
+        if (!mpls_output_possible(out_dev) ||
+            !lwtstate || skb_warn_if_lro(skb))
+                goto drop;
+
+        skb_forward_csum(skb);
+
+        tun_encap_info = mpls_lwtunnel_encap(lwtstate);
+
+        /* Verify the destination can hold the packet */
+        new_header_size = mpls_encap_size(tun_encap_info);
+        mtu = mpls_dev_mtu(out_dev);
+        if (mpls_pkt_too_big(skb, mtu - new_header_size))
+                goto drop;
+
+        hh_len = LL_RESERVED_SPACE(out_dev);
+        if (!out_dev->header_ops)
+                hh_len = 0;
+
+        /* Ensure there is enough space for the headers in the skb */
+        if (skb_cow(skb, hh_len + new_header_size))
+                goto drop;
+
+        skb_push(skb, new_header_size);
+        skb_reset_network_header(skb);
+
+        skb->dev = out_dev;
+        skb->protocol = htons(ETH_P_MPLS_UC);
+
+        /* Push the new labels */
+        hdr = mpls_hdr(skb);
+        bos = true;
+        for (i = tun_encap_info->labels - 1; i >= 0; i--) {
+                hdr[i] = mpls_entry_encode(tun_encap_info->label[i],
+                                           ttl, 0, bos);
+                bos = false;
+        }
+
+        if (rt)
+                err = neigh_xmit(NEIGH_ARP_TABLE, out_dev, &rt->rt_gateway,
+                                 skb);
+        else if (rt6)
+                err = neigh_xmit(NEIGH_ND_TABLE, out_dev, &rt6->rt6i_gateway,
+                                 skb);
+        if (err)
+                net_dbg_ratelimited("%s: packet transmission failed: %d\n",
+                                    __func__, err);
+
+        return 0;
+
+drop:
+        kfree_skb(skb);
+        return -EINVAL;
+}
+
+static int mpls_build_state(struct net_device *dev, struct nlattr *nla,
+                            struct lwtunnel_state **ts)
+{
+        struct mpls_iptunnel_encap *tun_encap_info;
+        struct nlattr *tb[MPLS_IPTUNNEL_MAX + 1];
+        struct lwtunnel_state *newts;
+        int tun_encap_info_len;
+        int ret;
+
+        ret = nla_parse_nested(tb, MPLS_IPTUNNEL_MAX, nla,
+                               mpls_iptunnel_policy);
+        if (ret < 0)
+                return ret;
+
+        if (!tb[MPLS_IPTUNNEL_DST])
+                return -EINVAL;
+
+        tun_encap_info_len = sizeof(*tun_encap_info);
+
+        newts = lwtunnel_state_alloc(tun_encap_info_len);
+        if (!newts)
+                return -ENOMEM;
+
+        newts->len = tun_encap_info_len;
+        tun_encap_info = mpls_lwtunnel_encap(newts);
+        ret = nla_get_labels(tb[MPLS_IPTUNNEL_DST], MAX_NEW_LABELS,
+                             &tun_encap_info->labels, tun_encap_info->label);
+        if (ret)
+                goto errout;
+        newts->type = LWTUNNEL_ENCAP_MPLS;
+        newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
+
+        *ts = newts;
+
+        return 0;
+
+errout:
+        kfree(newts);
+        *ts = NULL;
+
+        return ret;
+}
+
+static int mpls_fill_encap_info(struct sk_buff *skb,
+                                struct lwtunnel_state *lwtstate)
+{
+        struct mpls_iptunnel_encap *tun_encap_info;
+        
+        tun_encap_info = mpls_lwtunnel_encap(lwtstate);
+
+        if (nla_put_labels(skb, MPLS_IPTUNNEL_DST, tun_encap_info->labels,
+                           tun_encap_info->label))
+                goto nla_put_failure;
+
+        return 0;
+
+nla_put_failure:
+        return -EMSGSIZE;
+}
+
+static int mpls_encap_nlsize(struct lwtunnel_state *lwtstate)
+{
+        struct mpls_iptunnel_encap *tun_encap_info;
+
+        tun_encap_info = mpls_lwtunnel_encap(lwtstate);
+
+        return nla_total_size(tun_encap_info->labels * 4);
+}
+
+static int mpls_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
+{
+        struct mpls_iptunnel_encap *a_hdr = mpls_lwtunnel_encap(a);
+        struct mpls_iptunnel_encap *b_hdr = mpls_lwtunnel_encap(b);
+        int l;
+
+        if (a_hdr->labels != b_hdr->labels)
+                return 1;
+
+        for (l = 0; l < MAX_NEW_LABELS; l++)
+                if (a_hdr->label[l] != b_hdr->label[l])
+                        return 1;
+        return 0;
+}
+
+static const struct lwtunnel_encap_ops mpls_iptun_ops = {
+        .build_state = mpls_build_state,
+        .output = mpls_output,
+        .fill_encap = mpls_fill_encap_info,
+        .get_encap_size = mpls_encap_nlsize,
+        .cmp_encap = mpls_encap_cmp,
+};
+
+static int __init mpls_iptunnel_init(void)
+{
+        return lwtunnel_encap_add_ops(&mpls_iptun_ops, LWTUNNEL_ENCAP_MPLS);
+}
+module_init(mpls_iptunnel_init);
+
+static void __exit mpls_iptunnel_exit(void)
+{
+        lwtunnel_encap_del_ops(&mpls_iptun_ops, LWTUNNEL_ENCAP_MPLS);
+}
+module_exit(mpls_iptunnel_exit);
+
+MODULE_DESCRIPTION("MultiProtocol Label Switching IP Tunnels");
+MODULE_LICENSE("GPL v2");