net/mpls/mpls_iptunnel.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * mpls tunnels An implementation mpls tunnels using the light weight tunnel
   4  *              infrastructure
   5  *
   6  * Authors:     Roopa Prabhu, <roopa@cumulusnetworks.com>
   7  */
   8 #include <linux/types.h>
   9 #include <linux/skbuff.h>
  10 #include <linux/net.h>
  11 #include <linux/module.h>
  12 #include <linux/mpls.h>
  13 #include <linux/vmalloc.h>
  14 #include <net/ip.h>
  15 #include <net/dst.h>
  16 #include <net/lwtunnel.h>
  17 #include <net/netevent.h>
  18 #include <net/netns/generic.h>
  19 #include <net/ip6_fib.h>
  20 #include <net/route.h>
  21 #include <net/mpls_iptunnel.h>
  22 #include <linux/mpls_iptunnel.h>
  23 #include "internal.h"
  24
  25 static const struct nla_policy mpls_iptunnel_policy[MPLS_IPTUNNEL_MAX + 1] = {
  26         [MPLS_IPTUNNEL_DST]     = { .len = sizeof(u32) },
  27         [MPLS_IPTUNNEL_TTL]     = { .type = NLA_U8 },
  28 };
  29
  30 static unsigned int mpls_encap_size(struct mpls_iptunnel_encap *en)
  31 {
  32         /* The size of the layer 2.5 labels to be added for this route */
  33         return en->labels * sizeof(struct mpls_shim_hdr);
  34 }
  35
  36 static int mpls_xmit(struct sk_buff *skb)
  37 {
  38         struct mpls_iptunnel_encap *tun_encap_info;
  39         struct mpls_shim_hdr *hdr;
  40         struct net_device *out_dev;
  41         unsigned int hh_len;
  42         unsigned int new_header_size;
  43         unsigned int mtu;
  44         struct dst_entry *dst = skb_dst(skb);
  45         struct rtable *rt = NULL;
  46         struct rt6_info *rt6 = NULL;
  47         struct mpls_dev *out_mdev;
  48         struct net *net;
  49         int err = 0;
  50         bool bos;
  51         int i;
  52         unsigned int ttl;
  53
  54         /* Find the output device */
  55         out_dev = dst->dev;
  56         net = dev_net(out_dev);
  57
  58         if (!mpls_output_possible(out_dev) ||
  59             !dst->lwtstate || skb_warn_if_lro(skb))
  60                 goto drop;
  61
  62         skb_forward_csum(skb);
  63
  64         tun_encap_info = mpls_lwtunnel_encap(dst->lwtstate);
  65
  66         /* Obtain the ttl using the following set of rules.
  67          *
  68          * LWT ttl propagation setting:
  69          *  - disabled => use default TTL value from LWT
  70          *  - enabled  => use TTL value from IPv4/IPv6 header
  71          *  - default  =>
  72          *   Global ttl propagation setting:
  73          *    - disabled => use default TTL value from global setting
  74          *    - enabled => use TTL value from IPv4/IPv6 header
  75          */
  76         if (dst->ops->family == AF_INET) {
  77                 if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DISABLED)
  78                         ttl = tun_encap_info->default_ttl;
  79                 else if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DEFAULT &&
  80                          !net->mpls.ip_ttl_propagate)
  81                         ttl = net->mpls.default_ttl;
  82                 else
  83                         ttl = ip_hdr(skb)->ttl;
  84                 rt = dst_rtable(dst);
  85         } else if (dst->ops->family == AF_INET6) {
  86                 if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DISABLED)
  87                         ttl = tun_encap_info->default_ttl;
  88                 else if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DEFAULT &&
  89                          !net->mpls.ip_ttl_propagate)
  90                         ttl = net->mpls.default_ttl;
  91                 else
  92                         ttl = ipv6_hdr(skb)->hop_limit;
  93                 rt6 = dst_rt6_info(dst);
  94         } else {
  95                 goto drop;
  96         }
  97
  98         /* Verify the destination can hold the packet */
  99         new_header_size = mpls_encap_size(tun_encap_info);
 100         mtu = mpls_dev_mtu(out_dev);
 101         if (mpls_pkt_too_big(skb, mtu - new_header_size))
 102                 goto drop;
 103
 104         hh_len = LL_RESERVED_SPACE(out_dev);
 105         if (!out_dev->header_ops)
 106                 hh_len = 0;
 107
 108         /* Ensure there is enough space for the headers in the skb */
 109         if (skb_cow_head(skb, hh_len + new_header_size))
 110                 goto drop;
 111
 112         skb_set_inner_protocol(skb, skb->protocol);
 113         skb_reset_inner_network_header(skb);
 114
 115         skb_push(skb, new_header_size);
 116
 117         skb_reset_network_header(skb);
 118
 119         skb->dev = out_dev;
 120         skb->protocol = htons(ETH_P_MPLS_UC);
 121
 122         /* Push the new labels */
 123         hdr = mpls_hdr(skb);
 124         bos = true;
 125         for (i = tun_encap_info->labels - 1; i >= 0; i--) {
 126                 hdr[i] = mpls_entry_encode(tun_encap_info->label[i],
 127                                            ttl, 0, bos);
 128                 bos = false;
 129         }
 130
 131         mpls_stats_inc_outucastpkts(out_dev, skb);
 132
 133         if (rt) {
 134                 if (rt->rt_gw_family == AF_INET6)
 135                         err = neigh_xmit(NEIGH_ND_TABLE, out_dev, &rt->rt_gw6,
 136                                          skb);
 137                 else
 138                         err = neigh_xmit(NEIGH_ARP_TABLE, out_dev, &rt->rt_gw4,
 139                                          skb);
 140         } else if (rt6) {
 141                 if (ipv6_addr_v4mapped(&rt6->rt6i_gateway)) {
 142                         /* 6PE (RFC 4798) */
 143                         err = neigh_xmit(NEIGH_ARP_TABLE, out_dev, &rt6->rt6i_gateway.s6_addr32[3],
 144                                          skb);
 145                 } else
 146                         err = neigh_xmit(NEIGH_ND_TABLE, out_dev, &rt6->rt6i_gateway,
 147                                          skb);
 148         }
 149         if (err)
 150                 net_dbg_ratelimited("%s: packet transmission failed: %d\n",
 151                                     __func__, err);
 152
 153         return LWTUNNEL_XMIT_DONE;
 154
 155 drop:
 156         out_mdev = out_dev ? mpls_dev_get(out_dev) : NULL;
 157         if (out_mdev)
 158                 MPLS_INC_STATS(out_mdev, tx_errors);
 159         kfree_skb(skb);
 160         return -EINVAL;
 161 }
 162
 163 static int mpls_build_state(struct net *net, struct nlattr *nla,
 164                             unsigned int family, const void *cfg,
 165                             struct lwtunnel_state **ts,
 166                             struct netlink_ext_ack *extack)
 167 {
 168         struct mpls_iptunnel_encap *tun_encap_info;
 169         struct nlattr *tb[MPLS_IPTUNNEL_MAX + 1];
 170         struct lwtunnel_state *newts;
 171         u8 n_labels;
 172         int ret;
 173
 174         ret = nla_parse_nested_deprecated(tb, MPLS_IPTUNNEL_MAX, nla,
 175                                           mpls_iptunnel_policy, extack);
 176         if (ret < 0)
 177                 return ret;
 178
 179         if (!tb[MPLS_IPTUNNEL_DST]) {
 180                 NL_SET_ERR_MSG(extack, "MPLS_IPTUNNEL_DST attribute is missing");
 181                 return -EINVAL;
 182         }
 183
 184         /* determine number of labels */
 185         if (nla_get_labels(tb[MPLS_IPTUNNEL_DST], MAX_NEW_LABELS,
 186                            &n_labels, NULL, extack))
 187                 return -EINVAL;
 188
 189         newts = lwtunnel_state_alloc(struct_size(tun_encap_info, label,
 190                                                  n_labels));
 191         if (!newts)
 192                 return -ENOMEM;
 193
 194         tun_encap_info = mpls_lwtunnel_encap(newts);
 195         ret = nla_get_labels(tb[MPLS_IPTUNNEL_DST], n_labels,
 196                              &tun_encap_info->labels, tun_encap_info->label,
 197                              extack);
 198         if (ret)
 199                 goto errout;
 200
 201         tun_encap_info->ttl_propagate = MPLS_TTL_PROP_DEFAULT;
 202
 203         if (tb[MPLS_IPTUNNEL_TTL]) {
 204                 tun_encap_info->default_ttl = nla_get_u8(tb[MPLS_IPTUNNEL_TTL]);
 205                 /* TTL 0 implies propagate from IP header */
 206                 tun_encap_info->ttl_propagate = tun_encap_info->default_ttl ?
 207                         MPLS_TTL_PROP_DISABLED :
 208                         MPLS_TTL_PROP_ENABLED;
 209         }
 210
 211         newts->type = LWTUNNEL_ENCAP_MPLS;
 212         newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT;
 213         newts->headroom = mpls_encap_size(tun_encap_info);
 214
 215         *ts = newts;
 216
 217         return 0;
 218
 219 errout:
 220         kfree(newts);
 221         *ts = NULL;
 222
 223         return ret;
 224 }
 225
 226 static int mpls_fill_encap_info(struct sk_buff *skb,
 227                                 struct lwtunnel_state *lwtstate)
 228 {
 229         struct mpls_iptunnel_encap *tun_encap_info;
 230
 231         tun_encap_info = mpls_lwtunnel_encap(lwtstate);
 232
 233         if (nla_put_labels(skb, MPLS_IPTUNNEL_DST, tun_encap_info->labels,
 234                            tun_encap_info->label))
 235                 goto nla_put_failure;
 236
 237         if (tun_encap_info->ttl_propagate != MPLS_TTL_PROP_DEFAULT &&
 238             nla_put_u8(skb, MPLS_IPTUNNEL_TTL, tun_encap_info->default_ttl))
 239                 goto nla_put_failure;
 240
 241         return 0;
 242
 243 nla_put_failure:
 244         return -EMSGSIZE;
 245 }
 246
 247 static int mpls_encap_nlsize(struct lwtunnel_state *lwtstate)
 248 {
 249         struct mpls_iptunnel_encap *tun_encap_info;
 250         int nlsize;
 251
 252         tun_encap_info = mpls_lwtunnel_encap(lwtstate);
 253
 254         nlsize = nla_total_size(tun_encap_info->labels * 4);
 255
 256         if (tun_encap_info->ttl_propagate != MPLS_TTL_PROP_DEFAULT)
 257                 nlsize += nla_total_size(1);
 258
 259         return nlsize;
 260 }
 261
 262 static int mpls_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
 263 {
 264         struct mpls_iptunnel_encap *a_hdr = mpls_lwtunnel_encap(a);
 265         struct mpls_iptunnel_encap *b_hdr = mpls_lwtunnel_encap(b);
 266         int l;
 267
 268         if (a_hdr->labels != b_hdr->labels ||
 269             a_hdr->ttl_propagate != b_hdr->ttl_propagate ||
 270             a_hdr->default_ttl != b_hdr->default_ttl)
 271                 return 1;
 272
 273         for (l = 0; l < a_hdr->labels; l++)
 274                 if (a_hdr->label[l] != b_hdr->label[l])
 275                         return 1;
 276         return 0;
 277 }
 278
 279 static const struct lwtunnel_encap_ops mpls_iptun_ops = {
 280         .build_state = mpls_build_state,
 281         .xmit = mpls_xmit,
 282         .fill_encap = mpls_fill_encap_info,
 283         .get_encap_size = mpls_encap_nlsize,
 284         .cmp_encap = mpls_encap_cmp,
 285         .owner = THIS_MODULE,
 286 };
 287
 288 static int __init mpls_iptunnel_init(void)
 289 {
 290         return lwtunnel_encap_add_ops(&mpls_iptun_ops, LWTUNNEL_ENCAP_MPLS);
 291 }
 292 module_init(mpls_iptunnel_init);
 293
 294 static void __exit mpls_iptunnel_exit(void)
 295 {
 296         lwtunnel_encap_del_ops(&mpls_iptun_ops, LWTUNNEL_ENCAP_MPLS);
 297 }
 298 module_exit(mpls_iptunnel_exit);
 299
 300 MODULE_ALIAS_RTNL_LWT(MPLS);
 301 MODULE_SOFTDEP("post: mpls_gso");
 302 MODULE_DESCRIPTION("MultiProtocol Label Switching IP Tunnels");
 303 MODULE_LICENSE("GPL v2");