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         skb_orphan(skb);
  59
  60         if (!mpls_output_possible(out_dev) ||
  61             !dst->lwtstate || skb_warn_if_lro(skb))
  62                 goto drop;
  63
  64         skb_forward_csum(skb);
  65
  66         tun_encap_info = mpls_lwtunnel_encap(dst->lwtstate);
  67
  68         /* Obtain the ttl using the following set of rules.
  69          *
  70          * LWT ttl propagation setting:
  71          *  - disabled => use default TTL value from LWT
  72          *  - enabled  => use TTL value from IPv4/IPv6 header
  73          *  - default  =>
  74          *   Global ttl propagation setting:
  75          *    - disabled => use default TTL value from global setting
  76          *    - enabled => use TTL value from IPv4/IPv6 header
  77          */
  78         if (dst->ops->family == AF_INET) {
  79                 if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DISABLED)
  80                         ttl = tun_encap_info->default_ttl;
  81                 else if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DEFAULT &&
  82                          !net->mpls.ip_ttl_propagate)
  83                         ttl = net->mpls.default_ttl;
  84                 else
  85                         ttl = ip_hdr(skb)->ttl;
  86                 rt = (struct rtable *)dst;
  87         } else if (dst->ops->family == AF_INET6) {
  88                 if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DISABLED)
  89                         ttl = tun_encap_info->default_ttl;
  90                 else if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DEFAULT &&
  91                          !net->mpls.ip_ttl_propagate)
  92                         ttl = net->mpls.default_ttl;
  93                 else
  94                         ttl = ipv6_hdr(skb)->hop_limit;
  95                 rt6 = (struct rt6_info *)dst;
  96         } else {
  97                 goto drop;
  98         }
  99
 100         /* Verify the destination can hold the packet */
 101         new_header_size = mpls_encap_size(tun_encap_info);
 102         mtu = mpls_dev_mtu(out_dev);
 103         if (mpls_pkt_too_big(skb, mtu - new_header_size))
 104                 goto drop;
 105
 106         hh_len = LL_RESERVED_SPACE(out_dev);
 107         if (!out_dev->header_ops)
 108                 hh_len = 0;
 109
 110         /* Ensure there is enough space for the headers in the skb */
 111         if (skb_cow(skb, hh_len + new_header_size))
 112                 goto drop;
 113
 114         skb_set_inner_protocol(skb, skb->protocol);
 115         skb_reset_inner_network_header(skb);
 116
 117         skb_push(skb, new_header_size);
 118
 119         skb_reset_network_header(skb);
 120
 121         skb->dev = out_dev;
 122         skb->protocol = htons(ETH_P_MPLS_UC);
 123
 124         /* Push the new labels */
 125         hdr = mpls_hdr(skb);
 126         bos = true;
 127         for (i = tun_encap_info->labels - 1; i >= 0; i--) {
 128                 hdr[i] = mpls_entry_encode(tun_encap_info->label[i],
 129                                            ttl, 0, bos);
 130                 bos = false;
 131         }
 132
 133         mpls_stats_inc_outucastpkts(out_dev, skb);
 134
 135         if (rt) {
 136                 if (rt->rt_gw_family == AF_INET6)
 137                         err = neigh_xmit(NEIGH_ND_TABLE, out_dev, &rt->rt_gw6,
 138                                          skb);
 139                 else
 140                         err = neigh_xmit(NEIGH_ARP_TABLE, out_dev, &rt->rt_gw4,
 141                                          skb);
 142         } else if (rt6) {
 143                 if (ipv6_addr_v4mapped(&rt6->rt6i_gateway)) {
 144                         /* 6PE (RFC 4798) */
 145                         err = neigh_xmit(NEIGH_ARP_TABLE, out_dev, &rt6->rt6i_gateway.s6_addr32[3],
 146                                          skb);
 147                 } else
 148                         err = neigh_xmit(NEIGH_ND_TABLE, out_dev, &rt6->rt6i_gateway,
 149                                          skb);
 150         }
 151         if (err)
 152                 net_dbg_ratelimited("%s: packet transmission failed: %d\n",
 153                                     __func__, err);
 154
 155         return LWTUNNEL_XMIT_DONE;
 156
 157 drop:
 158         out_mdev = out_dev ? mpls_dev_get(out_dev) : NULL;
 159         if (out_mdev)
 160                 MPLS_INC_STATS(out_mdev, tx_errors);
 161         kfree_skb(skb);
 162         return -EINVAL;
 163 }
 164
 165 static int mpls_build_state(struct nlattr *nla,
 166                             unsigned int family, const void *cfg,
 167                             struct lwtunnel_state **ts,
 168                             struct netlink_ext_ack *extack)
 169 {
 170         struct mpls_iptunnel_encap *tun_encap_info;
 171         struct nlattr *tb[MPLS_IPTUNNEL_MAX + 1];
 172         struct lwtunnel_state *newts;
 173         u8 n_labels;
 174         int ret;
 175
 176         ret = nla_parse_nested_deprecated(tb, MPLS_IPTUNNEL_MAX, nla,
 177                                           mpls_iptunnel_policy, extack);
 178         if (ret < 0)
 179                 return ret;
 180
 181         if (!tb[MPLS_IPTUNNEL_DST]) {
 182                 NL_SET_ERR_MSG(extack, "MPLS_IPTUNNEL_DST attribute is missing");
 183                 return -EINVAL;
 184         }
 185
 186         /* determine number of labels */
 187         if (nla_get_labels(tb[MPLS_IPTUNNEL_DST], MAX_NEW_LABELS,
 188                            &n_labels, NULL, extack))
 189                 return -EINVAL;
 190
 191         newts = lwtunnel_state_alloc(struct_size(tun_encap_info, label,
 192                                                  n_labels));
 193         if (!newts)
 194                 return -ENOMEM;
 195
 196         tun_encap_info = mpls_lwtunnel_encap(newts);
 197         ret = nla_get_labels(tb[MPLS_IPTUNNEL_DST], n_labels,
 198                              &tun_encap_info->labels, tun_encap_info->label,
 199                              extack);
 200         if (ret)
 201                 goto errout;
 202
 203         tun_encap_info->ttl_propagate = MPLS_TTL_PROP_DEFAULT;
 204
 205         if (tb[MPLS_IPTUNNEL_TTL]) {
 206                 tun_encap_info->default_ttl = nla_get_u8(tb[MPLS_IPTUNNEL_TTL]);
 207                 /* TTL 0 implies propagate from IP header */
 208                 tun_encap_info->ttl_propagate = tun_encap_info->default_ttl ?
 209                         MPLS_TTL_PROP_DISABLED :
 210                         MPLS_TTL_PROP_ENABLED;
 211         }
 212
 213         newts->type = LWTUNNEL_ENCAP_MPLS;
 214         newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT;
 215         newts->headroom = mpls_encap_size(tun_encap_info);
 216
 217         *ts = newts;
 218
 219         return 0;
 220
 221 errout:
 222         kfree(newts);
 223         *ts = NULL;
 224
 225         return ret;
 226 }
 227
 228 static int mpls_fill_encap_info(struct sk_buff *skb,
 229                                 struct lwtunnel_state *lwtstate)
 230 {
 231         struct mpls_iptunnel_encap *tun_encap_info;
 232
 233         tun_encap_info = mpls_lwtunnel_encap(lwtstate);
 234
 235         if (nla_put_labels(skb, MPLS_IPTUNNEL_DST, tun_encap_info->labels,
 236                            tun_encap_info->label))
 237                 goto nla_put_failure;
 238
 239         if (tun_encap_info->ttl_propagate != MPLS_TTL_PROP_DEFAULT &&
 240             nla_put_u8(skb, MPLS_IPTUNNEL_TTL, tun_encap_info->default_ttl))
 241                 goto nla_put_failure;
 242
 243         return 0;
 244
 245 nla_put_failure:
 246         return -EMSGSIZE;
 247 }
 248
 249 static int mpls_encap_nlsize(struct lwtunnel_state *lwtstate)
 250 {
 251         struct mpls_iptunnel_encap *tun_encap_info;
 252         int nlsize;
 253
 254         tun_encap_info = mpls_lwtunnel_encap(lwtstate);
 255
 256         nlsize = nla_total_size(tun_encap_info->labels * 4);
 257
 258         if (tun_encap_info->ttl_propagate != MPLS_TTL_PROP_DEFAULT)
 259                 nlsize += nla_total_size(1);
 260
 261         return nlsize;
 262 }
 263
 264 static int mpls_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
 265 {
 266         struct mpls_iptunnel_encap *a_hdr = mpls_lwtunnel_encap(a);
 267         struct mpls_iptunnel_encap *b_hdr = mpls_lwtunnel_encap(b);
 268         int l;
 269
 270         if (a_hdr->labels != b_hdr->labels ||
 271             a_hdr->ttl_propagate != b_hdr->ttl_propagate ||
 272             a_hdr->default_ttl != b_hdr->default_ttl)
 273                 return 1;
 274
 275         for (l = 0; l < a_hdr->labels; l++)
 276                 if (a_hdr->label[l] != b_hdr->label[l])
 277                         return 1;
 278         return 0;
 279 }
 280
 281 static const struct lwtunnel_encap_ops mpls_iptun_ops = {
 282         .build_state = mpls_build_state,
 283         .xmit = mpls_xmit,
 284         .fill_encap = mpls_fill_encap_info,
 285         .get_encap_size = mpls_encap_nlsize,
 286         .cmp_encap = mpls_encap_cmp,
 287         .owner = THIS_MODULE,
 288 };
 289
 290 static int __init mpls_iptunnel_init(void)
 291 {
 292         return lwtunnel_encap_add_ops(&mpls_iptun_ops, LWTUNNEL_ENCAP_MPLS);
 293 }
 294 module_init(mpls_iptunnel_init);
 295
 296 static void __exit mpls_iptunnel_exit(void)
 297 {
 298         lwtunnel_encap_del_ops(&mpls_iptun_ops, LWTUNNEL_ENCAP_MPLS);
 299 }
 300 module_exit(mpls_iptunnel_exit);
 301
 302 MODULE_ALIAS_RTNL_LWT(MPLS);
 303 MODULE_DESCRIPTION("MultiProtocol Label Switching IP Tunnels");
 304 MODULE_LICENSE("GPL v2");