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Linux/net/mpls/mpls_iptunnel.c

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  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");
305 

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