datapath/vport-gre.c

   1 /*
   2  * Copyright (c) 2007-2011 Nicira Networks.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of version 2 of the GNU General Public
   6  * License as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this program; if not, write to the Free Software
  15  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  16  * 02110-1301, USA
  17  */
  18
  19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  20
  21 #include <linux/if.h>
  22 #include <linux/skbuff.h>
  23 #include <linux/ip.h>
  24 #include <linux/if_tunnel.h>
  25 #include <linux/if_vlan.h>
  26 #include <linux/in.h>
  27
  28 #include <net/icmp.h>
  29 #include <net/ip.h>
  30 #include <net/protocol.h>
  31
  32 #include "tunnel.h"
  33 #include "vport.h"
  34 #include "vport-generic.h"
  35
  36 /*
  37  * The GRE header is composed of a series of sections: a base and then a variable
  38  * number of options.
  39  */
  40 #define GRE_HEADER_SECTION 4
  41
  42 struct gre_base_hdr {
  43         __be16 flags;
  44         __be16 protocol;
  45 };
  46
  47 static int gre_hdr_len(const struct tnl_mutable_config *mutable)
  48 {
  49         int len;
  50
  51         len = GRE_HEADER_SECTION;
  52
  53         if (mutable->flags & TNL_F_CSUM)
  54                 len += GRE_HEADER_SECTION;
  55
  56         if (mutable->out_key || mutable->flags & TNL_F_OUT_KEY_ACTION)
  57                 len += GRE_HEADER_SECTION;
  58
  59         return len;
  60 }
  61
  62 /* Returns the least-significant 32 bits of a __be64. */
  63 static __be32 be64_get_low32(__be64 x)
  64 {
  65 #ifdef __BIG_ENDIAN
  66         return (__force __be32)x;
  67 #else
  68         return (__force __be32)((__force u64)x >> 32);
  69 #endif
  70 }
  71
  72 static void gre_build_header(const struct vport *vport,
  73                              const struct tnl_mutable_config *mutable,
  74                              void *header)
  75 {
  76         struct gre_base_hdr *greh = header;
  77         __be32 *options = (__be32 *)(greh + 1);
  78
  79         greh->protocol = htons(ETH_P_TEB);
  80         greh->flags = 0;
  81
  82         if (mutable->flags & TNL_F_CSUM) {
  83                 greh->flags |= GRE_CSUM;
  84                 *options = 0;
  85                 options++;
  86         }
  87
  88         if (mutable->out_key || mutable->flags & TNL_F_OUT_KEY_ACTION)
  89                 greh->flags |= GRE_KEY;
  90
  91         if (mutable->out_key)
  92                 *options = be64_get_low32(mutable->out_key);
  93 }
  94
  95 static struct sk_buff *gre_update_header(const struct vport *vport,
  96                                          const struct tnl_mutable_config *mutable,
  97                                          struct dst_entry *dst,
  98                                          struct sk_buff *skb)
  99 {
 100         __be32 *options = (__be32 *)(skb_network_header(skb) + mutable->tunnel_hlen
 101                                                - GRE_HEADER_SECTION);
 102
 103         /* Work backwards over the options so the checksum is last. */
 104         if (mutable->flags & TNL_F_OUT_KEY_ACTION) {
 105                 *options = be64_get_low32(OVS_CB(skb)->tun_id);
 106                 options--;
 107         }
 108
 109         if (mutable->flags & TNL_F_CSUM)
 110                 *(__sum16 *)options = csum_fold(skb_checksum(skb,
 111                                                 skb_transport_offset(skb),
 112                                                 skb->len - skb_transport_offset(skb),
 113                                                 0));
 114         /*
 115          * Allow our local IP stack to fragment the outer packet even if the
 116          * DF bit is set as a last resort.  We also need to force selection of
 117          * an IP ID here because Linux will otherwise leave it at 0 if the
 118          * packet originally had DF set.
 119          */
 120         skb->local_df = 1;
 121         __ip_select_ident(ip_hdr(skb), dst, 0);
 122
 123         return skb;
 124 }
 125
 126 /* Zero-extends a __be32 into the least-significant 32 bits of a __be64. */
 127 static __be64 be32_extend_to_be64(__be32 x)
 128 {
 129 #ifdef __BIG_ENDIAN
 130         return (__force __be64)x;
 131 #else
 132         return (__force __be64)((__force u64)x << 32);
 133 #endif
 134 }
 135
 136 static int parse_header(struct iphdr *iph, __be16 *flags, __be64 *key)
 137 {
 138         /* IP and ICMP protocol handlers check that the IHL is valid. */
 139         struct gre_base_hdr *greh = (struct gre_base_hdr *)((u8 *)iph + (iph->ihl << 2));
 140         __be32 *options = (__be32 *)(greh + 1);
 141         int hdr_len;
 142
 143         *flags = greh->flags;
 144
 145         if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))
 146                 return -EINVAL;
 147
 148         if (unlikely(greh->protocol != htons(ETH_P_TEB)))
 149                 return -EINVAL;
 150
 151         hdr_len = GRE_HEADER_SECTION;
 152
 153         if (greh->flags & GRE_CSUM) {
 154                 hdr_len += GRE_HEADER_SECTION;
 155                 options++;
 156         }
 157
 158         if (greh->flags & GRE_KEY) {
 159                 hdr_len += GRE_HEADER_SECTION;
 160
 161                 *key = be32_extend_to_be64(*options);
 162                 options++;
 163         } else
 164                 *key = 0;
 165
 166         if (unlikely(greh->flags & GRE_SEQ))
 167                 hdr_len += GRE_HEADER_SECTION;
 168
 169         return hdr_len;
 170 }
 171
 172 /* Called with rcu_read_lock and BH disabled. */
 173 static void gre_err(struct sk_buff *skb, u32 info)
 174 {
 175         struct vport *vport;
 176         const struct tnl_mutable_config *mutable;
 177         const int type = icmp_hdr(skb)->type;
 178         const int code = icmp_hdr(skb)->code;
 179         int mtu = ntohs(icmp_hdr(skb)->un.frag.mtu);
 180
 181         struct iphdr *iph;
 182         __be16 flags;
 183         __be64 key;
 184         int tunnel_hdr_len, tot_hdr_len;
 185         unsigned int orig_mac_header;
 186         unsigned int orig_nw_header;
 187
 188         if (type != ICMP_DEST_UNREACH || code != ICMP_FRAG_NEEDED)
 189                 return;
 190
 191         /*
 192          * The mimimum size packet that we would actually be able to process:
 193          * encapsulating IP header, minimum GRE header, Ethernet header,
 194          * inner IPv4 header.
 195          */
 196         if (!pskb_may_pull(skb, sizeof(struct iphdr) + GRE_HEADER_SECTION +
 197                                 ETH_HLEN + sizeof(struct iphdr)))
 198                 return;
 199
 200         iph = (struct iphdr *)skb->data;
 201         if (ipv4_is_multicast(iph->daddr))
 202                 return;
 203
 204         tunnel_hdr_len = parse_header(iph, &flags, &key);
 205         if (tunnel_hdr_len < 0)
 206                 return;
 207
 208         vport = tnl_find_port(iph->saddr, iph->daddr, key, TNL_T_PROTO_GRE,
 209                               &mutable);
 210         if (!vport)
 211                 return;
 212
 213         /*
 214          * Packets received by this function were previously sent by us, so
 215          * any comparisons should be to the output values, not the input.
 216          * However, it's not really worth it to have a hash table based on
 217          * output keys (especially since ICMP error handling of tunneled packets
 218          * isn't that reliable anyways).  Therefore, we do a lookup based on the
 219          * out key as if it were the in key and then check to see if the input
 220          * and output keys are the same.
 221          */
 222         if (mutable->key.in_key != mutable->out_key)
 223                 return;
 224
 225         if (!!(mutable->flags & TNL_F_IN_KEY_MATCH) !=
 226             !!(mutable->flags & TNL_F_OUT_KEY_ACTION))
 227                 return;
 228
 229         if ((mutable->flags & TNL_F_CSUM) && !(flags & GRE_CSUM))
 230                 return;
 231
 232         tunnel_hdr_len += iph->ihl << 2;
 233
 234         orig_mac_header = skb_mac_header(skb) - skb->data;
 235         orig_nw_header = skb_network_header(skb) - skb->data;
 236         skb_set_mac_header(skb, tunnel_hdr_len);
 237
 238         tot_hdr_len = tunnel_hdr_len + ETH_HLEN;
 239
 240         skb->protocol = eth_hdr(skb)->h_proto;
 241         if (skb->protocol == htons(ETH_P_8021Q)) {
 242                 tot_hdr_len += VLAN_HLEN;
 243                 skb->protocol = vlan_eth_hdr(skb)->h_vlan_encapsulated_proto;
 244         }
 245
 246         skb_set_network_header(skb, tot_hdr_len);
 247         mtu -= tot_hdr_len;
 248
 249         if (skb->protocol == htons(ETH_P_IP))
 250                 tot_hdr_len += sizeof(struct iphdr);
 251 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 252         else if (skb->protocol == htons(ETH_P_IPV6))
 253                 tot_hdr_len += sizeof(struct ipv6hdr);
 254 #endif
 255         else
 256                 goto out;
 257
 258         if (!pskb_may_pull(skb, tot_hdr_len))
 259                 goto out;
 260
 261         if (skb->protocol == htons(ETH_P_IP)) {
 262                 if (mtu < IP_MIN_MTU) {
 263                         if (ntohs(ip_hdr(skb)->tot_len) >= IP_MIN_MTU)
 264                                 mtu = IP_MIN_MTU;
 265                         else
 266                                 goto out;
 267                 }
 268
 269         }
 270 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 271         else if (skb->protocol == htons(ETH_P_IPV6)) {
 272                 if (mtu < IPV6_MIN_MTU) {
 273                         unsigned int packet_length = sizeof(struct ipv6hdr) +
 274                                               ntohs(ipv6_hdr(skb)->payload_len);
 275
 276                         if (packet_length >= IPV6_MIN_MTU
 277                             || ntohs(ipv6_hdr(skb)->payload_len) == 0)
 278                                 mtu = IPV6_MIN_MTU;
 279                         else
 280                                 goto out;
 281                 }
 282         }
 283 #endif
 284
 285         __skb_pull(skb, tunnel_hdr_len);
 286         tnl_frag_needed(vport, mutable, skb, mtu, key);
 287         __skb_push(skb, tunnel_hdr_len);
 288
 289 out:
 290         skb_set_mac_header(skb, orig_mac_header);
 291         skb_set_network_header(skb, orig_nw_header);
 292         skb->protocol = htons(ETH_P_IP);
 293 }
 294
 295 static bool check_checksum(struct sk_buff *skb)
 296 {
 297         struct iphdr *iph = ip_hdr(skb);
 298         struct gre_base_hdr *greh = (struct gre_base_hdr *)(iph + 1);
 299         __sum16 csum = 0;
 300
 301         if (greh->flags & GRE_CSUM) {
 302                 switch (skb->ip_summed) {
 303                 case CHECKSUM_COMPLETE:
 304                         csum = csum_fold(skb->csum);
 305
 306                         if (!csum)
 307                                 break;
 308                         /* Fall through. */
 309
 310                 case CHECKSUM_NONE:
 311                         skb->csum = 0;
 312                         csum = __skb_checksum_complete(skb);
 313                         skb->ip_summed = CHECKSUM_COMPLETE;
 314                         break;
 315                 }
 316         }
 317
 318         return (csum == 0);
 319 }
 320
 321 /* Called with rcu_read_lock and BH disabled. */
 322 static int gre_rcv(struct sk_buff *skb)
 323 {
 324         struct vport *vport;
 325         const struct tnl_mutable_config *mutable;
 326         int hdr_len;
 327         struct iphdr *iph;
 328         __be16 flags;
 329         __be64 key;
 330
 331         if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr) + ETH_HLEN)))
 332                 goto error;
 333
 334         if (unlikely(!check_checksum(skb)))
 335                 goto error;
 336
 337         hdr_len = parse_header(ip_hdr(skb), &flags, &key);
 338         if (unlikely(hdr_len < 0))
 339                 goto error;
 340
 341         if (unlikely(!pskb_may_pull(skb, hdr_len + ETH_HLEN)))
 342                 goto error;
 343
 344         iph = ip_hdr(skb);
 345         vport = tnl_find_port(iph->daddr, iph->saddr, key, TNL_T_PROTO_GRE,
 346                               &mutable);
 347         if (unlikely(!vport)) {
 348                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
 349                 goto error;
 350         }
 351
 352         if (mutable->flags & TNL_F_IN_KEY_MATCH)
 353                 OVS_CB(skb)->tun_id = key;
 354         else
 355                 OVS_CB(skb)->tun_id = 0;
 356
 357         __skb_pull(skb, hdr_len);
 358         skb_postpull_rcsum(skb, skb_transport_header(skb), hdr_len + ETH_HLEN);
 359
 360         tnl_rcv(vport, skb, iph->tos);
 361         return 0;
 362
 363 error:
 364         kfree_skb(skb);
 365         return 0;
 366 }
 367
 368 static const struct tnl_ops gre_tnl_ops = {
 369         .tunnel_type    = TNL_T_PROTO_GRE,
 370         .ipproto        = IPPROTO_GRE,
 371         .hdr_len        = gre_hdr_len,
 372         .build_header   = gre_build_header,
 373         .update_header  = gre_update_header,
 374 };
 375
 376 static struct vport *gre_create(const struct vport_parms *parms)
 377 {
 378         return tnl_create(parms, &gre_vport_ops, &gre_tnl_ops);
 379 }
 380
 381 static const struct net_protocol gre_protocol_handlers = {
 382         .handler        =       gre_rcv,
 383         .err_handler    =       gre_err,
 384 };
 385
 386 static int gre_init(void)
 387 {
 388         int err;
 389
 390         err = inet_add_protocol(&gre_protocol_handlers, IPPROTO_GRE);
 391         if (err)
 392                 pr_warn("cannot register gre protocol handler\n");
 393
 394         return err;
 395 }
 396
 397 static void gre_exit(void)
 398 {
 399         inet_del_protocol(&gre_protocol_handlers, IPPROTO_GRE);
 400 }
 401
 402 const struct vport_ops gre_vport_ops = {
 403         .type           = OVS_VPORT_TYPE_GRE,
 404         .flags          = VPORT_F_TUN_ID,
 405         .init           = gre_init,
 406         .exit           = gre_exit,
 407         .create         = gre_create,
 408         .destroy        = tnl_destroy,
 409         .set_addr       = tnl_set_addr,
 410         .get_name       = tnl_get_name,
 411         .get_addr       = tnl_get_addr,
 412         .get_options    = tnl_get_options,
 413         .set_options    = tnl_set_options,
 414         .get_dev_flags  = vport_gen_get_dev_flags,
 415         .is_running     = vport_gen_is_running,
 416         .get_operstate  = vport_gen_get_operstate,
 417         .send           = tnl_send,
 418 };