datapath/vport-gre.c

   1 /*
   2  * Copyright (c) 2010 Nicira Networks.
   3  * Distributed under the terms of the GNU GPL version 2.
   4  *
   5  * Significant portions of this file may be copied from parts of the Linux
   6  * kernel, by Linus Torvalds and others.
   7  */
   8
   9 #include <linux/if.h>
  10 #include <linux/skbuff.h>
  11 #include <linux/ip.h>
  12 #include <linux/if_tunnel.h>
  13 #include <linux/if_vlan.h>
  14 #include <linux/in.h>
  15
  16 #include <net/icmp.h>
  17 #include <net/ip.h>
  18 #include <net/protocol.h>
  19
  20 #include "tunnel.h"
  21 #include "vport.h"
  22 #include "vport-generic.h"
  23
  24 /*
  25  * The GRE header is composed of a series of sections: a base and then a variable
  26  * number of options.
  27  */
  28 #define GRE_HEADER_SECTION 4
  29
  30 struct gre_base_hdr {
  31         __be16 flags;
  32         __be16 protocol;
  33 };
  34
  35 static int gre_hdr_len(const struct tnl_port_config *port_config)
  36 {
  37         int len;
  38
  39         len = GRE_HEADER_SECTION;
  40
  41         if (port_config->flags & TNL_F_CSUM)
  42                 len += GRE_HEADER_SECTION;
  43
  44         if (port_config->out_key ||
  45             port_config->flags & TNL_F_OUT_KEY_ACTION)
  46                 len += GRE_HEADER_SECTION;
  47
  48         return len;
  49 }
  50
  51 static struct sk_buff *gre_build_header(struct sk_buff *skb,
  52                                         const struct vport *vport,
  53                                         const struct tnl_mutable_config *mutable,
  54                                         struct dst_entry *dst)
  55 {
  56         struct gre_base_hdr *greh = (struct gre_base_hdr *)skb_transport_header(skb);
  57         __be32 *options = (__be32 *)(skb_network_header(skb) + mutable->tunnel_hlen
  58                                                - GRE_HEADER_SECTION);
  59
  60         greh->protocol = htons(ETH_P_TEB);
  61         greh->flags = 0;
  62
  63         /* Work backwards over the options so the checksum is last. */
  64         if (mutable->port_config.out_key ||
  65             mutable->port_config.flags & TNL_F_OUT_KEY_ACTION) {
  66                 greh->flags |= GRE_KEY;
  67
  68                 if (mutable->port_config.flags & TNL_F_OUT_KEY_ACTION)
  69                         *options = OVS_CB(skb)->tun_id;
  70                 else
  71                         *options = mutable->port_config.out_key;
  72
  73                 options--;
  74         }
  75
  76         if (mutable->port_config.flags & TNL_F_CSUM) {
  77                 greh->flags |= GRE_CSUM;
  78
  79                 *options = 0;
  80                 *(__sum16 *)options = csum_fold(skb_checksum(skb,
  81                                                 sizeof(struct iphdr),
  82                                                 skb->len - sizeof(struct iphdr),
  83                                                 0));
  84         }
  85
  86         /*
  87          * Allow our local IP stack to fragment the outer packet even if the
  88          * DF bit is set as a last resort.
  89          */
  90         skb->local_df = 1;
  91
  92         return skb;
  93 }
  94
  95 static int parse_header(struct iphdr *iph, __be16 *flags, __be32 *key)
  96 {
  97         /* IP and ICMP protocol handlers check that the IHL is valid. */
  98         struct gre_base_hdr *greh = (struct gre_base_hdr *)((u8 *)iph + (iph->ihl << 2));
  99         __be32 *options = (__be32 *)(greh + 1);
 100         int hdr_len;
 101
 102         *flags = greh->flags;
 103
 104         if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))
 105                 return -EINVAL;
 106
 107         if (unlikely(greh->protocol != htons(ETH_P_TEB)))
 108                 return -EINVAL;
 109
 110         hdr_len = GRE_HEADER_SECTION;
 111
 112         if (greh->flags & GRE_CSUM) {
 113                 hdr_len += GRE_HEADER_SECTION;
 114                 options++;
 115         }
 116
 117         if (greh->flags & GRE_KEY) {
 118                 hdr_len += GRE_HEADER_SECTION;
 119
 120                 *key = *options;
 121                 options++;
 122         } else
 123                 *key = 0;
 124
 125         if (unlikely(greh->flags & GRE_SEQ))
 126                 hdr_len += GRE_HEADER_SECTION;
 127
 128         return hdr_len;
 129 }
 130
 131 /* Called with rcu_read_lock and BH disabled. */
 132 static void gre_err(struct sk_buff *skb, u32 info)
 133 {
 134         struct vport *vport;
 135         const struct tnl_mutable_config *mutable;
 136         const int type = icmp_hdr(skb)->type;
 137         const int code = icmp_hdr(skb)->code;
 138         int mtu = ntohs(icmp_hdr(skb)->un.frag.mtu);
 139
 140         struct iphdr *iph;
 141         __be16 flags;
 142         __be32 key;
 143         int tunnel_hdr_len, tot_hdr_len;
 144         unsigned int orig_mac_header;
 145         unsigned int orig_nw_header;
 146
 147         if (type != ICMP_DEST_UNREACH || code != ICMP_FRAG_NEEDED)
 148                 return;
 149
 150         /*
 151          * The mimimum size packet that we would actually be able to process:
 152          * encapsulating IP header, minimum GRE header, Ethernet header,
 153          * inner IPv4 header.
 154          */
 155         if (!pskb_may_pull(skb, sizeof(struct iphdr) + GRE_HEADER_SECTION +
 156                                 ETH_HLEN + sizeof(struct iphdr)))
 157                 return;
 158
 159         iph = (struct iphdr *)skb->data;
 160
 161         tunnel_hdr_len = parse_header(iph, &flags, &key);
 162         if (tunnel_hdr_len < 0)
 163                 return;
 164
 165         vport = tnl_find_port(iph->saddr, iph->daddr, key,
 166                               TNL_T_PROTO_GRE | TNL_T_KEY_EITHER, &mutable);
 167         if (!vport)
 168                 return;
 169
 170         /*
 171          * Packets received by this function were previously sent by us, so
 172          * any comparisons should be to the output values, not the input.
 173          * However, it's not really worth it to have a hash table based on
 174          * output keys (especially since ICMP error handling of tunneled packets
 175          * isn't that reliable anyways).  Therefore, we do a lookup based on the
 176          * out key as if it were the in key and then check to see if the input
 177          * and output keys are the same.
 178          */
 179         if (mutable->port_config.in_key != mutable->port_config.out_key)
 180                 return;
 181
 182         if (!!(mutable->port_config.flags & TNL_F_IN_KEY_MATCH) !=
 183             !!(mutable->port_config.flags & TNL_F_OUT_KEY_ACTION))
 184                 return;
 185
 186         if ((mutable->port_config.flags & TNL_F_CSUM) && !(flags & GRE_CSUM))
 187                 return;
 188
 189         tunnel_hdr_len += iph->ihl << 2;
 190
 191         orig_mac_header = skb_mac_header(skb) - skb->data;
 192         orig_nw_header = skb_network_header(skb) - skb->data;
 193         skb_set_mac_header(skb, tunnel_hdr_len);
 194
 195         tot_hdr_len = tunnel_hdr_len + ETH_HLEN;
 196
 197         skb->protocol = eth_hdr(skb)->h_proto;
 198         if (skb->protocol == htons(ETH_P_8021Q)) {
 199                 tot_hdr_len += VLAN_HLEN;
 200                 skb->protocol = vlan_eth_hdr(skb)->h_vlan_encapsulated_proto;
 201         }
 202
 203         skb_set_network_header(skb, tot_hdr_len);
 204         mtu -= tot_hdr_len;
 205
 206         if (skb->protocol == htons(ETH_P_IP))
 207                 tot_hdr_len += sizeof(struct iphdr);
 208 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 209         else if (skb->protocol == htons(ETH_P_IPV6))
 210                 tot_hdr_len += sizeof(struct ipv6hdr);
 211 #endif
 212         else
 213                 goto out;
 214
 215         if (!pskb_may_pull(skb, tot_hdr_len))
 216                 goto out;
 217
 218         if (skb->protocol == htons(ETH_P_IP)) {
 219                 if (mtu < IP_MIN_MTU) {
 220                         if (ntohs(ip_hdr(skb)->tot_len) >= IP_MIN_MTU)
 221                                 mtu = IP_MIN_MTU;
 222                         else
 223                                 goto out;
 224                 }
 225
 226         }
 227 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 228         else if (skb->protocol == htons(ETH_P_IPV6)) {
 229                 if (mtu < IPV6_MIN_MTU) {
 230                         unsigned int packet_length = sizeof(struct ipv6hdr) +
 231                                               ntohs(ipv6_hdr(skb)->payload_len);
 232
 233                         if (packet_length >= IPV6_MIN_MTU
 234                             || ntohs(ipv6_hdr(skb)->payload_len) == 0)
 235                                 mtu = IPV6_MIN_MTU;
 236                         else
 237                                 goto out;
 238                 }
 239         }
 240 #endif
 241
 242         __skb_pull(skb, tunnel_hdr_len);
 243         tnl_frag_needed(vport, mutable, skb, mtu, key);
 244         __skb_push(skb, tunnel_hdr_len);
 245
 246 out:
 247         skb_set_mac_header(skb, orig_mac_header);
 248         skb_set_network_header(skb, orig_nw_header);
 249         skb->protocol = htons(ETH_P_IP);
 250 }
 251
 252 static bool check_checksum(struct sk_buff *skb)
 253 {
 254         struct iphdr *iph = ip_hdr(skb);
 255         struct gre_base_hdr *greh = (struct gre_base_hdr *)(iph + 1);
 256         __sum16 csum = 0;
 257
 258         if (greh->flags & GRE_CSUM) {
 259                 switch (skb->ip_summed) {
 260                 case CHECKSUM_COMPLETE:
 261                         csum = csum_fold(skb->csum);
 262
 263                         if (!csum)
 264                                 break;
 265                         /* Fall through. */
 266
 267                 case CHECKSUM_NONE:
 268                         skb->csum = 0;
 269                         csum = __skb_checksum_complete(skb);
 270                         skb->ip_summed = CHECKSUM_COMPLETE;
 271                         break;
 272                 }
 273         }
 274
 275         return (csum == 0);
 276 }
 277
 278 /* Called with rcu_read_lock and BH disabled. */
 279 static int gre_rcv(struct sk_buff *skb)
 280 {
 281         struct vport *vport;
 282         const struct tnl_mutable_config *mutable;
 283         int hdr_len;
 284         struct iphdr *iph;
 285         __be16 flags;
 286         __be32 key;
 287
 288         if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr) + ETH_HLEN)))
 289                 goto error;
 290
 291         if (unlikely(!check_checksum(skb)))
 292                 goto error;
 293
 294         hdr_len = parse_header(ip_hdr(skb), &flags, &key);
 295         if (unlikely(hdr_len < 0))
 296                 goto error;
 297
 298         if (unlikely(!pskb_may_pull(skb, hdr_len + ETH_HLEN)))
 299                 goto error;
 300
 301         iph = ip_hdr(skb);
 302         vport = tnl_find_port(iph->daddr, iph->saddr, key,
 303                               TNL_T_PROTO_GRE | TNL_T_KEY_EITHER, &mutable);
 304         if (unlikely(!vport)) {
 305                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
 306                 goto error;
 307         }
 308
 309         if (mutable->port_config.flags & TNL_F_IN_KEY_MATCH)
 310                 OVS_CB(skb)->tun_id = key;
 311         else
 312                 OVS_CB(skb)->tun_id = 0;
 313
 314         __skb_pull(skb, hdr_len);
 315         skb_postpull_rcsum(skb, skb_transport_header(skb), hdr_len + ETH_HLEN);
 316
 317         tnl_rcv(vport, skb);
 318         return 0;
 319
 320 error:
 321         kfree_skb(skb);
 322         return 0;
 323 }
 324
 325 struct tnl_ops gre_tnl_ops = {
 326         .tunnel_type    = TNL_T_PROTO_GRE,
 327         .ipproto        = IPPROTO_GRE,
 328         .hdr_len        = gre_hdr_len,
 329         .build_header   = gre_build_header,
 330 };
 331
 332 static struct vport *gre_create(const char *name, const void __user *config)
 333 {
 334         return tnl_create(name, config, &gre_vport_ops, &gre_tnl_ops);
 335 }
 336
 337 static struct net_protocol gre_protocol_handlers = {
 338         .handler        =       gre_rcv,
 339         .err_handler    =       gre_err,
 340 };
 341
 342 static int gre_init(void)
 343 {
 344         int err;
 345
 346         err = inet_add_protocol(&gre_protocol_handlers, IPPROTO_GRE);
 347         if (err) {
 348                 printk(KERN_WARNING "openvswitch: cannot register gre protocol handler\n");
 349                 goto out;
 350         }
 351
 352         err = tnl_init();
 353
 354 out:
 355         return err;
 356 }
 357
 358 static void gre_exit(void)
 359 {
 360         tnl_exit();
 361         inet_del_protocol(&gre_protocol_handlers, IPPROTO_GRE);
 362 }
 363
 364 struct vport_ops gre_vport_ops = {
 365         .type           = "gre",
 366         .flags          = VPORT_F_GEN_STATS | VPORT_F_TUN_ID,
 367         .init           = gre_init,
 368         .exit           = gre_exit,
 369         .create         = gre_create,
 370         .modify         = tnl_modify,
 371         .destroy        = tnl_destroy,
 372         .set_mtu        = tnl_set_mtu,
 373         .set_addr       = tnl_set_addr,
 374         .get_name       = tnl_get_name,
 375         .get_addr       = tnl_get_addr,
 376         .get_dev_flags  = vport_gen_get_dev_flags,
 377         .is_running     = vport_gen_is_running,
 378         .get_operstate  = vport_gen_get_operstate,
 379         .get_mtu        = tnl_get_mtu,
 380         .send           = tnl_send,
 381 };