datapath/forward.c

   1 /*
   2  * Distributed under the terms of the GNU GPL version 2.
   3  * Copyright (c) 2007, 2008 The Board of Trustees of The Leland
   4  * Stanford Junior University
   5  */
   6
   7 #include <linux/if_ether.h>
   8 #include <linux/if_vlan.h>
   9 #include <linux/in.h>
  10 #include <linux/ip.h>
  11 #include <linux/tcp.h>
  12 #include <linux/udp.h>
  13 #include <linux/in6.h>
  14 #include <asm/uaccess.h>
  15 #include <linux/types.h>
  16 #include <net/checksum.h>
  17 #include "forward.h"
  18 #include "datapath.h"
  19 #include "chain.h"
  20 #include "flow.h"
  21
  22 /* FIXME: do we need to use GFP_ATOMIC everywhere here? */
  23
  24 static int make_writable(struct sk_buff **);
  25
  26 static struct sk_buff *retrieve_skb(uint32_t id);
  27 static void discard_skb(uint32_t id);
  28
  29 /* 'skb' was received on 'in_port', a physical switch port between 0 and
  30  * OFPP_MAX.  Process it according to 'chain'. */
  31 void fwd_port_input(struct sw_chain *chain, struct sk_buff *skb, int in_port)
  32 {
  33         struct sw_flow_key key;
  34         struct sw_flow *flow;
  35
  36         flow_extract(skb, in_port, &key);
  37         flow = chain_lookup(chain, &key);
  38         if (likely(flow != NULL)) {
  39                 flow_used(flow, skb);
  40                 execute_actions(chain->dp, skb, &key,
  41                                 flow->actions, flow->n_actions);
  42         } else {
  43                 dp_output_control(chain->dp, skb, fwd_save_skb(skb),
  44                                   chain->dp->miss_send_len,
  45                                   OFPR_NO_MATCH);
  46         }
  47 }
  48
  49 static int do_output(struct datapath *dp, struct sk_buff *skb, size_t max_len,
  50                         int out_port)
  51 {
  52         if (!skb)
  53                 return -ENOMEM;
  54         return (likely(out_port != OFPP_CONTROLLER)
  55                 ? dp_output_port(dp, skb, out_port)
  56                 : dp_output_control(dp, skb, fwd_save_skb(skb),
  57                                          max_len, OFPR_ACTION));
  58 }
  59
  60 void execute_actions(struct datapath *dp, struct sk_buff *skb,
  61                                 const struct sw_flow_key *key,
  62                                 const struct ofp_action *actions, int n_actions)
  63 {
  64         /* Every output action needs a separate clone of 'skb', but the common
  65          * case is just a single output action, so that doing a clone and
  66          * then freeing the original skbuff is wasteful.  So the following code
  67          * is slightly obscure just to avoid that. */
  68         int prev_port;
  69         size_t max_len=0;        /* Initialze to make compiler happy */
  70         uint16_t eth_proto;
  71         int i;
  72
  73         prev_port = -1;
  74         eth_proto = ntohs(key->dl_type);
  75
  76         for (i = 0; i < n_actions; i++) {
  77                 const struct ofp_action *a = &actions[i];
  78
  79                 if (prev_port != -1) {
  80                         do_output(dp, skb_clone(skb, GFP_ATOMIC),
  81                                   max_len, prev_port);
  82                         prev_port = -1;
  83                 }
  84
  85                 if (likely(a->type == htons(OFPAT_OUTPUT))) {
  86                         prev_port = ntohs(a->arg.output.port);
  87                         max_len = ntohs(a->arg.output.max_len);
  88                 } else {
  89                         if (!make_writable(&skb)) {
  90                                 printk("make_writable failed\n");
  91                                 break;
  92                         }
  93                         skb = execute_setter(skb, eth_proto, key, a);
  94                 }
  95         }
  96         if (prev_port != -1)
  97                 do_output(dp, skb, max_len, prev_port);
  98         else
  99                 kfree_skb(skb);
 100 }
 101
 102 /* Updates 'sum', which is a field in 'skb''s data, given that a 4-byte field
 103  * covered by the sum has been changed from 'from' to 'to'.  If set,
 104  * 'pseudohdr' indicates that the field is in the TCP or UDP pseudo-header.
 105  * Based on nf_proto_csum_replace4. */
 106 static void update_csum(__sum16 *sum, struct sk_buff *skb,
 107                         __be32 from, __be32 to, int pseudohdr)
 108 {
 109         __be32 diff[] = { ~from, to };
 110         if (skb->ip_summed != CHECKSUM_PARTIAL) {
 111                 *sum = csum_fold(csum_partial((char *)diff, sizeof(diff),
 112                                 ~csum_unfold(*sum)));
 113                 if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr)
 114                         skb->csum = ~csum_partial((char *)diff, sizeof(diff),
 115                                                 ~skb->csum);
 116         } else if (pseudohdr)
 117                 *sum = ~csum_fold(csum_partial((char *)diff, sizeof(diff),
 118                                 csum_unfold(*sum)));
 119 }
 120
 121 static void modify_nh(struct sk_buff *skb, uint16_t eth_proto,
 122                         uint8_t nw_proto, const struct ofp_action *a)
 123 {
 124         if (eth_proto == ETH_P_IP) {
 125                 struct iphdr *nh = ip_hdr(skb);
 126                 uint32_t new, *field;
 127
 128                 new = a->arg.nw_addr;
 129
 130                 if (a->type == htons(OFPAT_SET_NW_SRC))
 131                         field = &nh->saddr;
 132                 else
 133                         field = &nh->daddr;
 134
 135                 if (nw_proto == IPPROTO_TCP) {
 136                         struct tcphdr *th = tcp_hdr(skb);
 137                         update_csum(&th->check, skb, *field, new, 1);
 138                 } else if (nw_proto == IPPROTO_UDP) {
 139                         struct udphdr *th = udp_hdr(skb);
 140                         update_csum(&th->check, skb, *field, new, 1);
 141                 }
 142                 update_csum(&nh->check, skb, *field, new, 0);
 143                 *field = new;
 144         }
 145 }
 146
 147 static void modify_th(struct sk_buff *skb, uint16_t eth_proto,
 148                         uint8_t nw_proto, const struct ofp_action *a)
 149 {
 150         if (eth_proto == ETH_P_IP) {
 151                 uint16_t new, *field;
 152
 153                 new = a->arg.tp;
 154
 155                 if (nw_proto == IPPROTO_TCP) {
 156                         struct tcphdr *th = tcp_hdr(skb);
 157
 158                         if (a->type == htons(OFPAT_SET_TP_SRC))
 159                                 field = &th->source;
 160                         else
 161                                 field = &th->dest;
 162
 163                         update_csum(&th->check, skb, *field, new, 1);
 164                         *field = new;
 165                 } else if (nw_proto == IPPROTO_UDP) {
 166                         struct udphdr *th = udp_hdr(skb);
 167
 168                         if (a->type == htons(OFPAT_SET_TP_SRC))
 169                                 field = &th->source;
 170                         else
 171                                 field = &th->dest;
 172
 173                         update_csum(&th->check, skb, *field, new, 1);
 174                         *field = new;
 175                 }
 176         }
 177 }
 178
 179 static struct sk_buff *vlan_pull_tag(struct sk_buff *skb)
 180 {
 181         struct vlan_ethhdr *vh = vlan_eth_hdr(skb);
 182         struct ethhdr *eh;
 183
 184
 185         /* Verify we were given a vlan packet */
 186         if (vh->h_vlan_proto != htons(ETH_P_8021Q))
 187                 return skb;
 188
 189         memmove(skb->data + VLAN_HLEN, skb->data, 2 * VLAN_ETH_ALEN);
 190
 191         eh = (struct ethhdr *)skb_pull(skb, VLAN_HLEN);
 192
 193         skb->protocol = eh->h_proto;
 194         skb->mac_header += VLAN_HLEN;
 195
 196         return skb;
 197 }
 198
 199 static struct sk_buff *modify_vlan(struct sk_buff *skb,
 200                 const struct sw_flow_key *key, const struct ofp_action *a)
 201 {
 202         uint16_t new_id = a->arg.vlan_id;
 203
 204         if (new_id != OFP_VLAN_NONE) {
 205                 if (key->dl_vlan != htons(OFP_VLAN_NONE)) {
 206                         /* Modify vlan id, but maintain other TCI values */
 207                         struct vlan_ethhdr *vh = vlan_eth_hdr(skb);
 208                         vh->h_vlan_TCI = (vh->h_vlan_TCI
 209                                         & ~(htons(VLAN_VID_MASK))) | htons(new_id);
 210                 } else  {
 211                         /* Add vlan header */
 212                         skb = vlan_put_tag(skb, new_id);
 213                 }
 214         } else  {
 215                 /* Remove an existing vlan header if it exists */
 216                 vlan_pull_tag(skb);
 217         }
 218
 219         return skb;
 220 }
 221
 222 struct sk_buff *execute_setter(struct sk_buff *skb, uint16_t eth_proto,
 223                         const struct sw_flow_key *key, const struct ofp_action *a)
 224 {
 225         switch (ntohs(a->type)) {
 226         case OFPAT_SET_DL_VLAN:
 227                 skb = modify_vlan(skb, key, a);
 228                 break;
 229
 230         case OFPAT_SET_DL_SRC: {
 231                 struct ethhdr *eh = eth_hdr(skb);
 232                 memcpy(eh->h_source, a->arg.dl_addr, sizeof eh->h_source);
 233                 break;
 234         }
 235         case OFPAT_SET_DL_DST: {
 236                 struct ethhdr *eh = eth_hdr(skb);
 237                 memcpy(eh->h_dest, a->arg.dl_addr, sizeof eh->h_dest);
 238                 break;
 239         }
 240
 241         case OFPAT_SET_NW_SRC:
 242         case OFPAT_SET_NW_DST:
 243                 modify_nh(skb, eth_proto, key->nw_proto, a);
 244                 break;
 245
 246         case OFPAT_SET_TP_SRC:
 247         case OFPAT_SET_TP_DST:
 248                 modify_th(skb, eth_proto, key->nw_proto, a);
 249                 break;
 250
 251         default:
 252                 if (net_ratelimit())
 253                         printk("execute_setter: unknown action: %d\n", ntohs(a->type));
 254         }
 255
 256         return skb;
 257 }
 258
 259 static int
 260 recv_features_request(struct sw_chain *chain, const struct sender *sender,
 261                       const void *msg)
 262 {
 263         return dp_send_features_reply(chain->dp, sender);
 264 }
 265
 266 static int
 267 recv_get_config_request(struct sw_chain *chain, const struct sender *sender,
 268                         const void *msg)
 269 {
 270         return dp_send_config_reply(chain->dp, sender);
 271 }
 272
 273 static int
 274 recv_set_config(struct sw_chain *chain, const struct sender *sender,
 275                 const void *msg)
 276 {
 277         const struct ofp_switch_config *osc = msg;
 278
 279         chain->dp->flags = ntohs(osc->flags);
 280         chain->dp->miss_send_len = ntohs(osc->miss_send_len);
 281
 282         return 0;
 283 }
 284
 285 static int
 286 recv_packet_out(struct sw_chain *chain, const struct sender *sender,
 287                 const void *msg)
 288 {
 289         const struct ofp_packet_out *opo = msg;
 290         struct sk_buff *skb;
 291         struct vlan_ethhdr *mac;
 292         int nh_ofs;
 293
 294         if (ntohl(opo->buffer_id) == (uint32_t) -1) {
 295                 int data_len = ntohs(opo->header.length) - sizeof *opo;
 296
 297                 /* FIXME: there is likely a way to reuse the data in msg. */
 298                 skb = alloc_skb(data_len, GFP_ATOMIC);
 299                 if (!skb)
 300                         return -ENOMEM;
 301
 302                 /* FIXME?  We don't reserve NET_IP_ALIGN or NET_SKB_PAD since
 303                  * we're just transmitting this raw without examining anything
 304                  * at those layers. */
 305                 memcpy(skb_put(skb, data_len), opo->u.data, data_len);
 306                 dp_set_origin(chain->dp, ntohs(opo->in_port), skb);
 307
 308                 skb_set_mac_header(skb, 0);
 309                 mac = vlan_eth_hdr(skb);
 310                 if (likely(mac->h_vlan_proto != htons(ETH_P_8021Q)))
 311                         nh_ofs = sizeof(struct ethhdr);
 312                 else
 313                         nh_ofs = sizeof(struct vlan_ethhdr);
 314                 skb_set_network_header(skb, nh_ofs);
 315
 316                 dp_output_port(chain->dp, skb, ntohs(opo->out_port));
 317         } else {
 318                 struct sw_flow_key key;
 319                 int n_acts;
 320
 321                 skb = retrieve_skb(ntohl(opo->buffer_id));
 322                 if (!skb)
 323                         return -ESRCH;
 324                 dp_set_origin(chain->dp, ntohs(opo->in_port), skb);
 325
 326                 n_acts = (ntohs(opo->header.length) - sizeof *opo)
 327                                 / sizeof *opo->u.actions;
 328                 flow_extract(skb, ntohs(opo->in_port), &key);
 329                 execute_actions(chain->dp, skb, &key, opo->u.actions, n_acts);
 330         }
 331         return 0;
 332 }
 333
 334 static int
 335 recv_port_mod(struct sw_chain *chain, const struct sender *sender,
 336               const void *msg)
 337 {
 338         const struct ofp_port_mod *opm = msg;
 339
 340         dp_update_port_flags(chain->dp, &opm->desc);
 341
 342         return 0;
 343 }
 344
 345 static int
 346 add_flow(struct sw_chain *chain, const struct ofp_flow_mod *ofm)
 347 {
 348         int error = -ENOMEM;
 349         int i;
 350         int n_acts;
 351         struct sw_flow *flow;
 352
 353
 354         /* To prevent loops, make sure there's no action to send to the
 355          * OFP_TABLE virtual port.
 356          */
 357         n_acts = (ntohs(ofm->header.length) - sizeof *ofm) / sizeof *ofm->actions;
 358         for (i=0; i<n_acts; i++) {
 359                 const struct ofp_action *a = &ofm->actions[i];
 360
 361                 if (a->type == htons(OFPAT_OUTPUT)
 362                                         && a->arg.output.port == htons(OFPP_TABLE)) {
 363                         /* xxx Send fancy new error message? */
 364                         goto error;
 365                 }
 366         }
 367
 368         /* Allocate memory. */
 369         flow = flow_alloc(n_acts, GFP_ATOMIC);
 370         if (flow == NULL)
 371                 goto error;
 372
 373         /* Fill out flow. */
 374         flow_extract_match(&flow->key, &ofm->match);
 375         flow->max_idle = ntohs(ofm->max_idle);
 376         flow->priority = flow->key.wildcards ? ntohs(ofm->priority) : -1;
 377         flow->timeout = jiffies + flow->max_idle * HZ;
 378         flow->n_actions = n_acts;
 379         flow->init_time = jiffies;
 380         flow->byte_count = 0;
 381         flow->packet_count = 0;
 382         atomic_set(&flow->deleted, 0);
 383         spin_lock_init(&flow->lock);
 384         memcpy(flow->actions, ofm->actions, n_acts * sizeof *flow->actions);
 385
 386         /* Act. */
 387         error = chain_insert(chain, flow);
 388         if (error)
 389                 goto error_free_flow;
 390         error = 0;
 391         if (ntohl(ofm->buffer_id) != (uint32_t) -1) {
 392                 struct sk_buff *skb = retrieve_skb(ntohl(ofm->buffer_id));
 393                 if (skb) {
 394                         struct sw_flow_key key;
 395                         flow_used(flow, skb);
 396                         flow_extract(skb, ntohs(ofm->match.in_port), &key);
 397                         execute_actions(chain->dp, skb, &key,
 398                                         ofm->actions, n_acts);
 399                 }
 400                 else
 401                         error = -ESRCH;
 402         }
 403         return error;
 404
 405 error_free_flow:
 406         flow_free(flow);
 407 error:
 408         if (ntohl(ofm->buffer_id) != (uint32_t) -1)
 409                 discard_skb(ntohl(ofm->buffer_id));
 410         return error;
 411 }
 412
 413 static int
 414 recv_flow(struct sw_chain *chain, const struct sender *sender, const void *msg)
 415 {
 416         const struct ofp_flow_mod *ofm = msg;
 417         uint16_t command = ntohs(ofm->command);
 418
 419         if (command == OFPFC_ADD) {
 420                 return add_flow(chain, ofm);
 421         }  else if (command == OFPFC_DELETE) {
 422                 struct sw_flow_key key;
 423                 flow_extract_match(&key, &ofm->match);
 424                 return chain_delete(chain, &key, 0, 0) ? 0 : -ESRCH;
 425         } else if (command == OFPFC_DELETE_STRICT) {
 426                 struct sw_flow_key key;
 427                 uint16_t priority;
 428                 flow_extract_match(&key, &ofm->match);
 429                 priority = key.wildcards ? ntohs(ofm->priority) : -1;
 430                 return chain_delete(chain, &key, priority, 1) ? 0 : -ESRCH;
 431         } else {
 432                 return -ENOTSUPP;
 433         }
 434 }
 435
 436 /* 'msg', which is 'length' bytes long, was received across Netlink from
 437  * 'sender'.  Apply it to 'chain'. */
 438 int
 439 fwd_control_input(struct sw_chain *chain, const struct sender *sender,
 440                   const void *msg, size_t length)
 441 {
 442
 443         struct openflow_packet {
 444                 size_t min_size;
 445                 int (*handler)(struct sw_chain *, const struct sender *,
 446                                const void *);
 447         };
 448
 449         static const struct openflow_packet packets[] = {
 450                 [OFPT_FEATURES_REQUEST] = {
 451                         sizeof (struct ofp_header),
 452                         recv_features_request,
 453                 },
 454                 [OFPT_GET_CONFIG_REQUEST] = {
 455                         sizeof (struct ofp_header),
 456                         recv_get_config_request,
 457                 },
 458                 [OFPT_SET_CONFIG] = {
 459                         sizeof (struct ofp_switch_config),
 460                         recv_set_config,
 461                 },
 462                 [OFPT_PACKET_OUT] = {
 463                         sizeof (struct ofp_packet_out),
 464                         recv_packet_out,
 465                 },
 466                 [OFPT_FLOW_MOD] = {
 467                         sizeof (struct ofp_flow_mod),
 468                         recv_flow,
 469                 },
 470                 [OFPT_PORT_MOD] = {
 471                         sizeof (struct ofp_port_mod),
 472                         recv_port_mod,
 473                 },
 474         };
 475
 476         const struct openflow_packet *pkt;
 477         struct ofp_header *oh;
 478
 479         oh = (struct ofp_header *) msg;
 480         if (oh->version != OFP_VERSION || oh->type >= ARRAY_SIZE(packets)
 481                 || ntohs(oh->length) > length)
 482                 return -EINVAL;
 483
 484         pkt = &packets[oh->type];
 485         if (!pkt->handler)
 486                 return -ENOSYS;
 487         if (length < pkt->min_size)
 488                 return -EFAULT;
 489
 490         return pkt->handler(chain, sender, msg);
 491 }
 492
 493 /* Packet buffering. */
 494
 495 #define OVERWRITE_SECS  1
 496 #define OVERWRITE_JIFFIES (OVERWRITE_SECS * HZ)
 497
 498 struct packet_buffer {
 499         struct sk_buff *skb;
 500         uint32_t cookie;
 501         unsigned long exp_jiffies;
 502 };
 503
 504 static struct packet_buffer buffers[N_PKT_BUFFERS];
 505 static unsigned int buffer_idx;
 506 static DEFINE_SPINLOCK(buffer_lock);
 507
 508 uint32_t fwd_save_skb(struct sk_buff *skb)
 509 {
 510         struct packet_buffer *p;
 511         unsigned long int flags;
 512         uint32_t id;
 513
 514         spin_lock_irqsave(&buffer_lock, flags);
 515         buffer_idx = (buffer_idx + 1) & PKT_BUFFER_MASK;
 516         p = &buffers[buffer_idx];
 517         if (p->skb) {
 518                 /* Don't buffer packet if existing entry is less than
 519                  * OVERWRITE_SECS old. */
 520                 if (time_before(jiffies, p->exp_jiffies)) {
 521                         spin_unlock_irqrestore(&buffer_lock, flags);
 522                         return -1;
 523                 } else
 524                         kfree_skb(p->skb);
 525         }
 526         /* Don't use maximum cookie value since the all-bits-1 id is
 527          * special. */
 528         if (++p->cookie >= (1u << PKT_COOKIE_BITS) - 1)
 529                 p->cookie = 0;
 530         skb_get(skb);
 531         p->skb = skb;
 532         p->exp_jiffies = jiffies + OVERWRITE_JIFFIES;
 533         id = buffer_idx | (p->cookie << PKT_BUFFER_BITS);
 534         spin_unlock_irqrestore(&buffer_lock, flags);
 535
 536         return id;
 537 }
 538
 539 static struct sk_buff *retrieve_skb(uint32_t id)
 540 {
 541         unsigned long int flags;
 542         struct sk_buff *skb = NULL;
 543         struct packet_buffer *p;
 544
 545         spin_lock_irqsave(&buffer_lock, flags);
 546         p = &buffers[id & PKT_BUFFER_MASK];
 547         if (p->cookie == id >> PKT_BUFFER_BITS) {
 548                 skb = p->skb;
 549                 p->skb = NULL;
 550         } else {
 551                 printk("cookie mismatch: %x != %x\n",
 552                                 id >> PKT_BUFFER_BITS, p->cookie);
 553         }
 554         spin_unlock_irqrestore(&buffer_lock, flags);
 555
 556         return skb;
 557 }
 558
 559 void fwd_discard_all(void)
 560 {
 561         unsigned long int flags;
 562         int i;
 563
 564         spin_lock_irqsave(&buffer_lock, flags);
 565         for (i = 0; i < N_PKT_BUFFERS; i++) {
 566                 kfree_skb(buffers[i].skb);
 567                 buffers[i].skb = NULL;
 568         }
 569         spin_unlock_irqrestore(&buffer_lock, flags);
 570 }
 571
 572 static void discard_skb(uint32_t id)
 573 {
 574         unsigned long int flags;
 575         struct packet_buffer *p;
 576
 577         spin_lock_irqsave(&buffer_lock, flags);
 578         p = &buffers[id & PKT_BUFFER_MASK];
 579         if (p->cookie == id >> PKT_BUFFER_BITS) {
 580                 kfree_skb(p->skb);
 581                 p->skb = NULL;
 582         }
 583         spin_unlock_irqrestore(&buffer_lock, flags);
 584 }
 585
 586 void fwd_exit(void)
 587 {
 588         fwd_discard_all();
 589 }
 590
 591 /* Utility functions. */
 592
 593 /* Makes '*pskb' writable, possibly copying it and setting '*pskb' to point to
 594  * the copy.
 595  * Returns 1 if successful, 0 on failure. */
 596 static int
 597 make_writable(struct sk_buff **pskb)
 598 {
 599         /* Based on skb_make_writable() in net/netfilter/core.c. */
 600         struct sk_buff *nskb;
 601
 602         /* Not exclusive use of packet?  Must copy. */
 603         if (skb_shared(*pskb) || skb_cloned(*pskb))
 604                 goto copy_skb;
 605
 606         return pskb_may_pull(*pskb, 64); /* FIXME? */
 607
 608 copy_skb:
 609         nskb = skb_copy(*pskb, GFP_ATOMIC);
 610         if (!nskb)
 611                 return 0;
 612         BUG_ON(skb_is_nonlinear(nskb));
 613
 614         /* Rest of kernel will get very unhappy if we pass it a
 615            suddenly-orphaned skbuff */
 616         if ((*pskb)->sk)
 617                 skb_set_owner_w(nskb, (*pskb)->sk);
 618         kfree_skb(*pskb);
 619         *pskb = nskb;
 620         return 1;
 621 }