net/ipv4/ipcomp.c

   1 /*
   2  * IP Payload Compression Protocol (IPComp) - RFC3173.
   3  *
   4  * Copyright (c) 2003 James Morris <jmorris@intercode.com.au>
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the Free
   8  * Software Foundation; either version 2 of the License, or (at your option)
   9  * any later version.
  10  *
  11  * Todo:
  12  *   - Tunable compression parameters.
  13  *   - Compression stats.
  14  *   - Adaptive compression.
  15  */
  16 #include <linux/config.h>
  17 #include <linux/module.h>
  18 #include <asm/scatterlist.h>
  19 #include <asm/semaphore.h>
  20 #include <linux/crypto.h>
  21 #include <linux/pfkeyv2.h>
  22 #include <linux/percpu.h>
  23 #include <linux/smp.h>
  24 #include <linux/list.h>
  25 #include <linux/vmalloc.h>
  26 #include <linux/rtnetlink.h>
  27 #include <linux/mutex.h>
  28 #include <net/ip.h>
  29 #include <net/xfrm.h>
  30 #include <net/icmp.h>
  31 #include <net/ipcomp.h>
  32 #include <net/protocol.h>
  33
  34 struct ipcomp_tfms {
  35         struct list_head list;
  36         struct crypto_tfm **tfms;
  37         int users;
  38 };
  39
  40 static DEFINE_MUTEX(ipcomp_resource_mutex);
  41 static void **ipcomp_scratches;
  42 static int ipcomp_scratch_users;
  43 static LIST_HEAD(ipcomp_tfms_list);
  44
  45 static int ipcomp_decompress(struct xfrm_state *x, struct sk_buff *skb)
  46 {
  47         int err, plen, dlen;
  48         struct iphdr *iph;
  49         struct ipcomp_data *ipcd = x->data;
  50         u8 *start, *scratch;
  51         struct crypto_tfm *tfm;
  52         int cpu;
  53
  54         plen = skb->len;
  55         dlen = IPCOMP_SCRATCH_SIZE;
  56         start = skb->data;
  57
  58         cpu = get_cpu();
  59         scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
  60         tfm = *per_cpu_ptr(ipcd->tfms, cpu);
  61
  62         err = crypto_comp_decompress(tfm, start, plen, scratch, &dlen);
  63         if (err)
  64                 goto out;
  65
  66         if (dlen < (plen + sizeof(struct ip_comp_hdr))) {
  67                 err = -EINVAL;
  68                 goto out;
  69         }
  70
  71         err = pskb_expand_head(skb, 0, dlen - plen, GFP_ATOMIC);
  72         if (err)
  73                 goto out;
  74
  75         skb_put(skb, dlen - plen);
  76         memcpy(skb->data, scratch, dlen);
  77         iph = skb->nh.iph;
  78         iph->tot_len = htons(dlen + iph->ihl * 4);
  79 out:
  80         put_cpu();
  81         return err;
  82 }
  83
  84 static int ipcomp_input(struct xfrm_state *x,
  85                         struct xfrm_decap_state *decap, struct sk_buff *skb)
  86 {
  87         u8 nexthdr;
  88         int err = 0;
  89         struct iphdr *iph;
  90         union {
  91                 struct iphdr    iph;
  92                 char            buf[60];
  93         } tmp_iph;
  94
  95
  96         if ((skb_is_nonlinear(skb) || skb_cloned(skb)) &&
  97             skb_linearize(skb, GFP_ATOMIC) != 0) {
  98                 err = -ENOMEM;
  99                 goto out;
 100         }
 101
 102         skb->ip_summed = CHECKSUM_NONE;
 103
 104         /* Remove ipcomp header and decompress original payload */
 105         iph = skb->nh.iph;
 106         memcpy(&tmp_iph, iph, iph->ihl * 4);
 107         nexthdr = *(u8 *)skb->data;
 108         skb_pull(skb, sizeof(struct ip_comp_hdr));
 109         skb->nh.raw += sizeof(struct ip_comp_hdr);
 110         memcpy(skb->nh.raw, &tmp_iph, tmp_iph.iph.ihl * 4);
 111         iph = skb->nh.iph;
 112         iph->tot_len = htons(ntohs(iph->tot_len) - sizeof(struct ip_comp_hdr));
 113         iph->protocol = nexthdr;
 114         skb->h.raw = skb->data;
 115         err = ipcomp_decompress(x, skb);
 116
 117 out:
 118         return err;
 119 }
 120
 121 static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb)
 122 {
 123         int err, plen, dlen, ihlen;
 124         struct iphdr *iph = skb->nh.iph;
 125         struct ipcomp_data *ipcd = x->data;
 126         u8 *start, *scratch;
 127         struct crypto_tfm *tfm;
 128         int cpu;
 129
 130         ihlen = iph->ihl * 4;
 131         plen = skb->len - ihlen;
 132         dlen = IPCOMP_SCRATCH_SIZE;
 133         start = skb->data + ihlen;
 134
 135         cpu = get_cpu();
 136         scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
 137         tfm = *per_cpu_ptr(ipcd->tfms, cpu);
 138
 139         err = crypto_comp_compress(tfm, start, plen, scratch, &dlen);
 140         if (err)
 141                 goto out;
 142
 143         if ((dlen + sizeof(struct ip_comp_hdr)) >= plen) {
 144                 err = -EMSGSIZE;
 145                 goto out;
 146         }
 147
 148         memcpy(start + sizeof(struct ip_comp_hdr), scratch, dlen);
 149         put_cpu();
 150
 151         pskb_trim(skb, ihlen + dlen + sizeof(struct ip_comp_hdr));
 152         return 0;
 153
 154 out:
 155         put_cpu();
 156         return err;
 157 }
 158
 159 static int ipcomp_output(struct xfrm_state *x, struct sk_buff *skb)
 160 {
 161         int err;
 162         struct iphdr *iph;
 163         struct ip_comp_hdr *ipch;
 164         struct ipcomp_data *ipcd = x->data;
 165         int hdr_len = 0;
 166
 167         iph = skb->nh.iph;
 168         iph->tot_len = htons(skb->len);
 169         hdr_len = iph->ihl * 4;
 170         if ((skb->len - hdr_len) < ipcd->threshold) {
 171                 /* Don't bother compressing */
 172                 goto out_ok;
 173         }
 174
 175         if ((skb_is_nonlinear(skb) || skb_cloned(skb)) &&
 176             skb_linearize(skb, GFP_ATOMIC) != 0) {
 177                 goto out_ok;
 178         }
 179
 180         err = ipcomp_compress(x, skb);
 181         iph = skb->nh.iph;
 182
 183         if (err) {
 184                 goto out_ok;
 185         }
 186
 187         /* Install ipcomp header, convert into ipcomp datagram. */
 188         iph->tot_len = htons(skb->len);
 189         ipch = (struct ip_comp_hdr *)((char *)iph + iph->ihl * 4);
 190         ipch->nexthdr = iph->protocol;
 191         ipch->flags = 0;
 192         ipch->cpi = htons((u16 )ntohl(x->id.spi));
 193         iph->protocol = IPPROTO_COMP;
 194         ip_send_check(iph);
 195         return 0;
 196
 197 out_ok:
 198         if (x->props.mode)
 199                 ip_send_check(iph);
 200         return 0;
 201 }
 202
 203 static void ipcomp4_err(struct sk_buff *skb, u32 info)
 204 {
 205         u32 spi;
 206         struct iphdr *iph = (struct iphdr *)skb->data;
 207         struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
 208         struct xfrm_state *x;
 209
 210         if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
 211             skb->h.icmph->code != ICMP_FRAG_NEEDED)
 212                 return;
 213
 214         spi = ntohl(ntohs(ipch->cpi));
 215         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr,
 216                               spi, IPPROTO_COMP, AF_INET);
 217         if (!x)
 218                 return;
 219         NETDEBUG(KERN_DEBUG "pmtu discovery on SA IPCOMP/%08x/%u.%u.%u.%u\n",
 220                  spi, NIPQUAD(iph->daddr));
 221         xfrm_state_put(x);
 222 }
 223
 224 /* We always hold one tunnel user reference to indicate a tunnel */
 225 static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
 226 {
 227         struct xfrm_state *t;
 228
 229         t = xfrm_state_alloc();
 230         if (t == NULL)
 231                 goto out;
 232
 233         t->id.proto = IPPROTO_IPIP;
 234         t->id.spi = x->props.saddr.a4;
 235         t->id.daddr.a4 = x->id.daddr.a4;
 236         memcpy(&t->sel, &x->sel, sizeof(t->sel));
 237         t->props.family = AF_INET;
 238         t->props.mode = 1;
 239         t->props.saddr.a4 = x->props.saddr.a4;
 240         t->props.flags = x->props.flags;
 241
 242         if (xfrm_init_state(t))
 243                 goto error;
 244
 245         atomic_set(&t->tunnel_users, 1);
 246 out:
 247         return t;
 248
 249 error:
 250         t->km.state = XFRM_STATE_DEAD;
 251         xfrm_state_put(t);
 252         t = NULL;
 253         goto out;
 254 }
 255
 256 /*
 257  * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
 258  * always incremented on success.
 259  */
 260 static int ipcomp_tunnel_attach(struct xfrm_state *x)
 261 {
 262         int err = 0;
 263         struct xfrm_state *t;
 264
 265         t = xfrm_state_lookup((xfrm_address_t *)&x->id.daddr.a4,
 266                               x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
 267         if (!t) {
 268                 t = ipcomp_tunnel_create(x);
 269                 if (!t) {
 270                         err = -EINVAL;
 271                         goto out;
 272                 }
 273                 xfrm_state_insert(t);
 274                 xfrm_state_hold(t);
 275         }
 276         x->tunnel = t;
 277         atomic_inc(&t->tunnel_users);
 278 out:
 279         return err;
 280 }
 281
 282 static void ipcomp_free_scratches(void)
 283 {
 284         int i;
 285         void **scratches;
 286
 287         if (--ipcomp_scratch_users)
 288                 return;
 289
 290         scratches = ipcomp_scratches;
 291         if (!scratches)
 292                 return;
 293
 294         for_each_cpu(i) {
 295                 void *scratch = *per_cpu_ptr(scratches, i);
 296                 if (scratch)
 297                         vfree(scratch);
 298         }
 299
 300         free_percpu(scratches);
 301 }
 302
 303 static void **ipcomp_alloc_scratches(void)
 304 {
 305         int i;
 306         void **scratches;
 307
 308         if (ipcomp_scratch_users++)
 309                 return ipcomp_scratches;
 310
 311         scratches = alloc_percpu(void *);
 312         if (!scratches)
 313                 return NULL;
 314
 315         ipcomp_scratches = scratches;
 316
 317         for_each_cpu(i) {
 318                 void *scratch = vmalloc(IPCOMP_SCRATCH_SIZE);
 319                 if (!scratch)
 320                         return NULL;
 321                 *per_cpu_ptr(scratches, i) = scratch;
 322         }
 323
 324         return scratches;
 325 }
 326
 327 static void ipcomp_free_tfms(struct crypto_tfm **tfms)
 328 {
 329         struct ipcomp_tfms *pos;
 330         int cpu;
 331
 332         list_for_each_entry(pos, &ipcomp_tfms_list, list) {
 333                 if (pos->tfms == tfms)
 334                         break;
 335         }
 336
 337         BUG_TRAP(pos);
 338
 339         if (--pos->users)
 340                 return;
 341
 342         list_del(&pos->list);
 343         kfree(pos);
 344
 345         if (!tfms)
 346                 return;
 347
 348         for_each_cpu(cpu) {
 349                 struct crypto_tfm *tfm = *per_cpu_ptr(tfms, cpu);
 350                 crypto_free_tfm(tfm);
 351         }
 352         free_percpu(tfms);
 353 }
 354
 355 static struct crypto_tfm **ipcomp_alloc_tfms(const char *alg_name)
 356 {
 357         struct ipcomp_tfms *pos;
 358         struct crypto_tfm **tfms;
 359         int cpu;
 360
 361         /* This can be any valid CPU ID so we don't need locking. */
 362         cpu = raw_smp_processor_id();
 363
 364         list_for_each_entry(pos, &ipcomp_tfms_list, list) {
 365                 struct crypto_tfm *tfm;
 366
 367                 tfms = pos->tfms;
 368                 tfm = *per_cpu_ptr(tfms, cpu);
 369
 370                 if (!strcmp(crypto_tfm_alg_name(tfm), alg_name)) {
 371                         pos->users++;
 372                         return tfms;
 373                 }
 374         }
 375
 376         pos = kmalloc(sizeof(*pos), GFP_KERNEL);
 377         if (!pos)
 378                 return NULL;
 379
 380         pos->users = 1;
 381         INIT_LIST_HEAD(&pos->list);
 382         list_add(&pos->list, &ipcomp_tfms_list);
 383
 384         pos->tfms = tfms = alloc_percpu(struct crypto_tfm *);
 385         if (!tfms)
 386                 goto error;
 387
 388         for_each_cpu(cpu) {
 389                 struct crypto_tfm *tfm = crypto_alloc_tfm(alg_name, 0);
 390                 if (!tfm)
 391                         goto error;
 392                 *per_cpu_ptr(tfms, cpu) = tfm;
 393         }
 394
 395         return tfms;
 396
 397 error:
 398         ipcomp_free_tfms(tfms);
 399         return NULL;
 400 }
 401
 402 static void ipcomp_free_data(struct ipcomp_data *ipcd)
 403 {
 404         if (ipcd->tfms)
 405                 ipcomp_free_tfms(ipcd->tfms);
 406         ipcomp_free_scratches();
 407 }
 408
 409 static void ipcomp_destroy(struct xfrm_state *x)
 410 {
 411         struct ipcomp_data *ipcd = x->data;
 412         if (!ipcd)
 413                 return;
 414         xfrm_state_delete_tunnel(x);
 415         mutex_lock(&ipcomp_resource_mutex);
 416         ipcomp_free_data(ipcd);
 417         mutex_unlock(&ipcomp_resource_mutex);
 418         kfree(ipcd);
 419 }
 420
 421 static int ipcomp_init_state(struct xfrm_state *x)
 422 {
 423         int err;
 424         struct ipcomp_data *ipcd;
 425         struct xfrm_algo_desc *calg_desc;
 426
 427         err = -EINVAL;
 428         if (!x->calg)
 429                 goto out;
 430
 431         if (x->encap)
 432                 goto out;
 433
 434         err = -ENOMEM;
 435         ipcd = kmalloc(sizeof(*ipcd), GFP_KERNEL);
 436         if (!ipcd)
 437                 goto out;
 438
 439         memset(ipcd, 0, sizeof(*ipcd));
 440         x->props.header_len = 0;
 441         if (x->props.mode)
 442                 x->props.header_len += sizeof(struct iphdr);
 443
 444         mutex_lock(&ipcomp_resource_mutex);
 445         if (!ipcomp_alloc_scratches())
 446                 goto error;
 447
 448         ipcd->tfms = ipcomp_alloc_tfms(x->calg->alg_name);
 449         if (!ipcd->tfms)
 450                 goto error;
 451         mutex_unlock(&ipcomp_resource_mutex);
 452
 453         if (x->props.mode) {
 454                 err = ipcomp_tunnel_attach(x);
 455                 if (err)
 456                         goto error_tunnel;
 457         }
 458
 459         calg_desc = xfrm_calg_get_byname(x->calg->alg_name, 0);
 460         BUG_ON(!calg_desc);
 461         ipcd->threshold = calg_desc->uinfo.comp.threshold;
 462         x->data = ipcd;
 463         err = 0;
 464 out:
 465         return err;
 466
 467 error_tunnel:
 468         mutex_lock(&ipcomp_resource_mutex);
 469 error:
 470         ipcomp_free_data(ipcd);
 471         mutex_unlock(&ipcomp_resource_mutex);
 472         kfree(ipcd);
 473         goto out;
 474 }
 475
 476 static struct xfrm_type ipcomp_type = {
 477         .description    = "IPCOMP4",
 478         .owner          = THIS_MODULE,
 479         .proto          = IPPROTO_COMP,
 480         .init_state     = ipcomp_init_state,
 481         .destructor     = ipcomp_destroy,
 482         .input          = ipcomp_input,
 483         .output         = ipcomp_output
 484 };
 485
 486 static struct net_protocol ipcomp4_protocol = {
 487         .handler        =       xfrm4_rcv,
 488         .err_handler    =       ipcomp4_err,
 489         .no_policy      =       1,
 490 };
 491
 492 static int __init ipcomp4_init(void)
 493 {
 494         if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
 495                 printk(KERN_INFO "ipcomp init: can't add xfrm type\n");
 496                 return -EAGAIN;
 497         }
 498         if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
 499                 printk(KERN_INFO "ipcomp init: can't add protocol\n");
 500                 xfrm_unregister_type(&ipcomp_type, AF_INET);
 501                 return -EAGAIN;
 502         }
 503         return 0;
 504 }
 505
 506 static void __exit ipcomp4_fini(void)
 507 {
 508         if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
 509                 printk(KERN_INFO "ip ipcomp close: can't remove protocol\n");
 510         if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
 511                 printk(KERN_INFO "ip ipcomp close: can't remove xfrm type\n");
 512 }
 513
 514 module_init(ipcomp4_init);
 515 module_exit(ipcomp4_fini);
 516
 517 MODULE_LICENSE("GPL");
 518 MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) - RFC3173");
 519 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
 520