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