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