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