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_comp **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         struct ipcomp_data *ipcd = x->data;
  47         const int plen = skb->len;
  48         int dlen = IPCOMP_SCRATCH_SIZE;
  49         const u8 *start = skb->data;
  50         const int cpu = get_cpu();
  51         u8 *scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
  52         struct crypto_comp *tfm = *per_cpu_ptr(ipcd->tfms, cpu);
  53         int err = crypto_comp_decompress(tfm, start, plen, scratch, &dlen);
  54
  55         if (err)
  56                 goto out;
  57
  58         if (dlen < (plen + sizeof(struct ip_comp_hdr))) {
  59                 err = -EINVAL;
  60                 goto out;
  61         }
  62
  63         err = pskb_expand_head(skb, 0, dlen - plen, GFP_ATOMIC);
  64         if (err)
  65                 goto out;
  66
  67         skb->truesize += dlen - plen;
  68         __skb_put(skb, dlen - plen);
  69         skb_copy_to_linear_data(skb, scratch, dlen);
  70 out:
  71         put_cpu();
  72         return err;
  73 }
  74
  75 static int ipcomp_input(struct xfrm_state *x, struct sk_buff *skb)
  76 {
  77         int err = -ENOMEM;
  78         struct iphdr *iph;
  79         struct ip_comp_hdr *ipch;
  80
  81         if (skb_linearize_cow(skb))
  82                 goto out;
  83
  84         skb->ip_summed = CHECKSUM_NONE;
  85
  86         /* Remove ipcomp header and decompress original payload */
  87         iph = ip_hdr(skb);
  88         ipch = (void *)skb->data;
  89         iph->protocol = ipch->nexthdr;
  90         skb->transport_header = skb->network_header + sizeof(*ipch);
  91         __skb_pull(skb, sizeof(*ipch));
  92         err = ipcomp_decompress(x, skb);
  93
  94 out:
  95         return err;
  96 }
  97
  98 static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb)
  99 {
 100         struct ipcomp_data *ipcd = x->data;
 101         const int ihlen = ip_hdrlen(skb);
 102         const int plen = skb->len - ihlen;
 103         int dlen = IPCOMP_SCRATCH_SIZE;
 104         u8 *start = skb->data + ihlen;
 105         const int cpu = get_cpu();
 106         u8 *scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
 107         struct crypto_comp *tfm = *per_cpu_ptr(ipcd->tfms, cpu);
 108         int err = crypto_comp_compress(tfm, start, plen, scratch, &dlen);
 109
 110         if (err)
 111                 goto out;
 112
 113         if ((dlen + sizeof(struct ip_comp_hdr)) >= plen) {
 114                 err = -EMSGSIZE;
 115                 goto out;
 116         }
 117
 118         memcpy(start + sizeof(struct ip_comp_hdr), scratch, dlen);
 119         put_cpu();
 120
 121         pskb_trim(skb, ihlen + dlen + sizeof(struct ip_comp_hdr));
 122         return 0;
 123
 124 out:
 125         put_cpu();
 126         return err;
 127 }
 128
 129 static int ipcomp_output(struct xfrm_state *x, struct sk_buff *skb)
 130 {
 131         int err;
 132         struct ip_comp_hdr *ipch;
 133         struct ipcomp_data *ipcd = x->data;
 134         int hdr_len = 0;
 135         struct iphdr *iph = ip_hdr(skb);
 136
 137         iph->tot_len = htons(skb->len);
 138         hdr_len = iph->ihl * 4;
 139         if ((skb->len - hdr_len) < ipcd->threshold) {
 140                 /* Don't bother compressing */
 141                 goto out_ok;
 142         }
 143
 144         if (skb_linearize_cow(skb))
 145                 goto out_ok;
 146
 147         err = ipcomp_compress(x, skb);
 148         iph = ip_hdr(skb);
 149
 150         if (err) {
 151                 goto out_ok;
 152         }
 153
 154         /* Install ipcomp header, convert into ipcomp datagram. */
 155         iph->tot_len = htons(skb->len);
 156         ipch = (struct ip_comp_hdr *)((char *)iph + iph->ihl * 4);
 157         ipch->nexthdr = iph->protocol;
 158         ipch->flags = 0;
 159         ipch->cpi = htons((u16 )ntohl(x->id.spi));
 160         iph->protocol = IPPROTO_COMP;
 161         ip_send_check(iph);
 162         return 0;
 163
 164 out_ok:
 165         if (x->props.mode == XFRM_MODE_TUNNEL)
 166                 ip_send_check(iph);
 167         return 0;
 168 }
 169
 170 static void ipcomp4_err(struct sk_buff *skb, u32 info)
 171 {
 172         __be32 spi;
 173         struct iphdr *iph = (struct iphdr *)skb->data;
 174         struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
 175         struct xfrm_state *x;
 176
 177         if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
 178             icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 179                 return;
 180
 181         spi = htonl(ntohs(ipch->cpi));
 182         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr,
 183                               spi, IPPROTO_COMP, AF_INET);
 184         if (!x)
 185                 return;
 186         NETDEBUG(KERN_DEBUG "pmtu discovery on SA IPCOMP/%08x/%u.%u.%u.%u\n",
 187                  spi, NIPQUAD(iph->daddr));
 188         xfrm_state_put(x);
 189 }
 190
 191 /* We always hold one tunnel user reference to indicate a tunnel */
 192 static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
 193 {
 194         struct xfrm_state *t;
 195         u8 mode = XFRM_MODE_TUNNEL;
 196
 197         t = xfrm_state_alloc();
 198         if (t == NULL)
 199                 goto out;
 200
 201         t->id.proto = IPPROTO_IPIP;
 202         t->id.spi = x->props.saddr.a4;
 203         t->id.daddr.a4 = x->id.daddr.a4;
 204         memcpy(&t->sel, &x->sel, sizeof(t->sel));
 205         t->props.family = AF_INET;
 206         if (x->props.mode == XFRM_MODE_BEET)
 207                 mode = x->props.mode;
 208         t->props.mode = mode;
 209         t->props.saddr.a4 = x->props.saddr.a4;
 210         t->props.flags = x->props.flags;
 211
 212         if (xfrm_init_state(t))
 213                 goto error;
 214
 215         atomic_set(&t->tunnel_users, 1);
 216 out:
 217         return t;
 218
 219 error:
 220         t->km.state = XFRM_STATE_DEAD;
 221         xfrm_state_put(t);
 222         t = NULL;
 223         goto out;
 224 }
 225
 226 /*
 227  * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
 228  * always incremented on success.
 229  */
 230 static int ipcomp_tunnel_attach(struct xfrm_state *x)
 231 {
 232         int err = 0;
 233         struct xfrm_state *t;
 234
 235         t = xfrm_state_lookup((xfrm_address_t *)&x->id.daddr.a4,
 236                               x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
 237         if (!t) {
 238                 t = ipcomp_tunnel_create(x);
 239                 if (!t) {
 240                         err = -EINVAL;
 241                         goto out;
 242                 }
 243                 xfrm_state_insert(t);
 244                 xfrm_state_hold(t);
 245         }
 246         x->tunnel = t;
 247         atomic_inc(&t->tunnel_users);
 248 out:
 249         return err;
 250 }
 251
 252 static void ipcomp_free_scratches(void)
 253 {
 254         int i;
 255         void **scratches;
 256
 257         if (--ipcomp_scratch_users)
 258                 return;
 259
 260         scratches = ipcomp_scratches;
 261         if (!scratches)
 262                 return;
 263
 264         for_each_possible_cpu(i)
 265                 vfree(*per_cpu_ptr(scratches, i));
 266
 267         free_percpu(scratches);
 268 }
 269
 270 static void **ipcomp_alloc_scratches(void)
 271 {
 272         int i;
 273         void **scratches;
 274
 275         if (ipcomp_scratch_users++)
 276                 return ipcomp_scratches;
 277
 278         scratches = alloc_percpu(void *);
 279         if (!scratches)
 280                 return NULL;
 281
 282         ipcomp_scratches = scratches;
 283
 284         for_each_possible_cpu(i) {
 285                 void *scratch = vmalloc(IPCOMP_SCRATCH_SIZE);
 286                 if (!scratch)
 287                         return NULL;
 288                 *per_cpu_ptr(scratches, i) = scratch;
 289         }
 290
 291         return scratches;
 292 }
 293
 294 static void ipcomp_free_tfms(struct crypto_comp **tfms)
 295 {
 296         struct ipcomp_tfms *pos;
 297         int cpu;
 298
 299         list_for_each_entry(pos, &ipcomp_tfms_list, list) {
 300                 if (pos->tfms == tfms)
 301                         break;
 302         }
 303
 304         BUG_TRAP(pos);
 305
 306         if (--pos->users)
 307                 return;
 308
 309         list_del(&pos->list);
 310         kfree(pos);
 311
 312         if (!tfms)
 313                 return;
 314
 315         for_each_possible_cpu(cpu) {
 316                 struct crypto_comp *tfm = *per_cpu_ptr(tfms, cpu);
 317                 crypto_free_comp(tfm);
 318         }
 319         free_percpu(tfms);
 320 }
 321
 322 static struct crypto_comp **ipcomp_alloc_tfms(const char *alg_name)
 323 {
 324         struct ipcomp_tfms *pos;
 325         struct crypto_comp **tfms;
 326         int cpu;
 327
 328         /* This can be any valid CPU ID so we don't need locking. */
 329         cpu = raw_smp_processor_id();
 330
 331         list_for_each_entry(pos, &ipcomp_tfms_list, list) {
 332                 struct crypto_comp *tfm;
 333
 334                 tfms = pos->tfms;
 335                 tfm = *per_cpu_ptr(tfms, cpu);
 336
 337                 if (!strcmp(crypto_comp_name(tfm), alg_name)) {
 338                         pos->users++;
 339                         return tfms;
 340                 }
 341         }
 342
 343         pos = kmalloc(sizeof(*pos), GFP_KERNEL);
 344         if (!pos)
 345                 return NULL;
 346
 347         pos->users = 1;
 348         INIT_LIST_HEAD(&pos->list);
 349         list_add(&pos->list, &ipcomp_tfms_list);
 350
 351         pos->tfms = tfms = alloc_percpu(struct crypto_comp *);
 352         if (!tfms)
 353                 goto error;
 354
 355         for_each_possible_cpu(cpu) {
 356                 struct crypto_comp *tfm = crypto_alloc_comp(alg_name, 0,
 357                                                             CRYPTO_ALG_ASYNC);
 358                 if (!tfm)
 359                         goto error;
 360                 *per_cpu_ptr(tfms, cpu) = tfm;
 361         }
 362
 363         return tfms;
 364
 365 error:
 366         ipcomp_free_tfms(tfms);
 367         return NULL;
 368 }
 369
 370 static void ipcomp_free_data(struct ipcomp_data *ipcd)
 371 {
 372         if (ipcd->tfms)
 373                 ipcomp_free_tfms(ipcd->tfms);
 374         ipcomp_free_scratches();
 375 }
 376
 377 static void ipcomp_destroy(struct xfrm_state *x)
 378 {
 379         struct ipcomp_data *ipcd = x->data;
 380         if (!ipcd)
 381                 return;
 382         xfrm_state_delete_tunnel(x);
 383         mutex_lock(&ipcomp_resource_mutex);
 384         ipcomp_free_data(ipcd);
 385         mutex_unlock(&ipcomp_resource_mutex);
 386         kfree(ipcd);
 387 }
 388
 389 static int ipcomp_init_state(struct xfrm_state *x)
 390 {
 391         int err;
 392         struct ipcomp_data *ipcd;
 393         struct xfrm_algo_desc *calg_desc;
 394
 395         err = -EINVAL;
 396         if (!x->calg)
 397                 goto out;
 398
 399         if (x->encap)
 400                 goto out;
 401
 402         err = -ENOMEM;
 403         ipcd = kzalloc(sizeof(*ipcd), GFP_KERNEL);
 404         if (!ipcd)
 405                 goto out;
 406
 407         x->props.header_len = 0;
 408         if (x->props.mode == XFRM_MODE_TUNNEL)
 409                 x->props.header_len += sizeof(struct iphdr);
 410
 411         mutex_lock(&ipcomp_resource_mutex);
 412         if (!ipcomp_alloc_scratches())
 413                 goto error;
 414
 415         ipcd->tfms = ipcomp_alloc_tfms(x->calg->alg_name);
 416         if (!ipcd->tfms)
 417                 goto error;
 418         mutex_unlock(&ipcomp_resource_mutex);
 419
 420         if (x->props.mode == XFRM_MODE_TUNNEL) {
 421                 err = ipcomp_tunnel_attach(x);
 422                 if (err)
 423                         goto error_tunnel;
 424         }
 425
 426         calg_desc = xfrm_calg_get_byname(x->calg->alg_name, 0);
 427         BUG_ON(!calg_desc);
 428         ipcd->threshold = calg_desc->uinfo.comp.threshold;
 429         x->data = ipcd;
 430         err = 0;
 431 out:
 432         return err;
 433
 434 error_tunnel:
 435         mutex_lock(&ipcomp_resource_mutex);
 436 error:
 437         ipcomp_free_data(ipcd);
 438         mutex_unlock(&ipcomp_resource_mutex);
 439         kfree(ipcd);
 440         goto out;
 441 }
 442
 443 static struct xfrm_type ipcomp_type = {
 444         .description    = "IPCOMP4",
 445         .owner          = THIS_MODULE,
 446         .proto          = IPPROTO_COMP,
 447         .init_state     = ipcomp_init_state,
 448         .destructor     = ipcomp_destroy,
 449         .input          = ipcomp_input,
 450         .output         = ipcomp_output
 451 };
 452
 453 static struct net_protocol ipcomp4_protocol = {
 454         .handler        =       xfrm4_rcv,
 455         .err_handler    =       ipcomp4_err,
 456         .no_policy      =       1,
 457 };
 458
 459 static int __init ipcomp4_init(void)
 460 {
 461         if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
 462                 printk(KERN_INFO "ipcomp init: can't add xfrm type\n");
 463                 return -EAGAIN;
 464         }
 465         if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
 466                 printk(KERN_INFO "ipcomp init: can't add protocol\n");
 467                 xfrm_unregister_type(&ipcomp_type, AF_INET);
 468                 return -EAGAIN;
 469         }
 470         return 0;
 471 }
 472
 473 static void __exit ipcomp4_fini(void)
 474 {
 475         if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
 476                 printk(KERN_INFO "ip ipcomp close: can't remove protocol\n");
 477         if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
 478                 printk(KERN_INFO "ip ipcomp close: can't remove xfrm type\n");
 479 }
 480
 481 module_init(ipcomp4_init);
 482 module_exit(ipcomp4_fini);
 483
 484 MODULE_LICENSE("GPL");
 485 MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) - RFC3173");
 486 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
 487
 488 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);