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 <linux/crypto.h>
  20 #include <linux/pfkeyv2.h>
  21 #include <net/inet_ecn.h>
  22 #include <net/ip.h>
  23 #include <net/xfrm.h>
  24 #include <net/icmp.h>
  25 #include <net/ipcomp.h>
  26
  27 static int ipcomp_decompress(struct xfrm_state *x, struct sk_buff *skb)
  28 {
  29         int err, plen, dlen;
  30         struct iphdr *iph;
  31         struct ipcomp_data *ipcd = x->data;
  32         u8 *start, *scratch = ipcd->scratch;
  33
  34         plen = skb->len;
  35         dlen = IPCOMP_SCRATCH_SIZE;
  36         start = skb->data;
  37
  38         err = crypto_comp_decompress(ipcd->tfm, start, plen, scratch, &dlen);
  39         if (err)
  40                 goto out;
  41
  42         if (dlen < (plen + sizeof(struct ip_comp_hdr))) {
  43                 err = -EINVAL;
  44                 goto out;
  45         }
  46
  47         err = pskb_expand_head(skb, 0, dlen - plen, GFP_ATOMIC);
  48         if (err)
  49                 goto out;
  50
  51         skb_put(skb, dlen - plen);
  52         memcpy(skb->data, scratch, dlen);
  53         iph = skb->nh.iph;
  54         iph->tot_len = htons(dlen + iph->ihl * 4);
  55 out:
  56         return err;
  57 }
  58
  59 static int ipcomp_input(struct xfrm_state *x,
  60                         struct xfrm_decap_state *decap, struct sk_buff *skb)
  61 {
  62         u8 nexthdr;
  63         int err = 0;
  64         struct iphdr *iph;
  65         union {
  66                 struct iphdr    iph;
  67                 char            buf[60];
  68         } tmp_iph;
  69
  70
  71         if ((skb_is_nonlinear(skb) || skb_cloned(skb)) &&
  72             skb_linearize(skb, GFP_ATOMIC) != 0) {
  73                 err = -ENOMEM;
  74                 goto out;
  75         }
  76
  77         skb->ip_summed = CHECKSUM_NONE;
  78
  79         /* Remove ipcomp header and decompress original payload */
  80         iph = skb->nh.iph;
  81         memcpy(&tmp_iph, iph, iph->ihl * 4);
  82         nexthdr = *(u8 *)skb->data;
  83         skb_pull(skb, sizeof(struct ip_comp_hdr));
  84         skb->nh.raw += sizeof(struct ip_comp_hdr);
  85         memcpy(skb->nh.raw, &tmp_iph, tmp_iph.iph.ihl * 4);
  86         iph = skb->nh.iph;
  87         iph->tot_len = htons(ntohs(iph->tot_len) - sizeof(struct ip_comp_hdr));
  88         iph->protocol = nexthdr;
  89         skb->h.raw = skb->data;
  90         err = ipcomp_decompress(x, skb);
  91
  92 out:
  93         return err;
  94 }
  95
  96 static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb)
  97 {
  98         int err, plen, dlen, ihlen;
  99         struct iphdr *iph = skb->nh.iph;
 100         struct ipcomp_data *ipcd = x->data;
 101         u8 *start, *scratch = ipcd->scratch;
 102
 103         ihlen = iph->ihl * 4;
 104         plen = skb->len - ihlen;
 105         dlen = IPCOMP_SCRATCH_SIZE;
 106         start = skb->data + ihlen;
 107
 108         err = crypto_comp_compress(ipcd->tfm, start, plen, scratch, &dlen);
 109         if (err)
 110                 goto out;
 111
 112         if ((dlen + sizeof(struct ip_comp_hdr)) >= plen) {
 113                 err = -EMSGSIZE;
 114                 goto out;
 115         }
 116
 117         memcpy(start, scratch, dlen);
 118         pskb_trim(skb, ihlen + dlen);
 119
 120 out:
 121         return err;
 122 }
 123
 124 static void ipcomp_tunnel_encap(struct xfrm_state *x, struct sk_buff *skb)
 125 {
 126         struct dst_entry *dst = skb->dst;
 127         struct iphdr *iph, *top_iph;
 128
 129         iph = skb->nh.iph;
 130         top_iph = (struct iphdr *)skb_push(skb, sizeof(struct iphdr));
 131         top_iph->ihl = 5;
 132         top_iph->version = 4;
 133         top_iph->tos = iph->tos;
 134         top_iph->tot_len = htons(skb->len);
 135         if (!(iph->frag_off&htons(IP_DF)))
 136                 __ip_select_ident(top_iph, dst, 0);
 137         top_iph->ttl = iph->ttl;
 138         top_iph->check = 0;
 139         top_iph->saddr = x->props.saddr.a4;
 140         top_iph->daddr = x->id.daddr.a4;
 141         top_iph->frag_off = iph->frag_off&~htons(IP_MF|IP_OFFSET);
 142         memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
 143         skb->nh.raw = skb->data;
 144 }
 145
 146 static int ipcomp_output(struct sk_buff *skb)
 147 {
 148         int err;
 149         struct dst_entry *dst = skb->dst;
 150         struct xfrm_state *x = dst->xfrm;
 151         struct iphdr *iph, *top_iph;
 152         struct ip_comp_hdr *ipch;
 153         struct ipcomp_data *ipcd = x->data;
 154         union {
 155                 struct iphdr    iph;
 156                 char            buf[60];
 157         } tmp_iph;
 158         int hdr_len = 0;
 159
 160         if (skb->ip_summed == CHECKSUM_HW && skb_checksum_help(skb) == NULL) {
 161                 err = -EINVAL;
 162                 goto error_nolock;
 163         }
 164
 165         spin_lock_bh(&x->lock);
 166         err = xfrm_check_output(x, skb, AF_INET);
 167         if (err)
 168                 goto error;
 169
 170         /* Don't bother compressing */
 171         if (!x->props.mode) {
 172                 iph = skb->nh.iph;
 173                 hdr_len = iph->ihl * 4;
 174         }
 175         if ((skb->len - hdr_len) < ipcd->threshold) {
 176                 if (x->props.mode) {
 177                         ipcomp_tunnel_encap(x, skb);
 178                         iph = skb->nh.iph;
 179                         iph->protocol = IPPROTO_IPIP;
 180                         ip_send_check(iph);
 181                 }
 182                 goto out_ok;
 183         }
 184
 185         if (x->props.mode)
 186                 ipcomp_tunnel_encap(x, skb);
 187
 188         if ((skb_is_nonlinear(skb) || skb_cloned(skb)) &&
 189             skb_linearize(skb, GFP_ATOMIC) != 0) {
 190                 err = -ENOMEM;
 191                 goto error;
 192         }
 193
 194         err = ipcomp_compress(x, skb);
 195         if (err) {
 196                 if (err == -EMSGSIZE) {
 197                         if (x->props.mode) {
 198                                 iph = skb->nh.iph;
 199                                 iph->protocol = IPPROTO_IPIP;
 200                                 ip_send_check(iph);
 201                         }
 202                         goto out_ok;
 203                 }
 204                 goto error;
 205         }
 206
 207         /* Install ipcomp header, convert into ipcomp datagram. */
 208         iph = skb->nh.iph;
 209         memcpy(&tmp_iph, iph, iph->ihl * 4);
 210         top_iph = (struct iphdr *)skb_push(skb, sizeof(struct ip_comp_hdr));
 211         memcpy(top_iph, &tmp_iph, iph->ihl * 4);
 212         iph = top_iph;
 213         if (x->props.mode && (x->props.flags & XFRM_STATE_NOECN))
 214                 IP_ECN_clear(iph);
 215         iph->tot_len = htons(skb->len);
 216         iph->protocol = IPPROTO_COMP;
 217         iph->check = 0;
 218         ipch = (struct ip_comp_hdr *)((char *)iph + iph->ihl * 4);
 219         ipch->nexthdr = x->props.mode ? IPPROTO_IPIP : tmp_iph.iph.protocol;
 220         ipch->flags = 0;
 221         ipch->cpi = htons((u16 )ntohl(x->id.spi));
 222         ip_send_check(iph);
 223         skb->nh.raw = skb->data;
 224
 225 out_ok:
 226         x->curlft.bytes += skb->len;
 227         x->curlft.packets++;
 228         spin_unlock_bh(&x->lock);
 229
 230         if ((skb->dst = dst_pop(dst)) == NULL) {
 231                 err = -EHOSTUNREACH;
 232                 goto error_nolock;
 233         }
 234         err = NET_XMIT_BYPASS;
 235
 236 out_exit:
 237         return err;
 238 error:
 239         spin_unlock_bh(&x->lock);
 240 error_nolock:
 241         kfree_skb(skb);
 242         goto out_exit;
 243 }
 244
 245 static void ipcomp4_err(struct sk_buff *skb, u32 info)
 246 {
 247         u32 spi;
 248         struct iphdr *iph = (struct iphdr *)skb->data;
 249         struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
 250         struct xfrm_state *x;
 251
 252         if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
 253             skb->h.icmph->code != ICMP_FRAG_NEEDED)
 254                 return;
 255
 256         spi = ntohl(ntohs(ipch->cpi));
 257         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr,
 258                               spi, IPPROTO_COMP, AF_INET);
 259         if (!x)
 260                 return;
 261         NETDEBUG(printk(KERN_DEBUG "pmtu discovery on SA IPCOMP/%08x/%u.%u.%u.%u\n",
 262                spi, NIPQUAD(iph->daddr)));
 263         xfrm_state_put(x);
 264 }
 265
 266 /* We always hold one tunnel user reference to indicate a tunnel */
 267 static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
 268 {
 269         struct xfrm_state *t;
 270
 271         t = xfrm_state_alloc();
 272         if (t == NULL)
 273                 goto out;
 274
 275         t->id.proto = IPPROTO_IPIP;
 276         t->id.spi = x->props.saddr.a4;
 277         t->id.daddr.a4 = x->id.daddr.a4;
 278         memcpy(&t->sel, &x->sel, sizeof(t->sel));
 279         t->props.family = AF_INET;
 280         t->props.mode = 1;
 281         t->props.saddr.a4 = x->props.saddr.a4;
 282         t->props.flags = x->props.flags;
 283
 284         t->type = xfrm_get_type(IPPROTO_IPIP, t->props.family);
 285         if (t->type == NULL)
 286                 goto error;
 287
 288         if (t->type->init_state(t, NULL))
 289                 goto error;
 290
 291         t->km.state = XFRM_STATE_VALID;
 292         atomic_set(&t->tunnel_users, 1);
 293 out:
 294         return t;
 295
 296 error:
 297         t->km.state = XFRM_STATE_DEAD;
 298         xfrm_state_put(t);
 299         t = NULL;
 300         goto out;
 301 }
 302
 303 /*
 304  * Must be protected by xfrm_cfg_sem.  State and tunnel user references are
 305  * always incremented on success.
 306  */
 307 static int ipcomp_tunnel_attach(struct xfrm_state *x)
 308 {
 309         int err = 0;
 310         struct xfrm_state *t;
 311
 312         t = xfrm_state_lookup((xfrm_address_t *)&x->id.daddr.a4,
 313                               x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
 314         if (!t) {
 315                 t = ipcomp_tunnel_create(x);
 316                 if (!t) {
 317                         err = -EINVAL;
 318                         goto out;
 319                 }
 320                 xfrm_state_insert(t);
 321                 xfrm_state_hold(t);
 322         }
 323         x->tunnel = t;
 324         atomic_inc(&t->tunnel_users);
 325 out:
 326         return err;
 327 }
 328
 329 static void ipcomp_free_data(struct ipcomp_data *ipcd)
 330 {
 331         if (ipcd->tfm)
 332                 crypto_free_tfm(ipcd->tfm);
 333         if (ipcd->scratch)
 334                 kfree(ipcd->scratch);
 335 }
 336
 337 static void ipcomp_destroy(struct xfrm_state *x)
 338 {
 339         struct ipcomp_data *ipcd = x->data;
 340         if (!ipcd)
 341                 return;
 342         ipcomp_free_data(ipcd);
 343         kfree(ipcd);
 344 }
 345
 346 static int ipcomp_init_state(struct xfrm_state *x, void *args)
 347 {
 348         int err;
 349         struct ipcomp_data *ipcd;
 350         struct xfrm_algo_desc *calg_desc;
 351
 352         err = -EINVAL;
 353         if (!x->calg)
 354                 goto out;
 355
 356         err = -ENOMEM;
 357         ipcd = kmalloc(sizeof(*ipcd), GFP_KERNEL);
 358         if (!ipcd)
 359                 goto error;
 360
 361         memset(ipcd, 0, sizeof(*ipcd));
 362         x->props.header_len = sizeof(struct ip_comp_hdr);
 363         if (x->props.mode)
 364                 x->props.header_len += sizeof(struct iphdr);
 365
 366         ipcd->scratch = kmalloc(IPCOMP_SCRATCH_SIZE, GFP_KERNEL);
 367         if (!ipcd->scratch)
 368                 goto error;
 369
 370         ipcd->tfm = crypto_alloc_tfm(x->calg->alg_name, 0);
 371         if (!ipcd->tfm)
 372                 goto error;
 373
 374         if (x->props.mode) {
 375                 err = ipcomp_tunnel_attach(x);
 376                 if (err)
 377                         goto error;
 378         }
 379
 380         calg_desc = xfrm_calg_get_byname(x->calg->alg_name);
 381         BUG_ON(!calg_desc);
 382         ipcd->threshold = calg_desc->uinfo.comp.threshold;
 383         x->data = ipcd;
 384         err = 0;
 385 out:
 386         return err;
 387
 388 error:
 389         if (ipcd) {
 390                 ipcomp_free_data(ipcd);
 391                 kfree(ipcd);
 392         }
 393         goto out;
 394 }
 395
 396 static struct xfrm_type ipcomp_type = {
 397         .description    = "IPCOMP4",
 398         .owner          = THIS_MODULE,
 399         .proto          = IPPROTO_COMP,
 400         .init_state     = ipcomp_init_state,
 401         .destructor     = ipcomp_destroy,
 402         .input          = ipcomp_input,
 403         .output         = ipcomp_output
 404 };
 405
 406 static struct inet_protocol ipcomp4_protocol = {
 407         .handler        =       xfrm4_rcv,
 408         .err_handler    =       ipcomp4_err,
 409         .no_policy      =       1,
 410 };
 411
 412 static int __init ipcomp4_init(void)
 413 {
 414         if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
 415                 printk(KERN_INFO "ipcomp init: can't add xfrm type\n");
 416                 return -EAGAIN;
 417         }
 418         if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
 419                 printk(KERN_INFO "ipcomp init: can't add protocol\n");
 420                 xfrm_unregister_type(&ipcomp_type, AF_INET);
 421                 return -EAGAIN;
 422         }
 423         return 0;
 424 }
 425
 426 static void __exit ipcomp4_fini(void)
 427 {
 428         if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
 429                 printk(KERN_INFO "ip ipcomp close: can't remove protocol\n");
 430         if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
 431                 printk(KERN_INFO "ip ipcomp close: can't remove xfrm type\n");
 432 }
 433
 434 module_init(ipcomp4_init);
 435 module_exit(ipcomp4_fini);
 436
 437 MODULE_LICENSE("GPL");
 438 MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) - RFC3173");
 439 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
 440