release/src-rt-6.x/linux/linux-2.6/net/ipv4/xfrm4_input.c

   1 /*
   2  * xfrm4_input.c
   3  *
   4  * Changes:
   5  *      YOSHIFUJI Hideaki @USAGI
   6  *              Split up af-specific portion
   7  *      Derek Atkins <derek@ihtfp.com>
   8  *              Add Encapsulation support
   9  *
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/string.h>
  14 #include <linux/netfilter.h>
  15 #include <linux/netfilter_ipv4.h>
  16 #include <net/ip.h>
  17 #include <net/xfrm.h>
  18 #include <net/xfrmudp.h>
  19
  20 static int xfrm4_parse_spi(struct sk_buff *skb, u8 nexthdr, __be32 *spi, __be32 *seq)
  21 {
  22         switch (nexthdr) {
  23         case IPPROTO_IPIP:
  24         case IPPROTO_IPV6:
  25                 *spi = ip_hdr(skb)->saddr;
  26                 *seq = 0;
  27                 return 0;
  28         }
  29
  30         return xfrm_parse_spi(skb, nexthdr, spi, seq);
  31 }
  32
  33 #ifdef CONFIG_NETFILTER
  34 static inline int xfrm4_rcv_encap_finish(struct sk_buff *skb)
  35 {
  36         if (skb->dst == NULL) {
  37                 const struct iphdr *iph = ip_hdr(skb);
  38
  39                 if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos,
  40                                    skb->dev))
  41                         goto drop;
  42         }
  43         return dst_input(skb);
  44 drop:
  45         kfree_skb(skb);
  46         return NET_RX_DROP;
  47 }
  48 #endif
  49
  50 static int xfrm4_rcv_encap(struct sk_buff *skb, __u16 encap_type)
  51 {
  52         __be32 spi, seq;
  53         struct xfrm_state *xfrm_vec[XFRM_MAX_DEPTH];
  54         struct xfrm_state *x;
  55         int xfrm_nr = 0;
  56         int decaps = 0;
  57         int err = xfrm4_parse_spi(skb, ip_hdr(skb)->protocol, &spi, &seq);
  58
  59         if (err != 0)
  60                 goto drop;
  61
  62         do {
  63                 const struct iphdr *iph = ip_hdr(skb);
  64
  65                 if (xfrm_nr == XFRM_MAX_DEPTH)
  66                         goto drop;
  67
  68                 x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, spi,
  69                                 iph->protocol != IPPROTO_IPV6 ? iph->protocol : IPPROTO_IPIP, AF_INET);
  70                 if (x == NULL)
  71                         goto drop;
  72
  73                 spin_lock(&x->lock);
  74                 if (unlikely(x->km.state != XFRM_STATE_VALID))
  75                         goto drop_unlock;
  76
  77                 if ((x->encap ? x->encap->encap_type : 0) != encap_type)
  78                         goto drop_unlock;
  79
  80                 if (x->props.replay_window && xfrm_replay_check(x, seq))
  81                         goto drop_unlock;
  82
  83                 if (xfrm_state_check_expire(x))
  84                         goto drop_unlock;
  85
  86                 if (x->type->input(x, skb))
  87                         goto drop_unlock;
  88
  89                 /* only the first xfrm gets the encap type */
  90                 encap_type = 0;
  91
  92                 if (x->props.replay_window)
  93                         xfrm_replay_advance(x, seq);
  94
  95                 x->curlft.bytes += skb->len;
  96                 x->curlft.packets++;
  97
  98                 spin_unlock(&x->lock);
  99
 100                 xfrm_vec[xfrm_nr++] = x;
 101
 102                 if (x->mode->input(x, skb))
 103                         goto drop;
 104
 105                 if (x->props.mode == XFRM_MODE_TUNNEL) {
 106                         decaps = 1;
 107                         break;
 108                 }
 109
 110                 err = xfrm_parse_spi(skb, ip_hdr(skb)->protocol, &spi, &seq);
 111                 if (err < 0)
 112                         goto drop;
 113         } while (!err);
 114
 115         /* Allocate new secpath or COW existing one. */
 116
 117         if (!skb->sp || atomic_read(&skb->sp->refcnt) != 1) {
 118                 struct sec_path *sp;
 119                 sp = secpath_dup(skb->sp);
 120                 if (!sp)
 121                         goto drop;
 122                 if (skb->sp)
 123                         secpath_put(skb->sp);
 124                 skb->sp = sp;
 125         }
 126         if (xfrm_nr + skb->sp->len > XFRM_MAX_DEPTH)
 127                 goto drop;
 128
 129         memcpy(skb->sp->xvec + skb->sp->len, xfrm_vec,
 130                xfrm_nr * sizeof(xfrm_vec[0]));
 131         skb->sp->len += xfrm_nr;
 132
 133         nf_reset(skb);
 134
 135         if (decaps) {
 136                 dst_release(skb->dst);
 137                 skb->dst = NULL;
 138                 netif_rx(skb);
 139                 return 0;
 140         } else {
 141 #ifdef CONFIG_NETFILTER
 142                 __skb_push(skb, skb->data - skb_network_header(skb));
 143                 ip_hdr(skb)->tot_len = htons(skb->len);
 144                 ip_send_check(ip_hdr(skb));
 145
 146                 NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, skb->dev, NULL,
 147                         xfrm4_rcv_encap_finish);
 148                 return 0;
 149 #else
 150                 return -ip_hdr(skb)->protocol;
 151 #endif
 152         }
 153
 154 drop_unlock:
 155         spin_unlock(&x->lock);
 156         xfrm_state_put(x);
 157 drop:
 158         while (--xfrm_nr >= 0)
 159                 xfrm_state_put(xfrm_vec[xfrm_nr]);
 160
 161         kfree_skb(skb);
 162         return 0;
 163 }
 164
 165 #ifdef CONFIG_IPSEC_NAT_TRAVERSAL
 166 static xfrm4_rcv_encap_t xfrm4_rcv_encap_func = NULL;
 167
 168 int udp4_register_esp_rcvencap(xfrm4_rcv_encap_t func,
 169                                xfrm4_rcv_encap_t *oldfunc)
 170 {
 171         if(oldfunc != NULL)
 172                 *oldfunc = xfrm4_rcv_encap_func;
 173
 174         xfrm4_rcv_encap_func = func;
 175         return 0;
 176 }
 177
 178 int udp4_unregister_esp_rcvencap(xfrm4_rcv_encap_t func)
 179 {
 180         if(xfrm4_rcv_encap_func != func)
 181                 return -1;
 182
 183         xfrm4_rcv_encap_func = NULL;
 184         return 0;
 185 }
 186 #endif /* CONFIG_IPSEC_NAT_TRAVERSAL */
 187
 188 /* If it's a keepalive packet, then just eat it.
 189  * If it's an encapsulated packet, then pass it to the
 190  * IPsec xfrm input.
 191  * Returns 0 if skb passed to xfrm or was dropped.
 192  * Returns >0 if skb should be passed to UDP.
 193  * Returns <0 if skb should be resubmitted (-ret is protocol)
 194  */
 195 int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
 196 {
 197         struct udp_sock *up = udp_sk(sk);
 198         struct udphdr *uh;
 199         struct iphdr *iph;
 200         int iphlen, len;
 201         int ret;
 202
 203         __u8 *udpdata;
 204         __be32 *udpdata32;
 205         __u16 encap_type = up->encap_type;
 206
 207         /* if this is not encapsulated socket, then just return now */
 208         if (!encap_type)
 209                 return 1;
 210
 211         /* If this is a paged skb, make sure we pull up
 212          * whatever data we need to look at. */
 213         len = skb->len - sizeof(struct udphdr);
 214         if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
 215                 return 1;
 216
 217         /* Now we can get the pointers */
 218         uh = udp_hdr(skb);
 219         udpdata = (__u8 *)uh + sizeof(struct udphdr);
 220         udpdata32 = (__be32 *)udpdata;
 221
 222         switch (encap_type) {
 223         default:
 224         case UDP_ENCAP_ESPINUDP:
 225                 /* Check if this is a keepalive packet.  If so, eat it. */
 226                 if (len == 1 && udpdata[0] == 0xff) {
 227                         goto drop;
 228                 } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
 229                         /* ESP Packet without Non-ESP header */
 230                         len = sizeof(struct udphdr);
 231                 } else
 232                         /* Must be an IKE packet.. pass it through */
 233                         return 1;
 234                 break;
 235         case UDP_ENCAP_ESPINUDP_NON_IKE:
 236                 /* Check if this is a keepalive packet.  If so, eat it. */
 237                 if (len == 1 && udpdata[0] == 0xff) {
 238                         goto drop;
 239                 } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
 240                            udpdata32[0] == 0 && udpdata32[1] == 0) {
 241
 242                         /* ESP Packet with Non-IKE marker */
 243                         len = sizeof(struct udphdr) + 2 * sizeof(u32);
 244                 } else
 245                         /* Must be an IKE packet.. pass it through */
 246                         return 1;
 247                 break;
 248         }
 249
 250         /* At this point we are sure that this is an ESPinUDP packet,
 251          * so we need to remove 'len' bytes from the packet (the UDP
 252          * header and optional ESP marker bytes) and then modify the
 253          * protocol to ESP, and then call into the transform receiver.
 254          */
 255         if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 256                 goto drop;
 257
 258         /* Now we can update and verify the packet length... */
 259         iph = ip_hdr(skb);
 260         iphlen = iph->ihl << 2;
 261         iph->tot_len = htons(ntohs(iph->tot_len) - len);
 262         if (skb->len < iphlen + len) {
 263                 /* packet is too small!?! */
 264                 goto drop;
 265         }
 266
 267         /* pull the data buffer up to the ESP header and set the
 268          * transport header to point to ESP.  Keep UDP on the stack
 269          * for later.
 270          */
 271         __skb_pull(skb, len);
 272         skb_reset_transport_header(skb);
 273
 274         /* modify the protocol (it's ESP!) */
 275         iph->protocol = IPPROTO_ESP;
 276
 277         /* process ESP */
 278 #ifdef CONFIG_IPSEC_NAT_TRAVERSAL
 279         if (xfrm4_rcv_encap_func != NULL)
 280                 ret = (*xfrm4_rcv_encap_func)(skb, encap_type);
 281         else
 282 #endif
 283         ret = xfrm4_rcv_encap(skb, encap_type);
 284         return ret;
 285
 286 drop:
 287         kfree_skb(skb);
 288         return 0;
 289 }
 290
 291 int xfrm4_rcv(struct sk_buff *skb)
 292 {
 293         return xfrm4_rcv_encap(skb, 0);
 294 }
 295
 296 EXPORT_SYMBOL(xfrm4_rcv);
 297
 298 #ifdef CONFIG_IPSEC_NAT_TRAVERSAL
 299 EXPORT_SYMBOL(udp4_register_esp_rcvencap);
 300 EXPORT_SYMBOL(udp4_unregister_esp_rcvencap);
 301 #endif