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 <linux/err.h>
  18 #include <linux/rtnetlink.h>
  19 #include <net/ip.h>
  20 #include <net/xfrm.h>
  21 #include <net/icmp.h>
  22 #include <net/ipcomp.h>
  23 #include <net/protocol.h>
  24 #include <net/sock.h>
  25
  26 static void ipcomp4_err(struct sk_buff *skb, u32 info)
  27 {
  28         struct net *net = dev_net(skb->dev);
  29         __be32 spi;
  30         const struct iphdr *iph = (const struct iphdr *)skb->data;
  31         struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
  32         struct xfrm_state *x;
  33
  34         if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
  35             icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
  36                 return;
  37
  38         spi = htonl(ntohs(ipch->cpi));
  39         x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
  40                               spi, IPPROTO_COMP, AF_INET);
  41         if (!x)
  42                 return;
  43         NETDEBUG(KERN_DEBUG "pmtu discovery on SA IPCOMP/%08x/%pI4\n",
  44                  spi, &iph->daddr);
  45         xfrm_state_put(x);
  46 }
  47
  48 /* We always hold one tunnel user reference to indicate a tunnel */
  49 static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
  50 {
  51         struct net *net = xs_net(x);
  52         struct xfrm_state *t;
  53
  54         t = xfrm_state_alloc(net);
  55         if (t == NULL)
  56                 goto out;
  57
  58         t->id.proto = IPPROTO_IPIP;
  59         t->id.spi = x->props.saddr.a4;
  60         t->id.daddr.a4 = x->id.daddr.a4;
  61         memcpy(&t->sel, &x->sel, sizeof(t->sel));
  62         t->props.family = AF_INET;
  63         t->props.mode = x->props.mode;
  64         t->props.saddr.a4 = x->props.saddr.a4;
  65         t->props.flags = x->props.flags;
  66         memcpy(&t->mark, &x->mark, sizeof(t->mark));
  67
  68         if (xfrm_init_state(t))
  69                 goto error;
  70
  71         atomic_set(&t->tunnel_users, 1);
  72 out:
  73         return t;
  74
  75 error:
  76         t->km.state = XFRM_STATE_DEAD;
  77         xfrm_state_put(t);
  78         t = NULL;
  79         goto out;
  80 }
  81
  82 /*
  83  * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
  84  * always incremented on success.
  85  */
  86 static int ipcomp_tunnel_attach(struct xfrm_state *x)
  87 {
  88         struct net *net = xs_net(x);
  89         int err = 0;
  90         struct xfrm_state *t;
  91         u32 mark = x->mark.v & x->mark.m;
  92
  93         t = xfrm_state_lookup(net, mark, (xfrm_address_t *)&x->id.daddr.a4,
  94                               x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
  95         if (!t) {
  96                 t = ipcomp_tunnel_create(x);
  97                 if (!t) {
  98                         err = -EINVAL;
  99                         goto out;
 100                 }
 101                 xfrm_state_insert(t);
 102                 xfrm_state_hold(t);
 103         }
 104         x->tunnel = t;
 105         atomic_inc(&t->tunnel_users);
 106 out:
 107         return err;
 108 }
 109
 110 static int ipcomp4_init_state(struct xfrm_state *x)
 111 {
 112         int err = -EINVAL;
 113
 114         x->props.header_len = 0;
 115         switch (x->props.mode) {
 116         case XFRM_MODE_TRANSPORT:
 117                 break;
 118         case XFRM_MODE_TUNNEL:
 119                 x->props.header_len += sizeof(struct iphdr);
 120                 break;
 121         default:
 122                 goto out;
 123         }
 124
 125         err = ipcomp_init_state(x);
 126         if (err)
 127                 goto out;
 128
 129         if (x->props.mode == XFRM_MODE_TUNNEL) {
 130                 err = ipcomp_tunnel_attach(x);
 131                 if (err)
 132                         goto out;
 133         }
 134
 135         err = 0;
 136 out:
 137         return err;
 138 }
 139
 140 static const struct xfrm_type ipcomp_type = {
 141         .description    = "IPCOMP4",
 142         .owner          = THIS_MODULE,
 143         .proto          = IPPROTO_COMP,
 144         .init_state     = ipcomp4_init_state,
 145         .destructor     = ipcomp_destroy,
 146         .input          = ipcomp_input,
 147         .output         = ipcomp_output
 148 };
 149
 150 static const struct net_protocol ipcomp4_protocol = {
 151         .handler        =       xfrm4_rcv,
 152         .err_handler    =       ipcomp4_err,
 153         .no_policy      =       1,
 154 };
 155
 156 static int __init ipcomp4_init(void)
 157 {
 158         if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
 159                 pr_info("%s: can't add xfrm type\n", __func__);
 160                 return -EAGAIN;
 161         }
 162         if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
 163                 pr_info("%s: can't add protocol\n", __func__);
 164                 xfrm_unregister_type(&ipcomp_type, AF_INET);
 165                 return -EAGAIN;
 166         }
 167         return 0;
 168 }
 169
 170 static void __exit ipcomp4_fini(void)
 171 {
 172         if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
 173                 pr_info("%s: can't remove protocol\n", __func__);
 174         if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
 175                 pr_info("%s: can't remove xfrm type\n", __func__);
 176 }
 177
 178 module_init(ipcomp4_init);
 179 module_exit(ipcomp4_fini);
 180
 181 MODULE_LICENSE("GPL");
 182 MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp/IPv4) - RFC3173");
 183 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
 184
 185 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);