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   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         struct iphdr *iph = (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, (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
  67         if (xfrm_init_state(t))
  68                 goto error;
  69
  70         atomic_set(&t->tunnel_users, 1);
  71 out:
  72         return t;
  73
  74 error:
  75         t->km.state = XFRM_STATE_DEAD;
  76         xfrm_state_put(t);
  77         t = NULL;
  78         goto out;
  79 }
  80
  81 /*
  82  * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
  83  * always incremented on success.
  84  */
  85 static int ipcomp_tunnel_attach(struct xfrm_state *x)
  86 {
  87         struct net *net = xs_net(x);
  88         int err = 0;
  89         struct xfrm_state *t;
  90
  91         t = xfrm_state_lookup(net, (xfrm_address_t *)&x->id.daddr.a4,
  92                               x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
  93         if (!t) {
  94                 t = ipcomp_tunnel_create(x);
  95                 if (!t) {
  96                         err = -EINVAL;
  97                         goto out;
  98                 }
  99                 xfrm_state_insert(t);
 100                 xfrm_state_hold(t);
 101         }
 102         x->tunnel = t;
 103         atomic_inc(&t->tunnel_users);
 104 out:
 105         return err;
 106 }
 107
 108 static int ipcomp4_init_state(struct xfrm_state *x)
 109 {
 110         int err = -EINVAL;
 111
 112         x->props.header_len = 0;
 113         switch (x->props.mode) {
 114         case XFRM_MODE_TRANSPORT:
 115                 break;
 116         case XFRM_MODE_TUNNEL:
 117                 x->props.header_len += sizeof(struct iphdr);
 118                 break;
 119         default:
 120                 goto out;
 121         }
 122
 123         err = ipcomp_init_state(x);
 124         if (err)
 125                 goto out;
 126
 127         if (x->props.mode == XFRM_MODE_TUNNEL) {
 128                 err = ipcomp_tunnel_attach(x);
 129                 if (err)
 130                         goto error_tunnel;
 131         }
 132
 133         err = 0;
 134 out:
 135         return err;
 136
 137 error_tunnel:
 138         ipcomp_destroy(x);
 139         goto out;
 140 }
 141
 142 static const struct xfrm_type ipcomp_type = {
 143         .description    = "IPCOMP4",
 144         .owner          = THIS_MODULE,
 145         .proto          = IPPROTO_COMP,
 146         .init_state     = ipcomp4_init_state,
 147         .destructor     = ipcomp_destroy,
 148         .input          = ipcomp_input,
 149         .output         = ipcomp_output
 150 };
 151
 152 static const struct net_protocol ipcomp4_protocol = {
 153         .handler        =       xfrm4_rcv,
 154         .err_handler    =       ipcomp4_err,
 155         .no_policy      =       1,
 156 };
 157
 158 static int __init ipcomp4_init(void)
 159 {
 160         if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
 161                 printk(KERN_INFO "ipcomp init: can't add xfrm type\n");
 162                 return -EAGAIN;
 163         }
 164         if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
 165                 printk(KERN_INFO "ipcomp init: can't add protocol\n");
 166                 xfrm_unregister_type(&ipcomp_type, AF_INET);
 167                 return -EAGAIN;
 168         }
 169         return 0;
 170 }
 171
 172 static void __exit ipcomp4_fini(void)
 173 {
 174         if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
 175                 printk(KERN_INFO "ip ipcomp close: can't remove protocol\n");
 176         if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
 177                 printk(KERN_INFO "ip ipcomp close: can't remove xfrm type\n");
 178 }
 179
 180 module_init(ipcomp4_init);
 181 module_exit(ipcomp4_fini);
 182
 183 MODULE_LICENSE("GPL");
 184 MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp/IPv4) - RFC3173");
 185 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
 186
 187 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);