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