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         ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_COMP, 0);
  46         xfrm_state_put(x);
  47 }
  48
  49 /* We always hold one tunnel user reference to indicate a tunnel */
  50 static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
  51 {
  52         struct net *net = xs_net(x);
  53         struct xfrm_state *t;
  54
  55         t = xfrm_state_alloc(net);
  56         if (t == NULL)
  57                 goto out;
  58
  59         t->id.proto = IPPROTO_IPIP;
  60         t->id.spi = x->props.saddr.a4;
  61         t->id.daddr.a4 = x->id.daddr.a4;
  62         memcpy(&t->sel, &x->sel, sizeof(t->sel));
  63         t->props.family = AF_INET;
  64         t->props.mode = x->props.mode;
  65         t->props.saddr.a4 = x->props.saddr.a4;
  66         t->props.flags = x->props.flags;
  67         memcpy(&t->mark, &x->mark, sizeof(t->mark));
  68
  69         if (xfrm_init_state(t))
  70                 goto error;
  71
  72         atomic_set(&t->tunnel_users, 1);
  73 out:
  74         return t;
  75
  76 error:
  77         t->km.state = XFRM_STATE_DEAD;
  78         xfrm_state_put(t);
  79         t = NULL;
  80         goto out;
  81 }
  82
  83 /*
  84  * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
  85  * always incremented on success.
  86  */
  87 static int ipcomp_tunnel_attach(struct xfrm_state *x)
  88 {
  89         struct net *net = xs_net(x);
  90         int err = 0;
  91         struct xfrm_state *t;
  92         u32 mark = x->mark.v & x->mark.m;
  93
  94         t = xfrm_state_lookup(net, mark, (xfrm_address_t *)&x->id.daddr.a4,
  95                               x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
  96         if (!t) {
  97                 t = ipcomp_tunnel_create(x);
  98                 if (!t) {
  99                         err = -EINVAL;
 100                         goto out;
 101                 }
 102                 xfrm_state_insert(t);
 103                 xfrm_state_hold(t);
 104         }
 105         x->tunnel = t;
 106         atomic_inc(&t->tunnel_users);
 107 out:
 108         return err;
 109 }
 110
 111 static int ipcomp4_init_state(struct xfrm_state *x)
 112 {
 113         int err = -EINVAL;
 114
 115         x->props.header_len = 0;
 116         switch (x->props.mode) {
 117         case XFRM_MODE_TRANSPORT:
 118                 break;
 119         case XFRM_MODE_TUNNEL:
 120                 x->props.header_len += sizeof(struct iphdr);
 121                 break;
 122         default:
 123                 goto out;
 124         }
 125
 126         err = ipcomp_init_state(x);
 127         if (err)
 128                 goto out;
 129
 130         if (x->props.mode == XFRM_MODE_TUNNEL) {
 131                 err = ipcomp_tunnel_attach(x);
 132                 if (err)
 133                         goto out;
 134         }
 135
 136         err = 0;
 137 out:
 138         return err;
 139 }
 140
 141 static const struct xfrm_type ipcomp_type = {
 142         .description    = "IPCOMP4",
 143         .owner          = THIS_MODULE,
 144         .proto          = IPPROTO_COMP,
 145         .init_state     = ipcomp4_init_state,
 146         .destructor     = ipcomp_destroy,
 147         .input          = ipcomp_input,
 148         .output         = ipcomp_output
 149 };
 150
 151 static const struct net_protocol ipcomp4_protocol = {
 152         .handler        =       xfrm4_rcv,
 153         .err_handler    =       ipcomp4_err,
 154         .no_policy      =       1,
 155 };
 156
 157 static int __init ipcomp4_init(void)
 158 {
 159         if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
 160                 pr_info("%s: can't add xfrm type\n", __func__);
 161                 return -EAGAIN;
 162         }
 163         if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
 164                 pr_info("%s: can't add protocol\n", __func__);
 165                 xfrm_unregister_type(&ipcomp_type, AF_INET);
 166                 return -EAGAIN;
 167         }
 168         return 0;
 169 }
 170
 171 static void __exit ipcomp4_fini(void)
 172 {
 173         if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
 174                 pr_info("%s: can't remove protocol\n", __func__);
 175         if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
 176                 pr_info("%s: can't remove xfrm type\n", __func__);
 177 }
 178
 179 module_init(ipcomp4_init);
 180 module_exit(ipcomp4_fini);
 181
 182 MODULE_LICENSE("GPL");
 183 MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp/IPv4) - RFC3173");
 184 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
 185
 186 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);