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         switch (icmp_hdr(skb)->type) {
  35         case ICMP_DEST_UNREACH:
  36                 if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
  37                         return;
  38         case ICMP_REDIRECT:
  39                 break;
  40         default:
  41                 return;
  42         }
  43
  44         spi = htonl(ntohs(ipch->cpi));
  45         x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
  46                               spi, IPPROTO_COMP, AF_INET);
  47         if (!x)
  48                 return;
  49
  50         if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
  51                 ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_COMP, 0);
  52         else
  53                 ipv4_redirect(skb, net, 0, 0, IPPROTO_COMP, 0);
  54         xfrm_state_put(x);
  55 }
  56
  57 /* We always hold one tunnel user reference to indicate a tunnel */
  58 static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
  59 {
  60         struct net *net = xs_net(x);
  61         struct xfrm_state *t;
  62
  63         t = xfrm_state_alloc(net);
  64         if (t == NULL)
  65                 goto out;
  66
  67         t->id.proto = IPPROTO_IPIP;
  68         t->id.spi = x->props.saddr.a4;
  69         t->id.daddr.a4 = x->id.daddr.a4;
  70         memcpy(&t->sel, &x->sel, sizeof(t->sel));
  71         t->props.family = AF_INET;
  72         t->props.mode = x->props.mode;
  73         t->props.saddr.a4 = x->props.saddr.a4;
  74         t->props.flags = x->props.flags;
  75         t->props.extra_flags = x->props.extra_flags;
  76         memcpy(&t->mark, &x->mark, sizeof(t->mark));
  77
  78         if (xfrm_init_state(t))
  79                 goto error;
  80
  81         atomic_set(&t->tunnel_users, 1);
  82 out:
  83         return t;
  84
  85 error:
  86         t->km.state = XFRM_STATE_DEAD;
  87         xfrm_state_put(t);
  88         t = NULL;
  89         goto out;
  90 }
  91
  92 /*
  93  * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
  94  * always incremented on success.
  95  */
  96 static int ipcomp_tunnel_attach(struct xfrm_state *x)
  97 {
  98         struct net *net = xs_net(x);
  99         int err = 0;
 100         struct xfrm_state *t;
 101         u32 mark = x->mark.v & x->mark.m;
 102
 103         t = xfrm_state_lookup(net, mark, (xfrm_address_t *)&x->id.daddr.a4,
 104                               x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
 105         if (!t) {
 106                 t = ipcomp_tunnel_create(x);
 107                 if (!t) {
 108                         err = -EINVAL;
 109                         goto out;
 110                 }
 111                 xfrm_state_insert(t);
 112                 xfrm_state_hold(t);
 113         }
 114         x->tunnel = t;
 115         atomic_inc(&t->tunnel_users);
 116 out:
 117         return err;
 118 }
 119
 120 static int ipcomp4_init_state(struct xfrm_state *x)
 121 {
 122         int err = -EINVAL;
 123
 124         x->props.header_len = 0;
 125         switch (x->props.mode) {
 126         case XFRM_MODE_TRANSPORT:
 127                 break;
 128         case XFRM_MODE_TUNNEL:
 129                 x->props.header_len += sizeof(struct iphdr);
 130                 break;
 131         default:
 132                 goto out;
 133         }
 134
 135         err = ipcomp_init_state(x);
 136         if (err)
 137                 goto out;
 138
 139         if (x->props.mode == XFRM_MODE_TUNNEL) {
 140                 err = ipcomp_tunnel_attach(x);
 141                 if (err)
 142                         goto out;
 143         }
 144
 145         err = 0;
 146 out:
 147         return err;
 148 }
 149
 150 static const struct xfrm_type ipcomp_type = {
 151         .description    = "IPCOMP4",
 152         .owner          = THIS_MODULE,
 153         .proto          = IPPROTO_COMP,
 154         .init_state     = ipcomp4_init_state,
 155         .destructor     = ipcomp_destroy,
 156         .input          = ipcomp_input,
 157         .output         = ipcomp_output
 158 };
 159
 160 static const struct net_protocol ipcomp4_protocol = {
 161         .handler        =       xfrm4_rcv,
 162         .err_handler    =       ipcomp4_err,
 163         .no_policy      =       1,
 164         .netns_ok       =       1,
 165 };
 166
 167 static int __init ipcomp4_init(void)
 168 {
 169         if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
 170                 pr_info("%s: can't add xfrm type\n", __func__);
 171                 return -EAGAIN;
 172         }
 173         if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
 174                 pr_info("%s: can't add protocol\n", __func__);
 175                 xfrm_unregister_type(&ipcomp_type, AF_INET);
 176                 return -EAGAIN;
 177         }
 178         return 0;
 179 }
 180
 181 static void __exit ipcomp4_fini(void)
 182 {
 183         if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
 184                 pr_info("%s: can't remove protocol\n", __func__);
 185         if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
 186                 pr_info("%s: can't remove xfrm type\n", __func__);
 187 }
 188
 189 module_init(ipcomp4_init);
 190 module_exit(ipcomp4_fini);
 191
 192 MODULE_LICENSE("GPL");
 193 MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp/IPv4) - RFC3173");
 194 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
 195
 196 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);