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                 atomic_inc(&flow_cache_genid);
  52                 rt_genid_bump(net);
  53
  54                 ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_COMP, 0);
  55         } else
  56                 ipv4_redirect(skb, net, 0, 0, IPPROTO_COMP, 0);
  57         xfrm_state_put(x);
  58 }
  59
  60 /* We always hold one tunnel user reference to indicate a tunnel */
  61 static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
  62 {
  63         struct net *net = xs_net(x);
  64         struct xfrm_state *t;
  65
  66         t = xfrm_state_alloc(net);
  67         if (t == NULL)
  68                 goto out;
  69
  70         t->id.proto = IPPROTO_IPIP;
  71         t->id.spi = x->props.saddr.a4;
  72         t->id.daddr.a4 = x->id.daddr.a4;
  73         memcpy(&t->sel, &x->sel, sizeof(t->sel));
  74         t->props.family = AF_INET;
  75         t->props.mode = x->props.mode;
  76         t->props.saddr.a4 = x->props.saddr.a4;
  77         t->props.flags = x->props.flags;
  78         t->props.extra_flags = x->props.extra_flags;
  79         memcpy(&t->mark, &x->mark, sizeof(t->mark));
  80
  81         if (xfrm_init_state(t))
  82                 goto error;
  83
  84         atomic_set(&t->tunnel_users, 1);
  85 out:
  86         return t;
  87
  88 error:
  89         t->km.state = XFRM_STATE_DEAD;
  90         xfrm_state_put(t);
  91         t = NULL;
  92         goto out;
  93 }
  94
  95 /*
  96  * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
  97  * always incremented on success.
  98  */
  99 static int ipcomp_tunnel_attach(struct xfrm_state *x)
 100 {
 101         struct net *net = xs_net(x);
 102         int err = 0;
 103         struct xfrm_state *t;
 104         u32 mark = x->mark.v & x->mark.m;
 105
 106         t = xfrm_state_lookup(net, mark, (xfrm_address_t *)&x->id.daddr.a4,
 107                               x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
 108         if (!t) {
 109                 t = ipcomp_tunnel_create(x);
 110                 if (!t) {
 111                         err = -EINVAL;
 112                         goto out;
 113                 }
 114                 xfrm_state_insert(t);
 115                 xfrm_state_hold(t);
 116         }
 117         x->tunnel = t;
 118         atomic_inc(&t->tunnel_users);
 119 out:
 120         return err;
 121 }
 122
 123 static int ipcomp4_init_state(struct xfrm_state *x)
 124 {
 125         int err = -EINVAL;
 126
 127         x->props.header_len = 0;
 128         switch (x->props.mode) {
 129         case XFRM_MODE_TRANSPORT:
 130                 break;
 131         case XFRM_MODE_TUNNEL:
 132                 x->props.header_len += sizeof(struct iphdr);
 133                 break;
 134         default:
 135                 goto out;
 136         }
 137
 138         err = ipcomp_init_state(x);
 139         if (err)
 140                 goto out;
 141
 142         if (x->props.mode == XFRM_MODE_TUNNEL) {
 143                 err = ipcomp_tunnel_attach(x);
 144                 if (err)
 145                         goto out;
 146         }
 147
 148         err = 0;
 149 out:
 150         return err;
 151 }
 152
 153 static const struct xfrm_type ipcomp_type = {
 154         .description    = "IPCOMP4",
 155         .owner          = THIS_MODULE,
 156         .proto          = IPPROTO_COMP,
 157         .init_state     = ipcomp4_init_state,
 158         .destructor     = ipcomp_destroy,
 159         .input          = ipcomp_input,
 160         .output         = ipcomp_output
 161 };
 162
 163 static const struct net_protocol ipcomp4_protocol = {
 164         .handler        =       xfrm4_rcv,
 165         .err_handler    =       ipcomp4_err,
 166         .no_policy      =       1,
 167         .netns_ok       =       1,
 168 };
 169
 170 static int __init ipcomp4_init(void)
 171 {
 172         if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
 173                 pr_info("%s: can't add xfrm type\n", __func__);
 174                 return -EAGAIN;
 175         }
 176         if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
 177                 pr_info("%s: can't add protocol\n", __func__);
 178                 xfrm_unregister_type(&ipcomp_type, AF_INET);
 179                 return -EAGAIN;
 180         }
 181         return 0;
 182 }
 183
 184 static void __exit ipcomp4_fini(void)
 185 {
 186         if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
 187                 pr_info("%s: can't remove protocol\n", __func__);
 188         if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
 189                 pr_info("%s: can't remove xfrm type\n", __func__);
 190 }
 191
 192 module_init(ipcomp4_init);
 193 module_exit(ipcomp4_fini);
 194
 195 MODULE_LICENSE("GPL");
 196 MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp/IPv4) - RFC3173");
 197 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
 198
 199 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);