linux/net/ipv4/ipcomp.c
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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
  26static 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, skb->mark, (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 */
  49static 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        memcpy(&t->mark, &x->mark, sizeof(t->mark));
  67
  68        if (xfrm_init_state(t))
  69                goto error;
  70
  71        atomic_set(&t->tunnel_users, 1);
  72out:
  73        return t;
  74
  75error:
  76        t->km.state = XFRM_STATE_DEAD;
  77        xfrm_state_put(t);
  78        t = NULL;
  79        goto out;
  80}
  81
  82/*
  83 * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
  84 * always incremented on success.
  85 */
  86static int ipcomp_tunnel_attach(struct xfrm_state *x)
  87{
  88        struct net *net = xs_net(x);
  89        int err = 0;
  90        struct xfrm_state *t;
  91        u32 mark = x->mark.v & x->mark.m;
  92
  93        t = xfrm_state_lookup(net, mark, (xfrm_address_t *)&x->id.daddr.a4,
  94                              x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
  95        if (!t) {
  96                t = ipcomp_tunnel_create(x);
  97                if (!t) {
  98                        err = -EINVAL;
  99                        goto out;
 100                }
 101                xfrm_state_insert(t);
 102                xfrm_state_hold(t);
 103        }
 104        x->tunnel = t;
 105        atomic_inc(&t->tunnel_users);
 106out:
 107        return err;
 108}
 109
 110static int ipcomp4_init_state(struct xfrm_state *x)
 111{
 112        int err = -EINVAL;
 113
 114        x->props.header_len = 0;
 115        switch (x->props.mode) {
 116        case XFRM_MODE_TRANSPORT:
 117                break;
 118        case XFRM_MODE_TUNNEL:
 119                x->props.header_len += sizeof(struct iphdr);
 120                break;
 121        default:
 122                goto out;
 123        }
 124
 125        err = ipcomp_init_state(x);
 126        if (err)
 127                goto out;
 128
 129        if (x->props.mode == XFRM_MODE_TUNNEL) {
 130                err = ipcomp_tunnel_attach(x);
 131                if (err)
 132                        goto out;
 133        }
 134
 135        err = 0;
 136out:
 137        return err;
 138}
 139
 140static const struct xfrm_type ipcomp_type = {
 141        .description    = "IPCOMP4",
 142        .owner          = THIS_MODULE,
 143        .proto          = IPPROTO_COMP,
 144        .init_state     = ipcomp4_init_state,
 145        .destructor     = ipcomp_destroy,
 146        .input          = ipcomp_input,
 147        .output         = ipcomp_output
 148};
 149
 150static const struct net_protocol ipcomp4_protocol = {
 151        .handler        =       xfrm4_rcv,
 152        .err_handler    =       ipcomp4_err,
 153        .no_policy      =       1,
 154};
 155
 156static int __init ipcomp4_init(void)
 157{
 158        if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
 159                printk(KERN_INFO "ipcomp init: can't add xfrm type\n");
 160                return -EAGAIN;
 161        }
 162        if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
 163                printk(KERN_INFO "ipcomp init: can't add protocol\n");
 164                xfrm_unregister_type(&ipcomp_type, AF_INET);
 165                return -EAGAIN;
 166        }
 167        return 0;
 168}
 169
 170static void __exit ipcomp4_fini(void)
 171{
 172        if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
 173                printk(KERN_INFO "ip ipcomp close: can't remove protocol\n");
 174        if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
 175                printk(KERN_INFO "ip ipcomp close: can't remove xfrm type\n");
 176}
 177
 178module_init(ipcomp4_init);
 179module_exit(ipcomp4_fini);
 180
 181MODULE_LICENSE("GPL");
 182MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp/IPv4) - RFC3173");
 183MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
 184
 185MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);
 186