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