net/ipv4/ipcomp.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * IP Payload Compression Protocol (IPComp) - RFC3173.
   4  *
   5  * Copyright (c) 2003 James Morris <jmorris@intercode.com.au>
   6  *
   7  * Todo:
   8  *   - Tunable compression parameters.
   9  *   - Compression stats.
  10  *   - Adaptive compression.
  11  */
  12 #include <linux/module.h>
  13 #include <linux/err.h>
  14 #include <linux/rtnetlink.h>
  15 #include <net/ip.h>
  16 #include <net/xfrm.h>
  17 #include <net/icmp.h>
  18 #include <net/ipcomp.h>
  19 #include <net/protocol.h>
  20 #include <net/sock.h>
  21
  22 static int ipcomp4_err(struct sk_buff *skb, u32 info)
  23 {
  24         struct net *net = dev_net(skb->dev);
  25         __be32 spi;
  26         const struct iphdr *iph = (const struct iphdr *)skb->data;
  27         struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
  28         struct xfrm_state *x;
  29
  30         switch (icmp_hdr(skb)->type) {
  31         case ICMP_DEST_UNREACH:
  32                 if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
  33                         return 0;
  34         case ICMP_REDIRECT:
  35                 break;
  36         default:
  37                 return 0;
  38         }
  39
  40         spi = htonl(ntohs(ipch->cpi));
  41         x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
  42                               spi, IPPROTO_COMP, AF_INET);
  43         if (!x)
  44                 return 0;
  45
  46         if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
  47                 ipv4_update_pmtu(skb, net, info, 0, IPPROTO_COMP);
  48         else
  49                 ipv4_redirect(skb, net, 0, IPPROTO_COMP);
  50         xfrm_state_put(x);
  51
  52         return 0;
  53 }
  54
  55 /* We always hold one tunnel user reference to indicate a tunnel */
  56 static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
  57 {
  58         struct net *net = xs_net(x);
  59         struct xfrm_state *t;
  60
  61         t = xfrm_state_alloc(net);
  62         if (!t)
  63                 goto out;
  64
  65         t->id.proto = IPPROTO_IPIP;
  66         t->id.spi = x->props.saddr.a4;
  67         t->id.daddr.a4 = x->id.daddr.a4;
  68         memcpy(&t->sel, &x->sel, sizeof(t->sel));
  69         t->props.family = AF_INET;
  70         t->props.mode = x->props.mode;
  71         t->props.saddr.a4 = x->props.saddr.a4;
  72         t->props.flags = x->props.flags;
  73         t->props.extra_flags = x->props.extra_flags;
  74         memcpy(&t->mark, &x->mark, sizeof(t->mark));
  75         t->if_id = x->if_id;
  76
  77         if (xfrm_init_state(t))
  78                 goto error;
  79
  80         atomic_set(&t->tunnel_users, 1);
  81 out:
  82         return t;
  83
  84 error:
  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  */
  95 static 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);
 115 out:
 116         return err;
 117 }
 118
 119 static 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;
 145 out:
 146         return err;
 147 }
 148
 149 static int ipcomp4_rcv_cb(struct sk_buff *skb, int err)
 150 {
 151         return 0;
 152 }
 153
 154 static const struct xfrm_type ipcomp_type = {
 155         .description    = "IPCOMP4",
 156         .owner          = THIS_MODULE,
 157         .proto          = IPPROTO_COMP,
 158         .init_state     = ipcomp4_init_state,
 159         .destructor     = ipcomp_destroy,
 160         .input          = ipcomp_input,
 161         .output         = ipcomp_output
 162 };
 163
 164 static struct xfrm4_protocol ipcomp4_protocol = {
 165         .handler        =       xfrm4_rcv,
 166         .input_handler  =       xfrm_input,
 167         .cb_handler     =       ipcomp4_rcv_cb,
 168         .err_handler    =       ipcomp4_err,
 169         .priority       =       0,
 170 };
 171
 172 static int __init ipcomp4_init(void)
 173 {
 174         if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
 175                 pr_info("%s: can't add xfrm type\n", __func__);
 176                 return -EAGAIN;
 177         }
 178         if (xfrm4_protocol_register(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
 179                 pr_info("%s: can't add protocol\n", __func__);
 180                 xfrm_unregister_type(&ipcomp_type, AF_INET);
 181                 return -EAGAIN;
 182         }
 183         return 0;
 184 }
 185
 186 static void __exit ipcomp4_fini(void)
 187 {
 188         if (xfrm4_protocol_deregister(&ipcomp4_protocol, IPPROTO_COMP) < 0)
 189                 pr_info("%s: can't remove protocol\n", __func__);
 190         xfrm_unregister_type(&ipcomp_type, AF_INET);
 191 }
 192
 193 module_init(ipcomp4_init);
 194 module_exit(ipcomp4_fini);
 195
 196 MODULE_LICENSE("GPL");
 197 MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp/IPv4) - RFC3173");
 198 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
 199
 200 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);