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
  76         if (xfrm_init_state(t))
  77                 goto error;
  78
  79         atomic_set(&t->tunnel_users, 1);
  80 out:
  81         return t;
  82
  83 error:
  84         t->km.state = XFRM_STATE_DEAD;
  85         xfrm_state_put(t);
  86         t = NULL;
  87         goto out;
  88 }
  89
  90 /*
  91  * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
  92  * always incremented on success.
  93  */
  94 static int ipcomp_tunnel_attach(struct xfrm_state *x)
  95 {
  96         struct net *net = xs_net(x);
  97         int err = 0;
  98         struct xfrm_state *t;
  99         u32 mark = x->mark.v & x->mark.m;
 100
 101         t = xfrm_state_lookup(net, mark, (xfrm_address_t *)&x->id.daddr.a4,
 102                               x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
 103         if (!t) {
 104                 t = ipcomp_tunnel_create(x);
 105                 if (!t) {
 106                         err = -EINVAL;
 107                         goto out;
 108                 }
 109                 xfrm_state_insert(t);
 110                 xfrm_state_hold(t);
 111         }
 112         x->tunnel = t;
 113         atomic_inc(&t->tunnel_users);
 114 out:
 115         return err;
 116 }
 117
 118 static int ipcomp4_init_state(struct xfrm_state *x)
 119 {
 120         int err = -EINVAL;
 121
 122         x->props.header_len = 0;
 123         switch (x->props.mode) {
 124         case XFRM_MODE_TRANSPORT:
 125                 break;
 126         case XFRM_MODE_TUNNEL:
 127                 x->props.header_len += sizeof(struct iphdr);
 128                 break;
 129         default:
 130                 goto out;
 131         }
 132
 133         err = ipcomp_init_state(x);
 134         if (err)
 135                 goto out;
 136
 137         if (x->props.mode == XFRM_MODE_TUNNEL) {
 138                 err = ipcomp_tunnel_attach(x);
 139                 if (err)
 140                         goto out;
 141         }
 142
 143         err = 0;
 144 out:
 145         return err;
 146 }
 147
 148 static int ipcomp4_rcv_cb(struct sk_buff *skb, int err)
 149 {
 150         return 0;
 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 struct xfrm4_protocol ipcomp4_protocol = {
 164         .handler        =       xfrm4_rcv,
 165         .input_handler  =       xfrm_input,
 166         .cb_handler     =       ipcomp4_rcv_cb,
 167         .err_handler    =       ipcomp4_err,
 168         .priority       =       0,
 169 };
 170
 171 static int __init ipcomp4_init(void)
 172 {
 173         if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
 174                 pr_info("%s: can't add xfrm type\n", __func__);
 175                 return -EAGAIN;
 176         }
 177         if (xfrm4_protocol_register(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
 178                 pr_info("%s: can't add protocol\n", __func__);
 179                 xfrm_unregister_type(&ipcomp_type, AF_INET);
 180                 return -EAGAIN;
 181         }
 182         return 0;
 183 }
 184
 185 static void __exit ipcomp4_fini(void)
 186 {
 187         if (xfrm4_protocol_deregister(&ipcomp4_protocol, IPPROTO_COMP) < 0)
 188                 pr_info("%s: can't remove protocol\n", __func__);
 189         xfrm_unregister_type(&ipcomp_type, AF_INET);
 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);