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                 break;
  35         case ICMP_REDIRECT:
  36                 break;
  37         default:
  38                 return 0;
  39         }
  40
  41         spi = htonl(ntohs(ipch->cpi));
  42         x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
  43                               spi, IPPROTO_COMP, AF_INET);
  44         if (!x)
  45                 return 0;
  46
  47         if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
  48                 ipv4_update_pmtu(skb, net, info, 0, IPPROTO_COMP);
  49         else
  50                 ipv4_redirect(skb, net, 0, IPPROTO_COMP);
  51         xfrm_state_put(x);
  52
  53         return 0;
  54 }
  55
  56 /* We always hold one tunnel user reference to indicate a tunnel */
  57 static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
  58 {
  59         struct net *net = xs_net(x);
  60         struct xfrm_state *t;
  61
  62         t = xfrm_state_alloc(net);
  63         if (!t)
  64                 goto out;
  65
  66         t->id.proto = IPPROTO_IPIP;
  67         t->id.spi = x->props.saddr.a4;
  68         t->id.daddr.a4 = x->id.daddr.a4;
  69         memcpy(&t->sel, &x->sel, sizeof(t->sel));
  70         t->props.family = AF_INET;
  71         t->props.mode = x->props.mode;
  72         t->props.saddr.a4 = x->props.saddr.a4;
  73         t->props.flags = x->props.flags;
  74         t->props.extra_flags = x->props.extra_flags;
  75         memcpy(&t->mark, &x->mark, sizeof(t->mark));
  76         t->if_id = x->if_id;
  77
  78         if (xfrm_init_state(t))
  79                 goto error;
  80
  81         atomic_set(&t->tunnel_users, 1);
  82 out:
  83         return t;
  84
  85 error:
  86         t->km.state = XFRM_STATE_DEAD;
  87         xfrm_state_put(t);
  88         t = NULL;
  89         goto out;
  90 }
  91
  92 /*
  93  * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
  94  * always incremented on success.
  95  */
  96 static int ipcomp_tunnel_attach(struct xfrm_state *x)
  97 {
  98         struct net *net = xs_net(x);
  99         int err = 0;
 100         struct xfrm_state *t;
 101         u32 mark = x->mark.v & x->mark.m;
 102
 103         t = xfrm_state_lookup(net, mark, (xfrm_address_t *)&x->id.daddr.a4,
 104                               x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
 105         if (!t) {
 106                 t = ipcomp_tunnel_create(x);
 107                 if (!t) {
 108                         err = -EINVAL;
 109                         goto out;
 110                 }
 111                 xfrm_state_insert(t);
 112                 xfrm_state_hold(t);
 113         }
 114         x->tunnel = t;
 115         atomic_inc(&t->tunnel_users);
 116 out:
 117         return err;
 118 }
 119
 120 static int ipcomp4_init_state(struct xfrm_state *x,
 121                               struct netlink_ext_ack *extack)
 122 {
 123         int err = -EINVAL;
 124
 125         x->props.header_len = 0;
 126         switch (x->props.mode) {
 127         case XFRM_MODE_TRANSPORT:
 128                 break;
 129         case XFRM_MODE_TUNNEL:
 130                 x->props.header_len += sizeof(struct iphdr);
 131                 break;
 132         default:
 133                 NL_SET_ERR_MSG(extack, "Unsupported XFRM mode for IPcomp");
 134                 goto out;
 135         }
 136
 137         err = ipcomp_init_state(x, extack);
 138         if (err)
 139                 goto out;
 140
 141         if (x->props.mode == XFRM_MODE_TUNNEL) {
 142                 err = ipcomp_tunnel_attach(x);
 143                 if (err) {
 144                         NL_SET_ERR_MSG(extack, "Kernel error: failed to initialize the associated state");
 145                         goto out;
 146                 }
 147         }
 148
 149         err = 0;
 150 out:
 151         return err;
 152 }
 153
 154 static int ipcomp4_rcv_cb(struct sk_buff *skb, int err)
 155 {
 156         return 0;
 157 }
 158
 159 static const struct xfrm_type ipcomp_type = {
 160         .owner          = THIS_MODULE,
 161         .proto          = IPPROTO_COMP,
 162         .init_state     = ipcomp4_init_state,
 163         .destructor     = ipcomp_destroy,
 164         .input          = ipcomp_input,
 165         .output         = ipcomp_output
 166 };
 167
 168 static struct xfrm4_protocol ipcomp4_protocol = {
 169         .handler        =       xfrm4_rcv,
 170         .input_handler  =       xfrm_input,
 171         .cb_handler     =       ipcomp4_rcv_cb,
 172         .err_handler    =       ipcomp4_err,
 173         .priority       =       0,
 174 };
 175
 176 static int __init ipcomp4_init(void)
 177 {
 178         if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
 179                 pr_info("%s: can't add xfrm type\n", __func__);
 180                 return -EAGAIN;
 181         }
 182         if (xfrm4_protocol_register(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
 183                 pr_info("%s: can't add protocol\n", __func__);
 184                 xfrm_unregister_type(&ipcomp_type, AF_INET);
 185                 return -EAGAIN;
 186         }
 187         return 0;
 188 }
 189
 190 static void __exit ipcomp4_fini(void)
 191 {
 192         if (xfrm4_protocol_deregister(&ipcomp4_protocol, IPPROTO_COMP) < 0)
 193                 pr_info("%s: can't remove protocol\n", __func__);
 194         xfrm_unregister_type(&ipcomp_type, AF_INET);
 195 }
 196
 197 module_init(ipcomp4_init);
 198 module_exit(ipcomp4_fini);
 199
 200 MODULE_LICENSE("GPL");
 201 MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp/IPv4) - RFC3173");
 202 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
 203
 204 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);