net/ipv4/ipcomp.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  * IP Payload Compression Protocol (IPComp) - RFC3173.
0004  *
0005  * Copyright (c) 2003 James Morris <jmorris@intercode.com.au>
0006  *
0007  * Todo:
0008  *   - Tunable compression parameters.
0009  *   - Compression stats.
0010  *   - Adaptive compression.
0011  */
0012 #include <linux/module.h>
0013 #include <linux/err.h>
0014 #include <linux/rtnetlink.h>
0015 #include <net/ip.h>
0016 #include <net/xfrm.h>
0017 #include <net/icmp.h>
0018 #include <net/ipcomp.h>
0019 #include <net/protocol.h>
0020 #include <net/sock.h>
0021
0022 static int ipcomp4_err(struct sk_buff *skb, u32 info)
0023 {
0024     struct net *net = dev_net(skb->dev);
0025     __be32 spi;
0026     const struct iphdr *iph = (const struct iphdr *)skb->data;
0027     struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
0028     struct xfrm_state *x;
0029
0030     switch (icmp_hdr(skb)->type) {
0031     case ICMP_DEST_UNREACH:
0032         if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
0033             return 0;
0034         break;
0035     case ICMP_REDIRECT:
0036         break;
0037     default:
0038         return 0;
0039     }
0040
0041     spi = htonl(ntohs(ipch->cpi));
0042     x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
0043                   spi, IPPROTO_COMP, AF_INET);
0044     if (!x)
0045         return 0;
0046
0047     if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
0048         ipv4_update_pmtu(skb, net, info, 0, IPPROTO_COMP);
0049     else
0050         ipv4_redirect(skb, net, 0, IPPROTO_COMP);
0051     xfrm_state_put(x);
0052
0053     return 0;
0054 }
0055
0056 /* We always hold one tunnel user reference to indicate a tunnel */
0057 static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
0058 {
0059     struct net *net = xs_net(x);
0060     struct xfrm_state *t;
0061
0062     t = xfrm_state_alloc(net);
0063     if (!t)
0064         goto out;
0065
0066     t->id.proto = IPPROTO_IPIP;
0067     t->id.spi = x->props.saddr.a4;
0068     t->id.daddr.a4 = x->id.daddr.a4;
0069     memcpy(&t->sel, &x->sel, sizeof(t->sel));
0070     t->props.family = AF_INET;
0071     t->props.mode = x->props.mode;
0072     t->props.saddr.a4 = x->props.saddr.a4;
0073     t->props.flags = x->props.flags;
0074     t->props.extra_flags = x->props.extra_flags;
0075     memcpy(&t->mark, &x->mark, sizeof(t->mark));
0076     t->if_id = x->if_id;
0077
0078     if (xfrm_init_state(t))
0079         goto error;
0080
0081     atomic_set(&t->tunnel_users, 1);
0082 out:
0083     return t;
0084
0085 error:
0086     t->km.state = XFRM_STATE_DEAD;
0087     xfrm_state_put(t);
0088     t = NULL;
0089     goto out;
0090 }
0091
0092 /*
0093  * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
0094  * always incremented on success.
0095  */
0096 static int ipcomp_tunnel_attach(struct xfrm_state *x)
0097 {
0098     struct net *net = xs_net(x);
0099     int err = 0;
0100     struct xfrm_state *t;
0101     u32 mark = x->mark.v & x->mark.m;
0102
0103     t = xfrm_state_lookup(net, mark, (xfrm_address_t *)&x->id.daddr.a4,
0104                   x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
0105     if (!t) {
0106         t = ipcomp_tunnel_create(x);
0107         if (!t) {
0108             err = -EINVAL;
0109             goto out;
0110         }
0111         xfrm_state_insert(t);
0112         xfrm_state_hold(t);
0113     }
0114     x->tunnel = t;
0115     atomic_inc(&t->tunnel_users);
0116 out:
0117     return err;
0118 }
0119
0120 static int ipcomp4_init_state(struct xfrm_state *x)
0121 {
0122     int err = -EINVAL;
0123
0124     x->props.header_len = 0;
0125     switch (x->props.mode) {
0126     case XFRM_MODE_TRANSPORT:
0127         break;
0128     case XFRM_MODE_TUNNEL:
0129         x->props.header_len += sizeof(struct iphdr);
0130         break;
0131     default:
0132         goto out;
0133     }
0134
0135     err = ipcomp_init_state(x);
0136     if (err)
0137         goto out;
0138
0139     if (x->props.mode == XFRM_MODE_TUNNEL) {
0140         err = ipcomp_tunnel_attach(x);
0141         if (err)
0142             goto out;
0143     }
0144
0145     err = 0;
0146 out:
0147     return err;
0148 }
0149
0150 static int ipcomp4_rcv_cb(struct sk_buff *skb, int err)
0151 {
0152     return 0;
0153 }
0154
0155 static const struct xfrm_type ipcomp_type = {
0156     .owner      = THIS_MODULE,
0157     .proto          = IPPROTO_COMP,
0158     .init_state = ipcomp4_init_state,
0159     .destructor = ipcomp_destroy,
0160     .input      = ipcomp_input,
0161     .output     = ipcomp_output
0162 };
0163
0164 static struct xfrm4_protocol ipcomp4_protocol = {
0165     .handler    =   xfrm4_rcv,
0166     .input_handler  =   xfrm_input,
0167     .cb_handler =   ipcomp4_rcv_cb,
0168     .err_handler    =   ipcomp4_err,
0169     .priority   =   0,
0170 };
0171
0172 static int __init ipcomp4_init(void)
0173 {
0174     if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
0175         pr_info("%s: can't add xfrm type\n", __func__);
0176         return -EAGAIN;
0177     }
0178     if (xfrm4_protocol_register(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
0179         pr_info("%s: can't add protocol\n", __func__);
0180         xfrm_unregister_type(&ipcomp_type, AF_INET);
0181         return -EAGAIN;
0182     }
0183     return 0;
0184 }
0185
0186 static void __exit ipcomp4_fini(void)
0187 {
0188     if (xfrm4_protocol_deregister(&ipcomp4_protocol, IPPROTO_COMP) < 0)
0189         pr_info("%s: can't remove protocol\n", __func__);
0190     xfrm_unregister_type(&ipcomp_type, AF_INET);
0191 }
0192
0193 module_init(ipcomp4_init);
0194 module_exit(ipcomp4_fini);
0195
0196 MODULE_LICENSE("GPL");
0197 MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp/IPv4) - RFC3173");
0198 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
0199
0200 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);