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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  
ipcomp4_err(struct sk_buff * skb,u32 info)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 */
ipcomp_tunnel_create(struct xfrm_state * x)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   */
ipcomp_tunnel_attach(struct xfrm_state * x)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  
ipcomp4_init_state(struct xfrm_state * x)120  static int ipcomp4_init_state(struct xfrm_state *x)
121  {
122  	int err = -EINVAL;
123  
124  	x->props.header_len = 0;
125  	switch (x->props.mode) {
126  	case XFRM_MODE_TRANSPORT:
127  		break;
128  	case XFRM_MODE_TUNNEL:
129  		x->props.header_len += sizeof(struct iphdr);
130  		break;
131  	default:
132  		goto out;
133  	}
134  
135  	err = ipcomp_init_state(x);
136  	if (err)
137  		goto out;
138  
139  	if (x->props.mode == XFRM_MODE_TUNNEL) {
140  		err = ipcomp_tunnel_attach(x);
141  		if (err)
142  			goto out;
143  	}
144  
145  	err = 0;
146  out:
147  	return err;
148  }
149  
ipcomp4_rcv_cb(struct sk_buff * skb,int err)150  static int ipcomp4_rcv_cb(struct sk_buff *skb, int err)
151  {
152  	return 0;
153  }
154  
155  static const struct xfrm_type ipcomp_type = {
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  
ipcomp4_init(void)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  
ipcomp4_fini(void)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);
201