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* IP Payload Compression Protocol (IPComp) - RFC3173.
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* Copyright (c) 2003 James Morris <jmorris@intercode.com.au>
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* - Tunable compression parameters.
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* - Compression stats.
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* - Adaptive compression.
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#include <linux/module.h>
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#include <linux/err.h>
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#include <linux/rtnetlink.h>
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#include <net/ipcomp.h>
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#include <net/protocol.h>
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static void ipcomp4_err(struct sk_buff *skb, u32 info)
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struct net *net = dev_net(skb->dev);
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const struct iphdr *iph = (const struct iphdr *)skb->data;
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struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
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if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
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icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
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spi = htonl(ntohs(ipch->cpi));
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x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
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spi, IPPROTO_COMP, AF_INET);
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NETDEBUG(KERN_DEBUG "pmtu discovery on SA IPCOMP/%08x/%pI4\n",
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/* We always hold one tunnel user reference to indicate a tunnel */
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static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
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struct net *net = xs_net(x);
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t = xfrm_state_alloc(net);
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t->id.proto = IPPROTO_IPIP;
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t->id.spi = x->props.saddr.a4;
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t->id.daddr.a4 = x->id.daddr.a4;
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memcpy(&t->sel, &x->sel, sizeof(t->sel));
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t->props.family = AF_INET;
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t->props.mode = x->props.mode;
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t->props.saddr.a4 = x->props.saddr.a4;
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t->props.flags = x->props.flags;
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memcpy(&t->mark, &x->mark, sizeof(t->mark));
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if (xfrm_init_state(t))
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atomic_set(&t->tunnel_users, 1);
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t->km.state = XFRM_STATE_DEAD;
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* Must be protected by xfrm_cfg_mutex. State and tunnel user references are
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* always incremented on success.
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static int ipcomp_tunnel_attach(struct xfrm_state *x)
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struct net *net = xs_net(x);
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u32 mark = x->mark.v & x->mark.m;
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t = xfrm_state_lookup(net, mark, (xfrm_address_t *)&x->id.daddr.a4,
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x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
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t = ipcomp_tunnel_create(x);
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xfrm_state_insert(t);
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atomic_inc(&t->tunnel_users);
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static int ipcomp4_init_state(struct xfrm_state *x)
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x->props.header_len = 0;
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switch (x->props.mode) {
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case XFRM_MODE_TRANSPORT:
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case XFRM_MODE_TUNNEL:
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x->props.header_len += sizeof(struct iphdr);
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err = ipcomp_init_state(x);
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if (x->props.mode == XFRM_MODE_TUNNEL) {
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err = ipcomp_tunnel_attach(x);
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static const struct xfrm_type ipcomp_type = {
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.description = "IPCOMP4",
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.owner = THIS_MODULE,
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.proto = IPPROTO_COMP,
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.init_state = ipcomp4_init_state,
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.destructor = ipcomp_destroy,
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.input = ipcomp_input,
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.output = ipcomp_output
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static const struct net_protocol ipcomp4_protocol = {
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.handler = xfrm4_rcv,
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.err_handler = ipcomp4_err,
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static int __init ipcomp4_init(void)
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if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
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printk(KERN_INFO "ipcomp init: can't add xfrm type\n");
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if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
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printk(KERN_INFO "ipcomp init: can't add protocol\n");
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xfrm_unregister_type(&ipcomp_type, AF_INET);
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static void __exit ipcomp4_fini(void)
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if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
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printk(KERN_INFO "ip ipcomp close: can't remove protocol\n");
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if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
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printk(KERN_INFO "ip ipcomp close: can't remove xfrm type\n");
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module_init(ipcomp4_init);
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module_exit(ipcomp4_fini);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp/IPv4) - RFC3173");
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MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
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MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);