/usr/src/west-chamber-20100405+svn20110916.r119/xt_UDPENCAP.c is in west-chamber-dkms 20100405+svn20110916.r119-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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* "UDPENCAP" target extension for Xtables
* Klzgrad <kizdiv@gmail.com>, 2011
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <net/ip.h>
#include <linux/ipv6.h>
#include <linux/udp.h>
#include <linux/netfilter/x_tables.h>
#include "compat_xtables.h"
#include "xt_UDPENCAP.h"
#define PFX KBUILD_MODNAME ": "
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
# define WITH_IPV6 1
#endif
static bool udpencap_insert_header(struct sk_buff *skb, const struct xt_udpencap_tginfo *info)
{
struct udphdr *uh;
if (!skb_make_writable(&skb, skb_transport_offset(skb)))
return false;
if (skb->len + sizeof(struct udphdr) > 65535)
return false;
if (skb_cow(skb, sizeof(struct udphdr) + LL_RESERVED_SPACE(skb_dst(skb)->dev)))
return false;
memmove(skb->data - sizeof(struct udphdr), skb->data, skb_transport_offset(skb));
__skb_push(skb, sizeof(struct udphdr));
skb->network_header -= sizeof(struct udphdr);
skb->transport_header -= sizeof(struct udphdr);
uh = udp_hdr(skb);
uh->source = info->sport;
uh->dest = info->dport;
uh->len = htons(skb->len - skb_transport_offset(skb));
uh->check = 0;
return true;
}
static bool udpencap_remove_header(struct sk_buff *skb, const struct xt_udpencap_tginfo *info)
{
unsigned int nlen = skb_transport_offset(skb);
if (!skb_make_writable(&skb, skb_transport_offset(skb) + sizeof(struct udphdr)))
return false;
if (skb->len < nlen + sizeof(struct udphdr))
return false;
if (!pskb_pull(skb, sizeof(struct udphdr)))
return false;
skb_postpull_rcsum(skb, skb_transport_header(skb), sizeof(struct udphdr));
memmove(skb->data, skb->data - sizeof(struct udphdr), nlen);
skb->network_header += sizeof(struct udphdr);
skb->transport_header += sizeof(struct udphdr);
return true;
}
static void udpencap_fix4(struct sk_buff *skb, const struct xt_udpencap_tginfo *info)
{
struct iphdr *iph = ip_hdr(skb);
bool fix_csum = (skb->ip_summed == CHECKSUM_COMPLETE && !info->encap);
__be16 newlen = htons(ntohs(iph->tot_len) + (info->encap ? 1 : -1) * sizeof(struct udphdr));
if (fix_csum) {
skb->csum = csum_sub(skb->csum, csum_partial(&iph->tot_len, 2, 0));
skb->csum = csum_sub(skb->csum, csum_partial(&iph->protocol, 3, 0));
}
csum_replace2(&iph->check, iph->tot_len, newlen);
iph->tot_len = newlen;
if (iph->protocol != info->proto) {
csum_replace2(&iph->check, htons(iph->protocol), htons(info->proto));
iph->protocol = info->proto;
}
if (fix_csum) {
skb->csum = csum_add(skb->csum, csum_partial(&iph->tot_len, 2, 0));
skb->csum = csum_add(skb->csum, csum_partial(&iph->protocol, 3, 0));
}
}
static void udpencap_fix6(struct sk_buff *skb, const struct xt_udpencap_tginfo *info)
{
struct ipv6hdr *iph = ipv6_hdr(skb);
bool fix_csum = (skb->ip_summed == CHECKSUM_COMPLETE && !info->encap);
if (fix_csum)
skb->csum = csum_sub(skb->csum, csum_partial(&iph->payload_len, 3, 0));
iph->payload_len = htons(ntohs(iph->payload_len) + (info->encap ? 1 : -1) * sizeof(struct udphdr));
iph->nexthdr = info->proto;
if (fix_csum)
skb->csum = csum_add(skb->csum, csum_partial(&iph->payload_len, 3, 0));
}
static unsigned int udpencap_tg(struct sk_buff **pskb, const struct xt_action_param *par)
{
const struct xt_udpencap_tginfo *info = par->targinfo;
struct sk_buff *skb = *pskb;
unsigned int tproto, nlen;
bool ipv4 = (par->family == NFPROTO_IPV4);
if (ipv4) {
nlen = ip_hdrlen(skb);
if (nlen < sizeof(struct iphdr))
return NF_DROP;
tproto = ip_hdr(skb)->protocol;
} else {
nlen = sizeof(struct ipv6hdr);
tproto = ipv6_hdr(skb)->nexthdr;
}
if (!info->encap && tproto != IPPROTO_UDP)
return NF_DROP;
skb_set_transport_header(skb, skb_network_offset(skb) + nlen);
if (!(info->encap ? udpencap_insert_header : udpencap_remove_header)(skb, info))
return NF_DROP;
(ipv4 ? udpencap_fix4 : udpencap_fix6)(skb, info);
return XT_CONTINUE;
}
static int udpencap_tg_check(const struct xt_tgchk_param *par)
{
const struct xt_udpencap_tginfo *info = par->targinfo;
if (info->encap && info->proto != IPPROTO_UDP) {
pr_err(PFX "encap protocol is not UDP\n");
return -EINVAL;
}
return 0;
}
static struct xt_target udpencap_tg_reg[] __read_mostly = {
{
.name = "UDPENCAP",
.revision = 0,
.family = NFPROTO_IPV4,
.table = "mangle",
.target = udpencap_tg,
.targetsize = sizeof(struct xt_udpencap_tginfo),
.checkentry = udpencap_tg_check,
.me = THIS_MODULE,
},
#ifdef WITH_IPV6
{
.name = "UDPENCAP",
.revision = 0,
.family = NFPROTO_IPV6,
.table = "mangle",
.target = udpencap_tg,
.targetsize = sizeof(struct xt_udpencap_tginfo),
.checkentry = udpencap_tg_check,
.me = THIS_MODULE,
},
#endif
};
static int __init udpencap_tg_init(void)
{
return xt_register_targets(udpencap_tg_reg, ARRAY_SIZE(udpencap_tg_reg));
}
static void __exit udpencap_tg_exit(void)
{
xt_unregister_targets(udpencap_tg_reg, ARRAY_SIZE(udpencap_tg_reg));
}
module_init(udpencap_tg_init);
module_exit(udpencap_tg_exit);
MODULE_DESCRIPTION("Xtables: Unconditional transport layer UDP encapsulation and decapsulation");
MODULE_AUTHOR("Klzgrad <kizdiv@gmail.com>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_UDPENCAP");
MODULE_ALIAS("ip6t_UDPENCAP");
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