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@@ -0,0 +1,325 @@
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+Index: linux-2.6.22.4/net/netfilter/Kconfig
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+===================================================================
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+--- linux-2.6.22.4.orig/net/netfilter/Kconfig
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++++ linux-2.6.22.4/net/netfilter/Kconfig
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+@@ -379,6 +379,23 @@ config NETFILTER_XT_TARGET_CONNSECMARK
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+
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+ To compile it as a module, choose M here. If unsure, say N.
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+
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++config NETFILTER_XT_TARGET_TARPIT
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++ tristate '"TARPIT" target support'
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++ depends on NETFILTER_XTABLES
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++ ---help---
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++ Adds a TARPIT target to iptables, which captures and holds
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++ incoming TCP connections using no local per-connection resources.
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++ Connections are accepted, but immediately switched to the persist
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++ state (0 byte window), in which the remote side stops sending data
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++ and asks to continue every 60-240 seconds. Attempts to close the
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++ connection are ignored, forcing the remote side to time out the
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++ connection in 12-24 minutes.
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++
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++ This offers similar functionality to LaBrea
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++ <http://www.hackbusters.net/LaBrea/>, but does not require dedicated
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++ hardware or IPs. Any TCP port that you would normally DROP or REJECT
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++ can instead become a tarpit.
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++
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+ config NETFILTER_XT_TARGET_TCPMSS
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+ tristate '"TCPMSS" target support'
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+ depends on NETFILTER_XTABLES && (IPV6 || IPV6=n)
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+Index: linux-2.6.22.4/net/netfilter/Makefile
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+===================================================================
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+--- linux-2.6.22.4.orig/net/netfilter/Makefile
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++++ linux-2.6.22.4/net/netfilter/Makefile
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+@@ -47,6 +47,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_NFQUEUE
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+ obj-$(CONFIG_NETFILTER_XT_TARGET_NFLOG) += xt_NFLOG.o
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+ obj-$(CONFIG_NETFILTER_XT_TARGET_NOTRACK) += xt_NOTRACK.o
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+ obj-$(CONFIG_NETFILTER_XT_TARGET_SECMARK) += xt_SECMARK.o
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++obj-$(CONFIG_NETFILTER_XT_TARGET_TARPIT) += xt_TARPIT.o
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+ obj-$(CONFIG_NETFILTER_XT_TARGET_TCPMSS) += xt_TCPMSS.o
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+ obj-$(CONFIG_NETFILTER_XT_TARGET_CONNSECMARK) += xt_CONNSECMARK.o
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+
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+Index: linux-2.6.22.4/net/netfilter/xt_TARPIT.c
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+===================================================================
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+--- /dev/null
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++++ linux-2.6.22.4/net/netfilter/xt_TARPIT.c
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+@@ -0,0 +1,280 @@
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++/*
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++ * Kernel module to capture and hold incoming TCP connections using
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++ * no local per-connection resources.
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++ *
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++ * Based on ipt_REJECT.c and offering functionality similar to
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++ * LaBrea <http://www.hackbusters.net/LaBrea/>.
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++ *
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++ * Copyright (c) 2002 Aaron Hopkins <[email protected]>
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++ *
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++ * This program is free software; you can redistribute it and/or modify
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++ * it under the terms of the GNU General Public License as published by
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++ * the Free Software Foundation; either version 2 of the License, or
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++ * (at your option) any later version.
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++ *
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++ * This program is distributed in the hope that it will be useful,
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++ * but WITHOUT ANY WARRANTY; without even the implied warranty of
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++ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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++ * GNU General Public License for more details.
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++ *
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++ * You should have received a copy of the GNU General Public License
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++ * along with this program; if not, write to the Free Software
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++ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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++ *
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++ * Goal:
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++ * - Allow incoming TCP connections to be established.
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++ * - Passing data should result in the connection being switched to the
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++ * persist state (0 byte window), in which the remote side stops sending
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++ * data and asks to continue every 60 seconds.
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++ * - Attempts to shut down the connection should be ignored completely, so
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++ * the remote side ends up having to time it out.
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++ *
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++ * This means:
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++ * - Reply to TCP SYN,!ACK,!RST,!FIN with SYN-ACK, window 5 bytes
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++ * - Reply to TCP SYN,ACK,!RST,!FIN with RST to prevent spoofing
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++ * - Reply to TCP !SYN,!RST,!FIN with ACK, window 0 bytes, rate-limited
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++ */
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++
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++#include <linux/version.h>
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++#include <linux/module.h>
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++#include <linux/skbuff.h>
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++#include <linux/ip.h>
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++#include <net/ip.h>
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++#include <net/tcp.h>
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++#include <net/icmp.h>
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++struct in_device;
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++#include <net/route.h>
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++#include <linux/random.h>
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++#include <linux/netfilter_ipv4/ip_tables.h>
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++
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++#if 0
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++#define DEBUGP printk
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++#else
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++#define DEBUGP(format, args...)
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++#endif
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++
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++/* Stolen from ip_finish_output2 */
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++static int ip_direct_send(struct sk_buff *skb)
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++{
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++ struct dst_entry *dst = skb->dst;
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++
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++ if (dst->hh != NULL)
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++ return neigh_hh_output(dst->hh, skb);
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++ else if (dst->neighbour != NULL)
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++ return dst->neighbour->output(skb);
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++
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++ if (net_ratelimit())
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++ printk(KERN_DEBUG "TARPIT ip_direct_send: no header cache and no neighbor!\n");
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++
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++ kfree_skb(skb);
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++ return -EINVAL;
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++}
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++
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++
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++/* Send reply */
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++static void tarpit_tcp(const struct sk_buff *oskb, struct rtable *ort,
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++ unsigned int local)
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++{
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++ struct sk_buff *nskb;
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++ struct rtable *nrt;
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++ struct tcphdr *otcph, *ntcph;
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++ struct flowi fl = {};
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++ unsigned int otcplen;
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++ u_int16_t tmp;
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++
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++ const struct iphdr *oiph = ip_hdr(oskb);
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++ struct iphdr *niph;
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++
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++ /* A truncated TCP header is not going to be useful */
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++ if (oskb->len < ip_hdrlen(oskb) + sizeof(struct tcphdr))
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++ return;
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++
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++ otcph = (void *)oiph + ip_hdrlen(oskb);
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++ otcplen = oskb->len - ip_hdrlen(oskb);
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++
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++ /* No replies for RST or FIN */
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++ if (otcph->rst || otcph->fin)
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++ return;
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++
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++ /* No reply to !SYN,!ACK. Rate-limit replies to !SYN,ACKs */
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++ if (!otcph->syn && (!otcph->ack || !xrlim_allow(&ort->u.dst, 1*HZ)))
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++ return;
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++
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++ /* Check checksum. */
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++ if (tcp_v4_check(otcplen, oiph->saddr, oiph->daddr,
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++ csum_partial((char *)otcph, otcplen, 0)) != 0)
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++ return;
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++
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++ /*
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++ * Copy skb (even if skb is about to be dropped, we cannot just
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++ * clone it because there may be other things, such as tcpdump,
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++ * interested in it)
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++ */
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++ nskb = skb_copy(oskb, GFP_ATOMIC);
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++ if (nskb == NULL)
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++ return;
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++
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++ niph = ip_hdr(nskb);
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++
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++ /* This packet will not be the same as the other: clear nf fields */
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++ nf_conntrack_put(nskb->nfct);
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++ nskb->nfct = NULL;
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++#ifdef CONFIG_NETFILTER_DEBUG
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++ nskb->nf_debug = 0;
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++#endif
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++
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++ ntcph = (void *)niph + ip_hdrlen(nskb);
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++
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++ /* Truncate to length (no data) */
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++ ntcph->doff = sizeof(struct tcphdr)/4;
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++ skb_trim(nskb, ip_hdrlen(nskb) + sizeof(struct tcphdr));
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++ niph->tot_len = htons(nskb->len);
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++
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++ /* Swap source and dest */
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++ niph->daddr = xchg(&niph->saddr, niph->daddr);
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++ tmp = ntcph->source;
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++ ntcph->source = ntcph->dest;
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++ ntcph->dest = tmp;
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++
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++ /* Use supplied sequence number or make a new one */
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++ ntcph->seq = otcph->ack ? otcph->ack_seq
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++ : htonl(secure_tcp_sequence_number(niph->saddr,
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++ niph->daddr,
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++ ntcph->source,
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++ ntcph->dest));
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++
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++ /* Our SYN-ACKs must have a >0 window */
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++ ntcph->window = (otcph->syn && !otcph->ack) ? htons(5) : 0;
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++
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++ ntcph->urg_ptr = 0;
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++
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++ /* Reset flags */
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++ ((u_int8_t *)ntcph)[13] = 0;
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++
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++ if (otcph->syn && otcph->ack) {
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++ ntcph->rst = 1;
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++ ntcph->ack_seq = 0;
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++ } else {
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++ ntcph->syn = otcph->syn;
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++ ntcph->ack = 1;
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++ ntcph->ack_seq = htonl(ntohl(otcph->seq) + otcph->syn);
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++ }
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++
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++ /* Adjust TCP checksum */
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++ ntcph->check = 0;
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++ ntcph->check = tcp_v4_check(sizeof(struct tcphdr),
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++ niph->saddr,
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++ niph->daddr,
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++ csum_partial((char *)ntcph,
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++ sizeof(struct tcphdr), 0));
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++
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++ fl.nl_u.ip4_u.daddr = niph->daddr;
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++ fl.nl_u.ip4_u.saddr = local ? niph->saddr : 0;
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++ fl.nl_u.ip4_u.tos = RT_TOS(niph->tos) | RTO_CONN;
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++ fl.oif = 0;
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++
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++ if (ip_route_output_key(&nrt, &fl))
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++ goto free_nskb;
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++
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++ dst_release(nskb->dst);
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++ nskb->dst = &nrt->u.dst;
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++
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++ /* Adjust IP TTL */
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++ niph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);
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++
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++ /* Set DF, id = 0 */
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++ niph->frag_off = htons(IP_DF);
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++ niph->id = 0;
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++
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++ /* Adjust IP checksum */
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++ niph->check = 0;
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++ niph->check = ip_fast_csum((unsigned char *)niph, niph->ihl);
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++
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++ /* "Never happens" */
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++ if (nskb->len > dst_mtu(nskb->dst))
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++ goto free_nskb;
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++
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++ ip_direct_send(nskb);
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++ return;
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++
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++ free_nskb:
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++ kfree_skb(nskb);
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++}
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++
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++static unsigned int xt_tarpit_target(struct sk_buff **pskb,
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++ const struct net_device *in,
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++ const struct net_device *out,
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++ unsigned int hooknum,
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++ const struct xt_target *target,
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++ const void *targinfo)
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++{
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++ const struct sk_buff *skb = *pskb;
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++ const struct iphdr *iph = ip_hdr(skb);
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++ struct rtable *rt = (void *)skb->dst;
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++
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++ /* Do we have an input route cache entry? */
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++ if (rt == NULL)
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++ return NF_DROP;
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++
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++ /* No replies to physical multicast/broadcast */
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++ if (skb->pkt_type != PACKET_HOST && skb->pkt_type != PACKET_OTHERHOST)
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++ return NF_DROP;
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++
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++ /* Now check at the protocol level */
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++ if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
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++ return NF_DROP;
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++
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++ /*
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++ * Our naive response construction does not deal with IP
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++ * options, and probably should not try.
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++ */
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++ if (iph->ihl * 4 != sizeof(struct iphdr))
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++ return NF_DROP;
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++
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++ /* We are not interested in fragments */
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++ if (iph->frag_off & htons(IP_OFFSET))
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++ return NF_DROP;
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++
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++ tarpit_tcp(skb, rt, hooknum == NF_IP_LOCAL_IN);
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++ return NF_DROP;
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++}
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++
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++static bool xt_tarpit_check(const char *tablename, const void *entry,
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++ const struct xt_target *target, void *targinfo,
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++ unsigned int hook_mask)
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++{
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++ bool invalid;
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++
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++ if (strcmp(tablename, "raw") == 0 && hook_mask == NF_IP_PRE_ROUTING)
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++ return true;
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++ if (strcmp(tablename, "filter") != 0)
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++ return false;
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++ invalid = hook_mask & ~((1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD));
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++ return !invalid;
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++}
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++
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++static struct xt_target xt_tarpit_reg = {
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++ .name = "TARPIT",
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++ .family = AF_INET,
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++ .proto = IPPROTO_TCP,
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++ .target = xt_tarpit_target,
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++ .checkentry = xt_tarpit_check,
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++ .me = THIS_MODULE,
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++};
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++
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++static int __init xt_tarpit_init(void)
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++{
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++ return xt_register_target(&xt_tarpit_reg);
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++}
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++
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++static void __exit xt_tarpit_exit(void)
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++{
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++ xt_unregister_target(&xt_tarpit_reg);
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++}
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++
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++module_init(xt_tarpit_init);
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++module_exit(xt_tarpit_exit);
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++MODULE_DESCRIPTION("netfilter xt_TARPIT target module");
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++MODULE_AUTHOR("Jan Engelhardt <[email protected]>");
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++MODULE_LICENSE("GPL");
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++MODULE_ALIAS("ipt_TARPIT");
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Gabor Juhos