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#define __NO_VERSION__
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/netfilter.h>
#include <linux/module.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/string.h>
#include <net/tcp.h>
#include <linux/netfilter_ipv4/ip_conntrack.h>
#include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
#include <linux/netfilter_ipv4/lockhelp.h>
#define DEBUGP(format, args...)
/* Protects conntrack->proto.tcp */
static DECLARE_RWLOCK(tcp_lock);
/* Actually, I believe that neither ipmasq (where this code is stolen
from) nor ipfilter do it exactly right. A new conntrack machine taking
into account packet loss (which creates uncertainty as to exactly
the conntrack of the connection) is required. RSN. --RR */
static const char *tcp_conntrack_names[] = {
"NONE",
"ESTABLISHED",
"SYN_SENT",
"SYN_RECV",
"FIN_WAIT",
"TIME_WAIT",
"CLOSE",
"CLOSE_WAIT",
"LAST_ACK",
"LISTEN"
};
#define sNO TCP_CONNTRACK_NONE
#define sES TCP_CONNTRACK_ESTABLISHED
#define sSS TCP_CONNTRACK_SYN_SENT
#define sSR TCP_CONNTRACK_SYN_RECV
#define sFW TCP_CONNTRACK_FIN_WAIT
#define sTW TCP_CONNTRACK_TIME_WAIT
#define sCL TCP_CONNTRACK_CLOSE
#define sCW TCP_CONNTRACK_CLOSE_WAIT
#define sLA TCP_CONNTRACK_LAST_ACK
#define sLI TCP_CONNTRACK_LISTEN
#define sIV TCP_CONNTRACK_MAX
static enum tcp_conntrack tcp_conntracks[2][5][TCP_CONNTRACK_MAX] = {
{
/* ORIGINAL */
/* sNO, sES, sSS, sSR, sFW, sTW, sCL, sCW, sLA, sLI */
/*syn*/ {sSS, sES, sSS, sSR, sSS, sSS, sSS, sSS, sSS, sLI },
/*fin*/ {sTW, sFW, sSS, sTW, sFW, sTW, sCL, sTW, sLA, sLI },
/*ack*/ {sES, sES, sSS, sES, sFW, sTW, sCL, sCW, sLA, sES },
/*rst*/ {sCL, sCL, sSS, sCL, sCL, sTW, sCL, sCL, sCL, sCL },
/*none*/{sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
},
{
/* REPLY */
/* sNO, sES, sSS, sSR, sFW, sTW, sCL, sCW, sLA, sLI */
/*syn*/ {sSR, sES, sSR, sSR, sSR, sSR, sSR, sSR, sSR, sSR },
/*fin*/ {sCL, sCW, sSS, sTW, sTW, sTW, sCL, sCW, sLA, sLI },
/*ack*/ {sCL, sES, sSS, sSR, sFW, sTW, sCL, sCW, sCL, sLI },
/*rst*/ {sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sLA, sLI },
/*none*/{sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
}
};
static int tcp_pkt_to_tuple(const void *datah, size_t datalen,
struct ip_conntrack_tuple *tuple)
{
const struct tcphdr *hdr = datah;
tuple->src.u.tcp.port = hdr->source;
tuple->dst.u.tcp.port = hdr->dest;
return 1;
}
static int tcp_invert_tuple(struct ip_conntrack_tuple *tuple,
const struct ip_conntrack_tuple *orig)
{
tuple->src.u.tcp.port = orig->dst.u.tcp.port;
tuple->dst.u.tcp.port = orig->src.u.tcp.port;
return 1;
}
/* Print out the per-protocol part of the tuple. */
static unsigned int tcp_print_tuple(char *buffer,
const struct ip_conntrack_tuple *tuple)
{
return sprintf(buffer, "sport=%hu dport=%hu ",
ntohs(tuple->src.u.tcp.port),
ntohs(tuple->dst.u.tcp.port));
}
/* Print out the private part of the conntrack. */
static unsigned int tcp_print_conntrack(char *buffer,
const struct ip_conntrack *conntrack)
{
enum tcp_conntrack state;
READ_LOCK(&tcp_lock);
state = conntrack->proto.tcp.state;
READ_UNLOCK(&tcp_lock);
return sprintf(buffer, "%s ", tcp_conntrack_names[state]);
}
static unsigned int get_conntrack_index(const struct tcphdr *tcph)
{
if (tcph->rst) return 3;
else if (tcph->syn) return 0;
else if (tcph->fin) return 1;
else if (tcph->ack) return 2;
else return 4;
}
/* Returns verdict for packet, or -1 for invalid. */
static int tcp_packet(struct ip_conntrack *conntrack,
struct iphdr *iph, size_t len,
enum ip_conntrack_info ctinfo)
{
enum tcp_conntrack newconntrack, oldtcpstate;
struct tcphdr *tcph = (struct tcphdr *)((u_int32_t *)iph + iph->ihl);
/* We're guaranteed to have the base header, but maybe not the
options. */
if (len < (iph->ihl + tcph->doff) * 4) {
DEBUGP("ip_conntrack_tcp: Truncated packet.\n");
return -1;
}
WRITE_LOCK(&tcp_lock);
oldtcpstate = conntrack->proto.tcp.state;
newconntrack
= tcp_conntracks
[CTINFO2DIR(ctinfo)]
[get_conntrack_index(tcph)][oldtcpstate];
/* Invalid */
if (newconntrack == TCP_CONNTRACK_MAX) {
DEBUGP("ip_conntrack_tcp: Invalid dir=%i index=%u conntrack=%u\n",
CTINFO2DIR(ctinfo), get_conntrack_index(tcph),
conntrack->proto.tcp.state);
WRITE_UNLOCK(&tcp_lock);
return -1;
}
conntrack->proto.tcp.state = newconntrack;
/* Poor man's window tracking: record SYN/ACK for handshake check */
if (oldtcpstate == TCP_CONNTRACK_SYN_SENT
&& CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY
&& tcph->syn && tcph->ack)
conntrack->proto.tcp.handshake_ack
= htonl(ntohl(tcph->seq) + 1);
if (oldtcpstate == TCP_CONNTRACK_SYN_SENT
&& CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY
&& tcph->syn && !tcph->ack){
WRITE_UNLOCK(&tcp_lock);
return -1;
}
/* If only reply is a RST, we can consider ourselves not to
have an established connection: this is a fairly common
problem case, so we can delete the conntrack
immediately. --RR */
if (!(conntrack->status & IPS_SEEN_REPLY) && tcph->rst) {
WRITE_UNLOCK(&tcp_lock);
if (del_timer(&conntrack->timeout))
conntrack->timeout.function((unsigned long)conntrack);
} else {
/* Set ASSURED if we see see valid ack in ESTABLISHED after SYN_RECV */
if (oldtcpstate == TCP_CONNTRACK_SYN_RECV
&& CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL
&& tcph->ack && !tcph->syn
&& tcph->ack_seq == conntrack->proto.tcp.handshake_ack)
set_bit(IPS_ASSURED_BIT, &conntrack->status);
WRITE_UNLOCK(&tcp_lock);
ip_ct_refresh(conntrack,
sysctl_ip_conntrack_tcp_timeouts[newconntrack]);
}
return NF_ACCEPT;
}
/* Called when a new connection for this protocol found. */
static int tcp_new(struct ip_conntrack *conntrack,
struct iphdr *iph, size_t len)
{
enum tcp_conntrack newconntrack;
struct tcphdr *tcph = (struct tcphdr *)((u_int32_t *)iph + iph->ihl);
/* Don't need lock here: this conntrack not in circulation yet */
newconntrack
= tcp_conntracks[0][get_conntrack_index(tcph)]
[TCP_CONNTRACK_NONE];
/* Invalid: delete conntrack */
if (newconntrack == TCP_CONNTRACK_MAX) {
DEBUGP("ip_conntrack_tcp: invalid new deleting.\n");
return 0;
}
if (tcph->syn && tcph->ack)
{
DEBUGP("ip_conntrack_tcp: invalid new deleting.\n");
return 0;
}
conntrack->proto.tcp.state = newconntrack;
return 1;
}
static int tcp_exp_matches_pkt(struct ip_conntrack_expect *exp,
struct sk_buff **pskb)
{
struct iphdr *iph = (*pskb)->nh.iph;
struct tcphdr *tcph = (struct tcphdr *)((u_int32_t *)iph + iph->ihl);
unsigned int datalen;
datalen = (*pskb)->len - iph->ihl*4 - tcph->doff*4;
return between(exp->seq, ntohl(tcph->seq), ntohl(tcph->seq) + datalen);
}
struct ip_conntrack_protocol ip_conntrack_protocol_tcp
= { { NULL, NULL }, IPPROTO_TCP, "tcp",
tcp_pkt_to_tuple, tcp_invert_tuple, tcp_print_tuple, tcp_print_conntrack,
tcp_packet, tcp_new, NULL, tcp_exp_matches_pkt, NULL };
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