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/*
The l7-queue class handles libnetfilter-queue events and passes
packets to their appropriate conntack for classification.
By Ethan Sommer <sommere@users.sf.net> and Matthew Strait
<quadong@users.sf.net>, 2006-2007
http://l7-filter.sf.net
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version
2 of the License, or (at your option) any later version.
http://www.gnu.org/licenses/gpl.txt
Based on nfqnl_test.c from libnetfilter-queue 0.0.12
If you get error messages about running out of buffer space, increase it
with something like:
echo 524280 > /proc/sys/net/core/rmem_default
echo 524280 > /proc/sys/net/core/rmem_max
echo 524280 > /proc/sys/net/core/wmem_default
echo 524280 > /proc/sys/net/core/wmem_max
*/
using namespace std;
#include <pthread.h>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <signal.h>
#include <map>
#include <netinet/in.h>
#include <linux/types.h>
#include <cstring>
#include "l7-conntrack.h"
#include "l7-queue.h"
#include "util.h"
// Probably shouldn't really be global, but it's SO much easier
int maxpackets = 10; // by default.
int clobbermark = 0;
extern unsigned int markmask;
extern unsigned int maskfirstbit;
extern "C" {
#include <linux/netfilter.h>
#include <libnetfilter_queue/libnetfilter_queue.h>
}
static int l7_queue_cb(struct nfq_q_handle *qh, struct nfgenmsg *nfmsg,
struct nfq_data *nfa, void *data)
{
struct nfqnl_msg_packet_hdr *ph;
u_int32_t id = 0;
ph = nfq_get_msg_packet_hdr(nfa);
if(ph)
id = ntohl(ph->packet_id);
u_int32_t wholemark = nfq_get_nfmark(nfa);
// If it already has a mark (and we don't want to clobber it),
// just pass it back with the same mark
if((wholemark<<maskfirstbit)&markmask != UNTOUCHED && !clobbermark){
static unsigned int naaltered = 0;
naaltered++;
if((naaltered^(naaltered-1)) == (2*naaltered-1)) // is it a power of 2?
cerr << "My part of the mark has already been altered, ignoring these "
"packets!\n(" << naaltered << " ignored so far.) "
"Fix your rules or use l7-filter -c.\n";
return nfq_set_verdict_mark(qh, id, NF_ACCEPT, htonl(wholemark), 0, NULL);
}
return ((l7_queue *)data)->handle_packet(nfa, qh);
}
l7_queue::l7_queue(l7_conntrack *connection_tracker)
{
l7_connection_tracker = connection_tracker;
}
l7_queue::~l7_queue()
{
}
void l7_queue::start(int queuenum)
{
struct nfq_handle *h;
struct nfq_q_handle *qh;
struct nfnl_handle *nh;
int fd;
int rv;
char buf[4096];
l7printf(3, "opening library handle\n");
h = nfq_open();
if(!h) {
cerr << "error during nfq_open()\n";
exit(1);
}
l7printf(3, "unbinding existing nf_queue handler for AF_INET (if any)\n");
/* As per Patrick McHardy's suggestion at
http://www.spinics.net/lists/netfilter/msg42063.html
we, for now, ignore the return value of nfq_unbind_pf() */
if(nfq_unbind_pf(h, AF_INET) < 0 && 0) {
cerr << "error during nfq_unbind_pf()\n";
exit(1);
}
l7printf(3, "binding nfnetlink_queue as nf_queue handler for AF_INET\n");
if(nfq_bind_pf(h, AF_INET) < 0) {
cerr << "error during nfq_bind_pf()\n";
exit(1);
}
l7printf(3, "binding this socket to queue '0'\n");
qh = nfq_create_queue(h, queuenum, &l7_queue_cb, this);
if(!qh) {
cerr << "error during nfq_create_queue()\n";
exit(1);
}
l7printf(3, "setting copy_packet mode\n");
if(nfq_set_mode(qh, NFQNL_COPY_PACKET, 0xffff) < 0) {
cerr << "can't set packet_copy mode\n";
exit(1);
}
nh = nfq_nfnlh(h);
fd = nfnl_fd(nh);
// this is the main loop
while (true){
while ((rv = recv(fd, buf, sizeof(buf), 0)) && rv >= 0)
nfq_handle_packet(h, buf, rv);
cerr << "Error: recv() returned negative value." << endl;
cerr << "rv=" << rv << endl;
cerr << "errno=" << errno << endl;
cerr << "errstr=" << strerror(errno) << endl << endl;
}
l7printf(3, "unbinding from queue 0\n");
nfq_destroy_queue(qh);
l7printf(3, "closing library handle\n");
nfq_close(h);
exit(0);
}
u_int32_t l7_queue::handle_packet(nfq_data * tb, struct nfq_q_handle *qh)
{
int id = 0, ret, dataoffset, datalen;
u_int32_t wholemark, mark, ifi;
struct nfqnl_msg_packet_hdr *ph;
char * data;
l7_connection * connection;
ph = nfq_get_msg_packet_hdr(tb);
if(ph){
id = ntohl(ph->packet_id);
l7printf(4, "hw_protocol = 0x%04x hook = %u id = %u ",
ntohs(ph->hw_protocol), ph->hook, id);
}
// Need to get the wholemark so that we can pass the unmasked part back
// Except for the print statement and debugging, there's not really any
// reason to pull out the masked part, because it's always modified without
// looking at it...
wholemark = (nfq_get_nfmark(tb));
if(clobbermark){
mark = UNTOUCHED;
wholemark = wholemark&(~markmask); // zero out our part of the mark
}
else mark = ((wholemark&markmask) >> maskfirstbit);
l7printf(4, "wholemark = %#08x ", wholemark);
l7printf(4, "mark = %d ", mark);
ifi = nfq_get_indev(tb);
if(ifi) l7printf(4, "indev = %d ", ifi);
ifi = nfq_get_outdev(tb);
if(ifi) l7printf(4, "outdev = %d ", ifi);
ret = nfq_get_payload(tb, &data);
if(ret >= 0) l7printf(4, "payload_len = %d\n", ret);
char ip_protocol = data[9];
// Ignore anything that's not TCP or UDP
if(ip_protocol != IPPROTO_TCP && ip_protocol != IPPROTO_UDP)
return nfq_set_verdict(qh, id, NF_ACCEPT, 0, NULL);
dataoffset = app_data_offset((const unsigned char*)data);
datalen = ret - dataoffset;
//find the conntrack
string key = get_conntrack_key((const unsigned char*)data, false);
connection = l7_connection_tracker->get_l7_connection(key);
if(connection)
l7printf(3, "Found connection orig:\t%s\n", key.c_str());
if(!connection){
//find the conntrack (backwards)
string key = get_conntrack_key((const unsigned char*)data, true);
connection = l7_connection_tracker->get_l7_connection(key);
if(connection)
l7printf(3, "Found connection reply:\t%s\n", key.c_str());
// It seems to routinely not get the UDP conntrack until the 2nd or 3rd
// packet. Tested with DNS.
if(!connection)
l7printf(2, "Got packet, had no ct:\t%s\n", key.c_str());
}
// mark = the mark we found on the packet
// connection->get_mark() = the mark that we have made internally
if(connection){
connection->increment_num_packets();
if(datalen <= 0){
l7printf(3, "Connection with no new application data ignored.\n");
mark = NO_MATCH_YET; // no application data
}
else{
if(connection->get_mark() != NO_MATCH_YET &&
connection->get_mark() != UNTOUCHED){
// It is classified already. Reapply existing mark.
mark = connection->get_mark();
}
else if(connection->get_num_packets() <= maxpackets){
// Do the heavy lifting.
connection->append_to_buffer((char*)(data+dataoffset),ret-dataoffset);
l7printf(3, "Packet #%d, data is: %s\n", connection->get_num_packets(),
friendly_print((unsigned char *)connection->buffer,
connection->lengthsofar).c_str());
mark = connection->classify();
if(mark != NO_MATCH_YET){ // Got a match, no need to keep data
free(connection->buffer);
connection->buffer = NULL; // marks it not to be free'd again
}
}
else{ // num_packets > maxpackets and hasn't been classified
mark = NO_MATCH;
// if this is the first packet after we've given up, clean up
if(connection->get_num_packets() == maxpackets+1){
print_give_up(key, (unsigned char *)connection->buffer,
connection->lengthsofar);
free(connection->buffer);
connection->buffer = NULL; // marks it not to be free'd again
} // endif should clean up
} // endif whether should run match or what
} // endif there is any new data
} // endif we found the connection
else{
l7printf(3, "Didn't yet find\t%s\n", key.c_str());
mark = NO_MATCH_YET;
}
if(mark == UNTOUCHED) cerr << "NOT REACHED. mark is still UNTOUCHED.\n";
l7printf(4,"Set verdict ACCEPT, mark %#08x\n",(mark<<maskfirstbit)|wholemark);
return nfq_set_verdict_mark(qh, id, NF_ACCEPT,
htonl((mark<<maskfirstbit)|wholemark), 0, NULL);
}
// Returns a string that uniquely defines the connection
string l7_queue::get_conntrack_key(const unsigned char *data, bool reverse)
{
char * buf = (char *)malloc(256);
int ip_hl = 4*(data[0] & 0x0f);
char ip_protocol = data[9];
if(ip_protocol == IPPROTO_TCP){
if(reverse){
snprintf(buf, 255,
"tcp 6 src=%d.%d.%d.%d dst=%d.%d.%d.%d sport=%d dport=%d",
data[12], data[13], data[14], data[15],
data[16], data[17], data[18], data[19],
data[ip_hl]*256+data[ip_hl+1], data[ip_hl+2]*256+data[ip_hl+3]);
}
else{
snprintf(buf, 255,
"tcp 6 src=%d.%d.%d.%d dst=%d.%d.%d.%d sport=%d dport=%d",
data[16], data[17], data[18], data[19],
data[12], data[13], data[14], data[15],
data[ip_hl+2]*256+data[ip_hl+3], data[ip_hl]*256+data[ip_hl+1]);
}
}
else if(ip_protocol == IPPROTO_UDP){
if(reverse){
snprintf(buf, 255,
"udp 17 src=%d.%d.%d.%d dst=%d.%d.%d.%d sport=%d dport=%d",
data[12], data[13], data[14], data[15],
data[16], data[17], data[18], data[19],
data[ip_hl]*256+data[ip_hl+1], data[ip_hl+2]*256+data[ip_hl+3]);
}
else{
snprintf(buf, 255,
"udp 17 src=%d.%d.%d.%d dst=%d.%d.%d.%d sport=%d dport=%d",
data[16], data[17], data[18], data[19],
data[12], data[13], data[14], data[15],
data[ip_hl+2]*256+data[ip_hl+3], data[ip_hl]*256+data[ip_hl+1]);
}
}
else{
l7printf(0, "Tried to get conntrack key for unsupported protocol!\n");
buf[0] = '\0';
}
string answer = buf;
free(buf);
l7printf(3, "Made key from packet:\t%s\n", answer.c_str());
return answer;
}
/* Returns offset the into the skb->data that the application data starts */
int l7_queue::app_data_offset(const unsigned char *data)
{
int ip_hl = 4*(data[0] & 0x0f);
char ip_protocol = data[9];
if(ip_protocol == IPPROTO_TCP){
// 12 == offset into TCP header for the header length field.
int tcp_hl = 4*(data[ip_hl + 12]>>4);
return ip_hl + tcp_hl;
}
else if(ip_protocol == IPPROTO_UDP){
return ip_hl + 8; /* UDP header is always 8 bytes */
}
else{
l7printf(0, "Tried to get app data offset for unsupported protocol!\n");
return ip_hl + 8; /* something reasonable */
}
}
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