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Date:      Tue, 20 Jan 2004 21:20:47 +0700 (GMT-7)
From:      "lattera" <lattera@nosleep.info>
To:        freebsd-ipfw@freebsd.org
Subject:   divert sockets code
Message-ID:  <49344.216.190.11.115.1074608447.squirrel@vulcan.g3host.net>
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I can't seem to get pointers right in my code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define USE_BSD
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

#include <netinet/tcp.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>

#define PORT 6137

int main(int argc, char *argv[])
{
	int sockfd, n, clisize, ipsize, tcpsize, i;
	struct sockaddr_in server, client;
	char buf[65536], *payload;
	struct tcphdr *tcp;
	struct ip *iphdr;

	if ((sockfd = socket(PF_INET, SOCK_RAW, IPPROTO_DIVERT)) < 0)
	{
		perror("socket");
		exit(1);
	}
	server.sin_family = PF_INET;
	server.sin_port = htons(PORT);
	server.sin_addr.s_addr = INADDR_ANY;
	if (bind(sockfd, (struct sockaddr *)&server, sizeof(server)) < 0)
	{
		perror("bind");
		exit(1);
	}	exit(1);

	while (1)
	{
		clisize = sizeof(client);
		if ((n=recvfrom(sockfd, buf, sizeof(buf), 0, (struct sockaddr *)&client,
&clisize))<0)
		{
			perror("recv");
			exit(1);
		}
		iphdr = (struct ip *)buf;
		if (iphdr->ip_p != IPPROTO_TCP)
		{
			if (sendto(sockfd, buf, n, 0, (struct sockaddr *)&client, clisize) != n)
			{
				perror("send");
				exit(1);
			}
		}
		tcp = (struct tcphdr *)(buf + (4*(iphdr->ip_hl)));
		if (!(tcp->th_flags & TH_PUSH))
		{
			if (sendto(sockfd, buf, n, 0, (struct sockaddr *)&client, clisize) != n)
			{
				perror("send");
				exit(1);
			}
			continue;
		}

		payload = (char *)(tcp + ((tcp->th_off)*4));
		if (strstr(payload, "GET /etc/passwd"))
			continue;

		if (sendto(sockfd, buf, n, 0, (struct sockaddr *)&client, clisize) != n)
		{
			perror("send");
			exit(1);
		}
	}
}

Can someone tell me what I need to do?

Attached is the C source file of the above code (for readability)


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