win_adv_capture.c

mobile ip 在linux下的一种实现

/* $Id: win_adv_capture.c,v 1.2 2001/10/03 13:47:25 jm Exp $
 * MN helper for getting L2 data for agent advertisement in Windows environment
 *
 * Dynamic hierarchial IP tunnel
 * Copyright (C) 2001, Jouni Malinen
 *
 * 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. See README and COPYING for
 * more details.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <pcap.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <cygwin/in.h>

#include "debug.h"
#include "mn.h"


/* ethhdr - 14 octets; iphdr - 20 octets */
static struct bpf_insn agentadv_filter[] = {
	/* A <- P[14+9:1] - load byte - IP protocol */
	BPF_STMT(BPF_LD+BPF_B+BPF_ABS, 14+9),
	/* pc += (A == IPPROTO_ICMP) ? 0 : 3 */
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, IPPROTO_ICMP, 0, 3),
	/* A <- P[14+20:1] - load byte - ICMP type */
	BPF_STMT(BPF_LD+BPF_B+BPF_ABS, 14+20),
	/* pc += (A == 9) ? 0 : 1 (agentadv) */
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 9, 0, 1),
	BPF_STMT(BPF_RET+BPF_K, (unsigned int)-1), /* accept the packet */
	BPF_STMT(BPF_RET+BPF_K, 0) /* filter packet */
};

static struct bpf_program agentadv_fprog = {
	sizeof(agentadv_filter) / sizeof(struct bpf_insn),
	agentadv_filter
};


struct dst_data {
	int s;
	struct sockaddr_in addr;
};

static void dispatcher_handler(u_char *user, const struct pcap_pkthdr *header,
			       const u_char *pkt_data)
{
	struct dst_data *dst = (struct dst_data *) user;

	DEBUG(DEBUG_INFO, "%lu:%lu len=%lu ==> %s:%i\n",
	      header->ts.tv_sec, header->ts.tv_usec,
	      (unsigned long) header->len,
	      inet_ntoa(dst->addr.sin_addr), ntohs(dst->addr.sin_port));

	/* send agent advertisement for dynmnd using UDP port 4344 */
	/* buf=pkt_data, len=header->len */
	if (sendto(dst->s, pkt_data, header->len, 0,
		   (struct sockaddr *) &dst->addr, sizeof(dst->addr)) < 0) {
		DEBUG(DEBUG_INFO, "dispatcher_handler: sendto failed: %s\n",
		      strerror(errno));
	}
}


pid_t init_pcap_for_advs(void)
{
	pcap_t *fp;
	char error[PCAP_ERRBUF_SIZE];
	char *dev;
	struct dst_data dst;
	pid_t pid;

	pid = fork();
	if (pid < 0) {
		DEBUG(DEBUG_INFO, "init_pcap_for_advs: fork failed: %s\n",
		      strerror(errno));
		return -1;
	}

	if (pid > 0) {
		/* in parent - return */
		return pid;
	}

	dst.s = socket(AF_INET, SOCK_DGRAM, 0);
	if (dst.s < 0) {
		perror("socket");
		exit(1);
	}
	dst.addr.sin_family = AF_INET;
	dst.addr.sin_addr.s_addr = htonl((127 << 24 | 1));
	dst.addr.sin_port = htons(4344);

	/* FIX: should support more than one interface and also detect new
	 * interfaces when, e.g., wireless LAN card is inserted */

	dev = pcap_lookupdev(error);
	if (dev == NULL) {
		DEBUG(DEBUG_INFO,
		      "init_pcap_for_advs: Could not get device (%s)\n",
		      error);
		return -1;
	}

	DEBUG(DEBUG_INFO, "init_pcap_for_advs: using device '%s'\n", dev);
	fp = pcap_open_live(dev, 1500, 0, 20, error);
	if (fp == NULL) {
		DEBUG(DEBUG_INFO, "pcap_open_live failed (%s)\n", error);
		return -1;
	}

	if (pcap_setfilter(fp, &agentadv_fprog) < 0) {
		DEBUG(DEBUG_INFO,
		      "init_pcap_for_advs: Could not attach BPF\n");
		return -1;
	}

	/* in child - start capturing packets */
	DEBUG(DEBUG_INFO, "init_pcap_for_advs: child starting to capture "
	      "packets\n");

	pcap_loop(fp, 0, dispatcher_handler, (u_char *) &dst);

	/* never reached */
	DEBUG(DEBUG_INFO, "pcap_loop returned?!\n");
	return 0;
}