#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <arpa/inet.h>

void do_header(int in, int out);
void do_packets(int in, int out);
int do_packet(int in, int out);

int main(int argc, char **argv) {
	int in, out;

	if(argc != 3) {
		fputs("Usage: hdlc2en infile outfile\n", stderr);
		exit(1);
	}

	in = open(argv[1], O_RDONLY);
	if(!in) {
		perror(argv[1]);
		exit(1);
	}

	out = open(argv[2], O_WRONLY | O_TRUNC, 0660);
	if(!out) {
		perror(argv[2]);
		exit(1);
	}

	do_header(in, out);
	do_packets(in, out);

	close(in);
	close(out);
}

typedef struct pcap_hdr_s {
	uint32_t magic_number;   /* magic number */
	uint16_t version_major;  /* major version number */
	uint16_t version_minor;  /* minor version number */
	int32_t  thiszone;       /* GMT to local correction */
	uint32_t sigfigs;	/* accuracy of timestamps */
	uint32_t snaplen;	/* max length of captured packets, in octets */
	uint32_t network;	/* data link type */
} pcap_hdr_t;

void do_header(int in, int out) {
	pcap_hdr_t buf;
	read(in, &buf, sizeof(buf));
	printf("Type: %x\n", buf.network);
	buf.snaplen += 10; // Increase frame size to ethernet size
	buf.network = 0x1; // Set type to ethernet
	write(out, &buf, sizeof(buf));
}

typedef struct pcaprec_hdr_s {
	uint32_t ts_sec;	 /* timestamp seconds */
	uint32_t ts_usec;	/* timestamp microseconds */
	uint32_t incl_len;       /* number of octets of packet saved in file */
	uint32_t orig_len;       /* actual length of packet */
} pcaprec_hdr_t;

char dummy_ethernet[] = {
	0x00, 0x16, 0x6f, 0x35, 0xe7, 0xbd,  // Destination MAC
	0x00, 0x0f, 0x66, 0xe3, 0xfc, 0xa6,  // Source MAC
	0x08, 0x00 // Protocol Type
};

void do_packets(int in, int out) {
	while(do_packet(in, out));
}

int do_packet(int in, int out) {
	pcaprec_hdr_t hdr;
	int ret;
	char *buf;
	read(in, &hdr, sizeof(hdr));
	printf("Packet size: %i\n", hdr.incl_len);
	if(hdr.incl_len > 1600) {
		printf("Bad incl_len");
		exit(1);
	}

	buf = malloc(hdr.incl_len);
	ret = read(in, buf, hdr.incl_len);
	hdr.incl_len += 10;
	hdr.orig_len += 10;
	write(out, &hdr, sizeof(hdr));
	write(out, dummy_ethernet, 14);
	write(out, buf + 4, hdr.incl_len - 14); // write without HDLC header
	free(buf);
	return ret;
}