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rrb.c
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rrb.c
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#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <sys/time.h>
#include <poll.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <linux/if_ether.h>
#include <linux/if_packet.h>
#include "err.h"
#include "mac.h"
#define BIGGEST_FRAME 4096
typedef union {
struct ethhdr eth;
char buffer[BIGGEST_FRAME];
} framedata_t;
typedef struct frame {
/* How long is the frame */
int length; /* don't use size_t read() returns -1 */
/* What time to send at */
struct timeval timetogo;
/* Next member in a linked list */
struct frame *next;
/* The frame - this must be last for our memory plans */
framedata_t data;
} frame_t;
void create_sockets(int *input, int *output);
void bind_sockets(char *iface1, int input, char *iface2, int output);
inline void schedule_frame(frame_t *f);
inline void queue_frame(frame_t *f);
inline void dole_frame(int outfd);
inline void translate_frame(frame_t *f);
inline int ttn_frame(void);
inline int count_frames(void);
int main(void) {
int input, output;
create_sockets(&input, &output);
bind_sockets("wlan0", input, "lo", output);
/* main program part.. */
frame_t work;
struct pollfd pollinput;
pollinput.fd = input;
pollinput.events = POLLIN;
int mswait;
while ( 1 ) {
printf("%40d frames in buffer.\r", count_frames());
work.length = read(input, work.data.buffer, BIGGEST_FRAME);
if ( work.length > 0 ) {
translate_frame(&work);
schedule_frame(&work);
queue_frame(&work);
// freaking woo hoo
}
dole_frame(output);
mswait = ttn_frame();
poll(&pollinput, 1, mswait);
}
return 0;
}
/* Output parameters are the new file descripters */
void create_sockets(int *input, int *output)
{
/* stevens 793 */
if ( 0 > (*input = socket (PF_PACKET, SOCK_RAW, htons(ETH_P_IP))) )
err("socket()");
if ( 0 > (*output = socket (PF_PACKET, SOCK_RAW, htons(ETH_P_IP))) )
err("socket()");
/* Input set to non blocking */
if ( 0 > fcntl(*input, F_SETFL, fcntl(F_GETFL, 0) | O_NONBLOCK) )
err("fcntl()");
}
void bind_sockets(char *iface1, int input, char *iface2, int output)
{
/* SIOCGIFINDEX */
/* see also packet/af_packet.c */
struct sockaddr_ll in_nic, out_nic;
memset(&in_nic, 0, sizeof(in_nic));
memset(&out_nic, 0, sizeof(out_nic));
in_nic.sll_family = out_nic.sll_family = AF_PACKET;
in_nic.sll_protocol = out_nic.sll_protocol = htons(ETH_P_ALL);
if ( ! (in_nic.sll_ifindex = if_nametoindex(iface1) ) )
err("if_nametoindex()");
if ( ! (out_nic.sll_ifindex = if_nametoindex(iface2) ) )
err("if_nametoindex()");
/* nic.sll_hatype .. not sure what values are .. leave as 0 */
/* nic.sll_pkttype = */
/* nic.sll_halen = ? */
/* nic.sll_addr = ? */
if ( 0 > bind(input, (struct sockaddr *)&in_nic, sizeof(in_nic) ) )
err("bind()");
if ( 0 > bind(output, (struct sockaddr *)&out_nic, sizeof(out_nic) ) )
err("bind()");
}
inline void schedule_frame(frame_t *f) {
struct timeval tv, diff;
diff.tv_sec = 1;
diff.tv_usec = 500000;
// how could gettimeofday fail?
if ( 0 > gettimeofday(&tv, 0) )
err("gettimeofday()");
/* TIMERADD(3) */
timeradd(&tv, &diff, &f->timetogo);
}
inline void translate_frame(frame_t *f) {
mac_atob("F5:0:0:0:0:1", f->data.eth.h_source);
mac_atob("F5:0:0:0:0:2", f->data.eth.h_dest);
}
frame_t *first_frame = NULL;
inline void queue_frame(frame_t *f) {
frame_t *new_frame, *last_frame;
/* allocate memory the size of f */
int f_size = sizeof(frame_t) - sizeof(framedata_t) + f->length;
if ( ! (new_frame = malloc(f_size) ) )
err("malloc()");
/* copy f into the memory */
memcpy(new_frame, f, f_size);
/* find the last frame */
if ( first_frame == NULL ) {
first_frame = new_frame;
last_frame = new_frame;
} else {
last_frame = first_frame;
while ( last_frame->next )
last_frame = last_frame->next;
}
/* set its next to the new memory */
last_frame->next = new_frame;
/* this is the last frame */
new_frame->next = NULL;
}
inline void dole_frame(int outfd) {
/* return if first_frame is not ready to send
* (or no first frame)*/
if ( (first_frame == NULL) || (ttn_frame() > 0) )
return;
/* send it away - update first_frame then free the memory */
if ( 0 > write(outfd, first_frame->data.buffer, first_frame->length) )
err("write()");
frame_t *tmp = first_frame;
first_frame = first_frame->next;
free(tmp);
}
/* return the time to the next frame */
inline int ttn_frame(void)
{
struct timeval tv, diff;
if ( first_frame == NULL)
/* return a large value. when one comes in it will
* break the poll() and we will be called again
* with a real first_frame */
return 5000; /* 5 seconds .. pros? cons? */
gettimeofday(&tv, 0);
timersub(&first_frame->timetogo, &tv, &diff);
/* if the next packet is ready to go, sec will be < 0.
* for example, if it is 1 microsecond past its time to go,
* diff will be sec = -1, usec = 999999. */
int retval;
if ( diff.tv_sec < 0 )
retval = 0;
else
retval = diff.tv_sec * 1000 + diff.tv_usec / 1000;
return retval;
}
inline int count_frames(void) {
int c=0;
frame_t *ptr = first_frame;
while(ptr != NULL) {
c++;
ptr = ptr->next;
}
return c;
}