#define _XOPEN_SOURCE 500
#include <ftw.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static char interface_match[32];
static char interface_address[13];
static char interface_slot[13]="not found";

static int
find_slot(const char *fpath, const struct stat *sb,
	  int tflag, struct FTW *ftwbuf)
{
  char slot_address[11];
  int  ret;
  FILE *address_file;
  char *myfpath;
  char *this_tok;
  char *last_tok = NULL;

  /* so, are we at a point in the tree where the basename is
     "address" ? */
  if (strcmp("address",fpath + ftwbuf->base) == 0) {
    address_file = fopen(fpath,"r");
    if (address_file == NULL) {
      strcpy(interface_slot,"fopen");
      return 0;
    }
    /* we make the simplifying assumption that PCI domain, bus, slot
       and function, with associated separators, are 10 characters or
       less */
    ret = fread(slot_address,1,10,address_file);
    if (ret != 10) {
      strcpy(interface_slot,"fread");
      fclose(address_file);
      return 0;
    }
    slot_address[ret] = 0;
    /* the slot address will be a substring of the full bus address of
       the interface we seek */
    if (strstr(interface_address,slot_address)) {
	myfpath = strdup(fpath);
	if (myfpath == NULL) {
	  strcpy(interface_slot,"strcpy");
	  return 1;
	}

	this_tok = strtok(myfpath,"/");
	while (strcmp(this_tok,"address")) {
	  last_tok = this_tok;
	  this_tok = strtok(NULL,"/");
	}
	if (last_tok != NULL)
	  strcpy(interface_slot,last_tok);
	else
	  strcpy(interface_slot,"last_tok");
	free(myfpath);
	fclose(address_file);
	return 1;
    }
    fclose(address_file);
  }
  return 0;
}

static int
find_interface(const char *fpath, const struct stat *sb,
	       int tflag, struct FTW *ftwbuf)
{
  char *myfpath;
  char *this_tok;
  char *last_tok = NULL;

  if (strcmp(interface_match,fpath + ftwbuf->base) == 0) {
    myfpath = strdup(fpath);
    if (myfpath == NULL) {
      strcpy(interface_address,"strcpy");
      return 1;
    }
    this_tok = strtok(myfpath,"/");
    while (strcmp(this_tok,interface_match)) {
      last_tok = this_tok;
      this_tok = strtok(NULL,"/");
    }
    if (last_tok != NULL)
      strcpy(interface_address,last_tok);
    else
      strcpy(interface_address,"last_tok");
    free(myfpath);
    return 1;
  }
  return 0;
}

char *
find_interface_slot(char *interface_name) {

  int flags = 0;
  int ret;

  flags |= FTW_PHYS;  /* don't follow symlinks for they will lead us
			 off the path */
  ret = snprintf(interface_match,31,"net:%s",interface_name);
  interface_match[31]=0;
  /* having setup the basename we will be seeking, go find it and the
     corresponding interface_address */
  nftw("/sys/devices", find_interface, 20, flags);
  /* now that we ostensibly have the pci address of the interface
     (interface_address, lets find that slot shall we? */
  nftw("/sys/bus/pci/slots", find_slot, 20, flags);
  return strdup(interface_slot);
}

static int
get_val_from_file(char *valsource) {
  FILE *valfile;
  char buffer[6]; /* 0xabcd */
  int ret;

  valfile = fopen(valsource,"r");
  if (valfile == NULL) return -1;

  ret = fread(buffer,1,sizeof(buffer), valfile);
  if (ret != sizeof(buffer)) {
    fclose(valfile);
    return -1;
  }

  ret = (int)strtol(buffer,NULL,0);

  fclose(valfile);
  return ret;

}

void
find_interface_ids(char *interface_name, int *vendor, int *device, int *sub_vend, int *sub_dev) {

  int ret;

  char sysfile[128];  /* gotta love constants */

  /* first the vendor id */
  ret = snprintf(sysfile,128,"/sys/class/net/%s/device/vendor",interface_name);
  *vendor = get_val_from_file(sysfile);

  /* next the device */
  ret = snprintf(sysfile,128,"/sys/class/net/%s/device/device",interface_name);
  *device = get_val_from_file(sysfile);

  /* next the subsystem vendor */
  ret = snprintf(sysfile,128,"/sys/class/net/%s/device/subsystem_vendor",interface_name);
  *sub_vend = get_val_from_file(sysfile);

  /* next the subsystem device */
  ret = snprintf(sysfile,128,"/sys/class/net/%s/device/subsystem_device",interface_name);
  *sub_dev = get_val_from_file(sysfile);

}