#include <net/if.h>

#include <net/if_tap.h>

#include <dirent.h>

/* this function lists the tap device in /dev

input : ** char already allocated

output : integer represents the number of tap file found */

int dirDev(char ** tbl)

{

        /* Openning directory */

        DIR *d;

        int i = 0; // number of interface found

        struct dirent *dir;

        d = opendir("/dev/");

        /* readding file in directory if not empty */

        if (d) {

                while ((dir = readdir(d)) != NULL) {

                        /* looking for tap file and implement it on the table tbl */

                        if(strncmp("tap", dir->d_name, 3) == 0) {

                                tbl = realloc(tbl,i+1);

                                tbl[i] = (char *)malloc(sizeof(dir->d_name));

                                sprintf(tbl[i],"%s",dir->d_name);

                                i++;

                        }

                }

                /* closing directory */

                closedir(d);

        }

        return(i);

}

/* this function returns the name of the device according to the name in input

input : * char is the interface name (or alias)

output : * char is the name present in /dev

if the interface does not exist the function return the input by default */

char * findDevName(char * intName) {

        /* variable implementation */

        int i, nbrIntTap, fd;

        char * path = "/dev/";

        char *tbuf, *devName;

        char ** tblTapInt;

        struct ifreq myTapInfo; //use to find the tap name

        /* variable initialisation */

        tbuf = (char*) malloc(sizeof(char*));

        devName = (char*) malloc(sizeof(char*));

        devName = strdup(intName);

        tblTapInt = malloc(1);

        nbrIntTap = dirDev(tblTapInt); // get the list of tap device in /dev

        /* for each entry, we check the tap name */

        for (i=0;i<nbrIntTap;i++) {

                tbuf = (char *) realloc(tbuf,sizeof(path) + sizeof(tblTapInt[i]) -1 );

                tbuf = strdup(path);

                strcat(tbuf, tblTapInt[i]);

                fd = open(tbuf, O_RDONLY); // opening the device

                ioctl(fd, TAPGIFNAME, &myTapInfo); // looking for the tap device name

                /* If finded we break the loop */

                if(strcmp(myTapInfo.ifr_name,intName) == 0 || strcmp(tblTapInt[i],intName) == 0) {

                        devName = strdup(tblTapInt[i]);

                        close(fd);

                        break;

                }

                close(fd);

        }

        free(tblTapInt);

        free(tbuf);

        return devName;

}