/* syncppp.h */
 
#include<semaphore.h>
 
#define MAX_PPP_NUM 30
#define keyfilename "/tmp/pppkeyfile"
#define lockfilename "/tmp/ppplockfile"
 
void syncppp(void);
 
struct semaphores {
    sem_t count;  /* count the pppd processes which has recieved the challenge */
};

/* syncpppinit.c 
 * lock the lockfile, and count pppd, then unlock the lockfile
 * to release all pppd
 */
#include <stdio.h>
#include <sys/types.h>
#include <sys/shm.h>
#include <sys/ipc.h>
#include <stdlib.h>
#include <semaphore.h>
#include <fcntl.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <unistd.h>
#include "initppp.h"
 
int openlockfile()
{
    int fdlock;
 
    if ((fdlock = creat(lockfilename, 0644)) < 0) {
        perror("fdlock open error");
        exit(1);
    }
    return fdlock;
}
 
void lockfile(int fdlock)
{
    if (flock(fdlock, LOCK_EX) < 0) {
        perror("flock lock error");
        exit(1);
    }    
    fprintf(stderr,"initppp: locked\n");
}
 
void unlockfile(int fdlock)
{
    if (flock(fdlock, LOCK_UN) < 0) {
        perror("flock unlock error");
        exit(1);
    }
}
 
 
int main(int argc, char *argv[])
{
    int shm_id;
    int ppp_num;
    int fdlock;
    sem_t *p_sem;
    key_t key;
    struct semaphores *semphs;
 
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <number of pppd>\n", argv[0]);
        exit(1);
    }
 
    ppp_num = atoi(argv[1]);
    if (ppp_num > MAX_PPP_NUM || ppp_num <= 0) {
        fprintf(stderr, "Number of pppd beyoung limit\n");
        exit(1);
    }
 
    /* create a uniqe key */
    creat(keyfilename, 0755);
    key = ftok(keyfilename, 4);
    if (key < 0) {
        perror("key error\n");
        exit(1);
    }
 
    shm_id = shmget(key, sizeof(struct semaphores), IPC_CREAT | IPC_EXCL | 0644);
    if (shm_id < 0) {
        /* exist */
        shm_id = shmget(key, 1, 0644);
    }
 
    if ( (void *)(semphs = shmat(shm_id, 0, 0)) == (void *)-1) {
        perror("shmat error");
        exit(1);
    }
 
    if (sem_init(&(semphs->count), 1, 0) != 0) { /* shared between processes, init 0 */
        fprintf(stderr, "sem_init error\n");
        return 1;
    }
 
    fdlock = openlockfile();
    lockfile(fdlock);
 
    while (ppp_num > 0) {
        sem_wait(&(semphs->count));
        fprintf(stderr,"%d ",ppp_num);
        ppp_num--;
    }
    unlockfile(fdlock);
    fprintf(stderr,"\ninitppp: unlocked\n");
 
    return 0;
}

/* syncppp.c
 * sync all pppd
 */
#include<stdio.h>
#include<sys/types.h>
#include<sys/shm.h>
#include<sys/ipc.h>
#include<stdlib.h>
#include<semaphore.h>
#include <fcntl.h>
#include <sys/file.h>
#include"initppp.h"
#include <sys/stat.h>
#include<unistd.h>
 
void syncppp(void)
{
    int shm_id;
    key_t key;
    int fdlock;
    struct semaphores *semphs;
 
    key = ftok(keyfilename, 4);
 
    if (key < 0) {
        perror("key error\n");
        exit(1);
    }
 
    shm_id = shmget(key, 1, 0644);
    if (shm_id < 0) {
        perror("shmget");
        exit(1);
    }
 
    if ( (void *)(semphs = shmat(shm_id, 0, 0)) == (void *)-1) {
        perror("shmat error");
        exit(1);
    }
 
    sem_post(&(semphs->count));
    shmdt(semphs);
 
    if ((fdlock = open(lockfilename,O_RDONLY, 0644)) < 0) {
        perror("lockfile open error");
        exit(1);
    }
 
    flock(fdlock,LOCK_SH);
    close(fdlock);
 
}

# run syncpppinit first, PPP_NUM is the number of pppd processes
./synpppinit ${PPP_NUM} &
# start all pppd with a loop
for i in $(seq -w 01 $PPP_NUM)
do
    echo -n "executing pppd for connection ${i} ... "
    ./pppd plugin /usr/lib/pppd/2.4.4/rp-pppoe.so mtu 1492 mru 1492 nic-eth${i} persist \
    usepeerdns user ${USERNAME} password ${PASSWORD} ipparam wan ifname ${PPP_IF_PREFIX}${i} nodetach &
    echo "done"
done