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Help with fork, wait, kill in C

Hi all,

Edit for brevity:
My current code:

Code:

for( x = 0; x < 5; x++ ) {



    libnet_write( context ); // sends ARP who-has

    // The following line blocks until a packet is captured, then passes it to

    // pcap_callback_fct, which dissembles and puts the source MAC in

    // temp_mac, a global char*



    pcap_dispatch( pkt_descriptor, 0, ( void * )pcap_callback_fct, NULL );



    memcpy( target_mac[ x ], temp_mac, MAX_SIZE_ETHADDR );

}

This will not work, as Linux does not implement the read timeout in pcap_open_live(), so if I am sending packets to a non-replying address, pcap_dispatch blocks indefinitely. I need to:

1. Fork a child that will execute pcap_dispatch and return when a packet is captured
2. Have the parent wait for pehaps a second for the child to return and if it does not, then kill it
3. Implement temp_mac as shared memory so that when the child's pcap_dispatch call in turn calls pcap_callback_fct, that last will be able to write to memory space that the parent can read.

There, I think I have removed excess varbiage. TIA!

I'm trying this:

Code:

pid_t child_pid;

char *shared_mem; // This will be shared for getting the MAC into target_mac[]

int shmseg_id;

shmseg_id = shmget( IPC_PRIVATE, MAX_SIZE_ETHADDR, IPC_CREAT | IPC_EXCL | S_IRUSR | S_IWUSR );

for( x = 0; x < 5; x++ ) {

    libnet_write( context );

    child_pid = fork();

    if( child_pid == 0 ) {

          // attach to shared memory

          shared_mem = ( char * ) shmat( shmseg_id, 0, 0 );

          pcap_dispatch( pkt_descriptor, 0, ( void * )pcap_callback_fct, NULL );

          memcpy( shared_mem, temp_mac, MAX_SIZE_ETHADDR );

          exit( 0 );

    }

    else {

          sleep( 2 );

          shared_mem = ( char * ) shmat( shmseg_id, 0, 0 );

          if( strlen( shared_mem ) == 0 ) {

              // the child has blocked, kill it

              kill( child_pid, SIGTERM );

          }

    }

    memcpy( target_mac[ x ], shared_mem, MAX_SIZE_ETHADDR );

}

// detach shared memory and deallocate

shmdt( shared_mem );

shmctl( shmseg_id, IPC_RMID, 0 );

It compiles, and seems to run, but I am getting a new error now that pcap_dispatch is not blocking indefinitely. New thread on the way...:(