[Linux]Custom ioctl command for sockets

於network interface可定義下面的 operations

dev->open = henbin_open;
dev->stop = henbin_close;

如有需要透過sockets呼叫custom ioctl，可增加一個如下的ioctl function



int henbin_ioctl (struct net_device *dev, struct ifreq *ifr, int cmd){

          switch (cmd){

                            SIOCDEVPRIVATE:

                            SIOCDEVPRIVATE+1:

                            ...

                            SIOCDEVPRIVATE+15:
          }
          return 0;
}

dev->do_ioct = henbin_ioctl;

可使用的custom command的範圍從SIOCDEVPRIVATE到SIOCDEVPRIVATE+15, 此為Device private ioctl calls

如此即可透過下列方式去呼叫ioctl
{
    ...
    struct ifreq ifr;
    int skfd;
    struct sockaddr_in *info;

    skfd = socket(PF_INET, SOCK_DGRAM, 0 );
   
    memset(&ifr,0,sizeof(struct ifreq));

    strcpy(ifr.ifr_name, "eth0");
 
    ifr.ifr_hwaddr.sa_family = AF_INET;
    ioctl(skfd, SIOCDEVPRIVATE+1, &ifr);
}

另外還有SIOCPROTOPRIVATE到SIOCPROTOPRIVATE+15, 這就是protocol private, 可以在af_inet.c內增加一個OEM ioctl command,

再利用下面方式去呼叫即可

#include <sys/ioctl.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/if_ether.h>
#include <netinet/in.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>

int main(){
  int s = socket(AF_INET, SOCK_DGRAM, 0);
  ioctl(s, (SIOCPROTOPRIVATE+1));

  close(s);
 return 0;

}