Get 'ifconfig' information via Python

[pehr anderson]

Dear David,
I really like the idea of writing an extension module.
I was writing Java aplications under windows and
ran into a complete brick wall because there was
no "inherent" way to get this data with the defined APIs.
There was just no expectation for multi-homed systems
as far as I could tell.

Please add me to your list of interested parties, if you
are compiling such a thing.
I've never written an extension module for python
but have done several python scripts which grabbed the relevant
numbers out of os.popen("ifconfig").read()
I'm really interested in seing this solved "the right way".
Perhaps a request should be made on cosource.com?

This  is a problem that needs a real cross-platform solution.
      -pehr


"M.-A. Lemburg" wrote:

> David N. Welton wrote:
> >
> > So, I think I'm getting close...
> >
> > import fcntl
> > import IN
> > import struct
> >
> > s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
> >
> > res = fcntl.ioctl(s, IN.SIOCSIFHWADDR, ??????)
> >
> > I can't seem to find what goes in ?????.
> >
> > Is this the right way to be doing things?  I suppose I can always go
> > pull apart the sources for ifconfig itself, and make a .so that does
> > what I need, but I get the feeling that I can do what I need from
> > within Python.
> >
> > Yeah, I could popen ifconfig, too, but that's ugly.
> >
> > Downloading python sources now to see what I can see in the fcntl
> > module...
>
> The .ioctl() function can take a string or an integer as
> third argument. To find out what to pass for a given option,
> look at man ioctl and man ioctl_list. The exact meaning is
> not mentioned there unfortunately, though.
>
> On Linux, just dig into the net/core/dev.c file to find out
> what happens for the above option:
>
> The argument is being interpreted as struct ifreq and then copied
> to ifr...
>
>                 case SIOCGIFHWADDR:
>                         memcpy(ifr.ifr_hwaddr.sa_data,dev->dev_addr, MAX_ADDR_LE
>                         ifr.ifr_hwaddr.sa_family=dev->type;
>                         goto rarok;
>
>                 case SIOCSIFHWADDR:
>                         if(dev->set_mac_address==NULL)
>                                 return -EOPNOTSUPP;
>                         if(securelevel > 0)
>                                 return -EPERM;
>                         if(ifr.ifr_hwaddr.sa_family!=dev->type)
>                                 return -EINVAL;
>                         ret=dev->set_mac_address(dev,&ifr.ifr_hwaddr);
>                         break;
>
> The basic ifreq struct is defined in include/linux/if.h:
>
> /*
>  * Interface request structure used for socket
>  * ioctl's.  All interface ioctl's must have parameter
>  * definitions which begin with ifr_name.  The
>  * remainder may be interface specific.
>  */
>
> struct ifreq
> {
> #define IFHWADDRLEN     6
> #define IFNAMSIZ        16
>         union
>         {
>                 char    ifrn_name[IFNAMSIZ];            /* if name, e.g. "en0" *
>         } ifr_ifrn;
>
>         union {
>                 struct  sockaddr ifru_addr;
>                 struct  sockaddr ifru_dstaddr;
>                 struct  sockaddr ifru_broadaddr;
>                 struct  sockaddr ifru_netmask;
>                 struct  sockaddr ifru_hwaddr;
>                 short   ifru_flags;
>                 int     ifru_metric;
>                 int     ifru_mtu;
>                 struct  ifmap ifru_map;
>                 char    ifru_slave[IFNAMSIZ];   /* Just fits the size */
>                 caddr_t ifru_data;
>         } ifr_ifru;
> };
>
> #define ifr_name        ifr_ifrn.ifrn_name      /* interface name       */
> #define ifr_hwaddr      ifr_ifru.ifru_hwaddr    /* MAC address          */
> #define ifr_addr        ifr_ifru.ifru_addr      /* address              */
> #define ifr_dstaddr     ifr_ifru.ifru_dstaddr   /* other end of p-p lnk */
> #define ifr_broadaddr   ifr_ifru.ifru_broadaddr /* broadcast address    */
> #define ifr_netmask     ifr_ifru.ifru_netmask   /* interface net mask   */
> #define ifr_flags       ifr_ifru.ifru_flags     /* flags                */
> #define ifr_metric      ifr_ifru.ifru_metric    /* metric               */
> #define ifr_mtu         ifr_ifru.ifru_mtu       /* mtu                  */
> #define ifr_map         ifr_ifru.ifru_map       /* device map           */
> #define ifr_slave       ifr_ifru.ifru_slave     /* slave device         */
> #define ifr_data        ifr_ifru.ifru_data      /* for use by interface */
>
> Building these structs can be done using the Python struct
> module... playing around with this can probably crash your system
> though.
>
> In the end, I think you're better off hacking together a
> new extension module.
>
> Hope that helps.
>
> --
> Marc-Andre Lemburg
> ______________________________________________________________________
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