How to identify which interface a broadcast packet comes in on?

Discussion in 'Python' started by Lincoln Yeoh, Sep 3, 2005.

  1. Lincoln Yeoh

    Lincoln Yeoh Guest

    Hi,

    If I have a program listening on 0.0.0.0:(someport) on all interfaces,
    how do I know which network interface a broadcast packet is coming in
    on - assuming Linux and _many_ interfaces. And how do I set which
    interface a frame will leave on, assuming I'm sending a raw frame (no
    IP address, just the ethernet address).

    If I use C, it seems I'm to use the IP_PKTINFO socket options,
    send/recv the ancillary messages and set/check the ipi_ifindex value.

    struct in_pktinfo {
    unsigned int ipi_ifindex; /* Interface index */
    struct in_addr ipi_spec_dst; /* Local address */
    struct in_addr ipi_addr; /* Header Destination address
    */
    };

    How would I achieve the same thing in Python?

    This would be useful for writing something like a DHCP server - such a
    server could receive packets with source IP addresses of 0.0.0.0
    destined to 255.255.255.255, and will need to know which interface the
    packet is coming in from AND the source ethernet (or other link layer)
    address so that it can send the replies out the right interface.

    Thanks!
    Link.
     
    Lincoln Yeoh, Sep 3, 2005
    #1
    1. Advertising

  2. Lincoln Yeoh

    Jorgen Grahn Guest

    On Sat, 03 Sep 2005 18:46:05 +0800, Lincoln Yeoh <> wrote:
    > Hi,
    >
    > If I have a program listening on 0.0.0.0:(someport) on all interfaces,
    > how do I know which network interface a broadcast packet is coming in
    > on - assuming Linux and _many_ interfaces. And how do I set which
    > interface a frame will leave on, assuming I'm sending a raw frame (no
    > IP address, just the ethernet address).
    >
    > If I use C, it seems I'm to use the IP_PKTINFO socket options,
    > send/recv the ancillary messages and set/check the ipi_ifindex value.

    ....
    > How would I achieve the same thing in Python?


    Someone may want to correct me, but from what I can see, the socket module
    is almost a 1:1 mapping between the socket support your C lib has, and
    Python. Plus some compatibility code for Windows.

    You should be able to do everything you can do in C. Your code may
    become Linux-specific if you're not careful, though.

    /Jorgen

    --
    // Jorgen Grahn <jgrahn@ Ph'nglui mglw'nafh Cthulhu
    \X/ algonet.se> R'lyeh wgah'nagl fhtagn!
     
    Jorgen Grahn, Sep 3, 2005
    #2
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Li Han
    Replies:
    2
    Views:
    532
    bobicanprogram
    Feb 9, 2009
  2. Gelonida N
    Replies:
    4
    Views:
    952
    Gelonida N
    Sep 11, 2011
  3. Martin Farnik

    UDP Broadcast Packet (offtopic)

    Martin Farnik, Jul 4, 2003, in forum: Ruby
    Replies:
    3
    Views:
    176
  4. Lincoln Yeoh
    Replies:
    0
    Views:
    113
    Lincoln Yeoh
    Sep 3, 2005
  5. Lincoln Yeoh
    Replies:
    2
    Views:
    124
    Lincoln Yeoh
    Sep 6, 2005
Loading...

Share This Page