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    SubjectRe: TCP/IP with virtual device dsn0 experience?
    On Thu, 27 Feb 1997, Alan Cox wrote:

    > > kernel interfaces, but discovered the the kernel's higher-level network
    > > code had changed such that only one application at a time could open a
    > > SOCK_PACKET for any specific socket type, which prevented the whole scheme
    > > from working.
    >
    > It isnt supposed to have been. Are you sure about this ?
    >
    > > Has this behaviour of SOCK_PACKET changed since circa 1.3.70? If so,
    > > dosnet.c could be modified to work with new kernels. (Of course, if
    > > somebody's already done this I may be flapping my jaw needlessly. :)
    >
    > Its changed a bit in that you can bind() them and pass protocol id hints
    > when you want (eg for PPP)

    Okay I started reading some kernel code in 2.0.29 and I came across this
    section, which appears to be identical in 2.1.27, btw.

    From net/core/dev.c, about line 650, in net_bh():

    /*
    * We got a packet ID. Now loop over the "known protocols"
    * list. There are two lists. The ptype_all list of taps (normally empty)
    * and the main protocol list which is hashed perfectly for normal protocols.
    */

    pt_prev = NULL;
    for (ptype = ptype_all; ptype!=NULL; ptype=ptype->next)
    {
    if(pt_prev)
    {
    struct sk_buff *skb2=skb_clone(skb, GFP_ATOMIC);
    if(skb2)
    pt_prev->func(skb2,skb->dev, pt_prev);
    }
    pt_prev=ptype;
    }

    Either this is a bug or my brain isn't functioning properly. (The latter
    is a distinct possibility as it's almost midnight. :)

    The problem I see is with the pt_prev variable. Why is it even there? It
    looks like this loop will never process the last entry in the ptype_all
    list.

    +-----------------------+---------------------------------------+
    | Nathan Bryant | Unsolicited commercial e-mail WILL be |
    | nathan@burgessinc.com | charged an $80/hr proofreading fee. |
    +-----------------------+---------------------------------------+


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