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    SubjectRe: [PATCH 0/10] af_unix: add multicast and filtering features to AF_UNIX
    On 02/28/2012 03:28 PM, David Lamparter wrote:
    > On Tue, Feb 28, 2012 at 11:47:39AM +0100, Rodrigo Moya wrote:
    >> > - slow readers: dropping packets vs blocking the sender. Although
    >> > datagrams are not reliable on IP, datagrams on Unix sockets are
    >> never
    >> > lost. So if one receiver has its buffer full the sender is blocked
    >> > instead of dropping packets. That way we guarantee a reliable
    >> > communication channel.
    >
    > This sounds like a terribly nice way to f*ck the entire D-Bus system by
    > having one broken (or malicious) desktop application. What's the
    > intended way of coping with users that block the socket by not reading?
    >
    >
    > -David L.

    The problem is that D-bus expects a reliable transport method (TCP or
    SOCK_STREAM Unix socks) but this is not the case with multicast Unix
    sockets. Since our implementation is for SOCK_SEQPACKET and SOCK_DGRAM
    socket types.

    So, you have to either add another layer to the D-bus protocol to make
    it reliable (acks, retransmissions, flow control, etc) or avoid losing
    D-bus messages (by blocking the sender if one of the receivers has its
    buffer full).

    Regards,
    Javier


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