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    SubjectRe: [PATCH,TRIVIAL] AF_UNIX, accept() and addrlen
    David Miller, le Sun 23 Mar 2008 21:56:41 -0700, a écrit :
    > From: Samuel Thibault <samuel.thibault@ens-lyon.org>
    > Date: Sat, 8 Mar 2008 02:23:21 +0000
    >
    > > Accept and getpeername are supposed to return the amount of bytes
    > > written in the returned address. However, on unnamed sockets, only
    > > sizeof(short) is returned, while a 0 is put in the sun_path member.
    > > This patch adds 1 for that additional byte.
    > >
    > > Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
    >
    > This change isn't correct. It's the fact that the
    > length returned is sizeof(short) that tells the caller
    > that the unix socket is unnamed.

    Mmm, where that is documented?

    I can't find any details about that in SUS, and man 7 unix says

    `If sun_path starts with a null byte ('' '), then it refers to the
    abstract namespace main- tained by the Unix protocol module.'

    It doesn't talk about the size being only sizeof(short) (which I guess
    you meant sizeof(sa_family_t) actually).

    > We zero out the sun_path[0] member just to be polite and tidy.
    >
    > You would break applications if you changed this, so
    > marking this patch as "trivial" is extremely premature.

    See documentation above. If applications don't follow documentation,
    then they deserve breaking :)

    Note also that on some (BSD-ish) systems, sockaddr_un contains a sun_len
    field, containing the length of the data, and thus on them accept and
    getpeername return more that sizeof(sa_family_t) as length (it actually
    returns 16). So such applications are really broken.

    Samuel
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