Re: /dev/random probs in 2.4test(12-pre3)

From: H. Peter Anvin (hpa@zytor.com)
Date: Fri Dec 01 2000 - 13:18:56 EST

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    Followup to: <Pine.LNX.4.10.10012011720050.23462-100000@sphinx.mythic-beasts.com>
    By author: Matthew Kirkwood <matthew@hairy.beasts.org>
    In newsgroup: linux.dev.kernel
    >
    > Hi,
    >
    > It looks like the random driver in 2.4test will return a
    > short read, rather than blocking. This is breaking vpnd
    > (http://sunsite.dk/vpnd/) which breaks with "failed to
    > gather random data" or similar.
    >
    > Here's a sample strace:
    >
    > open("/dev/random", O_RDONLY) = 3
    > read(3, "q\321Nu\204\251^\234i\254\350\370\363\"\305\366R\2708V"..., 72) = 29
    > close(3) = 0
    >
    > Have the semantics of the device changed, or is vpnd doing
    > something wrong?
    >

    vpnd is doing something wrong: it's assuming short reads won't
    happen. /dev/random will block if there is NOTHING to be read;
    however, if there are bytes to be read, it will return them even if it
    is less than the user asked for.

            -hpa 

    -- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
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