if_tap unaligned access problem

From: Gleb Smirnoff (glebius_at_FreeBSD.org)
Date: 04/28/05

  • Next message: Maksim Yevmenkin: "Re: if_tap unaligned access problem" 
    Date: Thu, 28 Apr 2005 17:51:20 +0400
To: net@FreeBSD.org

    Forward this to expose to wider audience.

    ----- Forwarded message from Sten Spans <sten@blinkenlights.nl> -----

    From: Sten Spans <sten@blinkenlights.nl>
    To: glebius@FreeBSD.org
    Cc: Julian Elischer <julian@FreeBSD.org>
    Subject: if_tap unaligned access problem
    Date: Wed, 27 Apr 2005 14:54:29 +0200 (CEST)
    Delivered-To: glebius@freebsd.org

    A quick question about if_tap, the tapwrite function
    ( which copies an ethernet frame into an mbuf using uiotombuf )
    is broken on alpha and sparc64.
    The 14 byte ethernet header causes the rest of the frame to
    be misaligned on 4 byte boundaries. This causes crashes in
    various other parts of the kernel. The solution would be to
    shift the mbuf by two bytes, but I am not quite sure where
    this should happen.

    If_tun which is almost the same code has no such problem because
    it lacks the 14 byte ethernet header. Openbsd has a combined
    tun/tap driver, with some alignment hacks to fix this.

    Should I create a pr for this problem, or is there a simple
    quick fix possible ? 

    -- 
Sten Spans
"There is a crack in everything, that's how the light gets in."
Leonard Cohen - Anthem
----- End forwarded message -----
-- 
Totus tuus, Glebius.
GLEBIUS-RIPN GLEB-RIPE
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  • Next message: Maksim Yevmenkin: "Re: if_tap unaligned access problem"