Re: Alternative fix for FreeBSD-SA-03:14.arp

From: Jacques A. Vidrine (nectar_at_FreeBSD.org)
Date: 09/26/03

  • Next message: Dambielle Yannick: "tcpdump - tun/tap virtual interfaces" 
    Date: Fri, 26 Sep 2003 10:59:21 -0500
To: freebsd-net@freebsd.org

    On Fri, Sep 26, 2003 at 04:23:49PM +0100, Bruce M Simpson wrote:
    > Hi,
    >
    > Based on discussion between ru@ and I, there's a patch attached which
    > tries to fix the problem without deleting GENMASK routes, and is
    > stricter about not touching STATIC routes.
    >
    > Comments and reviews solicited, appreciated...
    >
    > Thanks!
    > BMS

    > --- if_ether.c.orig Mon Sep 22 21:11:59 2003
    > +++ if_ether.c Fri Sep 26 13:43:20 2003
    > @@ -922,9 +922,19 @@
    > if (why && create) {
    > log(LOG_DEBUG, "arplookup %s failed: %s\n",
    > inet_ntoa(sin.sin_addr), why);
    > - return 0;
    > +
    > + if ((rt->rt_refcnt == 0) &&
    > + (rt->rt_flags & RTF_STATIC) == 0 &&
    > + (rt->rt_flags & (RTF_HOST|RTF_WASCLONED)) ==
    > + (RTF_HOST|RTF_WASCLONED)) {
    > + rtrequest(RTM_DELETE, (struct sockaddr *)rt_key(rt),
    > + rt->rt_gateway, rt_mask(rt),
    > + rt->rt_flags, 0);
    > + }
    > +
    > + return (0);
    > } else if (why) {
    > - return 0;
    > + return (0);
    > }
    > return ((struct llinfo_arp *)rt->rt_llinfo);
    > }

    Trivial nit. In this file, the style is

       Test for flag set: if (rt->rt_flags & RTF_STATIC)
       Test for flag not set: if ((rt->rt_flags & RTF_STATIC) == 0)

    The comparison operators make it harder to read, especially those
    comparison operations that don't involve a zero operand.
    [Personally, for flag not set, I prefer `!(rt->rt_flags & RTF_STATIC)'
    but that goes against the style of this file, at least.]

    This seems OK to me, although I find it hard to understand how we
    get into the situation where the genmask route entry (which we are
    protecting) would have the RTF_WASCLONED bit set. That's likely to do
    with my lack of familiarity with genmask routes.

    Cheers, 

    -- 
Jacques Vidrine   . NTT/Verio SME      . FreeBSD UNIX       . Heimdal
nectar@celabo.org . jvidrine@verio.net . nectar@freebsd.org . nectar@kth.se
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