Re: kern/73129: [patch] IPFW misbehaviour in RELENG_5

From: Maxim Konovalov (maxim_at_macomnet.ru)
Date: 12/04/04

  • Next message: Andre Oppermann: "Re: New Networking Project..." 
    Date: Sun, 5 Dec 2004 00:53:52 +0300 (MSK)
To: Andre Oppermann <andre@freebsd.org>

    On Sat, 4 Dec 2004, 21:37+0100, Andre Oppermann wrote:

    [...]
    > > Investigating pre-PFIL_HOOKS ipfw I have not found any analog of
    > > this check. These checks do break some useful functionality:
    > >
    > > 1) policy routing of hosts from connected networks
    > > 2) policy routing of locally originated traffic
    > >
    > > The second one is used very widely. When you have lines to two
    > > ISPs and run natd for both of them, you policy route nated packets
    > > to them.
    >
    > I know. On the other hand having these checks avoids breaking responses
    > from the host doing the policy routing towards hosts on connected networks.
    >
    > In my case I had a problem where the MTU of the policy-routing target
    > interface was lower than 1500 but the ICMP fragmentation needed packets
    > never made it back to the real host; they were forwarded to the policy
    > destination.
    >
    > This is how I came to this check. It is more correct but indeed breaks
    > forwarding packets that were targeted at an IP address configured on a
    > local interface. This is an unintended side effect but I haven't found
    > a nice solution to work around that. I'm not entirely sure what the
    > best way is to handle this and it's also the reason why I haven't changed
    > it so far.
    >
    > If you have suggestions I'm all ears. But think through all cases at least
    > twice, there are some nice traps. Fixing one end without breaking another
    > one is hard.

    IMHO restoring the historic behaviour (even broken in some respects)
    is the best thing we can do at the moment.

    > > P.S. kern/73129, kern/73910, kern/71910 

    -- 
Maxim Konovalov
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