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    SubjectRe: [PATCH] netfilter: add CHECKSUM target
    Am 11.07.2010 12:47, schrieb Michael S. Tsirkin:
    > On Fri, Jul 09, 2010 at 05:17:36PM +0200, Patrick McHardy wrote:
    >> Am 09.07.2010 00:29, schrieb Michael S. Tsirkin:
    >>> This adds a `CHECKSUM' target, which can be used in the iptables mangle
    >>> table.
    >>>
    >>> You can use this target to compute and fill in the checksum in
    >>> an IP packet that lacks a checksum. This is particularly useful,
    >>> if you need to work around old applications such as dhcp clients,
    >>> that do not work well with checksum offloads, but don't want to
    >>> disable checksum offload in your device.
    >>>
    >>> The problem happens in the field with virtualized applications.
    >>> For reference, see Red Hat bz 605555, as well as
    >>> http://www.spinics.net/lists/kvm/msg37660.html
    >>>
    >>> Typical expected use (helps old dhclient binary running in a VM):
    >>> iptables -A POSTROUTING -t mangle -p udp --dport 68 -j CHECKSUM
    >>> --checksum-fill
    >>
    >> I'm not sure this is something we want to merge upstream and
    >> support indefinitely. Dave suggested this as a temporary
    >> out-of-tree workaround until the majority of guest dhcp clients
    >> are fixed. Has anything changed that makes this course of
    >> action impractical?
    >
    > If I understand what Dave said correctly, it's up to you ...
    >
    > The arguments for putting this upstream are:
    >
    > Given the track record, I wouldn't hope for quick fix in the majority of
    > guest dhcp clients, unfortunately :(. We are talking years here.
    > Even after that, one of the uses of virtualization is
    > to keep old guests running. So yes, I think we'll
    > keep using work-arounds for this for a very long time.
    >
    > Further, since we have to add the module and we have to teach management
    > to program it, it will be much less painful for everyone
    > involved if we can put the code upstream, rather than forking
    > management code.

    Fair enough, its simple enough that I don't expect much maintenance
    overhead.


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