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    SubjectRe: [PATCH 18/29] netfilter: notify about NF_QUEUE vs emergency skbs
    Peter Zijlstra wrote:
    > Emergency skbs should never touch user-space, however NF_QUEUE is fully user
    > configurable. Notify the user of his mistake and try to continue.
    >
    > --- linux-2.6-git.orig/net/netfilter/core.c 2007-02-14 12:09:07.000000000 +0100
    > +++ linux-2.6-git/net/netfilter/core.c 2007-02-14 12:09:18.000000000 +0100
    > @@ -187,6 +187,11 @@ next_hook:
    > kfree_skb(*pskb);
    > ret = -EPERM;
    > } else if ((verdict & NF_VERDICT_MASK) == NF_QUEUE) {
    > + if (unlikely((*pskb)->emergency)) {
    > + printk(KERN_ERR "nf_hook: NF_QUEUE encountered for "
    > + "emergency skb - skipping rule.\n");
    > + goto next_hook;
    > + }

    If I'm not mistaken any skb on the receive side might get
    allocated from the reserve. I don't see how the user could
    avoid this except by not using queueing at all.

    I also didn't see a patch dropping packets allocated from
    the reserve that are forwarded or processed directly without
    getting queued to a socket, so this would allow them to
    bypass userspace queueing and still go through.

    I think the user should just exclude packets necessary for
    swapping from queueing manually, based on IP addresses,
    port numbers or something like that.

    -
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