Florian Westphal <[email protected]> writes: > Aaron Conole <[email protected]> wrote: >> > verdict with NF_DROP_REASON() helper, >> > >> > This helper releases the skb instantly (so drop_monitor can pinpoint >> > precise location) and returns NF_STOLEN. >> > >> > Prepare call sites to deal with this before introducing such changes >> > in conntrack and nat core. >> > >> > Signed-off-by: Florian Westphal <[email protected]> >> > --- >> >> AFAIU, these changes are only impacting the existing NF_DROP cases, and >> won't impact how ovs + netfilter communicate about invalid packets. One >> important thing to note is that we rely on: >> >> * Note that if the packet is deemed invalid by conntrack, skb->_nfct will be >> * set to NULL and 0 will be returned. > > Right, this is about how to communicate 'packet dropped'. > > NF_DROP means 'please call kfree_skb for me'. Problem from introspection > point > of view is that drop monitor will blame nf_hook_slow() (for netfilter) > and ovs resp. act_ct for the drop. > > Plan is to allow conntrack/nat engine to return STOLEN verdict ("skb > might have been free'd already"). > > Example change: > @@ -52,10 +53,8 @@ nf_nat_masquerade_ipv4(struct sk_buff *skb, > unsigned int hooknum, > rt = skb_rtable(skb); > nh = rt_nexthop(rt, ip_hdr(skb)->daddr); > newsrc = inet_select_addr(out, nh, RT_SCOPE_UNIVERSE); > - if (!newsrc) { > - pr_info("%s ate my IP address\n", out->name); > - return NF_DROP; > - } > + if (!newsrc) > + return NF_DROP_REASON(skb, SKB_DROP_REASON_NETFILTER_DROP, > EADDRNOTAVAIL); > > > Where NF_DROP_REASON() is: > > static __always_inline int > NF_DROP_REASON(struct sk_buff *skb, enum skb_drop_reason reason, u32 err) > { > BUILD_BUG_ON(err > 0xffff); > > kfree_skb_reason(skb, reason); > > return ((err << 16) | NF_STOLEN); > } > > So drop monitoring tools will blame > nf_nat_masquerade.c:nf_nat_masquerade_ipv4 and not > the consumer of the NF_DROP verdict. > > I can't make such changes ATM because ovs and act_ct assume conntrack > returns only ACCEPT and DROP, so we'd get double-free. Hope that makes > sense. > > Thanks!
Makes sense to me, thanks! _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
