Jason Xing <kerneljasonxing@xxxxxxxxx> wrote: > > This change disables most of the tcp_in_window() test, this will > > pretend everything is fine even though tcp_in_window says otherwise. > > Thanks for the information. It does make sense. > > What I've done is quite similar to nf_conntrack_tcp_be_liberal sysctl > knob which you also pointed out. It also pretends to ignore those > out-of-window skbs. > > > > > You could: > > - drop invalid tcp packets in input hook > > How about changing the return value only as below? Only two cases will > be handled: > > diff --git a/net/netfilter/nf_conntrack_proto_tcp.c > b/net/netfilter/nf_conntrack_proto_tcp.c > index ae493599a3ef..c88ce4cd041e 100644 > --- a/net/netfilter/nf_conntrack_proto_tcp.c > +++ b/net/netfilter/nf_conntrack_proto_tcp.c > @@ -1259,7 +1259,7 @@ int nf_conntrack_tcp_packet(struct nf_conn *ct, > case NFCT_TCP_INVALID: > nf_tcp_handle_invalid(ct, dir, index, skb, state); > spin_unlock_bh(&ct->lock); > - return -NF_ACCEPT; > + return -NF_DROP; Lets not do this. conntrack should never drop packets and defer to ruleset whereever possible. > > - set nf_conntrack_tcp_be_liberal=1 > > Sure, it can workaround this case, but I would like to refuse the > out-of-window in netfilter or TCP layer as default instead of turning > on this sysctl knob. If I understand wrong, please correct me. Thats contradictory, you make a patch to always accept, then another patch to always drop such packets? You can get the drop behaviour via '-m conntrack --ctstate DROP' in prerouting or inut hooks. You can get the 'accept + do nat processing' via nf_conntrack_tcp_be_liberal=1.
