[ovs-dev] [PATCH ovn] northd: Remove the usage of 'ct.inv' in logical flows.

Han Zhou hzhou at ovn.org
Thu Feb 25 19:45:02 UTC 2021


On Thu, Feb 25, 2021 at 1:25 AM Numan Siddique <numans at ovn.org> wrote:
>
> On Thu, Feb 25, 2021 at 1:12 PM Han Zhou <hzhou at ovn.org> wrote:
> >
> > On Wed, Feb 24, 2021 at 5:27 AM <numans at ovn.org> wrote:
> > >
> > > From: Numan Siddique <numans at ovn.org>
> > >
> > > Presently we add 65535 priority lflows in the stages -
> > > 'ls_in_acl' and 'ls_out_acl' to drop packets which
> > > match on 'ct.inv'.
> > >
> > > As per the 'ovs-fields' man page, this
> > > ct state field can be used to identify problems such as:
> > >  •  L3/L4 protocol handler is not loaded/unavailable.
> > >
> > >  •  L3/L4 protocol handler determines that the packet is
> > >     malformed.
> > >
> > >  •  Packets are unexpected length for protocol.
> > >
> > > This patch removes the usage of this field for the following
> > > reasons:
> > >
> > >  • Some of the smart NICs which support offloading datapath
> > >    flows don't support this field.
> >
> > What do you mean by "don't support this field"? Do you mean the NIC
> > offloading supports connection tracking, but cannot detect if a packet
is
> > invalid and always populate the ct.inv as 0?
>
> I think so. From what I understand, the kernel conntrack feature is used
> for the actual connection tracking. So NIC can't tell if the packet is
> invalid or not
> (say due to out-of-window tcp errors).
>
I know some NICs support CT offloading and some doesn't.
So here what you are referring are the NICs that doesn't support CT
offloading, which falls back to kernel datapath when CT is used, is it? If
this is the case, then even without ct.inv it still couldn't support
ct.est, etc. right?
Or, do you mean this is specifically for NICs that support CT offloading
but not ct.inv, i.e. it can do regular conntrack in NIC but just can't
identify out-of-window packets, and that's why it supports ct.est but not
ct.inv?
I am still quite confused. Could clarify a little more, which types of NICs
would benefit from this, and how?

> >
> > >
> > >  • A recent commit in kernel ovs datapath sets the committed
> > >    connection tracking entry to be liberal for out-of-window
> > >    tcp packets (nf_ct_set_tcp_be_liberal()).  Such TCP
> > >    packets will not be marked as invalid.
> > >
> >
> > Could you share a link to this commit?
>
> Sure.
>
https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net-next/+/e2ef5203c817a60bfb591343ffd851b6537370ff
>
Thanks for sharing. So OVS is not capable of detecting a out-of-window
packet now. Could you explain more about the motivation? I couldn't get the
full picture from commit message of that patch. Do you have a link that
discusses more details?

> >
> > >  • Even if a ct.inv packet is delivered to a VIF, the
> > >    networking stack of the VIF's kernel can handle such
> > >    packets.
> >
> > I have some concern for this point. We shouldn't make assumptions for
> > what's configured in the VIF's kernel, because it is independent of
what's
> > expected from OVN ACLs. In addition, egress rules are expected to drop
> > invalid packets sent by the VIF (regardless of how the VIF's kernel is
> > configured).
>
> Agree. I can delete this point from the commit message.
>
> >
> > However, I am not against this patch, but just want to double confirm. I
> > think this deserves a description in NEWS if we do so.
>
> Sure. I will add to the NEWS.
>
> If there are concerns about removing this, how about we use ct.inv by
> default and
> add a config option to not use this flag in ovn-northd ?
> Deployments who want to make use of HWOL nics can turn on this option ?
>
Yes, I think an option would help. However, before moving there, I am
wondering if the user could simply use stateless ACLs to achieve the same
outcome. What's the benefit of using stateful ACLs without the ability to
detect invalid packets v.s. using stateless ACLs?

> Thanks for the review.
>
> Numan
>
> >
> > Thanks,
> > Han
> >
> > >
> > > Signed-off-by: Numan Siddique <numans at ovn.org>
> > > ---
> > >  northd/ovn-northd.c | 24 ++++++++++++------------
> > >  tests/ovn-northd.at | 24 ++++++++++++------------
> > >  2 files changed, 24 insertions(+), 24 deletions(-)
> > >
> > > diff --git a/northd/ovn-northd.c b/northd/ovn-northd.c
> > > index dcdb777a2..e30fb532c 100644
> > > --- a/northd/ovn-northd.c
> > > +++ b/northd/ovn-northd.c
> > > @@ -5617,10 +5617,10 @@ build_acls(struct ovn_datapath *od, struct
hmap
> > *lflows,
> > >           *
> > >           * This is enforced at a higher priority than ACLs can be
> > defined. */
> > >          ovn_lflow_add(lflows, od, S_SWITCH_IN_ACL, UINT16_MAX,
> > > -                      "ct.inv || (ct.est && ct.rpl &&
ct_label.blocked
> > == 1)",
> > > +                      "ct.est && ct.rpl && ct_label.blocked == 1",
> > >                        "drop;");
> > >          ovn_lflow_add(lflows, od, S_SWITCH_OUT_ACL, UINT16_MAX,
> > > -                      "ct.inv || (ct.est && ct.rpl &&
ct_label.blocked
> > == 1)",
> > > +                      "ct.est && ct.rpl && ct_label.blocked == 1",
> > >                        "drop;");
> > >
> > >          /* Ingress and Egress ACL Table (Priority 65535).
> > > @@ -5633,12 +5633,12 @@ build_acls(struct ovn_datapath *od, struct
hmap
> > *lflows,
> > >           *
> > >           * This is enforced at a higher priority than ACLs can be
> > defined. */
> > >          ovn_lflow_add(lflows, od, S_SWITCH_IN_ACL, UINT16_MAX,
> > > -                      "ct.est && !ct.rel && !ct.new && !ct.inv "
> > > -                      "&& ct.rpl && ct_label.blocked == 0",
> > > +                      "ct.est && !ct.rel && !ct.new && "
> > > +                      "ct.rpl && ct_label.blocked == 0",
> > >                        "next;");
> > >          ovn_lflow_add(lflows, od, S_SWITCH_OUT_ACL, UINT16_MAX,
> > > -                      "ct.est && !ct.rel && !ct.new && !ct.inv "
> > > -                      "&& ct.rpl && ct_label.blocked == 0",
> > > +                      "ct.est && !ct.rel && !ct.new && "
> > > +                      "ct.rpl && ct_label.blocked == 0",
> > >                        "next;");
> > >
> > >          /* Ingress and Egress ACL Table (Priority 65535).
> > > @@ -5653,12 +5653,12 @@ build_acls(struct ovn_datapath *od, struct
hmap
> > *lflows,
> > >           * related traffic such as an ICMP Port Unreachable through
> > >           * that's generated from a non-listening UDP port.  */
> > >          ovn_lflow_add(lflows, od, S_SWITCH_IN_ACL, UINT16_MAX,
> > > -                      "!ct.est && ct.rel && !ct.new && !ct.inv "
> > > -                      "&& ct_label.blocked == 0",
> > > +                      "!ct.est && ct.rel && !ct.new && "
> > > +                      "ct_label.blocked == 0",
> > >                        "next;");
> > >          ovn_lflow_add(lflows, od, S_SWITCH_OUT_ACL, UINT16_MAX,
> > > -                      "!ct.est && ct.rel && !ct.new && !ct.inv "
> > > -                      "&& ct_label.blocked == 0",
> > > +                      "!ct.est && ct.rel && !ct.new && "
> > > +                      "ct_label.blocked == 0",
> > >                        "next;");
> > >
> > >          /* Ingress and Egress ACL Table (Priority 65535).
> > > @@ -5846,11 +5846,11 @@ build_lb(struct ovn_datapath *od, struct hmap
> > *lflows)
> > >           *
> > >           * Send established traffic through conntrack for just NAT.
*/
> > >          ovn_lflow_add(lflows, od, S_SWITCH_IN_LB, UINT16_MAX - 1,
> > > -                      "ct.est && !ct.rel && !ct.new && !ct.inv && "
> > > +                      "ct.est && !ct.rel && !ct.new && "
> > >                        "ct_label.natted == 1",
> > >                        REGBIT_CONNTRACK_NAT" = 1; next;");
> > >          ovn_lflow_add(lflows, od, S_SWITCH_OUT_LB, UINT16_MAX - 1,
> > > -                      "ct.est && !ct.rel && !ct.new && !ct.inv && "
> > > +                      "ct.est && !ct.rel && !ct.new && "
> > >                        "ct_label.natted == 1",
> > >                        REGBIT_CONNTRACK_NAT" = 1; next;");
> > >      }
> > > diff --git a/tests/ovn-northd.at b/tests/ovn-northd.at
> > > index ad0f9f562..dc49c2543 100644
> > > --- a/tests/ovn-northd.at
> > > +++ b/tests/ovn-northd.at
> > > @@ -1940,9 +1940,9 @@ AT_CHECK([ovn-sbctl lflow-list ls | grep -e
> > ls_in_acl_hint -e ls_out_acl_hint -e
> > >    table=4 (ls_out_acl_hint    ), priority=6    , match=(!ct.new &&
> > ct.est && !ct.rpl && ct_label.blocked == 1), action=(reg0[[7]] = 1;
> > reg0[[9]] = 1; next;)
> > >    table=4 (ls_out_acl_hint    ), priority=7    , match=(ct.new &&
> > !ct.est), action=(reg0[[7]] = 1; reg0[[9]] = 1; next;)
> > >    table=5 (ls_out_acl         ), priority=1    , match=(ip &&
(!ct.est
> > || (ct.est && ct_label.blocked == 1))), action=(reg0[[1]] = 1; next;)
> > > -  table=5 (ls_out_acl         ), priority=65535, match=(!ct.est &&
> > ct.rel && !ct.new && !ct.inv && ct_label.blocked == 0), action=(next;)
> > > -  table=5 (ls_out_acl         ), priority=65535, match=(ct.est &&
> > !ct.rel && !ct.new && !ct.inv && ct.rpl && ct_label.blocked == 0),
> > action=(next;)
> > > -  table=5 (ls_out_acl         ), priority=65535, match=(ct.inv ||
> > (ct.est && ct.rpl && ct_label.blocked == 1)), action=(drop;)
> > > +  table=5 (ls_out_acl         ), priority=65535, match=(!ct.est &&
> > ct.rel && !ct.new && ct_label.blocked == 0), action=(next;)
> > > +  table=5 (ls_out_acl         ), priority=65535, match=(ct.est &&
> > !ct.rel && !ct.new && ct.rpl && ct_label.blocked == 0), action=(next;)
> > > +  table=5 (ls_out_acl         ), priority=65535, match=(ct.est &&
ct.rpl
> > && ct_label.blocked == 1), action=(drop;)
> > >    table=8 (ls_in_acl_hint     ), priority=1    , match=(ct.est &&
> > ct_label.blocked == 0), action=(reg0[[10]] = 1; next;)
> > >    table=8 (ls_in_acl_hint     ), priority=2    , match=(ct.est &&
> > ct_label.blocked == 1), action=(reg0[[9]] = 1; next;)
> > >    table=8 (ls_in_acl_hint     ), priority=3    , match=(!ct.est),
> > action=(reg0[[9]] = 1; next;)
> > > @@ -1951,9 +1951,9 @@ AT_CHECK([ovn-sbctl lflow-list ls | grep -e
> > ls_in_acl_hint -e ls_out_acl_hint -e
> > >    table=8 (ls_in_acl_hint     ), priority=6    , match=(!ct.new &&
> > ct.est && !ct.rpl && ct_label.blocked == 1), action=(reg0[[7]] = 1;
> > reg0[[9]] = 1; next;)
> > >    table=8 (ls_in_acl_hint     ), priority=7    , match=(ct.new &&
> > !ct.est), action=(reg0[[7]] = 1; reg0[[9]] = 1; next;)
> > >    table=9 (ls_in_acl          ), priority=1    , match=(ip &&
(!ct.est
> > || (ct.est && ct_label.blocked == 1))), action=(reg0[[1]] = 1; next;)
> > > -  table=9 (ls_in_acl          ), priority=65535, match=(!ct.est &&
> > ct.rel && !ct.new && !ct.inv && ct_label.blocked == 0), action=(next;)
> > > -  table=9 (ls_in_acl          ), priority=65535, match=(ct.est &&
> > !ct.rel && !ct.new && !ct.inv && ct.rpl && ct_label.blocked == 0),
> > action=(next;)
> > > -  table=9 (ls_in_acl          ), priority=65535, match=(ct.inv ||
> > (ct.est && ct.rpl && ct_label.blocked == 1)), action=(drop;)
> > > +  table=9 (ls_in_acl          ), priority=65535, match=(!ct.est &&
> > ct.rel && !ct.new && ct_label.blocked == 0), action=(next;)
> > > +  table=9 (ls_in_acl          ), priority=65535, match=(ct.est &&
> > !ct.rel && !ct.new && ct.rpl && ct_label.blocked == 0), action=(next;)
> > > +  table=9 (ls_in_acl          ), priority=65535, match=(ct.est &&
ct.rpl
> > && ct_label.blocked == 1), action=(drop;)
> > >  ])
> > >
> > >  AS_BOX([Check match ct_state with load balancer])
> > > @@ -1972,9 +1972,9 @@ AT_CHECK([ovn-sbctl lflow-list ls | grep -e
> > ls_in_acl_hint -e ls_out_acl_hint -e
> > >    table=4 (ls_out_acl_hint    ), priority=6    , match=(!ct.new &&
> > ct.est && !ct.rpl && ct_label.blocked == 1), action=(reg0[[7]] = 1;
> > reg0[[9]] = 1; next;)
> > >    table=4 (ls_out_acl_hint    ), priority=7    , match=(ct.new &&
> > !ct.est), action=(reg0[[7]] = 1; reg0[[9]] = 1; next;)
> > >    table=5 (ls_out_acl         ), priority=1    , match=(ip &&
(!ct.est
> > || (ct.est && ct_label.blocked == 1))), action=(reg0[[1]] = 1; next;)
> > > -  table=5 (ls_out_acl         ), priority=65535, match=(!ct.est &&
> > ct.rel && !ct.new && !ct.inv && ct_label.blocked == 0), action=(next;)
> > > -  table=5 (ls_out_acl         ), priority=65535, match=(ct.est &&
> > !ct.rel && !ct.new && !ct.inv && ct.rpl && ct_label.blocked == 0),
> > action=(next;)
> > > -  table=5 (ls_out_acl         ), priority=65535, match=(ct.inv ||
> > (ct.est && ct.rpl && ct_label.blocked == 1)), action=(drop;)
> > > +  table=5 (ls_out_acl         ), priority=65535, match=(!ct.est &&
> > ct.rel && !ct.new && ct_label.blocked == 0), action=(next;)
> > > +  table=5 (ls_out_acl         ), priority=65535, match=(ct.est &&
> > !ct.rel && !ct.new && ct.rpl && ct_label.blocked == 0), action=(next;)
> > > +  table=5 (ls_out_acl         ), priority=65535, match=(ct.est &&
ct.rpl
> > && ct_label.blocked == 1), action=(drop;)
> > >    table=8 (ls_in_acl_hint     ), priority=1    , match=(ct.est &&
> > ct_label.blocked == 0), action=(reg0[[10]] = 1; next;)
> > >    table=8 (ls_in_acl_hint     ), priority=2    , match=(ct.est &&
> > ct_label.blocked == 1), action=(reg0[[9]] = 1; next;)
> > >    table=8 (ls_in_acl_hint     ), priority=3    , match=(!ct.est),
> > action=(reg0[[9]] = 1; next;)
> > > @@ -1983,9 +1983,9 @@ AT_CHECK([ovn-sbctl lflow-list ls | grep -e
> > ls_in_acl_hint -e ls_out_acl_hint -e
> > >    table=8 (ls_in_acl_hint     ), priority=6    , match=(!ct.new &&
> > ct.est && !ct.rpl && ct_label.blocked == 1), action=(reg0[[7]] = 1;
> > reg0[[9]] = 1; next;)
> > >    table=8 (ls_in_acl_hint     ), priority=7    , match=(ct.new &&
> > !ct.est), action=(reg0[[7]] = 1; reg0[[9]] = 1; next;)
> > >    table=9 (ls_in_acl          ), priority=1    , match=(ip &&
(!ct.est
> > || (ct.est && ct_label.blocked == 1))), action=(reg0[[1]] = 1; next;)
> > > -  table=9 (ls_in_acl          ), priority=65535, match=(!ct.est &&
> > ct.rel && !ct.new && !ct.inv && ct_label.blocked == 0), action=(next;)
> > > -  table=9 (ls_in_acl          ), priority=65535, match=(ct.est &&
> > !ct.rel && !ct.new && !ct.inv && ct.rpl && ct_label.blocked == 0),
> > action=(next;)
> > > -  table=9 (ls_in_acl          ), priority=65535, match=(ct.inv ||
> > (ct.est && ct.rpl && ct_label.blocked == 1)), action=(drop;)
> > > +  table=9 (ls_in_acl          ), priority=65535, match=(!ct.est &&
> > ct.rel && !ct.new && ct_label.blocked == 0), action=(next;)
> > > +  table=9 (ls_in_acl          ), priority=65535, match=(ct.est &&
> > !ct.rel && !ct.new && ct.rpl && ct_label.blocked == 0), action=(next;)
> > > +  table=9 (ls_in_acl          ), priority=65535, match=(ct.est &&
ct.rpl
> > && ct_label.blocked == 1), action=(drop;)
> > >  ])
> > >
> > >  AT_CLEANUP
> > > --
> > > 2.29.2
> > >
> > > _______________________________________________
> > > dev mailing list
> > > dev at openvswitch.org
> > > https://mail.openvswitch.org/mailman/listinfo/ovs-dev
> > _______________________________________________
> > dev mailing list
> > dev at openvswitch.org
> > https://mail.openvswitch.org/mailman/listinfo/ovs-dev


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