[ovs-dev] [PATCH ovn] northd: fix ttl exceeded with FIP

Numan Siddique numans at ovn.org
Tue Nov 16 03:16:24 UTC 2021


On Thu, Nov 11, 2021 at 3:44 PM Mark Michelson <mmichels at redhat.com> wrote:
>
> Hi Lorenzo, the patch looks good to me.
>
> Acked-by: Mark Michelson <mmichels at redhat.com>
>
> On 11/10/21 17:35, Lorenzo Bianconi wrote:
> > Properly manage ttl exceeded ICMP error messages when traffic is
> > directed to a FIP. The issue can be verified running traceroute from an
> > external device to a FIP:
> > $traceroute -I -z 1 -n <FIP>
> >
> > Fix ttl exceeded priority respect to ping responder.
> >
> > Related bz: https://bugzilla.redhat.com/show_bug.cgi?id=2006349
> >
> > Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi at redhat.com>
> > ---
> >   northd/northd.c         | 59 ++++++++++++++++++++++++-----------------
> >   northd/ovn-northd.8.xml |  2 +-
> >   tests/ovn.at            | 10 +++----
> >   3 files changed, 41 insertions(+), 30 deletions(-)
> >
> > diff --git a/northd/northd.c b/northd/northd.c
> > index 1e8a3457c..ce962cdc4 100644
> > --- a/northd/northd.c
> > +++ b/northd/northd.c
> > @@ -11798,6 +11798,7 @@ build_ipv6_input_flows_for_lrouter_port(
> >           }
> >
> >           /* ICMPv6 time exceeded */
> > +        struct ds ip_ds = DS_EMPTY_INITIALIZER;
> >           for (int i = 0; i < op->lrp_networks.n_ipv6_addrs; i++) {
> >               /* skip link-local address */
> >               if (in6_is_lla(&op->lrp_networks.ipv6_addrs[i].network)) {
> > @@ -11806,7 +11807,13 @@ build_ipv6_input_flows_for_lrouter_port(
> >
> >               ds_clear(match);
> >               ds_clear(actions);
> > -
> > +            ds_clear(&ip_ds);
> > +            if (op->od->n_l3dgw_ports && op->od->l3dgw_ports[0] == op) {
> > +                ds_put_cstr(&ip_ds, "ip6.dst <-> ip6.src");
> > +            } else {
> > +                ds_put_format(&ip_ds, "ip6.dst = ip6.src; ip6.src = %s",
> > +                              op->lrp_networks.ipv6_addrs[i].addr_s);
> > +            }
> >               ds_put_format(match,
> >                             "inport == %s && ip6 && "
> >                             "ip6.src == %s/%d && "
> > @@ -11817,20 +11824,18 @@ build_ipv6_input_flows_for_lrouter_port(
> >               ds_put_format(actions,
> >                             "icmp6 {"
> >                             "eth.dst <-> eth.src; "
> > -                          "ip6.dst = ip6.src; "
> > -                          "ip6.src = %s; "
> > -                          "ip.ttl = 255; "
> > +                          "%s ; ip.ttl = 254; "

Hi Lorenzo,

Can you please explain why the ttl is changed to 254 ?


> >                             "icmp6.type = 3; /* Time exceeded */ "
> >                             "icmp6.code = 0; /* TTL exceeded in transit */ "
> > -                          "next; };",
> > -                          op->lrp_networks.ipv6_addrs[i].addr_s);
> > -            ovn_lflow_add_with_hint__(lflows, op->od, S_ROUTER_IN_IP_INPUT, 40,
> > -                                      ds_cstr(match), ds_cstr(actions), NULL,
> > -                                      copp_meter_get(COPP_ICMP6_ERR,
> > -                                                     op->od->nbr->copp,
> > -                                                     meter_groups),
> > -                                      &op->nbrp->header_);
> > +                          "outport = %s; flags.loopback = 1; output; };",
> > +                          ds_cstr(&ip_ds), op->json_key);
> > +            ovn_lflow_add_with_hint__(lflows, op->od, S_ROUTER_IN_IP_INPUT,
> > +                    100, ds_cstr(match), ds_cstr(actions), NULL,
> > +                    copp_meter_get(COPP_ICMP6_ERR, op->od->nbr->copp,
> > +                                   meter_groups),
> > +                    &op->nbrp->header_);
> >           }
> > +        ds_destroy(&ip_ds);
> >       }
> >
> >   }
> > @@ -11930,10 +11935,17 @@ build_lrouter_ipv4_ip_input(struct ovn_port *op,
> >           build_lrouter_bfd_flows(lflows, op, meter_groups);
> >
> >           /* ICMP time exceeded */
> > +        struct ds ip_ds = DS_EMPTY_INITIALIZER;
> >           for (int i = 0; i < op->lrp_networks.n_ipv4_addrs; i++) {
> >               ds_clear(match);
> >               ds_clear(actions);
> > -
> > +            ds_clear(&ip_ds);
> > +            if (op->od->n_l3dgw_ports && op->od->l3dgw_ports[0] == op) {
> > +                ds_put_cstr(&ip_ds, "ip4.dst <-> ip4.src");
> > +            } else {
> > +                ds_put_format(&ip_ds, "ip4.dst = ip4.src; ip4.src = %s",
> > +                              op->lrp_networks.ipv4_addrs[i].addr_s);
> > +            }
> >               ds_put_format(match,
> >                             "inport == %s && ip4 && "
> >                             "ip.ttl == {0, 1} && !ip.later_frag", op->json_key);
> > @@ -11942,18 +11954,17 @@ build_lrouter_ipv4_ip_input(struct ovn_port *op,
> >                             "eth.dst <-> eth.src; "
> >                             "icmp4.type = 11; /* Time exceeded */ "
> >                             "icmp4.code = 0; /* TTL exceeded in transit */ "
> > -                          "ip4.dst = ip4.src; "
> > -                          "ip4.src = %s; "
> > -                          "ip.ttl = 255; "
> > -                          "next; };",
> > -                          op->lrp_networks.ipv4_addrs[i].addr_s);
> > -            ovn_lflow_add_with_hint__(lflows, op->od, S_ROUTER_IN_IP_INPUT, 40,
> > -                                      ds_cstr(match), ds_cstr(actions), NULL,
> > -                                      copp_meter_get(COPP_ICMP4_ERR,
> > -                                                     op->od->nbr->copp,
> > -                                                     meter_groups),
> > -                                      &op->nbrp->header_);
> > +                          "%s ; ip.ttl = 254; "
> > +                          "outport = %s; flags.loopback = 1; output; };",
> > +                          ds_cstr(&ip_ds), op->json_key);
> > +            ovn_lflow_add_with_hint__(lflows, op->od, S_ROUTER_IN_IP_INPUT,
> > +                    100, ds_cstr(match), ds_cstr(actions), NULL,
> > +                    copp_meter_get(COPP_ICMP4_ERR, op->od->nbr->copp,
> > +                                   meter_groups),
> > +                    &op->nbrp->header_);
> > +
> >           }
> > +        ds_destroy(&ip_ds);
> >
> >           /* ARP reply.  These flows reply to ARP requests for the router's own
> >            * IP address. */
> > diff --git a/northd/ovn-northd.8.xml b/northd/ovn-northd.8.xml
> > index fb67395e3..aa51aeb24 100644
> > --- a/northd/ovn-northd.8.xml
> > +++ b/northd/ovn-northd.8.xml
> > @@ -2742,7 +2742,7 @@ nd.tll = <var>external_mac</var>;
> >         <li>
> >           <p>
> >             ICMP time exceeded.  For each router port <var>P</var>, whose IP
> > -          address is <var>A</var>, a priority-40 flow with match <code>inport
> > +          address is <var>A</var>, a priority-100 flow with match <code>inport

Since the ttl is changed to 254,  I think the flow description here
https://github.com/ovn-org/ovn/blob/main/northd/ovn-northd.8.xml#L2758
# L2758 should  also be updated right ?

You don't have to submit another version.  Before applying I wanted to be sure.


Thanks
Numan

> >             == <var>P</var> && ip.ttl == {0, 1} &&
> >             !ip.later_frag</code> matches packets whose TTL has expired, with the
> >             following actions to send an ICMP time exceeded reply for IPv4 and
> > diff --git a/tests/ovn.at b/tests/ovn.at
> > index 51e0dae0b..ae832918c 100644
> > --- a/tests/ovn.at
> > +++ b/tests/ovn.at
> > @@ -7203,7 +7203,7 @@ test_ipv4_icmp_request() {
> >       shift; shift
> >
> >       # Use ttl to exercise section 4.2.2.9 of RFC1812
> > -    local ip_ttl=01
> > +    local ip_ttl=02
> >       local icmp_id=5fbf
> >       local icmp_seq=0001
> >       local icmp_data=$(seq 1 56 | xargs printf "%02x")
> > @@ -7230,12 +7230,12 @@ l1_ip=$(ip_to_hex 192 168 1 2)
> >   l2_ip=$(ip_to_hex 172 16 1 2)
> >
> >   # Ping router ip address that is on same subnet as the logical port
> > -test_ipv4_icmp_request 1 000000010203 0000000102f1 $l1_ip $rtr_l1_ip 0000 8510 02ff 8d10
> > -test_ipv4_icmp_request 2 000000010204 0000000102f2 $l2_ip $rtr_l2_ip 0000 8510 02ff 8d10
> > +test_ipv4_icmp_request 1 000000010203 0000000102f1 $l1_ip $rtr_l1_ip 0000 8510 03ff 8d10
> > +test_ipv4_icmp_request 2 000000010204 0000000102f2 $l2_ip $rtr_l2_ip 0000 8510 03ff 8d10
> >
> >   # Ping router ip address that is on the other side of the logical ports
> > -test_ipv4_icmp_request 1 000000010203 0000000102f1 $l1_ip $rtr_l2_ip 0000 8510 02ff 8d10
> > -test_ipv4_icmp_request 2 000000010204 0000000102f2 $l2_ip $rtr_l1_ip 0000 8510 02ff 8d10
> > +test_ipv4_icmp_request 1 000000010203 0000000102f1 $l1_ip $rtr_l2_ip 0000 8510 03ff 8d10
> > +test_ipv4_icmp_request 2 000000010204 0000000102f2 $l2_ip $rtr_l1_ip 0000 8510 03ff 8d10
> >
> >
> >   echo "---------NB dump-----"
> >
>
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