[ovs-dev] [PATCH ovn] northd: set packet length in check_pkt_larger()

Lorenzo Bianconi lorenzo.bianconi at redhat.com
Wed Jun 17 11:08:41 UTC 2020


> lorenzo.bianconi at redhat.com> wrote:
> 
> > Set packet length in lr_in_chk_pkt_len router pipeline instead of
> > gw interface MTU since ovs kernel datapath usually works on L2 frames
> >
> > Fixes: 7d42c146be ("ovn: Generate ICMPv4 packet in router pipeline for
> > larger packets")
> > Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi at redhat.com>
> > ---
> >  northd/ovn-northd.c |  4 ++--
> >  tests/ovn.at        | 33 ++++++++++++++++++---------------
> >  2 files changed, 20 insertions(+), 17 deletions(-)
> >
> > diff --git a/northd/ovn-northd.c b/northd/ovn-northd.c
> > index b8c9e9325..53d5bf245 100644
> > --- a/northd/ovn-northd.c
> > +++ b/northd/ovn-northd.c
> > @@ -10076,7 +10076,7 @@ build_lrouter_flows(struct hmap *datapaths, struct
> > hmap *ports,
> >              ds_clear(&actions);
> >              ds_put_format(&actions,
> >                            REGBIT_PKT_LARGER" = check_pkt_larger(%d);"
> > -                          " next;", gw_mtu);
> > +                          " next;", gw_mtu + 18);
> >
> 
> Hi Lorenzo,
> 
> Thanks for the fix. Can you please add the comment why 18. May be a macro
> instead of "18" number.

Hi Numan,

ack, will do in v2

> 
> What would be the case if there is a VLAN tag set ?

I am not expert about how ovs manages vlan tags, but looking at [1] and [2], it seems
to me vlan header is not accounted in skb->len

Regards,
Lorenzo

[1] https://github.com/torvalds/linux/blob/master/net/core/dev.c#L5117
[2] https://github.com/torvalds/linux/blob/master/net/openvswitch/vport-netdev.c#L29

> 
> Thanks
> Numan
> 
> 
> 
> 
> >              ovn_lflow_add_with_hint(lflows, od, S_ROUTER_IN_CHK_PKT_LEN,
> > 50,
> >                                      ds_cstr(&match), ds_cstr(&actions),
> >                                      &od->l3dgw_port->nbrp->header_);
> > @@ -10109,7 +10109,7 @@ build_lrouter_flows(struct hmap *datapaths, struct
> > hmap *ports,
> >                      "next(pipeline=ingress, table=0); };",
> >                      rp->lrp_networks.ea_s,
> >                      rp->lrp_networks.ipv4_addrs[0].addr_s,
> > -                    gw_mtu - 18);
> > +                    gw_mtu);
> >                  ovn_lflow_add_with_hint(lflows, od,
> > S_ROUTER_IN_LARGER_PKTS,
> >                                          50, ds_cstr(&match),
> > ds_cstr(&actions),
> >                                          &rp->nbrp->header_);
> > diff --git a/tests/ovn.at b/tests/ovn.at
> > index 7e1ace556..1801a3151 100644
> > --- a/tests/ovn.at
> > +++ b/tests/ovn.at
> > @@ -14801,14 +14801,16 @@ test_ip_packet_larger() {
> >      dst_mac="00000000ff01" # sw0-lr0 mac (internal router leg)
> >      src_ip=`ip_to_hex 10 0 0 3`
> >      dst_ip=`ip_to_hex 172 168 0 3`
> > -    # Set the packet length to 100.
> > -    pkt_len=0064
> > -    packet=${dst_mac}${src_mac}08004500${pkt_len}0000000040010000
> > +    # Set the packet length to 118.
> > +    pkt_len=0076
> > +    packet=${dst_mac}${src_mac}08004500${pkt_len}000000004001c3d9
> >      orig_packet_l3=${src_ip}${dst_ip}0304000000000000
> >      orig_packet_l3=${orig_packet_l3}000000000000000000000000000000000000
> >      orig_packet_l3=${orig_packet_l3}000000000000000000000000000000000000
> >      orig_packet_l3=${orig_packet_l3}000000000000000000000000000000000000
> >      orig_packet_l3=${orig_packet_l3}000000000000000000000000000000000000
> > +    orig_packet_l3=${orig_packet_l3}000000000000000000000000000000000000
> > +
> >      packet=${packet}${orig_packet_l3}
> >
> >
> >  gw_ip_garp=ffffffffffff00002020121308060001080006040001000020201213aca80064000000000000aca80064
> > @@ -14818,32 +14820,33 @@ test_ip_packet_larger() {
> >      # localnet port.
> >      # If icmp_pmtu_reply_expected is 1, it means the packet is larger than
> >      # the gateway mtu and ovn-controller should drop the packet and
> > instead
> > -    # generate ICMPv4  Destination Unreachable message with pmtu set to
> > 42.
> > +    # generate ICMPv4  Destination Unreachable message with pmtu set to
> > 100.
> >      if test $icmp_pmtu_reply_expected = 0; then
> >          # Packet to expect at br-phys.
> >          src_mac="000020201213"
> >          dst_mac="00000012af11"
> >          src_ip=`ip_to_hex 10 0 0 3`
> >          dst_ip=`ip_to_hex 172 168 0 3`
> > -        expected=${dst_mac}${src_mac}08004500${pkt_len}000000003f010100
> > +        expected=${dst_mac}${src_mac}08004500${pkt_len}000000003f01c4d9
> >          expected=${expected}${src_ip}${dst_ip}0304000000000000
> >          expected=${expected}000000000000000000000000000000000000
> >          expected=${expected}000000000000000000000000000000000000
> >          expected=${expected}000000000000000000000000000000000000
> >          expected=${expected}000000000000000000000000000000000000
> > +        expected=${expected}000000000000000000000000000000000000
> >          echo $expected > br_phys_n1.expected
> >          echo $gw_ip_garp >> br_phys_n1.expected
> >      else
> > -        # MTU would be 100 - 18 = 82 (hex 0052)
> > -        mtu=0052
> > +        # MTU would be 118 - 18 = 100 (hex 0064)
> > +        mtu=0064
> >          src_ip=`ip_to_hex 10 0 0 1`
> >          dst_ip=`ip_to_hex 10 0 0 3`
> > -        # pkt len should be 128 (28 (icmp packet) + 100 (orig ip +
> > payload))
> > -        reply_pkt_len=0080
> > -        ip_csum=bd91
> > -
> > icmp_reply=${src_mac}${dst_mac}08004500${reply_pkt_len}00004000fe016879
> > +        # pkt len should be 146 (28 (icmp packet) + 118 (orig ip +
> > payload))
> > +        reply_pkt_len=0092
> > +        ip_csum=f993
> > +
> > icmp_reply=${src_mac}${dst_mac}08004500${reply_pkt_len}00004000fe016867
> >          icmp_reply=${icmp_reply}${src_ip}${dst_ip}0304${ip_csum}0000${mtu}
> > -        icmp_reply=${icmp_reply}4500${pkt_len}000000003f010100
> > +        icmp_reply=${icmp_reply}4500${pkt_len}000000003f01c4d9
> >          icmp_reply=${icmp_reply}${orig_packet_l3}
> >          echo $icmp_reply > hv1-vif1.expected
> >      fi
> > @@ -14883,12 +14886,12 @@ awk '{print $3}')
> >  ovn-sbctl create MAC_Binding ip=172.168.0.3 datapath=$dp_uuid \
> >  logical_port=lr0-public mac="00\:00\:00\:12\:af\:11"
> >
> > -# Set the gateway mtu to 100. If the packet length is > 100,
> > ovn-controller
> > +# Set the gateway mtu to 100. If the packet length is > 118,
> > ovn-controller
> >  # should send icmp host not reachable with pmtu set to 100.
> >  ovn-nbctl --wait=hv set logical_router_port lr0-public
> > options:gateway_mtu=100
> >  as hv3 ovs-appctl netdev-dummy/receive hv3-vif1 $arp_reply
> >  OVS_WAIT_UNTIL([
> > -    test `as hv1 ovs-ofctl dump-flows br-int | grep
> > "check_pkt_larger(100)" | \
> > +    test `as hv1 ovs-ofctl dump-flows br-int | grep
> > "check_pkt_larger(118)" | \
> >      wc -l` -eq 1
> >  ])
> >
> > @@ -14899,7 +14902,7 @@ test_ip_packet_larger $icmp_reply_expected
> >  ovn-nbctl --wait=hv set logical_router_port lr0-public
> > options:gateway_mtu=500
> >  as hv3 ovs-appctl netdev-dummy/receive hv3-vif1 $arp_reply
> >  OVS_WAIT_UNTIL([
> > -    test `as hv1 ovs-ofctl dump-flows br-int | grep
> > "check_pkt_larger(500)" | \
> > +    test `as hv1 ovs-ofctl dump-flows br-int | grep
> > "check_pkt_larger(518)" | \
> >      wc -l` -eq 1
> >  ])
> >
> > --
> > 2.26.2
> >
> > _______________________________________________
> > dev mailing list
> > dev at openvswitch.org
> > https://mail.openvswitch.org/mailman/listinfo/ovs-dev
> >
> >


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