Hi, team
This is a issue that the revalidator will delete datapath flow when
the dumped WC and generated WC mismatch.
### Enviroment
- ovs: 3.4.2
- Not ovs-dpdk
### Information
The following is the trace information:
```
[root@node-6 bpf]# ovs-appctl ofproto/trace
'recirc_id(0),dp_hash(0/0),skb_priority(0/0),in_port(tap50cd3638-d9),skb_mark(0/0),ct_state(0/0),ct_zone(0/0),ct_mark(0/0),ct_label(0/0),eth(src=fa:16:3e:74:74:32,dst=fa:16:3e:bf:01:a9),eth_type(0x86dd),ipv6(src=fd1f:8e62:3182:608c::c8,dst=fc00::/fe00::,label=0/0,proto=58,tclass=0/0,hlimit=64,frag=no),icmpv6(type=128/0xf8,code=0/0)'
Flow:
icmp6,in_port=17,vlan_tci=0x0000,dl_src=fa:16:3e:74:74:32,dl_dst=fa:16:3e:bf:01:a9,ipv6_src=fd1f:8e62:3182:608c::c8,ipv6_dst=fc00::,ipv6_label=0x00000,nw_tos=0,nw_ecn=0,nw_ttl=64,nw_frag=no,icmp_type=128,icmp_code=0
bridge("br-int")
----------------
0. in_port=17, priority 100, cookie 0xd67e3395
set_field:0xc/0xffff->reg13
set_field:0x9->reg11
set_field:0xb->reg12
set_field:0x4->metadata
set_field:0x9->reg14
set_field:0/0xffff0000->reg13
resubmit(,8)
8. metadata=0x4, priority 50, cookie 0x6d11c5b5
set_field:0/0x1000->reg10
resubmit(,73)
73.
ipv6,reg14=0x9,metadata=0x4,dl_src=fa:16:3e:74:74:32,ipv6_src=fd1f:8e62:3182:608c::c8,
priority 90, cookie 0xd67e3395
resubmit(,74)
74. No match.
drop
move:NXM_NX_REG10[12]->NXM_NX_XXREG0[111]
-> NXM_NX_XXREG0[111] is now 0
resubmit(,9)
9. metadata=0x4, priority 0, cookie 0x80a3e18f
resubmit(,10)
10. metadata=0x4, priority 0, cookie 0x62b6d61e
resubmit(,11)
11. metadata=0x4, priority 0, cookie 0x1c991896
resubmit(,12)
12. ipv6,metadata=0x4, priority 100, cookie 0x5f20cefd
set_field:0x1000000000000000000000000/0x1000000000000000000000000->xxreg0
resubmit(,13)
13. metadata=0x4, priority 0, cookie 0x3987ecf1
resubmit(,14)
14. ipv6,reg0=0x1/0x1,metadata=0x4, priority 100, cookie 0xd60f1d10
ct(table=15,zone=NXM_NX_REG13[0..15])
drop
-> A clone of the packet is forked to recirculate. The forked
pipeline will be resumed at table 15.
-> Sets the packet to an untracked state, and clears all the
conntrack fields.
Final flow:
icmp6,reg0=0x1,reg11=0x9,reg12=0xb,reg13=0xc,reg14=0x9,metadata=0x4,in_port=17,vlan_tci=0x0000,dl_src=fa:16:3e:74:74:32,dl_dst=fa:16:3e:bf:01:a9,ipv6_src=fd1f:8e62:3182:608c::c8,ipv6_dst=fc00::,ipv6_label=0x00000,nw_tos=0,nw_ecn=0,nw_ttl=64,nw_frag=no,icmp_type=128,icmp_code=0
Megaflow:
recirc_id=0,eth,icmp6,in_port=17,dl_src=fa:16:3e:74:74:32,dl_dst=fa:16:3e:bf:01:a9,ipv6_src=fd1f:8e62:3182:608c::c8,ipv6_dst=fc00::/7,nw_ttl=64,nw_frag=no,icmp_type=0x80/0xf8,nd_target=::,nd_tll=00:00:00:00:00:00
Datapath actions: ct(zone=12),recirc(0x2)
...
```
From above information, we can found that nd_target and nd_tll field
are included by megaflow. The generated datapath flow is below:
```
ufid:3eb805ba-7576-4caf-8b08-93c7517e575d,
recirc_id(0),dp_hash(0/0),skb_priority(0/0),in_port(tap50cd3638-d9),skb_mark(0/0),ct_state(0/0),ct_zone(0/0),ct_mark(0/0),ct_label(0/0),eth(src=fa:16:3e:74:74:32,dst=fa:16:3e:bf:01:a9),eth_type(0x86dd),ipv6(src=fd1f:8e62:3182:608c::c8,dst=fc00::/fe00::,label=0/0,proto=58,tclass=0/0,hlimit=64,frag=no),key32(00
00/00 00),icmpv6(type=128/0xf8,code=0/0), packets:44, bytes:5192,
used:0.752s, dp:ovs, actions:ct(zone=12),recirc(0x4)
```
During the sweep stage, the revalidator will compare the dumped WC with
a generated WC - these will mismatch because the generated WC will match
on the Neighbor Discovery fields, while the datapath WC will not match
on these fields. The revalidator will then invalidate the flow and as a
side effect force an upcall.
Deeply, we found the patch
https://github.com/openvswitch/ovs/commit/489553b1c21692063931a9f50b6849b23128443c
which adds masks on final stage causes this issue.
Simply, we can use below case to reproduce the issue.
```
AT_SETUP([flow classifier - ipv6 ND dependency from clone])
OVS_VSWITCHD_START
add_of_ports br0 1 2
AT_DATA([flows.txt], [dnl
table=0,priority=100,ipv6,ipv6_src=1000::/10 actions=resubmit(,1)
table=0,priority=0 actions=NORMAL
table=1,priority=110,ipv6,ipv6_dst=1000::3 actions=resubmit(,2)
table=1,priority=100,ipv6,ipv6_dst=1000::4 actions=resubmit(,2)
table=1,priority=0 actions=NORMAL
table=2,priority=120,icmp6,nw_ttl=255,icmp_type=136,icmp_code=0,nd_target=1000::1,nd_tll=fa:16:3e:74:74:32
actions=NORMAL
table=2,priority=100,tcp actions=NORMAL
table=2,priority=100,icmp6 actions=NORMAL
table=2,priority=0 actions=NORMAL
])
AT_CHECK([ovs-ofctl add-flows br0 flows.txt])
# test ICMPv6 echo request (which should have no nd_target field)
AT_CHECK([ovs-appctl ofproto/trace br0
"in_port=1,eth_src=f6:d2:b0:19:5e:7b,eth_dst=d2:49:19:91:78:fe,dl_type=0x86dd,ipv6_src=1000::3,ipv6_dst=1000::4,nw_proto=58,nw_ttl=255,icmpv6_type=128,icmpv6_code=0"],
[0], [stdout])
AT_CHECK([tail -2 stdout], [0],
[Megaflow:
recirc_id=0,eth,icmp6,in_port=1,dl_src=f6:d2:b0:19:5e:7b,dl_dst=d2:49:19:91:78:fe,ipv6_src=1000::/10,ipv6_dst=1000::4,nw_ttl=255,nw_frag=no,icmp_type=0x80/0xf8,nd_target=::,nd_tll=00:00:00:00:00:00
Datapath actions: 100,2
])
OVS_VSWITCHD_STOP
AT_CLEANUP
```
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