Hi VPP-Dev,
 
We recently moved to 1810 from 1801 and found the following issue.
Is this a known issue (or) any help on whats happening here ?
 
1. We are using memif in IP mode.
2. Some Control plane process sends message over MEMIF to VPP process ( memif 
mode = IP )
3. We are using a custom ip-proto value of 222 and tapping these packets in a 
separate graph node on VPP side.
4. This has been working fine till 1801.
5. When we moved to 1810, the packet is getting dropped in ip4-local with 
reason as "blackholed packets"
6. When we looked at the code, this drop can happen in the following reasons
 - SRC-IP invalid
 - TCP/UDP checksum wrong
 
7. The FIB contains the SRC-IP subnet. Hence, SRC-IP error might not be the 
reason
8. We are suspecting that this drop is due to TCP/UDP csum.
 
But, when the ip-proto is non-UDP-TCP, ideally this packet should have gone to 
the next layer bypassing all these checks.
 
Following is the packet trace / show output and fib details
 
===
##) 
vpp# show node counters
   Count                    Node                  Reason
         2                null-node               blackholed packets
 
##)
vpp# show trace
 
Packet 1
 
00:48:08:119264: memif-input
  memif: hw_if_index 3 next-index 0
    slot: ring 0
00:48:08:119354: ip4-input-no-checksum
  unknown 222: 192.168.1.2 -> 192.168.1.1
    tos 0x00, ttl 64, length 10020, checksum 0xcfbe
    fragment id 0x0000
00:48:08:120320: ip4-lookup
  fib 0 dpo-idx 5 flow hash: 0x00000000
  unknown 222: 192.168.1.2 -> 192.168.1.1
    tos 0x00, ttl 64, length 10020, checksum 0xcfbe
    fragment id 0x0000
00:48:08:120331: ip4-local
    unknown 222: 192.168.1.2 -> 192.168.1.1
      tos 0x00, ttl 64, length 10020, checksum 0xcfbe
      fragment id 0x0000
 
##)
 
vpp# show ip fib
ipv4-VRF:0, fib_index:0, flow hash:[src dst sport dport proto ] 
locks:[src:plugin-hi:2, src:default-route:1, ]
192.168.1.0/32
  unicast-ip4-chain
  [@0]: dpo-load-balance: [proto:ip4 index:10 buckets:1 uRPF:9 to:[0:0]]
    [0] [@0]: dpo-drop ip4
192.168.1.0/24
  unicast-ip4-chain
  [@0]: dpo-load-balance: [proto:ip4 index:9 buckets:1 uRPF:12 to:[0:0]]
    [0] [@5]: ipv4 via 0.0.0.0 memif0/0: mtu:9000
192.168.1.1/32
  unicast-ip4-chain
  [@0]: dpo-load-balance: [proto:ip4 index:12 buckets:1 uRPF:13 to:[1:10020]]
    [0] [@2]: dpo-receive: 192.168.1.1 on memif0/0
192.168.1.255/32
  unicast-ip4-chain
  [@0]: dpo-load-balance: [proto:ip4 index:11 buckets:1 uRPF:11 to:[0:0]]
    [0] [@0]: dpo-drop ip4
 
====
 
Also, is there anyway to get the exact sub-error-code which indicates that this 
is due to TCP/UDP checksum error etc ?
Appreciate any inputs in this regard.
 
Thanks & Regards,
Satish
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