Invalid packet DROPPED to host loopback when other IP is present

[margau]

Invalid packet DROPPED to host loopback when other IP is present

[YutaroHayakawa]

I believe this is because Cilium (device detector) doesn't recognize the addresses assigned to the loopback devices as "local" addresses. While it might be possible to improve that (let me CC @joamaki for comment), could you check if it works when you assign your IP to a dummy interface instead of loopback interface?

[margau]

Hi,
yes, moving the IP to dummy works:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host noprefixroute 
       valid_lft forever preferred_lft forever
164: dummy0: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
    link/ether 7a:e1:4f:b5:d9:36 brd ff:ff:ff:ff:ff:ff
    inet6 2001:...:3000::2/128 scope global 
       valid_lft forever preferred_lft forever

BGP to ::1 is now established.

Is this the intended behavior? If yes, can we document this somewhere?

[YutaroHayakawa]

Oh, wait, sorry, I misunderstood your problem. Your expected behavior is establishing a connection with ::1, then the expected behavior is the connection is established regardless of the address assigned to the lo. Can you provide us a sysdump (you can get it with cilium sysdump command) or at least Helm values you're using?