config interface shutdown/startup command could get ip address lost

[zhenggen-xu]

Description

Steps to reproduce the issue
admin@sonic:~$ sudo ifconfig Ethernet116
Ethernet116 Link encap:Ethernet HWaddr 00:e0:ec:3c:0a:3e
inet addr:10.0.1.20 Bcast:255.255.255.255 Mask:255.255.255.254
inet6 addr: 2002::1/64 Scope:Global
UP BROADCAST MULTICAST MTU:9100 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

admin@sonic:$ sudo config interface shutdown Ethernet116
admin@sonic:$ sudo ifconfig Ethernet116
Ethernet116 Link encap:Ethernet HWaddr 00:e0:ec:3c:0a:3e
inet addr:10.0.1.20 Bcast:255.255.255.255 Mask:255.255.255.254
BROADCAST MULTICAST MTU:9100 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

admin@sonic:$ sudo config interface startup Ethernet116
admin@sonic:$ sudo ifconfig Ethernet116
Ethernet116 Link encap:Ethernet HWaddr 00:e0:ec:3c:0a:3e
inet addr:10.0.1.20 Bcast:255.255.255.255 Mask:255.255.255.254
UP BROADCAST MULTICAST MTU:9100 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

Describe the results you received
ipv6 address is lost

Describe the results you expected
ipv6 address should be reserved.

Additional information you deem important (e.g. issue happens only occasionally)
cat /etc/network/interfaces | grep -A 5 Ethernet116
allow-hotplug Ethernet116
iface Ethernet116 inet static
mtu 9100
address 10.0.1.20
netmask 255.255.255.254

allow-hotplug Ethernet116
iface Ethernet116 inet6 static
mtu 9100
address 2002::1
netmask 64

ifdown/ifup work fine, if it is agreed to use those commands, I will send a PR for this.

Output of show version

(paste your output here)

[lguohan]

@stcheng , shuotian is working on a new config db -based ip address setup. /etc/network/interfaces is going to be deprecated, please sync up with him to avoid duplicated work.

[stcheng]

@zhenggen-xu this is due to the attribute introduced in the new kernel: keep_addr_on_down. The default value is 0, which causes the lost of the IPv6 addresses. I'll submit a pull request to change this value to 1 to retain the global IPv6 addresses. Thanks for reporting this!

[stcheng]

Please check below output as reference:

root@str-s6100-acs-2:/proc/sys/net/ipv6/conf/all# cat keep_addr_on_down
0
root@str-s6100-acs-2:/proc/sys/net/ipv6/conf/all# echo 1 > keep_addr_on_down
root@str-s6100-acs-2:/proc/sys/net/ipv6/conf/all# ip addr show PortChannel20
7: PortChannel20: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9100 qdisc noqueue state UP group default qlen 1000
    link/ether d8:9e:f3:d6:90:e0 brd ff:ff:ff:ff:ff:ff
    inet 10.0.0.12/31 scope global PortChannel20
       valid_lft forever preferred_lft forever
    inet6 fc00::19/126 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::da9e:f3ff:fed6:90e0/64 scope link
       valid_lft forever preferred_lft forever
root@str-s6100-acs-2:/proc/sys/net/ipv6/conf/all# ifconfig PortChannel20 down
root@str-s6100-acs-2:/proc/sys/net/ipv6/conf/all# ifconfig PortChannel20 up
root@str-s6100-acs-2:/proc/sys/net/ipv6/conf/all# ip addr show PortChannel20
7: PortChannel20: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9100 qdisc noqueue state UP group default qlen 1000
    link/ether d8:9e:f3:d6:90:e0 brd ff:ff:ff:ff:ff:ff
    inet 10.0.0.12/31 scope global PortChannel20
       valid_lft forever preferred_lft forever
    inet6 fc00::19/126 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::da9e:f3ff:fed6:90e0/64 scope link
       valid_lft forever preferred_lft forever

[stcheng]

sonic-net/sonic-buildimage#1992 Please do review!

[zhenggen-xu]

Thanks, I was swamped and didn't read this on time. It should be fine to fix that on master, but for the old branches (e,g, 201807 ), we may still need fix with a different approach.

[zhenggen-xu]

I can send a PR if you think "ifdown/ifup" approach is fine for old branches.

[stcheng]

@zhenggen-xu please do send a PR to fix the old branches! Thanks!