[202205] Re-add 127.0.0.1/8 when bringing down the interfaces #15462
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* Re-add 127.0.0.1/8 when bringing down the interfaces With sonic-net#5353, 127.0.0.1/16 was added to the lo interface, and then 127.0.0.1/8 was removed. However, when bringing down the lo interface, like during a config reload, 127.0.0.1/16 gets removed, but 127.0.0.1/8 isn't added back to the interface. This means that there's a period of time where 127.0.0.1 is not available at all, and services that need to connect to 127.0.01 (such as for redis DB) will fail. To fix this, when going down, add 127.0.0.1/8. Add this address before the existing configuration gets removed, so that 127.0.0.1 is available at all times. Note that running `ifdown lo` doesn't actually bring down the loopback interface; the interface always stays "physically" up. Signed-off-by: Saikrishna Arcot <sarcot@microsoft.com>
yxieca
approved these changes
Jun 14, 2023
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Cherry-pick of #15080
With #5353, 127.0.0.1/16 was added to the lo interface, and then 127.0.0.1/8 was removed. However, when bringing down the lo interface, like during a config reload, 127.0.0.1/16 gets removed, but 127.0.0.1/8 isn't added back to the interface. This means that there's a period of time where 127.0.0.1 is not available at all, and services that need to connect to 127.0.01 (such as for redis DB) will fail.
To fix this, when going down, add 127.0.0.1/8. Add this address before the existing configuration gets removed, so that 127.0.0.1 is available at all times.
Note that running
ifdown lodoesn't actually bring down the loopback interface; the interface always stays "physically" up.Why I did it
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