Change the loopback interface netmask from /8 to /16 #5353
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retest vsimage please |
prsunny
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santhosh-kt
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Feb 25, 2021
As per the VOQ HLDs, internal networking between the linecards and supervisor is required within a chassis. Allocating 127.X/16 subnets for private communication within a chassis is a good candidate. It doesn't require any external IP allocation as well as ensure that the traffic will not leave the chassis. References: sonic-net/SONiC#622 sonic-net/SONiC#639 **- How I did it** Changed the `interfaces.j2` file to add `127.0.0.1/16` as the `lo` ip address. Then once the interface is up, the post-up command removes the `127.0.0.1/8` ip address. The order in which the netmask change is made matters for `127.0.0.1` to be reachable at all times. **- How to verify it** ``` root@sonic:~# ip address show dev lo 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 127.0.0.1/16 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever ``` Co-authored-by: Baptiste Covolato <[email protected]>
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saiarcot895
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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 <[email protected]>
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yxieca
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Jun 14, 2023
* Re-add 127.0.0.1/8 when bringing down the interfaces 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 lo` doesn't actually bring down the loopback interface; the interface always stays "physically" up. Signed-off-by: Saikrishna Arcot <[email protected]>
mssonicbld
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Jun 14, 2023
* 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 <[email protected]>
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saiarcot895
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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 <[email protected]>
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10 tasks
yxieca
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Jun 14, 2023
* Re-add 127.0.0.1/8 when bringing down the interfaces 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 lo` doesn't actually bring down the loopback interface; the interface always stays "physically" up. Signed-off-by: Saikrishna Arcot <[email protected]>
mssonicbld
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Jun 16, 2023
* Re-add 127.0.0.1/8 when bringing down the interfaces 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 lo` doesn't actually bring down the loopback interface; the interface always stays "physically" up. Signed-off-by: Saikrishna Arcot <[email protected]>
sonic-otn
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Sep 20, 2023
* 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 <[email protected]>
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- Why I did it
As per the VOQ HLDs, internal networking between the linecards and supervisor is required within a chassis.
Allocating 127.X/16 subnets for private communication within a chassis is a good candidate.
It doesn't require any external IP allocation as well as ensure that the traffic will not leave the chassis.
References:
sonic-net/SONiC#622
sonic-net/SONiC#639
- How I did it
Changed the
interfaces.j2file to add127.0.0.1/16as theloip address.Then once the interface is up, the post-up command removes the
127.0.0.1/8ip address.The order in which the netmask change is made matters for
127.0.0.1to be reachable at all times.- How to verify it
- Which release branch to backport (provide reason below if selected)
- Description for the changelog
Change the loopback interface netmask from /8 to /16