net: add FlagRunning to the Flags of struct Interface, to exactly reflect the states of an interface or NIC #53482
Description
Hi, team,
What version of Go are you using (go version)?
$ go version go version go1.18.3 linux/amd64
Does this issue reproduce with the latest release?
Yes, it is.
What operating system and processor architecture are you using (go env)?
Ubuntu 20.04
What did you do?
I inspect the flags of an Interface object to check if this NIC is up and in running state.
intfs, _ := net.Interfaces()
for _, intf := range intfs {
log.Printf("NIC name: %s, flags: %s\n", intf.Name, intf.Flags)
if intf.Flags & net.FlagUp != 0 {
// I expect this interface 'intf' is up and in running state, but it is not.
}
}
But, althought some NIC(s) have the FlagUp flag, when I check again by ip addr | grep state, I found they are in DOWN state actually.
The situation is: there is no fiber or twisted-pair cable plugged in the NIC, and I run ip link set XXX up to set it up administratively and manually.
Environment:
- I manually set the NICs(ens1f0/eno1/ens1f1/eno2/eno3) up for administrative purpose, leave the NICs(ens2f0,ens2f1) down without any operation. And, there is no cable/fiber plugged in them.
- The NIC(eno4) is plugged, and it is automatically up.
The output of ip addr | grep state, please pay attention to the state DOWN words:
XXX@XXX:~# ip addr | grep state
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
2: ens1f0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000
3: eno1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000
4: ens1f1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000
5: eno2: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000
6: eno3: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000
7: eno4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
8: ens2f0: <BROADCAST,MULTICAST> mtu 1500 qdisc mq state DOWN group default qlen 1000
9: ens2f1: <BROADCAST,MULTICAST> mtu 1500 qdisc mq state DOWN group default qlen 1000
10: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
What did you expect to see?
I expect to see NICs(ens1f0/eno1/ens1f1/eno2/eno3) and NICs(ens2f0,ens2f1) are all down, and only NIC(eno4) is up.
What did you see instead?
I actually see NICs(ens1f0/eno1/ens1f1/eno2/eno3) and NIC(eno4) are up, and NICs(ens2f0,ens2f1) are down, the output of the above snippet program is as follow:
Please pay attention to the flags: up words.
2022/06/21 20:56:49 NIC name: lo, flags: up|loopback
2022/06/21 20:56:49 NIC name: ens1f0, flags: up|broadcast|multicast
2022/06/21 20:56:49 NIC name: eno1, flags: up|broadcast|multicast
2022/06/21 20:56:49 NIC name: ens1f1, flags: up|broadcast|multicast
2022/06/21 20:56:49 NIC name: eno2, flags: up|broadcast|multicast
2022/06/21 20:56:49 NIC name: eno3, flags: up|broadcast|multicast
2022/06/21 20:56:49 NIC name: eno4, flags: up|broadcast|multicast
2022/06/21 20:56:49 NIC name: ens2f0, flags: broadcast|multicast
2022/06/21 20:56:49 NIC name: ens2f1, flags: broadcast|multicast
2022/06/21 20:56:49 NIC name: docker0, flags: up|broadcast|multicast
In conclusion
We can't distinguish the state of a NIC through only the FlagUp flag in the following situations:
- interface is plugged, automatically up, and in running(UP) state
- interface is not plugged, administratively or manually set to up, but in DOWN state
I have fixed this bug, and will send a pull request soon :)
I add a new flag to exactly reflect the states of an interface or NIC, as the title says.
And I get the right and exact report as the follow output, you can see only NIC(lo/eno4) are reported in running state:
Please pay attention to the tailing running word.
2022/06/21 21:01:52 NIC name: lo, flags: up|loopback|running
2022/06/21 21:01:52 NIC name: ens1f0, flags: up|broadcast|multicast
2022/06/21 21:01:52 NIC name: eno1, flags: up|broadcast|multicast
2022/06/21 21:01:52 NIC name: ens1f1, flags: up|broadcast|multicast
2022/06/21 21:01:52 NIC name: eno2, flags: up|broadcast|multicast
2022/06/21 21:01:52 NIC name: eno3, flags: up|broadcast|multicast
2022/06/21 21:01:52 NIC name: eno4, flags: up|broadcast|multicast|running
2022/06/21 21:01:52 NIC name: ens2f0, flags: broadcast|multicast
2022/06/21 21:01:52 NIC name: ens2f1, flags: broadcast|multicast
2022/06/21 21:01:52 NIC name: docker0, flags: up|broadcast|multicast
In another words, the NIC(s) which only have up flag but no running flag, are set up administratively or manually.
Thanks,
Mao