net: add FlagRunning to the Flags of struct Interface, to exactly reflect the states of an interface or NIC #53482

MaoJianwei · 2022-06-21T15:39:19Z

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

The text was updated successfully, but these errors were encountered:

…lect the states of an interface or NIC. And a new flag(FlagRunning), and correctly set this flag while parsing the syscall result. The FlagUp flag can not distinguish the following situations: 1. interface is plugged, automatically up, and in running(UP) state 2. interface is not plugged, administratively or manually set to up, but in DOWN state So, We can't distinguish the state of a NIC through the FlagUp flag only. Fixes golang#53482 Signed-off-by: Jianwei Mao <maojianwei2012@126.com>

gopherbot · 2022-06-21T16:18:02Z

Change https://go.dev/cl/413454 mentions this issue: net: add FlagRunning to the Flags of struct Interface, to exactly reflect the states of an interface or NIC.

…lect the states of an interface or NIC. And a new flag(FlagRunning), and correctly set this flag while parsing the syscall result. The FlagUp flag can not distinguish the following situations: 1. interface is plugged, automatically up, and in running(UP) state 2. interface is not plugged, administratively or manually set to up, but in DOWN state So, We can't distinguish the state of a NIC through the FlagUp flag only. Fixes golang#53482 Signed-off-by: Jianwei Mao <maojianwei2012@126.com>

ianlancetaylor · 2022-06-21T19:25:32Z

Turning this issue into a proposal.

MaoJianwei · 2022-06-22T06:30:51Z

I see you have marked the issue as a proposal, thanks @ianlancetaylor .
What do I need to do, or just need to wait for weekly proposal review meetings to pick it to be active proposal? :)

rsc · 2022-06-22T18:03:04Z

I'm a little confused about inventing a new flag that does not appear in the ip addr output. Specifically:

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

The problem seems to be that we want to distinguish eno3 and eno4, where both have the UP flag set but one is 'state DOWN' and the other is 'state UP'. So the suggestion is to add a new flag RUNNING that means 'state UP'.

Is 'RUNNING' the right name for that? Is there a RUNNING bit on other systems that it might collide with?

MaoJianwei · 2022-06-23T03:33:23Z

Hi, @rsc ,

You get the core problem correctly, thanks :)

There are three reasons to choose the 'RUNNING' name:

The flag of an interface for its real up/down state is parsed from the syscall result, that is corresponding to the $go/src/net/interface_linux.go: linkFlags() function and the $go/src/syscall/zerrors_linux_amd64.go: const IFF_RUNNING flag. In other words, the existed constant flag was named 'IFF_RUNNING', so I just inherit the 'RUNNING' name here in this proposal.
The flag of an interface for the administrative UP is already named 'FlagUp', so in order to distinguish with it, I choose the 'FlagRunning' name.
the linkFlags() function and the 'IFF_RUNNING' flag are adopted by some systems and architectures, not only linux/amd64, as follow:

linkFlags() function:

$go/src/net/interface_linux.go
$go/src/net/interface_aix.go
$go/src/net/interface_bsd.go
$go/src/net/interface_solaris.go

'IFF_RUNNING' flag, constant:

$go/src/syscall/zerrors_linux_amd64.go
$go/src/syscall/zerrors_openbsd_arm64.go
$go/src/syscall/zerrors_linux_riscv64.go
$go/src/syscall/zerrors_linux_s390x.go
$go/src/syscall/zerrors_netbsd_386.go
$go/src/syscall/zerrors_aix_ppc64.go
... ...

This flag is defined in more than 30+ *.go files.
We can easily check out this situation by double-press shift
in the Goland IDE and search it.

'IFF_DRV_RUNNING' flag, the meaning is same as 'IFF_RUNNING':

$go/src/syscall/zerrors_freebsd_amd64.go
$go/src/syscall/zerrors_freebsd_arm64.go
$go/src/syscall/zerrors_freebsd_arm.go
$go/src/syscall/zerrors_freebsd_386.go

So, in my opinion, it is good to choose the RUNNING and FlagRunning name for this proposal :)

Thanks,
Mao

rsc · 2022-06-29T17:10:46Z

Just to confirm: it sounds like the ip addr program is reporting the kernel IFF_RUNNING bit when it prints 'state UP' (bit is set) or 'state DOWN' (bit is clear). Is that correct? (Certainly weird if so.)

What bit is it reporting when it says 'state UNKNOWN' like in the very first comment's:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000

?

Also, looking at PR #53484, does Windows ever distinguish UP from RUNNING? Do we need to do something more precise there?

MaoJianwei · 2022-06-29T18:39:15Z

Hi, @rsc

Yes, that is correct and reasonable.

Just to confirm:
it sounds like the ip addr program is reporting the kernel IFF_RUNNING bit when it prints 'state UP' (bit is set) or 'state DOWN' (bit is clear).
Is that correct? (Certainly weird if so.)

For the lo(loopback) interface, it report state UNKNOWN with IFF_RUNNING bit is set, because loopback is always UP and RUNNING.

What bit is it reporting when it says 'state UNKNOWN' like in the very first comment's:
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000

Windows doesn't distinguish UP from RUNNING, so we don't need to do more things, it is ok to sync the UP & RUNNING state.

does Windows ever distinguish UP from RUNNING? Do we need to do something more precise there?

Thanks,
Mao

rsc · 2022-07-01T17:39:58Z

This proposal has been added to the active column of the proposals project
and will now be reviewed at the weekly proposal review meetings.
— rsc for the proposal review group

rsc · 2022-07-13T17:15:09Z

Sounds like the bit exists and is called Running, so adding it here should be uncontroversial.

rsc · 2022-07-13T18:41:09Z

Based on the discussion above, this proposal seems like a likely accept.
— rsc for the proposal review group

MaoJianwei · 2022-07-14T14:52:32Z

Sounds like the bit exists and is called Running, so adding it here should be uncontroversial.

Yes, the bit is right here, and we want to provide it to everyone for using :)

Thanks,
Mao

rsc · 2022-07-20T18:03:52Z

No change in consensus, so accepted. 🎉
This issue now tracks the work of implementing the proposal.
— rsc for the proposal review group

MaoJianwei · 2022-07-25T02:31:08Z

Many thanks, wish the code will continue to be reviewed :)
@ianlancetaylor @neild @rsc

https://go-review.googlesource.com/c/go/+/413454

Github pull request: #53484

Correctly set this flag while parsing the syscall result. The FlagUp flag can not distinguish the following situations: 1. interface is plugged, automatically up, and in running(UP) state 2. interface is not plugged, administratively or manually set to up, but in DOWN state So, We can't distinguish the state of a NIC through the FlagUp flag only. Fixes golang#53482 Signed-off-by: Jianwei Mao <maojianwei2012@126.com>

Correctly set this flag while parsing the syscall result. The FlagUp flag can not distinguish the following situations: 1. interface is plugged, automatically up, and in running(UP) state 2. interface is not plugged, administratively or manually set to up, but in DOWN state So, We can't distinguish the state of a NIC by the FlagUp flag alone. Fixes golang#53482 Signed-off-by: Jianwei Mao <maojianwei2012@126.com>

Correctly set this flag while parsing the syscall result. The FlagUp flag can not distinguish the following situations: 1. interface is plugged, automatically up, and in running(UP) state 2. interface is not plugged, administratively or manually set to up, but in DOWN state So, We can't distinguish the state of a NIC by the FlagUp flag alone. Fixes golang#53482

MaoJianwei · 2022-08-27T12:10:24Z

Hi, @ianlancetaylor and @rsc , many thanks for your help, this PR has finally merged :)

Will this commit be automatically released in Go 1.20 ?
It was merged into the master branch, but has not marked with Go1.20 Milestone yet.

Cheers,
Mao

seankhliao · 2022-08-27T12:28:17Z

yes, everything in master goes into the next release

MaoJianwei · 2022-08-27T15:06:47Z

Thanks, @seankhliao :)

gopherbot · 2022-11-18T19:00:44Z

Change https://go.dev/cl/451420 mentions this issue: doc/go1.20: add release notes for net package

For #50101 For #51152 For #53482 For #55301 For #56515 Change-Id: I11edeb4be0a7f80fb72fd7680a3407d081f83b8b Reviewed-on: https://go-review.googlesource.com/c/go/+/451420 TryBot-Result: Gopher Robot <gobot@golang.org> Auto-Submit: Damien Neil <dneil@google.com> Run-TryBot: Damien Neil <dneil@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com>

MaoJianwei mentioned this issue Jun 21, 2022

net: add FlagRunning to exactly reflect the states of an interface. #53484

Closed

ianlancetaylor changed the title ~~net: add FlagRunning to the Flags of struct Interface, to exactly reflect the states of an interface or NIC.~~ proposal: net: add FlagRunning to the Flags of struct Interface, to exactly reflect the states of an interface or NIC Jun 21, 2022

gopherbot added this to the Proposal milestone Jun 21, 2022

gopherbot added the Proposal label Jun 21, 2022

ianlancetaylor added this to Incoming in Proposals (old) Jun 21, 2022

rsc moved this from Incoming to Active in Proposals (old) Jul 1, 2022

rsc moved this from Active to Likely Accept in Proposals (old) Jul 13, 2022

rsc added the Proposal-FinalCommentPeriod label Jul 13, 2022

rsc moved this from Likely Accept to Accepted in Proposals (old) Jul 20, 2022

rsc changed the title ~~proposal: net: add FlagRunning to the Flags of struct Interface, to exactly reflect the states of an interface or NIC~~ net: add FlagRunning to the Flags of struct Interface, to exactly reflect the states of an interface or NIC Jul 20, 2022

rsc added the Proposal-Accepted label Jul 20, 2022

rsc modified the milestones: Proposal, Backlog Jul 20, 2022

gopherbot closed this as completed in a2d2e6e Aug 27, 2022

seankhliao modified the milestones: Backlog, Go1.20 Aug 27, 2022

tklauser mentioned this issue Aug 30, 2022

net: add FlagRunning as network interface flag #29991

Closed

prattmic mentioned this issue Dec 6, 2022

api: audit for Go 1.20 #57126

Closed

HRogge mentioned this issue Oct 17, 2023

udp/server_test.go fails if first non-loopback interface is not running plgd-dev/go-coap#491

Closed

golang locked and limited conversation to collaborators Nov 18, 2023

gopherbot added the FrozenDueToAge label Nov 18, 2023

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

net: add FlagRunning to the Flags of struct Interface, to exactly reflect the states of an interface or NIC #53482

net: add FlagRunning to the Flags of struct Interface, to exactly reflect the states of an interface or NIC #53482

MaoJianwei commented Jun 21, 2022 •

edited

gopherbot commented Jun 21, 2022

ianlancetaylor commented Jun 21, 2022

MaoJianwei commented Jun 22, 2022

rsc commented Jun 22, 2022

MaoJianwei commented Jun 23, 2022 •

edited

rsc commented Jun 29, 2022

MaoJianwei commented Jun 29, 2022 •

edited

rsc commented Jul 1, 2022

rsc commented Jul 13, 2022

rsc commented Jul 13, 2022

MaoJianwei commented Jul 14, 2022 •

edited

rsc commented Jul 20, 2022

MaoJianwei commented Jul 25, 2022 •

edited

MaoJianwei commented Aug 27, 2022

seankhliao commented Aug 27, 2022

MaoJianwei commented Aug 27, 2022

gopherbot commented Nov 18, 2022

net: add FlagRunning to the Flags of struct Interface, to exactly reflect the states of an interface or NIC #53482

net: add FlagRunning to the Flags of struct Interface, to exactly reflect the states of an interface or NIC #53482

Comments

MaoJianwei commented Jun 21, 2022 • edited

What version of Go are you using (go version)?

Does this issue reproduce with the latest release?

What operating system and processor architecture are you using (go env)?

What did you do?

Environment:

What did you expect to see?

What did you see instead?

In conclusion

I have fixed this bug, and will send a pull request soon :)

gopherbot commented Jun 21, 2022

ianlancetaylor commented Jun 21, 2022

MaoJianwei commented Jun 22, 2022

rsc commented Jun 22, 2022

MaoJianwei commented Jun 23, 2022 • edited

rsc commented Jun 29, 2022

MaoJianwei commented Jun 29, 2022 • edited

rsc commented Jul 1, 2022

rsc commented Jul 13, 2022

rsc commented Jul 13, 2022

MaoJianwei commented Jul 14, 2022 • edited

rsc commented Jul 20, 2022

MaoJianwei commented Jul 25, 2022 • edited

MaoJianwei commented Aug 27, 2022

seankhliao commented Aug 27, 2022

MaoJianwei commented Aug 27, 2022

gopherbot commented Nov 18, 2022

MaoJianwei commented Jun 21, 2022 •

edited

What version of Go are you using (`go version`)?

What operating system and processor architecture are you using (`go env`)?

MaoJianwei commented Jun 23, 2022 •

edited

MaoJianwei commented Jun 29, 2022 •

edited

MaoJianwei commented Jul 14, 2022 •

edited

MaoJianwei commented Jul 25, 2022 •

edited