[PATCH] net-sysfs: Report link speed as signed integer

[PATCH] net-sysfs: Report link speed as signed integer

[Michal Privoznik]

The link speed is available at /sys/class/net/$nic/speed.
However, the speed is printed in unsigned integer format. This
makes userspace applications read an incorrect value (which
moreover changes through several architectures) while in fact
'-1' should be reported.

Before the change:
  # cat /sys/class/net/eth0/speed
  4294967295

After the change:
  # cat /sys/class/net/eth0/speed
  -1

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
---
 net/core/net-sysfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 1cac29e..99afdea 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -173,7 +173,7 @@ static ssize_t speed_show(struct device *dev,
 	if (netif_running(netdev)) {
 		struct ethtool_cmd cmd;
 		if (!__ethtool_get_settings(netdev, &cmd))
-			ret = sprintf(buf, fmt_udec, ethtool_cmd_speed(&cmd));
+			ret = sprintf(buf, fmt_dec, ethtool_cmd_speed(&cmd));
 	}
 	rtnl_unlock();
 	return ret;
-- 
2.0.0

Re: [PATCH] net-sysfs: Report link speed as signed integer

[Jiri Pirko]

Mon, Jun 02, 2014 at 04:25:15PM CEST, mprivozn@redhat.com wrote:
>The link speed is available at /sys/class/net/$nic/speed.
>However, the speed is printed in unsigned integer format. This
>makes userspace applications read an incorrect value (which
>moreover changes through several architectures) while in fact
>'-1' should be reported.
>
>Before the change:
>  # cat /sys/class/net/eth0/speed
>  4294967295
>
>After the change:
>  # cat /sys/class/net/eth0/speed
>  -1
>
>Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
>---
> net/core/net-sysfs.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
>index 1cac29e..99afdea 100644
>--- a/net/core/net-sysfs.c
>+++ b/net/core/net-sysfs.c
>@@ -173,7 +173,7 @@ static ssize_t speed_show(struct device *dev,
> 	if (netif_running(netdev)) {
> 		struct ethtool_cmd cmd;
> 		if (!__ethtool_get_settings(netdev, &cmd))
>-			ret = sprintf(buf, fmt_udec, ethtool_cmd_speed(&cmd));
>+			ret = sprintf(buf, fmt_dec, ethtool_cmd_speed(&cmd));

I wonder why this should be signed. What -1 means? What driver reports
this?

> 	}
> 	rtnl_unlock();
> 	return ret;
>-- 
>2.0.0
>

Re: [PATCH] net-sysfs: Report link speed as signed integer

[Bjørn Mork]

Jiri Pirko <jiri@resnulli.us> writes:
> Mon, Jun 02, 2014 at 04:25:15PM CEST, mprivozn@redhat.com wrote:
>>The link speed is available at /sys/class/net/$nic/speed.
>>However, the speed is printed in unsigned integer format. This
>>makes userspace applications read an incorrect value (which
>>moreover changes through several architectures) while in fact
>>'-1' should be reported.
>>
>>Before the change:
>>  # cat /sys/class/net/eth0/speed
>>  4294967295
>>
>>After the change:
>>  # cat /sys/class/net/eth0/speed
>>  -1
>>
>>Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
>>---
>> net/core/net-sysfs.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>>diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
>>index 1cac29e..99afdea 100644
>>--- a/net/core/net-sysfs.c
>>+++ b/net/core/net-sysfs.c
>>@@ -173,7 +173,7 @@ static ssize_t speed_show(struct device *dev,
>> 	if (netif_running(netdev)) {
>> 		struct ethtool_cmd cmd;
>> 		if (!__ethtool_get_settings(netdev, &cmd))
>>-			ret = sprintf(buf, fmt_udec, ethtool_cmd_speed(&cmd));
>>+			ret = sprintf(buf, fmt_dec, ethtool_cmd_speed(&cmd));
>
> I wonder why this should be signed. What -1 means? What driver reports
> this?

I believe many drivers will do this when the speed is unknown, e.g
because the link is down.  For example:

bjorn@nemi:~$ grep . /sys/class/net/eth0/speed
4294967295
bjorn@nemi:~$ ls -l /sys/class/net/eth0/device/driver
lrwxrwxrwx 1 root root 0 Jun  2 10:48 /sys/class/net/eth0/device/driver -> ../../../bus/pci/drivers/e1000e
bjorn@nemi:~$ ethtool eth0
Settings for eth0:
        Supported ports: [ TP ]
        Supported link modes:   10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
                                1000baseT/Full 
        Supported pause frame use: No
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
                                1000baseT/Full 
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Speed: Unknown!
        Duplex: Unknown! (255)
        Port: Twisted Pair
        PHYAD: 2
        Transceiver: internal
        Auto-negotiation: on
        MDI-X: Unknown
Cannot get wake-on-lan settings: Operation not permitted
        Current message level: 0x00000007 (7)
                               drv probe link
        Link detected: no



Bjørn

Re: [PATCH] net-sysfs: Report link speed as signed integer

[Michal Privoznik]

On 02.06.2014 16:35, Jiri Pirko wrote:
> Mon, Jun 02, 2014 at 04:25:15PM CEST, mprivozn@redhat.com wrote:
>> The link speed is available at /sys/class/net/$nic/speed.
>> However, the speed is printed in unsigned integer format. This
>> makes userspace applications read an incorrect value (which
>> moreover changes through several architectures) while in fact
>> '-1' should be reported.
>>
>> Before the change:
>>   # cat /sys/class/net/eth0/speed
>>   4294967295
>>
>> After the change:
>>   # cat /sys/class/net/eth0/speed
>>   -1
>>
>> Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
>> ---
>> net/core/net-sysfs.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
>> index 1cac29e..99afdea 100644
>> --- a/net/core/net-sysfs.c
>> +++ b/net/core/net-sysfs.c
>> @@ -173,7 +173,7 @@ static ssize_t speed_show(struct device *dev,
>> 	if (netif_running(netdev)) {
>> 		struct ethtool_cmd cmd;
>> 		if (!__ethtool_get_settings(netdev, &cmd))
>> -			ret = sprintf(buf, fmt_udec, ethtool_cmd_speed(&cmd));
>> +			ret = sprintf(buf, fmt_dec, ethtool_cmd_speed(&cmd));
>
> I wonder why this should be signed. What -1 means? What driver reports
> this?

This is e1000e. It seems like a default value. From e1000_get_settings() 
in drivers/net/ethernet/intel/e1000e/ethtool.c:

     speed = -1;
     ecmd->duplex = -1;

     if (netif_running(netdev)) {
         if (netif_carrier_ok(netdev)) {
             speed = adapter->link_speed;
             ecmd->duplex = adapter->link_duplex - 1;
         }
     } else if (!pm_runtime_suspended(netdev->dev.parent)) {
	...
     }

     ethtool_cmd_speed_set(ecmd, speed);

If I unplug the cord, NIC is nor running nor runtime suspended.

Michal

Re: [PATCH] net-sysfs: Report link speed as signed integer

[Veaceslav Falico]

On Mon, Jun 02, 2014 at 04:35:57PM +0200, Jiri Pirko wrote:
>Mon, Jun 02, 2014 at 04:25:15PM CEST, mprivozn@redhat.com wrote:
>>The link speed is available at /sys/class/net/$nic/speed.
>>However, the speed is printed in unsigned integer format. This
>>makes userspace applications read an incorrect value (which
>>moreover changes through several architectures) while in fact
>>'-1' should be reported.
>>
>>Before the change:
>>  # cat /sys/class/net/eth0/speed
>>  4294967295
>>
>>After the change:
>>  # cat /sys/class/net/eth0/speed
>>  -1
>>
>>Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
>>---
>> net/core/net-sysfs.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>>diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
>>index 1cac29e..99afdea 100644
>>--- a/net/core/net-sysfs.c
>>+++ b/net/core/net-sysfs.c
>>@@ -173,7 +173,7 @@ static ssize_t speed_show(struct device *dev,
>> 	if (netif_running(netdev)) {
>> 		struct ethtool_cmd cmd;
>> 		if (!__ethtool_get_settings(netdev, &cmd))
>>-			ret = sprintf(buf, fmt_udec, ethtool_cmd_speed(&cmd));
>>+			ret = sprintf(buf, fmt_dec, ethtool_cmd_speed(&cmd));
>
>I wonder why this should be signed. What -1 means? What driver reports
>this?

My first thoughts were exactly this. There is SPEED_UNKOWN (along with
_10, _100, _1000 etc.) that's -1, and quite a few drivers use it/set it.

I wonder, though, if we should document it or just output "Unknown" instead
of -1.

>
>> 	}
>> 	rtnl_unlock();
>> 	return ret;
>>--
>>2.0.0
>>
>--
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>the body of a message to majordomo@vger.kernel.org
>More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH] net-sysfs: Report link speed as signed integer

[Florian Fainelli]

2014-06-02 8:01 GMT-07:00 Veaceslav Falico <vfalico@redhat.com>:
> On Mon, Jun 02, 2014 at 04:35:57PM +0200, Jiri Pirko wrote:
>>
>> Mon, Jun 02, 2014 at 04:25:15PM CEST, mprivozn@redhat.com wrote:
>>>
>>> The link speed is available at /sys/class/net/$nic/speed.
>>> However, the speed is printed in unsigned integer format. This
>>> makes userspace applications read an incorrect value (which
>>> moreover changes through several architectures) while in fact
>>> '-1' should be reported.
>>>
>>> Before the change:
>>>  # cat /sys/class/net/eth0/speed
>>>  4294967295
>>>
>>> After the change:
>>>  # cat /sys/class/net/eth0/speed
>>>  -1
>>>
>>> Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
>>> ---
>>> net/core/net-sysfs.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
>>> index 1cac29e..99afdea 100644
>>> --- a/net/core/net-sysfs.c
>>> +++ b/net/core/net-sysfs.c
>>> @@ -173,7 +173,7 @@ static ssize_t speed_show(struct device *dev,
>>>         if (netif_running(netdev)) {
>>>                 struct ethtool_cmd cmd;
>>>                 if (!__ethtool_get_settings(netdev, &cmd))
>>> -                       ret = sprintf(buf, fmt_udec,
>>> ethtool_cmd_speed(&cmd));
>>> +                       ret = sprintf(buf, fmt_dec,
>>> ethtool_cmd_speed(&cmd));
>>
>>
>> I wonder why this should be signed. What -1 means? What driver reports
>> this?
>
>
> My first thoughts were exactly this. There is SPEED_UNKOWN (along with
> _10, _100, _1000 etc.) that's -1, and quite a few drivers use it/set it.
>
> I wonder, though, if we should document it or just output "Unknown" instead
> of -1.

I would document the special "Unkown" value in
Documentation/ABI/testing/sysfs-class-net and update speed_show() to
handle it. -1 is confusing for anyone to realize what this means.

>
>>
>>>         }
>>>         rtnl_unlock();
>>>         return ret;
>>> --
>>> 2.0.0
>>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe netdev" in
>>
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
> --
> To unsubscribe from this list: send the line "unsubscribe netdev" in
>
> the body of a message to majordomo@vger.kernel.org
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-- 
Florian

Re: [PATCH] net-sysfs: Report link speed as signed integer

[David Miller]

From: Veaceslav Falico <vfalico@redhat.com>
Date: Mon, 2 Jun 2014 17:01:50 +0200

> I wonder, though, if we should document it or just output "Unknown"
> instead of -1.

All of this discussion means that we can't change the format string
without potentially breaking something out there interpreting the -1
value, however it gets output now.

I think we just have to leave things as-is and document them in the
sysfs ABI docs.

I'm not applying this patch.

Re: [PATCH] net-sysfs: Report link speed as signed integer

[Michal Privoznik]

On 02.06.2014 20:10, David Miller wrote:
> From: Veaceslav Falico <vfalico@redhat.com>
> Date: Mon, 2 Jun 2014 17:01:50 +0200
>
>> I wonder, though, if we should document it or just output "Unknown"
>> instead of -1.
>
> All of this discussion means that we can't change the format string
> without potentially breaking something out there interpreting the -1
> value, however it gets output now.

No, the discussion means reporting -1 as link speed is confusing.

>
> I think we just have to leave things as-is and document them in the
> sysfs ABI docs.

Well, that's rather unpleasant.

>
> I'm not applying this patch.
>

Michal

Re: [PATCH] net-sysfs: Report link speed as signed integer

[Michal Privoznik]

On 03.06.2014 09:07, Michal Privoznik wrote:
> On 02.06.2014 20:10, David Miller wrote:
>> From: Veaceslav Falico <vfalico@redhat.com>
>> Date: Mon, 2 Jun 2014 17:01:50 +0200
>>
>>> I wonder, though, if we should document it or just output "Unknown"
>>> instead of -1.
>>
>> All of this discussion means that we can't change the format string
>> without potentially breaking something out there interpreting the -1
>> value, however it gets output now.
>

One more thing. The commit that changed the behavior is 8ae6daca which 
is part of the 3.0 release. So any 2.6.X kernel does report -1 while 
with 3.Y kernel you'll get this meaningless value. Having said that, we 
already broke the applications so how about unbreaking them?

Michal