[PATCH net] ethtool: fix ethtool msg len calculation for pause stats

[PATCH net] ethtool: fix ethtool msg len calculation for pause stats

[Jakub Kicinski]

ETHTOOL_A_PAUSE_STAT_MAX is the MAX attribute id,
so we need to subtract non-stats and add one to
get a count (IOW -2+1 == -1).

Otherwise we'll see:

  ethnl cmd 21: calculated reply length 40, but consumed 52

Fixes: 9a27a33027f2 ("ethtool: add standard pause stats")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/ethtool/pause.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ethtool/pause.c b/net/ethtool/pause.c
index 9009f412151e..c9171234130b 100644
--- a/net/ethtool/pause.c
+++ b/net/ethtool/pause.c
@@ -57,7 +57,7 @@ static int pause_reply_size(const struct ethnl_req_info *req_base,
 	if (req_base->flags & ETHTOOL_FLAG_STATS)
 		n += nla_total_size(0) +	/* _PAUSE_STATS */
 			nla_total_size_64bit(sizeof(u64)) *
-				(ETHTOOL_A_PAUSE_STAT_MAX - 2);
+				(ETHTOOL_A_PAUSE_STAT_MAX - 1);
 	return n;
 }
 
-- 
2.31.1

Re: [PATCH net] ethtool: fix ethtool msg len calculation for pause stats

[Saeed Mahameed]

On Mon, 2021-11-01 at 21:21 -0700, Jakub Kicinski wrote:
> ETHTOOL_A_PAUSE_STAT_MAX is the MAX attribute id,
> so we need to subtract non-stats and add one to
> get a count (IOW -2+1 == -1).
> 
> Otherwise we'll see:
> 
>   ethnl cmd 21: calculated reply length 40, but consumed 52
> 
> Fixes: 9a27a33027f2 ("ethtool: add standard pause stats")
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>

> ---
>  net/ethtool/pause.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/ethtool/pause.c b/net/ethtool/pause.c
> index 9009f412151e..c9171234130b 100644
> --- a/net/ethtool/pause.c
> +++ b/net/ethtool/pause.c
> @@ -57,7 +57,7 @@ static int pause_reply_size(const struct
> ethnl_req_info *req_base,
>         if (req_base->flags & ETHTOOL_FLAG_STATS)
>                 n += nla_total_size(0) +        /* _PAUSE_STATS */
>                         nla_total_size_64bit(sizeof(u64)) *
> -                               (ETHTOOL_A_PAUSE_STAT_MAX - 2);
> +                               (ETHTOOL_A_PAUSE_STAT_MAX - 1);

Maybe for net-next we can improve readability here.
Just by staring at these lines, you'd think that this should've been
(ETHTOOL_A_PAUSE_STAT_MAX + 1), or even better, just
(ETHTOOL_A_PAUSE_STAT_CNT) /* Count of only stats */

maybe we need to separate stats from non-stats, or define
ETHTOOL_A_PAUSE_STAT_CNT where it needs to be defined.

Re: [PATCH net] ethtool: fix ethtool msg len calculation for pause stats

[Jakub Kicinski]

On Tue, 2 Nov 2021 16:08:52 +0000 Saeed Mahameed wrote:
> > diff --git a/net/ethtool/pause.c b/net/ethtool/pause.c
> > index 9009f412151e..c9171234130b 100644
> > --- a/net/ethtool/pause.c
> > +++ b/net/ethtool/pause.c
> > @@ -57,7 +57,7 @@ static int pause_reply_size(const struct
> > ethnl_req_info *req_base,
> >         if (req_base->flags & ETHTOOL_FLAG_STATS)
> >                 n += nla_total_size(0) +        /* _PAUSE_STATS */
> >                         nla_total_size_64bit(sizeof(u64)) *
> > -                               (ETHTOOL_A_PAUSE_STAT_MAX - 2);
> > +                               (ETHTOOL_A_PAUSE_STAT_MAX - 1);  
> 
> Maybe for net-next we can improve readability here.
> Just by staring at these lines, you'd think that this should've been
> (ETHTOOL_A_PAUSE_STAT_MAX + 1), or even better, just
> (ETHTOOL_A_PAUSE_STAT_CNT) /* Count of only stats */
> 
> maybe we need to separate stats from non-stats, or define
> ETHTOOL_A_PAUSE_STAT_CNT where it needs to be defined.

Fair point, something like this?

+++ b/include/uapi/linux/ethtool_netlink.h
@@ -411,10 +411,14 @@ enum {
        ETHTOOL_A_PAUSE_STAT_TX_FRAMES,
        ETHTOOL_A_PAUSE_STAT_RX_FRAMES,
 
-       /* add new constants above here */
+       /* add new constants above here
+        * adjust ETHTOOL_PAUSE_STAT_CNT if adding non-stats!
+        */
        __ETHTOOL_A_PAUSE_STAT_CNT,
        ETHTOOL_A_PAUSE_STAT_MAX = (__ETHTOOL_A_PAUSE_STAT_CNT - 1)
 };
+#define ETHTOOL_PAUSE_STAT_CNT (__ETHTOOL_A_PAUSE_STAT_CNT -           \
+                                ETHTOOL_A_PAUSE_STAT_TX_FRAMES)
 
 /* EEE */
 

Re: [PATCH net] ethtool: fix ethtool msg len calculation for pause stats

[Saeed Mahameed]

On Tue, 2021-11-02 at 11:10 -0700, Jakub Kicinski wrote:
> On Tue, 2 Nov 2021 16:08:52 +0000 Saeed Mahameed wrote:
> > > 
...

> > 
> > maybe we need to separate stats from non-stats, or define
> > ETHTOOL_A_PAUSE_STAT_CNT where it needs to be defined.
> 
> Fair point, something like this?
> 

LGTM

> +++ b/include/uapi/linux/ethtool_netlink.h
> @@ -411,10 +411,14 @@ enum {
>         ETHTOOL_A_PAUSE_STAT_TX_FRAMES,
>         ETHTOOL_A_PAUSE_STAT_RX_FRAMES,
>  
> -       /* add new constants above here */
> +       /* add new constants above here
> +        * adjust ETHTOOL_PAUSE_STAT_CNT if adding non-stats!
> +        */
>         __ETHTOOL_A_PAUSE_STAT_CNT,
>         ETHTOOL_A_PAUSE_STAT_MAX = (__ETHTOOL_A_PAUSE_STAT_CNT - 1)
>  };
> +#define ETHTOOL_PAUSE_STAT_CNT (__ETHTOOL_A_PAUSE_STAT_CNT -
>            \
> +                                ETHTOOL_A_PAUSE_STAT_TX_FRAMES)
>  
>  /* EEE */
>  
>