Re: [PATCH iproute2-next v2 2/2] devlink: support u64-array values in devlink param show/set

[Ratheesh Kannoth]

On 2026-07-01 at 20:04:56, David Ahern (dsahern@xxxxxxxxxx) wrote:
> On 6/30/26 8:29 PM, Ratheesh Kannoth wrote:
> > On 2026-06-30 at 20:06:17, David Ahern (dsahern@xxxxxxxxxx) wrote:
> >> On 6/29/26 7:50 PM, Ratheesh Kannoth wrote:
> >>> diff --git a/devlink/devlink.c b/devlink/devlink.c
> >>> index 9372e92f..3c29601d 100644
> >>> --- a/devlink/devlink.c
> >>> +++ b/devlink/devlink.c
> >>> @@ -3496,13 +3496,115 @@ static const struct param_val_conv param_val_conv[] = {
> >>>  };
> >>>
> >>>  #define PARAM_VAL_CONV_LEN ARRAY_SIZE(param_val_conv)
> >>> +#define DEVLINK_PARAM_MAX_ARRAY_SIZE 32
> >>
> >> Why 32? Is that based on current code?
> > Yes, this aligns with the current kernel-side limits. See:
> > https://lore.kernel.org/all/20260609040453.711932-5-rkannoth@xxxxxxxxxxx/
> >
> >> How does the kernel side handle
> >> the number of parameters? What happens if the kernel sends more than 32
> >> parameters - from a user's perspective, not this code and processing the
> >> output?
> > The kernel strictly validates and restricts the number of parameters. To be safe, this patch
> > adds an explicit bounds check to prevent userspace issues if that threshold is ever crossed.
> >
> > Ideally, since "union devlink_param_value" is omitted from the UAPI, we have to define
> > DEVLINK_PARAM_MAX_ARRAY_SIZE here. Moving the underlying structures to the UAPI in the
> > future would allow us to share a single definition and avoid this hardcoded value in userspace.
>
> iproute2 needs to be backward and forward compatible. As it stands, a
> new kernel can allow more than 32 entries and an older iproute2 will not
> display all of them. That is wrong.
>
> Let's make the limit part of the uapi. If you do not want to do that
> now, then iproute2 code needs to handle a larger size.
ACK.