On Mon, 30 Sep 2024 12:56:20 +0200 Pablo Neira Ayuso wrote:
> On Mon, Sep 30, 2024 at 12:28:08PM +0200, Pablo Neira Ayuso wrote:
> > On Sun, Sep 29, 2024 at 10:42:44AM +0000, Danielle Ratson wrote:
> > > Hi,
> > >
> > > Is there a plan to build a new version soon?
> > > I am asking since I am planning to use this function in ethtool.
> >
> > ASAP
>
> but one question before... Is this related to NLA_UINT in the kernel?
>
> /**
> * nla_put_uint - Add a variable-size unsigned int to a socket buffer
> * @skb: socket buffer to add attribute to
> * @attrtype: attribute type
> * @value: numeric value
> */
> static inline int nla_put_uint(struct sk_buff *skb, int attrtype, u64 value)
> {
> u64 tmp64 = value;
> u32 tmp32 = value;
>
> if (tmp64 == tmp32)
> return nla_put_u32(skb, attrtype, tmp32);
> return nla_put(skb, attrtype, sizeof(u64), &tmp64);
> }
>
> if I'm correct, it seems kernel always uses either u32 or u64.
>
> Userspace assumes u8 and u16 are possible though:
>
> +/**
> + * mnl_attr_get_uint - returns 64-bit unsigned integer attribute.
> + * \param attr pointer to netlink attribute
> + *
> + * This function returns the 64-bit value of the attribute payload.
> + */
> +EXPORT_SYMBOL uint64_t mnl_attr_get_uint(const struct nlattr *attr)
> +{
> + switch (mnl_attr_get_payload_len(attr)) {
> + case sizeof(uint8_t):
> + return mnl_attr_get_u8(attr);
> + case sizeof(uint16_t):
> + return mnl_attr_get_u16(attr);
> + case sizeof(uint32_t):
> + return mnl_attr_get_u32(attr);
> + case sizeof(uint64_t):
> + return mnl_attr_get_u64(attr);
> + }
> +
> + return -1ULL;
> +}
>
> Or this is an attempt to provide a helper that allows you fetch for
> payload value of 2^3..2^6 bytes?
No preference here, FWIW. Looks like this patch does a different thing
than the kernel. But maybe a broader "automatic" helper is useful for
user space code.
