Re: [Minios-devel] [UNIKRAFT PATCH v4 05/11] lib/uknetdev: Netbuf headroom and tailroom helpers

[Sharan Santhanam <sharan.santhanam@xxxxxxxxx>]

Hello Simon,


There are minor typos in the comments which can be fixed while we 
pushing them. Please find them inline
Reviewed-by: Sharan Santhanam <sharan.santhanam@xxxxxxxxx>

On 10/10/2018 02:00 PM, Simon Kuenzer wrote:
> Introduce helpers for calculating available headroom and tailroom on a
> Netbuf's data buffer. A header manipulation function is added to
> simplify prepending bytes to the packet data or claiming bytes back to
> the headroom.
>
> Signed-off-by: Simon Kuenzer <simon.kuenzer@xxxxxxxxx>
> ---
>   lib/uknetdev/include/uk/netbuf.h | 86 ++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 86 insertions(+)
>
> diff --git a/lib/uknetdev/include/uk/netbuf.h b/lib/uknetdev/include/uk/netbuf.h
> index 5b0907c..0f8f6a3 100644
> --- a/lib/uknetdev/include/uk/netbuf.h
> +++ b/lib/uknetdev/include/uk/netbuf.h
> @@ -308,6 +308,18 @@ static inline struct uk_netbuf 
> *uk_netbuf_ref_single(struct uk_netbuf *m)
>   }
>   
>   /**
> + * Returns the reference to private data of a netbuf
> + * @param m
> + *   uk_netbuf to return private data of
> + */
> +static inline void *uk_netbuf_get_priv(struct uk_netbuf *m)
> +{
> +       UK_ASSERT(m);
> +
> +       return (m)->priv;
> +}
> +
> +/**
>    * Returns the current reference count of a single netbuf
>    * @param m
>    *   uk_netbuf to return the reference count of
> @@ -422,6 +434,80 @@ void uk_netbuf_free_single(struct uk_netbuf *m);
>                 (__ret);                                                \
>         })
>   
> +/**
> + * Calculates the current available headroom bytes of a netbuf
> + * @param m
> + *   uk_netbuf to return headroom bytes of
> + * @returns
> + *   available headroom bytes
> + */
> +static inline size_t uk_netbuf_headroom(struct uk_netbuf *m)
> +{
> +       UK_ASSERT(m);
> +       UK_ASSERT(m->buf);
> +       UK_ASSERT(m->data);
> +
> +       return (size_t) ((uintptr_t) (m)->data - (uintptr_t) (m)->buf);
> +}
> +
> +/**
> + * Calculates the current available tailroom bytes of a netbuf
> + * @param m
> + *   uk_netbuf to return tailroom bytes of
> + * @returns
> + *   available tailroom bytes
> + */
> +static inline size_t uk_netbuf_tailroom(struct uk_netbuf *m)
> +{
> +       UK_ASSERT(m);
> +       UK_ASSERT(m->buf);
> +       UK_ASSERT(m->data);
> +
> +       return ((size_t) (((uintptr_t) (m)->buf + (uintptr_t) (m)->buflen)
> +                         - ((uintptr_t) (m)->data + (uintptr_t) (m)->len)));
> +}
> +
replace m with head
> +/**
> + * Prepends (or returns) bytes from the headroom (back) to the data area.
> + * It basically moves m->data.
> + * @param head
> + *   uk_netbuf to modify (has to be the first netbuf of a chain)
> + * @param len
> + *   If > 0 takes bytes from the headroom and prepends them to data
> + *   If < 0 releases the -len first bytes from data to headroom
> + * @returns
> + *   - (-ENOSPC): Operation could not be perform within buffer bounds
> + *   - (-EFAULT): Operation could not be performed because data would get > 
> 64kB
> + *   - (1): netbuf successfully modified
> + */
> +static inline int uk_netbuf_header(struct uk_netbuf *head, int16_t len)
> +{
> +       UK_ASSERT(head);
> +       UK_ASSERT(head->buf);
> +       UK_ASSERT(head->data);
> +
replace m with head
> +       /* m has to be the first element of a netbuf chain. */
> +       UK_ASSERT(head->prev == NULL);
> +
> +       /* If len > 0, we take bytes from the headroom and add
> +        * them to data. We are limited to the available headroom size.
> +        * If len < 0, we return bytes back to the headroom.
> +        * We are limited to the available data length.
> +        */
> +       if (unlikely((len > (ssize_t) uk_netbuf_headroom(head))
> +                    || (-len > head->len)))
> +               return -ENOSPC;
> +
> +       /* We should never make the packet bigger than 64kB */
> +       if (unlikely((int32_t) len + (int32_t) head->len
> +                    > (int32_t) UINT16_MAX))
> +               return -EFAULT;
> +
> +       head->data   -= len;
> +       head->len    += len;
> +       return 1;
> +}
> +
>   #ifdef __cplusplus
>   }
>   #endif
Thanks & Regards
Sharan

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