[ovs-dev] [PATCH v7 07/13] dp-packet: Handle multi-seg mubfs in shift() func.

[Stokes, Ian]

> In its current implementation dp_packet_shift() is also unaware of multi-
> seg mbufs (that holds data in memory non-contiguously) and assumes that
> data exists contiguously in memory, memmove'ing data to perform the shift.
> 
> To add support for multi-seg mbuds a new set of functions was introduced,
> dp_packet_mbuf_shift() and dp_packet_mbuf_write(). These functions are
> used by dp_packet_shift(), when handling multi-seg mbufs, to shift and
> write data within a chain of mbufs.
> 
> Signed-off-by: Tiago Lam <tiago.lam at intel.com>
> Acked-by: Eelco Chaudron <echaudro at redhat.com>
> ---
>  lib/dp-packet.c | 97
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  lib/dp-packet.h | 10 ++++++
>  2 files changed, 107 insertions(+)
> 
> diff --git a/lib/dp-packet.c b/lib/dp-packet.c index 2aaeaae..d6e19eb
> 100644
> --- a/lib/dp-packet.c
> +++ b/lib/dp-packet.c
> @@ -294,6 +294,97 @@ dp_packet_prealloc_headroom(struct dp_packet *b,
> size_t size)
>      }
>  }
> 
> +#ifdef DPDK_NETDEV
> +/* Write len data bytes in a mbuf at specified offset.
> + *
> + * 'mbuf', pointer to the destination mbuf where 'ofs' is, and the mbuf
> +where
> + * the data will first be written.
> + * 'ofs', the offset within the provided 'mbuf' where 'data' is to be
> written.
> + * 'len', the size of the to be written 'data'.
> + * 'data', pointer to the to be written bytes.
> + *
> + * XXX: This function is the counterpart of the `rte_pktmbuf_read()`
> +function
> + * available with DPDK, in the rte_mbuf.h */ void
> +dp_packet_mbuf_write(struct rte_mbuf *mbuf, int16_t ofs, uint32_t len,
> +                     const void *data)
> +{
> +    char *dst_addr;
> +    uint16_t data_len;
> +    int len_copy;
> +    while (mbuf) {
> +        if (len == 0) {
> +            break;
> +        }
> +
> +        dst_addr = rte_pktmbuf_mtod_offset(mbuf, char *, ofs);
> +        data_len = MBUF_BUF_END(mbuf->buf_addr, mbuf->buf_len) -
> + dst_addr;
> +
> +        len_copy = MIN(len, data_len);
> +        /* We don't know if 'data' is the result of a rte_pktmbuf_read()
> call,
> +         * in which case we may end up writing to the same region of
> memory we
> +         * are reading from and overlapping. Hence the use of memmove()
> here */
> +        memmove(dst_addr, data, len_copy);
> +
> +        data = ((char *) data) + len_copy;
> +        len -= len_copy;
> +        ofs = 0;
> +
> +        mbuf = mbuf->next;
> +    }
> +}
> +
> +static void
> +dp_packet_mbuf_shift_(struct rte_mbuf *dbuf, int16_t dst_ofs,
> +                      const struct rte_mbuf *sbuf, uint16_t src_ofs,
> +int len) {
> +    char rd[len];

Above will break compilation with sparse.

lib/dp-packet.c:341:13: error: Variable length array is used.

Regards
Ian