RE: [PATCH v3] net: add bit fields to IPv6 header definition

[Morten Brørup]

>  struct rte_ipv6_hdr {
> -     rte_be32_t vtc_flow;    /**< IP version, traffic class & flow label.
> */
> +     union {
> +             rte_be32_t vtc_flow;        /**< IP version, traffic class & 
> flow
> label. */
> +             __extension__
> +             struct {
> +#if RTE_BYTE_ORDER == RTE_LITTLE_ENDIAN
> +                     rte_be32_t flow_label:20; /**< flow label */

I played around with this in Godbolt, and __attribute__((__packed__)) only 
packs bytes, not bits, so the packed structure grows from 4 to 5 bytes, because 
the compiler adds 4 bits of padding here, to byte align the union holding "tc".

Please revert to v2.

Sorry about the noise. ;-)

> +                     union {
> +                             rte_be32_t tc:8;
> +                             struct {
> +                                     rte_be32_t ecn:2; /**< ECN */
> +                                     rte_be32_t ds:6;  /**< differentiated
> services */
> +                             };
> +                     };