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

["Morten Brørup" <mb@smartsharesystems.com>]

>  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 */
> +				};
> +			};