[dpdk-stable] [PATCH v5] doc: add GRO API limitations in prog_guide

[Stephen Hemminger]

O        be merged.
> +
> +GRO Library Limitations
> +-----------------------
> +
> +- GRO library uses the values of MBUF->l2_len/l3_len/l4_len/
> +  outer_l2_len/outer_l3_len to get protocol headers for the
> +  input packet, rather than parsing the packet header. Therefore,
> +  before call GRO APIs to merge packets, user applications
> +  must set MBUF->l2_len/l3_len/l4_len/outer_l2_len/outer_l3_len
> +  to the same values as the protocol headers of the packet.
> +

Since these length values are critical to other functionality
why not require all poll mode drivers to set them.

Many poll mode drivers call rte_net_get_ptype() on the received
mbuf and it already handles setting this.

One could argue that GRO should just log and die if it
gets malformed data.