[PATCH v3] ip_frag: add IPv4 fragment copy packet API

[Stephen Hemminger]

On Fri, 22 Jul 2022 21:01:50 +0800
Huichao Cai <chcchc88 at 163.com> wrote:

> Some NIC drivers support MBUF_FAST_FREE(Device supports optimization
> for fast release of mbufs. When set application must guarantee that
> per-queue all mbufs comes from the same mempool and has refcnt = 1)
> offload. In order to adapt to this offload function, add this API.
> Add some test data for this API.
> 
> Signed-off-by: Huichao Cai <chcchc88 at 163.com>

The code should just be checking that refcnt == 1 directly.

There are cases where sender passes a cloned mbuf.  This is independent
of the fast free optimization.

Similar to what Linux kernel does with skb_cow().