Thank you for the clarification. Now, I understand more clearly. May I ask one more question? I used the rte_pktmbuf_clone function to duplicate the packet. Then, the new packet is cloned to the indirect memory. After the clone, I used the RTE_MBUF_DIRECT macro to check this, which returns false. So, to get a direct buffer, I need to use the alloc function and copy the data. Am I right?

I just want to use the "static inline int rte_vlan_insert(struct rte_mbuf **m)" function; a direct buffer is necessary for this function.

On Fri, Sep 1, 2023 at 4:08 PM Thomas Monjalon <thomas@monjalon.net> wrote:

01/09/2023 14:47, omer yamac:
> Hello,
>
> I need clarification while creating direct/indirect buffers for mbuf. I
> couldn't find exact documentation, and I just looked over the fragmentation
> test case and saw that two pools were created. One is a
> direct pool, and the other is an indirect pool. Here are the methods to
> create pools:
> direct_pool = rte_pktmbuf_pool_create("FRAG_D_MBUF_POOL",
>                           NUM_MBUFS, BURST, 0,
>                           RTE_MBUF_DEFAULT_BUF_SIZE,
>                           SOCKET_ID_ANY);
> indirect_pool = rte_pktmbuf_pool_create("FRAG_I_MBUF_POOL",
>                         NUM_MBUFS, BURST, 0,
>                         0, SOCKET_ID_ANY)
>
> I couldn't see the exact difference. Just the "data_room_size" parameter is
> different. If this parameter is 0, then is the pool indirect?

A pool is neither direct or indirect, it is just a pool of buffers
with a defined size for all buffers of a pool.
You are free to create any pool for your needs.

Now if you create a pool of buffers with size 0,
we can expect you will save some data elsewhere,
using rte_pktmbuf_attach_extbuf() for instance.

More explanations can be found in the doc:
https://doc.dpdk.org/guides/prog_guide/mbuf_lib.html#direct-and-indirect-buffers