Thanks for your response, got it. BR Narsimha
On Wed, Dec 10, 2025 at 3:14 PM Morten Brørup <[email protected]> wrote: > > From: narsimharaj pentam [mailto:[email protected]] > > Sent: Tuesday, 9 December 2025 18.05 > > > > Added dev group. > > > > On Tue, Dec 9, 2025 at 10:11 PM narsimharaj pentam < > [email protected]> wrote: > > Hi > > > > I have a query related to ip fragmentation handling in DPDK. > > > > The DPDK application is trying to send a larger packet than the > configured MTU on the interface, before sending the packet to the i40e PMD > the packet will > > undergo fragmentation . The DPDK library function > "rte_ipv4_fragment_packet" is used for fragmentation. Function > rte_ipv4_fragment_packet will create > > direct and indirect mbuf's for a fragment , the indirect buffers will > have reference to the mbuf of the actual packet (zero copy). > > > > The application will call function rte_eth_tx_burst to transmit > fragments , which internally invokes i40e_xmit_pkts , the question here is > when should main application > > mbuf should be freed , can It be freed immediately after i40e_xmit_pkts > returns success, not sure because the mbuf's are queued up in software ring > before actual transmit, > > I am worried about the fragments holding references to the main > application buffer. > > The original packet can be freed immediately when then fragments have been > created. > > This is what the fragmentation example does: > > https://elixir.bootlin.com/dpdk/v25.11/source/examples/ip_fragmentation/main.c#L289 > > This is what happens: > The original packet has a reference counter (which was incremented for > each of the indirect mbufs referring to it), so freeing it at that point > doesn't put it back in the pool. > When the last of the indirect mbufs is freed (by the driver called by > rte_eth_tx_burst()), the original packet's reference counter reaches zero, > and then the original mbuf is put back in the pool. > > > > > Thanks. > > > > BR > > Narsimha > >
