Hi Stephan, Thanks for your response. I'm building DPDK 24.11 on kernel version 5.15.0-130-generic. It does seem to work with the MTU you suggested, but how can I support even larger packets (up to 9000)? Are there any workarounds for such cases? I don't mind a performance penalty as these use cases are expected to support less traffic then the ones using dpdk drivers.
On Sun, Feb 2, 2025 at 7:33 PM Stephen Hemminger <step...@networkplumber.org> wrote: > On Sun, 2 Feb 2025 08: 53: 42 +0200 Ofer Dagan <ofer. d@ claroty. com> > wrote: > Hi all, > > We are trying to start using AF_XDP instead of libpcap > (for use cases where > dpdk drivers aren't a good fit for us). When using > XDP, we > ZjQcmQRYFpfptBannerStart > ------------------------------ > WARNING:External E-Mail - Use caution with links and attachments > > ZjQcmQRYFpfptBannerEnd > > On Sun, 2 Feb 2025 08:53:42 +0200 > Ofer Dagan <ofe...@claroty.com> wrote: > > > Hi all, > > > > We are trying to start using AF_XDP instead of libpcap (for use cases where > > dpdk drivers aren't a good fit for us). When using XDP, we can't set high > > MTU. How to still support jumbo packets in our application? > > > > Thanks, > > Ofer > > What error are you seeing? > What version of DPDK, and what version of kernel are you building for. > > The current version of AF_XDP Poll mode driver supports larger mtu sizes. > It is constrained because the receive buffer has to fit on a single page > and there is overhead for the various headers. > > > dev_info->min_mtu = RTE_ETHER_MIN_MTU; > #if defined(XDP_UMEM_UNALIGNED_CHUNK_FLAG) > dev_info->max_rx_pktlen = getpagesize() - > sizeof(struct rte_mempool_objhdr) - > sizeof(struct rte_mbuf) - > RTE_PKTMBUF_HEADROOM - XDP_PACKET_HEADROOM; > #else > dev_info->max_rx_pktlen = ETH_AF_XDP_FRAME_SIZE - XDP_PACKET_HEADROOM; > #endif > dev_info->max_mtu = dev_info->max_rx_pktlen - ETH_AF_XDP_ETH_OVERHEAD; > > If you have a relatively recent kernel the UNALIGNED_CHUNK_FLAG should be set. > Stepping through the maths for that > max_rx_pktlen = 4096 - 24 - 128 - 128 - 256 = 3560 > max_mtu = max_rx_pktlen - 14 - 4 = 3542 > >
