From a868ec0851adae0947faa13c0a39efede92496fc Mon Sep 17 00:00:00 2001 From: David Marchand Date: Fri, 19 Apr 2024 16:06:30 +0200 Subject: [PATCH] netdev-dpdk: Use guest TSO segmentation size hint. In a typical setup like: guest A <-virtio-> OVS A <-vxlan-> OVS B <-virtio-> guest B TSO packets from guest A are segmented against the OVS A physical port mtu adjusted by the vxlan tunnel header size, regardless of guest A interface mtu. As an example, let's say guest A and guest B mtu are set to 1500 bytes. OVS A and OVS B physical ports mtu are set to 1600 bytes. Guest A will request TCP segmentation for 1448 bytes segments. On the other hand, OVS A will request 1498 bytes segments to the HW. This results in OVS B dropping packets because decapsulated packets are larger than the vhost-user port (serving guest B) mtu. 2024-04-17T14:13:01.239Z|00002|netdev_dpdk(pmd-c03/id:7)|WARN|vhost0: Too big size 1564 max_packet_len 1518 vhost-user ports expose a guest mtu by filling mbuf->tso_segsz. Use it as a hint. This may result in segments (on the wire) slightly shorter than the optimal size. Reported-at: https://github.com/openvswitch/ovs-issues/issues/321 Signed-off-by: David Marchand Signed-off-by: 0-day Robot --- lib/netdev-dpdk.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c index 661269e4b6b..1dad2ef833b 100644 --- a/lib/netdev-dpdk.c +++ b/lib/netdev-dpdk.c @@ -2671,14 +2671,19 @@ netdev_dpdk_prep_hwol_packet(struct netdev_dpdk *dev, struct rte_mbuf *mbuf) if (mbuf->ol_flags & RTE_MBUF_F_TX_TCP_SEG) { struct tcp_header *th = dp_packet_l4(pkt); + uint16_t link_tso_segsz; int hdr_len; if (tunnel_type) { - mbuf->tso_segsz = dev->mtu - mbuf->l2_len - mbuf->l3_len - - mbuf->l4_len - mbuf->outer_l3_len; + link_tso_segsz = dev->mtu - mbuf->l2_len - mbuf->l3_len - + mbuf->l4_len - mbuf->outer_l3_len; } else { mbuf->l4_len = TCP_OFFSET(th->tcp_ctl) * 4; - mbuf->tso_segsz = dev->mtu - mbuf->l3_len - mbuf->l4_len; + link_tso_segsz = dev->mtu - mbuf->l3_len - mbuf->l4_len; + } + + if (!mbuf->tso_segsz || mbuf->tso_segsz > link_tso_segsz) { + mbuf->tso_segsz = link_tso_segsz; } hdr_len = mbuf->l2_len + mbuf->l3_len + mbuf->l4_len;