Hi, I am wondering if anyone can help me with this. I am having trouble to send tso/gso packet with af_packet socket with packet_vnet_hdr (through virtio_net_hdr) over vxlan tunnel in OVS. What I observed that, the following function eventually hitting and is returning false (net/core/skbuff.c), hence the packet is dropping. static inline bool skb_gso_size_check(const struct sk_buff *skb, unsigned int seg_len, unsigned int max_len) { const struct skb_shared_info *shinfo = skb_shinfo(skb); const struct sk_buff *iter; if (shinfo->gso_size != GSO_BY_FRAGS) return seg_len <= max_len; .......... } [ 678.756673] ip_finish_output_gso:235 packet_length:2762 (here packet_length = skb->len - skb_inner_network_offset(skb)) [ 678.756678] ip_fragment:510 packet length:1500 [ 678.756715] ip_fragment:510 packet length:1314 [ 678.956889] skb_gso_size_check:4474 and seg_len:1550 and max_len:1500 and shinfo->gso_size:1448 and GSO_BY_FRAGS:65535 Observation: When we send the large packet ( example here is packet_length:2762), its showing the seg_len(1550) > max_len(1500). Hence return seg_len <= max_len statement returning false. Because of this, ip_fragment calling icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu)); rather the code reaching to ip_finish_output2(sk, skb) function in net/ipv4/ip_output.c and is given below: static int ip_finish_output_gso(struct sock *sk, struct sk_buff *skb, unsigned int mtu) { netdev_features_t features; struct sk_buff *segs; int ret = 0; /* common case: seglen is <= mtu */ if (skb_gso_validate_mtu(skb, mtu)) return ip_finish_output2(sk, skb); ........... err = ip_fragment(sk, segs, mtu, ip_finish_output2); ........... } But when we send normal iperf traffic ( gso/tso traffic) over vxlan, the skb_gso_size_check returning a true value, and ip_finish_output2 getting executed. Here is the values of normal iperf traffic over vxlan. [ 1041.400537] skb_gso_size_check:4477 and seg_len:1500 and max_len:1500 and shinfo->gso_size:1398 and GSO_BY_FRAGS:65535 [ 1041.400587] skb_gso_size_check:4477 and seg_len:1450 and max_len:1450 and shinfo->gso_size:1398 and GSO_BY_FRAGS:65535 [ 1041.400594] skb_gso_size_check:4477 and seg_len:1500 and max_len:1500 and shinfo->gso_size:1398 and GSO_BY_FRAGS:65535 [ 1041.400732] skb_gso_size_check:4477 and seg_len:1450 and max_len:1450 and shinfo->gso_size:1398 and GSO_BY_FRAGS:65535 [ 1041.400741] skb_gso_size_check:4477 and seg_len:1450 and max_len:1450 and shinfo->gso_size:1398 and GSO_BY_FRAGS:65535 Can someone help me to solve what is missing, and where should I modify the code in OVS/ or outside of ovs, so that it works as expected. Thanks in advance. Some more info: [root@xx ~]# uname -r 3.10.0-1062.4.1.el7.x86_64 [root@xx ~]# cat /etc/redhat-release Red Hat Enterprise Linux Server release 7.7 (Maipo) [root@xx]# ovs-vsctl --version ovs-vsctl (Open vSwitch) 2.9.0 DB Schema 7.15.1 And dump_stack output with af_packet: [ 4833.637460] <IRQ> [<ffffffff81979612>] dump_stack+0x19/0x1b [ 4833.637474] [<ffffffff8197c3ca>] ip_fragment.constprop.55+0xc3/0x141 [ 4833.637481] [<ffffffff8189dd84>] ip_finish_output+0x314/0x350 [ 4833.637484] [<ffffffff8189eb83>] ip_output+0xb3/0x130 [ 4833.637490] [<ffffffff8189da70>] ? ip_do_fragment+0x910/0x910 [ 4833.637493] [<ffffffff8189cac9>] ip_local_out_sk+0xf9/0x180 [ 4833.637497] [<ffffffff818e6f6c>] iptunnel_xmit+0x18c/0x220 [ 4833.637505] [<ffffffffc073b2e7>] udp_tunnel_xmit_skb+0x117/0x130 [udp_tunnel] [ 4833.637538] [<ffffffffc074585a>] vxlan_xmit_one+0xb6a/0xb70 [vxlan] [ 4833.637545] [<ffffffff8129dad9>] ? vprintk_default+0x29/0x40 [ 4833.637551] [<ffffffffc074765e>] vxlan_xmit+0xc9e/0xef0 [vxlan] [ 4833.637555] [<ffffffff818356e7>] ? kfree_skbmem+0x37/0x90 [ 4833.637559] [<ffffffff81836c24>] ? consume_skb+0x34/0x90 [ 4833.637564] [<ffffffff819547bc>] ? packet_rcv+0x4c/0x3e0 [ 4833.637570] [<ffffffff8184d346>] dev_hard_start_xmit+0x246/0x3b0 [ 4833.637574] [<ffffffff81850339>] __dev_queue_xmit+0x519/0x650 [ 4833.637580] [<ffffffff812d9df0>] ? try_to_wake_up+0x190/0x390 [ 4833.637585] [<ffffffff81850480>] dev_queue_xmit+0x10/0x20 [ 4833.637592] [<ffffffffc0724316>] ovs_vport_send+0xa6/0x180 [openvswitch] [ 4833.637599] [<ffffffffc07150fe>] do_output+0x4e/0xd0 [openvswitch] [ 4833.637604] [<ffffffffc0716699>] do_execute_actions+0xa29/0xa40 [openvswitch] [ 4833.637610] [<ffffffff812d24d2>] ? __wake_up_common+0x82/0x120 [ 4833.637615] [<ffffffffc0716aac>] ovs_execute_actions+0x4c/0x140 [openvswitch] [ 4833.637621] [<ffffffffc071a824>] ovs_dp_process_packet+0x84/0x120 [openvswitch] [ 4833.637627] [<ffffffffc0725404>] ? ovs_ct_update_key+0xc4/0x150 [openvswitch] [ 4833.637633] [<ffffffffc0724213>] ovs_vport_receive+0x73/0xd0 [openvswitch] [ 4833.637638] [<ffffffff812d666f>] ? ttwu_do_activate+0x6f/0x80 [ 4833.637642] [<ffffffff812d9df0>] ? try_to_wake_up+0x190/0x390 [ 4833.637646] [<ffffffff812da0c2>] ? default_wake_function+0x12/0x20 [ 4833.637651] [<ffffffff812c61eb>] ? autoremove_wake_function+0x2b/0x40 [ 4833.637657] [<ffffffff812d24d2>] ? __wake_up_common+0x82/0x120 [ 4833.637661] [<ffffffff812e3ae9>] ? update_cfs_shares+0xa9/0xf0 [ 4833.637665] [<ffffffff812e3696>] ? update_curr+0x86/0x1e0 [ 4833.637669] [<ffffffff812dee88>] ? __enqueue_entity+0x78/0x80 [ 4833.637677] [<ffffffffc0724cbe>] netdev_frame_hook+0xde/0x180 [openvswitch] [ 4833.637682] [<ffffffff8184d6aa>] __netif_receive_skb_core+0x1fa/0xa10 [ 4833.637688] [<ffffffffc0724be0>] ? vport_netdev_free+0x30/0x30 [openvswitch] [ 4833.637692] [<ffffffff812d6539>] ? ttwu_do_wakeup+0x19/0xe0 [ 4833.637697] [<ffffffff8184ded8>] __netif_receive_skb+0x18/0x60 [ 4833.637703] [<ffffffff8184ee9e>] process_backlog+0xae/0x180 [ 4833.637707] [<ffffffff8184e57f>] net_rx_action+0x26f/0x390 [ 4833.637713] [<ffffffff812a41e5>] __do_softirq+0xf5/0x280 [ 4833.637719] [<ffffffff8199042c>] call_softirq+0x1c/0x30 [ 4833.637723] <EOI> [<ffffffff8122f675>] do_softirq+0x65/0xa0 [ 4833.637730] [<ffffffff812a363b>] __local_bh_enable_ip+0x9b/0xb0 [ 4833.637735] [<ffffffff812a3667>] local_bh_enable+0x17/0x20 [ 4833.637741] [<ffffffff81850065>] __dev_queue_xmit+0x245/0x650 [ 4833.637746] [<ffffffff81972e28>] ? printk+0x60/0x77 [ 4833.637752] [<ffffffff81850480>] dev_queue_xmit+0x10/0x20 [ 4833.637757] [<ffffffff81957a75>] packet_sendmsg+0xf65/0x1210 [ 4833.637761] [<ffffffff813d7524>] ? shmem_fault+0x84/0x1f0 [ 4833.637768] [<ffffffff8182d3a6>] sock_sendmsg+0xb6/0xf0 [ 4833.637772] [<ffffffff812e3696>] ? update_curr+0x86/0x1e0 [ 4833.637777] [<ffffffff812e3ae9>] ? update_cfs_shares+0xa9/0xf0 [ 4833.637781] [<ffffffff8122b621>] ? __switch_to+0x151/0x580 [ 4833.637786] [<ffffffff8182dad1>] SYSC_sendto+0x121/0x1c0 [ 4833.637793] [<ffffffff812c8d10>] ? hrtimer_get_res+0x50/0x50 [ 4833.637797] [<ffffffff8197e54b>] ? do_nanosleep+0x5b/0x100 [ 4833.637802] [<ffffffff8182f5ee>] SyS_sendto+0xe/0x10 [ 4833.637806] [<ffffffff8198cede>] system_call_fastpath+0x25/0x2a Looking forward to your reply. Regards, Ramana