Why traces like "WARNING: at net/core/dev.c:XXXX skb_warn_bad_offload+0xc2/0xf0()" are generated and system becomes inactive when "clusvcadm" command is run to enable some vmware service ?

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 6.5
  • kernel-2.6.32-431.1.2.el6.x86_64
  • HP ProLiant DL580 G7 systems.
  • netxen_nic NIC modules.
  • ixgbe NIC modules.

Issue

  • When a vmware service is started on a node with command clusvcadm -e Plato-VMWARE , system becomes inactive and following traces are generated:
Dec 19 11:37:46 HOSTNAME kernel: ------------[ cut here ]------------
Dec 19 11:37:46 HOSTNAME kernel: WARNING: at net/core/dev.c:1907 skb_warn_bad_offload+0xc2/0xf0() (Tainted: G        W  ---------------   )
Dec 19 11:37:46 HOSTNAME kernel: Hardware name: ProLiant DL580 G7
Dec 19 11:37:46 HOSTNAME kernel: netxen_nic: caps=(0x11c9b3, 0x0) len=146 data_len=0 ip_summed=1
Dec 19 11:37:46 HOSTNAME kernel: Modules linked in: vmnet(U) ppdev parport_pc parport fuse vsock(U) vmci(U) vmmon(U) nfsd exportfs autofs4 gfs2 nfs lockd fscache auth_rpcgss nfs_acl sunrpc dlm configfs cpufreq_ondemand freq_table pcc_cpufreq arpt_mangle arptable_filter arp_tables ipt_REJECT nf_conntrack_ipv4 nf_defrag_ipv4 xt_recent ipt_LOG iptable_filter ip_tables ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables ipv6 dm_round_robin dm_multipath uinput microcode iTCO_wdt iTCO_vendor_support power_meter lpc_ich mfd_core sg netxen_nic hpilo hpwdt i7core_edac edac_core shpchp ext4 jbd2 mbcache sr_mod cdrom sd_mod crc_t10dif qla2xxx scsi_transport_fc scsi_tgt pata_acpi ata_generic ata_piix hpsa radeon ttm drm_kms_helper drm i2c_algo_bit i2c_core dm_mirror dm_region_hash dm_log dm_mod [last unloaded: scsi_wait_scan]
Dec 19 11:37:46 HOSTNAME kernel: Pid: 0, comm: swapper Tainted: G        W  ---------------    2.6.32-431.1.2.el6.x86_64 #1
Dec 19 11:37:46 HOSTNAME kernel: Call Trace:
Dec 19 11:37:46 HOSTNAME kernel: <IRQ>  [<ffffffff81071e27>] ? warn_slowpath_common+0x87/0xc0
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff81071f16>] ? warn_slowpath_fmt+0x46/0x50
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffffa0342370>] ? netxen_nic_get_drvinfo+0xc0/0xf0 [netxen_nic]
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff8145afe2>] ? skb_warn_bad_offload+0xc2/0xf0
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff814600d1>] ? __skb_gso_segment+0x71/0xc0
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff81460133>] ? skb_gso_segment+0x13/0x20
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffffa069f9bd>] ? VNetBridgeSendLargePacket+0x1d/0x90 [vmnet]
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffffa06a0c70>] ? VNetBridgeReceiveFromDev+0x310/0x420 [vmnet]
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff8145b527>] ? __netif_receive_skb+0x477/0x750
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff8145f1c8>] ? netif_receive_skb+0x58/0x60
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffffa033e523>] ? netxen_process_rcv_ring+0x913/0xb00 [netxen_nic]
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffffa0340b84>] ? netxen_process_cmd_ring+0x44/0x2a0 [netxen_nic]
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff81058d53>] ? __wake_up+0x53/0x70
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffffa0339b65>] ? netxen_nic_poll+0x45/0xc0 [netxen_nic]
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff813301f6>] ? credit_entropy_bits+0x76/0xd0
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff81460b53>] ? net_rx_action+0x103/0x2f0
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff81330356>] ? add_timer_randomness+0x106/0x110
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff8107a8e1>] ? __do_softirq+0xc1/0x1e0
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff810e6f02>] ? handle_IRQ_event+0x92/0x170
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff8100c30c>] ? call_softirq+0x1c/0x30
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff8100fa75>] ? do_softirq+0x65/0xa0
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff8107a795>] ? irq_exit+0x85/0x90
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff81530ff5>] ? do_IRQ+0x75/0xf0
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff8100b9d3>] ? ret_from_intr+0x0/0x11
Dec 19 11:37:46 HOSTNAME kernel: <EOI>  [<ffffffff81426521>] ? poll_idle+0x41/0x80
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff814264f3>] ? poll_idle+0x13/0x80
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff81426707>] ? cpuidle_idle_call+0xa7/0x140
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff81009fc6>] ? cpu_idle+0xb6/0x110
Dec 19 11:37:46 HOSTNAME kernel: [<ffffffff81520e2c>] ? start_secondary+0x2ac/0x2ef
Dec 19 11:37:46 HOSTNAME kernel: ---[ end trace 228c1f1e9ed1b9eb ]---

Resolution

Disable Large Receive Offload (LRO) and/or Generic Recieve Offload (GRO).

This can be done during runtime with the following commands:

# ethtool -k ethX
# ethtool -K ethX lro off
# ethtool -K ethX gro off

You may persist these settings across reboot by writing /sbin/ifup-local as described here.

Note: It is incorrect to enable LRO when IP forwarding and/or bridging are in use.

Root Cause

  • This is a warning which is triggered when a GSO skb has skb->ip_summed != CHECKSUM_PARTIAL. Ideally, in order to do GSO the skb->ip_summed should be set to CHECKSUM_PARTIAL
  • skb->ip_summed could have been set to CHECKSUM_UNNECESSARY , probably by the VMware driver or by the guest.
  • skb_gso_segment() has been factored to support openvswitch which calls this function when it receives the packet. So, except for openvswitch, it shouldn't be used in the receiving path.
  • It may be possible that the LRO is providing a packet that VMware doesn't know how to handle properly. Disabling LRO provides a workaround.
  • This proves that the bug is within VMware

Diagnostic Steps

  • Check the genuineness of NIC module used.
  • Check the logs from the sosreport.
  • Collect strace logs as mentioned below for the clusvcadm command.
# strace -o /tmp/strace.txt clusvcadm -e Plato-VMWARE
  • As far as the physical machine is concerned, this seems to be a RX packet for which NetXen NIC sets skb->ip_summed = CHECKSUM_UNNECESSARY.

  • Then the packet reaches the VMware bridge and it seems to be sending it to another dev

rx-checksumming: on
tx-checksumming: on
scatter-gather: on
tcp-segmentation-offload: on
udp-fragmentation-offload: off
generic-segmentation-offload: off  (Issue happens with both GSO on and off)
generic-receive-offload: on
large-receive-offload: on

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