前提背景：
生产环境上，服务器网络突然断链，ssh连接失败。
问题初步定位：
查找内核日志，得到网卡异常信息
Jan 24 11:52:43 localhost kernel: ixgbe 0000:84:00.0: eth0: RXDCTL.ENABLE on Rx queue 14 not cleared within the polling period
Jan 24 11:52:43 localhost kernel: ixgbe 0000:84:00.0: eth0: RXDCTL.ENABLE on Rx queue 15 not cleared within the polling period
Jan 24 11:52:43 localhost kernel: bonding: bond5: link status definitely down for interface eth0, disabling it
Jan 24 11:52:43 localhost kernel: ixgbe 0000:84:00.0: eth0: detected SFP+: 5
Jan 24 11:52:43 localhost kernel: ixgbe 0000:84:00.0: eth0: NIC Link is Up 10 Gbps, Flow Control: RX/TX
Jan 24 11:52:43 localhost kernel: bond5: link status definitely up for interface eth0, 10000 Mbps full duplex.
Jan 24 11:52:47 localhost kernel: ixgbe 0000:84:00.0: eth0: Detected Tx Unit Hang
Jan 24 11:52:47 localhost kernel: ixgbe 0000:84:00.0: eth0: tx_buffer_info[next_to_clean]
Jan 24 11:52:47 localhost kernel: ixgbe 0000:84:00.0: eth0: tx hang 448 detected on queue 6, resetting adapter
Jan 24 11:52:47 localhost kernel: ixgbe 0000:84:00.0: eth0: Reset adapter
Jan 24 11:52:47 localhost kernel: ixgbe 0000:84:00.0: eth0: RXDCTL.ENABLE on Rx queue 0 not cleared within the polling period
Jan 24 11:52:47 localhost kernel: ixgbe 0000:84:00.0: eth0: RXDCTL.ENABLE on Rx queue 1 not cleared within the polling period
Jan 24 11:52:47 localhost kernel: ixgbe 0000:84:00.0: eth0: RXDCTL.ENABLE on Rx queue 2 not cleared within the polling period
Jan 24 11:52:47 localhost kernel: ixgbe 0000:84:00.0: eth0: RXDCTL.ENABLE on Rx queue 3 not cleared within the polling period
网卡PCI信息：
# lspci -vvv -s 84:00.0
84:00.0 Ethernet controller: Intel Corporation 82599EB 10-Gigabit SFI/SFP+ Network Connection (rev 01)
Control: I/O- Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
Interrupt: pin A routed to IRQ 16
Region 0: Memory at f7e20000 (64-bit, non-prefetchable) [disabled] [size=128K]
Region 2: I/O ports at f020 [disabled] [size=32]
Region 4: Memory at f7e44000 (64-bit, non-prefetchable) [disabled] [size=16K]
Capabilities: [40] Power Management version 3
Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0+,D1-,D2-,D3hot+,D3cold-)
Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=1 PME-
Capabilities: [50] MSI: Enable- Count=1/1 Maskable+ 64bit+
Address: 0000000000000000 Data: 0000
Masking: 00000000 Pending: 00000000
Capabilities: [70] MSI-X: Enable- Count=64 Masked-
Vector table: BAR=4 offset=00000000
PBA: BAR=4 offset=00002000
Capabilities: [a0] Express (v2) Endpoint, MSI 00
DevCap: MaxPayload 512 bytes, PhantFunc 0, Latency L0s <512ns, L1 <64us
ExtTag- AttnBtn- AttnInd- PwrInd- RBE+ FLReset+
DevCtl: Report errors: Correctable- Non-Fatal- Fatal- Unsupported-
RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+ FLReset-
MaxPayload 128 bytes, MaxReadReq 512 bytes
DevSta: CorrErr+ UncorrErr+ FatalErr- UnsuppReq+ AuxPwr- TransPend-
LnkCap: Port #4, Speed 5GT/s, Width x8, ASPM L0s, Latency L0 <2us, L1 <32us
ClockPM- Surprise- LLActRep- BwNot-
LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- Retrain- CommClk-
ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
LnkSta: Speed 5GT/s, Width x8, TrErr- Train- SlotClk+ DLActive- BWMgmt- ABWMgmt-
DevCap2: Completion Timeout: Range ABCD, TimeoutDis+
DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-
LnkCtl2: Target Link Speed: 5GT/s, EnterCompliance- SpeedDis-, Selectable De-emphasis: -6dB
Transmit Margin: Normal Operating Range, EnterModifiedCompliance- ComplianceSOS-
Compliance De-emphasis: -6dB
LnkSta2: Current De-emphasis Level: -6dB
Capabilities: [e0] Vital Product Data
Unknown small resource type 06, will not decode more.
Capabilities: [100] Advanced Error Reporting
UESta: DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq+ ACSViol-
UEMsk: DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol-
UESvrt: DLP+ SDES- TLP- FCP+ CmpltTO- CmpltAbrt- UnxCmplt- RxOF+ MalfTLP+ ECRC- UnsupReq- ACSViol-
CESta: RxErr+ BadTLP+ BadDLLP+ Rollover+ Timeout+ NonFatalErr+
CEMsk: RxErr- BadTLP- BadDLLP- Rollover- Timeout- NonFatalErr+
AERCap: First Error Pointer: 14, GenCap+ CGenEn- ChkCap+ ChkEn-
Capabilities: [140] Device Serial Number 98-f5-37-ff-ff-e3-64-73
Capabilities: [150] Alternative Routing-ID Interpretation (ARI)
ARICap: MFVC- ACS-, Next Function: 1
ARICtl: MFVC- ACS-, Function Group: 0
Capabilities: [160] Single Root I/O Virtualization (SR-IOV)
IOVCap: Migration-, Interrupt Message Number: 000
IOVCtl: Enable- Migration- Interrupt- MSE- ARIHierarchy-
IOVSta: Migration-
Initial VFs: 64, Total VFs: 64, Number of VFs: 0, Function Dependency Link: 00
VF offset: 384, stride: 2, Device ID: 10ed
Supported Page Size: 00000553, System Page Size: 00000001
Region 0: Memory at 0000000000000000 (64-bit, prefetchable)
Region 3: Memory at 0000000000000000 (64-bit, prefetchable)
VF Migration: offset: 00000000, BIR: 0
Kernel driver in use: ixgbe
Kernel modules: ixgbe
网卡寄存器信息：
# ethtool -d eth0
0x042A4: LINKS (Link Status register) 0xFFFFFFFF
Link Status: up
Link Speed: 10G
0x05080: FCTRL (Filter Control register) 0xFFFFFFFF
Receive Flow Control Packets: enabled
Receive Priority Flow Control Packets: enabled
Discard Pause Frames: enabled
Pass MAC Control Frames: enabled
Broadcast Accept: enabled
Unicast Promiscuous: enabled
Multicast Promiscuous: enabled
Store Bad Packets: enabled
0x05088: VLNCTRL (VLAN Control register) 0xFFFFFFFF
VLAN Mode: enabled
VLAN Filter: enabled
0x02100: SRRCTL0 (Split and Replic Rx Control 0) 0xFFFFFFFF
Receive Buffer Size: 16KB
0x03D00: RMCS (Receive Music Control register) 0xFFFFFFFF
Transmit Flow Control: enabled
Priority Flow Control: enabled
0x04250: HLREG0 (Highlander Control 0 register) 0xFFFFFFFF
Transmit CRC: enabled
Receive CRC Strip: enabled
Jumbo Frames: enabled
Pad Short Frames: enabled
Loopback: enabled
0x00000: CTRL (Device Control) 0xFFFFFFFF
0x00008: STATUS (Device Status) 0xFFFFFFFF
0x00018: CTRL_EXT (Extended Device Control) 0xFFFFFFFF
0x00020: ESDP (Extended SDP Control) 0xFFFFFFFF
0x00028: EODSDP (Extended OD SDP Control) 0xFFFFFFFF
0x00200: LEDCTL (LED Control) 0xFFFFFFFF
........
0x01010: RDH00 (Receive Descriptor Head 00) 0xFFFFFFFF
0x01050: RDH01 (Receive Descriptor Head 01) 0xFFFFFFFF
0x01090: RDH02 (Receive Descriptor Head 02) 0xFFFFFFFF
0x010D0: RDH03 (Receive Descriptor Head 03) 0xFFFFFFFF
0x01110: RDH04 (Receive Descriptor Head 04) 0xFFFFFFFF
..........
0x01028: RXDCTL00 (Receive Descriptor Control 00) 0xFFFFFFFF
0x01068: RXDCTL01 (Receive Descriptor Control 01) 0xFFFFFFFF
0x010A8: RXDCTL02 (Receive Descriptor Control 02) 0xFFFFFFFF
........
0x06010: TDH00 (Transmit Descriptor Head 00) 0xFFFFFFFF
0x06050: TDH01 (Transmit Descriptor Head 01) 0xFFFFFFFF
0x06090: TDH02 (Transmit Descriptor Head 02) 0xFFFFFFFF
0x060D0: TDH03 (Transmit Descriptor Head 03) 0xFFFFFFFF
0x06110: TDH04 (Transmit Descriptor Head 04) 0xFFFFFFFF
0x06150: TDH05 (Transmit Descriptor Head 05) 0xFFFFFFFF
问题可能原因：
Bar0地址看起来没有问题，但寄存器全是0xffffffff了； 82599寄存器开始是正常的， 跑了一段时间（10小时）就 变成FFFF了；
可能pcie 接口接触问题。