TS 系列之–ARP导致3850交换机CPU中断高

第一步: 找到CPU占用率高的进程

3850系列交换机使用4核CPU, 使用show process cpu 命令将会看到:

3850-2#show processes cpu sort | exclude 0.0

Core 0: CPU utilization for five seconds: 53%; one minute: 39%;  five minutes: 41%

Core 1: CPU utilization for five seconds: 43%; one minute: 57%;  five minutes: 54%

Core 2: CPU utilization for five seconds: 95%; one minute: 60%;  five minutes: 58%

Core 3: CPU utilization for five seconds: 32%; one minute: 31%;  five minutes: 29%

PID    Runtime(ms) Invoked  uSecs  5Sec     1Min     5Min     TTY   Process

8525   472560      2345554  7525   31.37    30.84    30.83    0     iosd

5661   2157452     9234031  698    13.17    12.56    12.54    1088  fed

6206   19630       74895    262    1.83     0.43     0.10     0     eicored

6197   725760      11967089 60     1.41     1.38     1.47     0     pdsd

根据以上输出,可以看到iosd和fed进程占用大量CPU.

*Forwarding Engine Driver (FED): This is the heart of the Cisco Catalyst 3850 Series Switch and is responsible for all hardware programming/forwarding.

当由于中断(interrupts)导致CPU利用率高,将会看到IOSd和FED进程占用大量CPU,以下子进程将占用CPU:

  • FED Punject TX
  • FED Punject RX
  • FED Punject replenish
  • FED Punject TX complete

我们可以使用 show process cpu detailed <process>命令去获得进程的更详细内容.

在这个案例中,我们看看这2个进程:

3850-2#show processes cpu detailed process iosd sort | ex 0.0

Core 0: CPU utilization for five seconds: 36%; one minute: 39%; five minutes: 40%

Core 1: CPU utilization for five seconds: 73%; one minute: 52%; five minutes: 53%

Core 2: CPU utilization for five seconds: 22%; one minute: 56%; five minutes: 58%

Core 3: CPU utilization for five seconds: 46%; one minute: 40%; five minutes: 31%

PID    T C  TID   Runtime(ms)Invoked uSecs 5Sec   1Min   5Min  TTY  Process

(%)    (%)    (%)

8525   L          556160     2356540 7526  30.42   30.77  30.83  0   iosd

8525   L 1  8525  712558     284117  0     23.14   23.33  23.38  0   iosd

59     I          1115452    4168181 0     42.22   39.55  39.33  0   ARP Snoop

198    I          3442960    4168186 0     25.33   24.22  24.77  0   IP Host Track Proce

30     I          3802130    4168183 0     24.66   27.88  27.66  0   ARP Input

283    I          574800     3225649 0     4.33    4.00   4.11   0   DAI Packet Process

3850-2#show processes cpu detailed process fed sorted | ex 0.0

Core 0: CPU utilization for five seconds: 45%; one minute: 44%; five minutes: 44%

Core 1: CPU utilization for five seconds: 38%; one minute: 44%; five minutes: 45%

Core 2: CPU utilization for five seconds: 42%; one minute: 41%; five minutes: 40%

Core 3: CPU utilization for five seconds: 32%; one minute: 30%; five minutes: 31%

PID    T C  TID   Runtime(ms)Invoked uSecs 5Sec   1Min   5Min   TTY  Process

(%)    (%)    (%)

5638   L          612840     1143306 536   13.22  12.90   12.93  1088  fed

5638   L 3  8998  396500     602433  0     9.87   9.63    9.61   0     PunjectTx

5638   L 3  8997  159890     66051   0     2.70   2.70    2.74   0     PunjectRx

在IOSd的输出中,看到ARP Snoop, IP Host Track Process, 和 ARP Input 比较高. 比较常见的是由于ARP包造成CPU中断高.

 第二步:确定导致CPU利用率高的CPU队列

思科3850系列交换机为不同类型的包提供了不同的队列(FED维护32个RX CPU Queue,这些queue会直接上CPU).

监视这些Queue可以发现哪些包被送上了CPU,哪些被IOSd进程处理. 这些Queue是基于每个Port-ASIC的. 例如,有2个Port-ASIC, 接口1到24属于Port-ASIC 0.

可以使用showplatform punt statistics port-asic <port-asic> cpuq <queue>direction <rx|tx>命令去看.

在showplatform punt statistics port-asic 0 cpuq -1 direction rx 命令中, -1参数代理所有queue, 引起,这条命令将显示Port-ASIC 0上所有receivequeue.

现在,必须确定哪个Queue有大量的数据包在以高速率进入queue.  在这个案例中, 检查发现了名叫 CPU_Q_PROTO_SNOOPING的第16queue有异常.

<snip>

RX (ASIC2CPU) Stats (asic 0 qn 16lqn 16):

RXQ 16: CPU_Q_PROTO_SNOOPING

----------------------------------------

Packets received from ASIC    : 79099152

Send to IOSd total attempts   : 79099152

Send to IOSd failed count     : 1240331

RX suspend count              : 1240331

RX unsuspend count            : 1240330

RX unsuspend send count       : 1240330

RX unsuspend send failed count : 0

RX dropped count              : 0

RX conversion failure dropped  : 0

RX pkt_hdr allocation failure  : 0

RX INTACK count               : 0

RX packets dq'd after intack   : 0

Active RxQ event              : 9906280

RX spurious interrupt         : 0

<snip>

另一种方法是使用show platform punt client 命令去发现:

3850-2#show platform punt client

tag      buffer       jumbo    fallback    packets   received   failures

65559    0/  16/1600    0/4       0/0       0     0         0     0     0

65560    0/  16/1600    0/4       0/0       0     0         0     0     0

s65561  421/ 512/1600    0/0       0/128  79565859131644697  478984244     0 37467

65563    0/ 512/1600    0/16      0/256     0     0         0     0     0

65564    0/ 512/1600    0/16      0/256     0     0         0     0     0

找到最多数据包这一行对应的tag,在这个案例中, tag为65561.

*Handle:A handle can be thought of as a pointer. It is a means to discover moredetailed information about specific variables that are used in the outputs thatthe box produces. This is similar to the concept of Local Target Logic (LTL)indices on the Cisco Catalyst 6500 Series Switch.

*PacketDelivery System (PDS): This is thearchitecture and process of how packets aredelivered to and from varioussubsystem. As an example, it controls how packetsare delivered from the FED tothe IOSd and vice versa.

输入以下命令,可以看到queue名是Rx Proto Snoop.

3850-2#show pds tag all | in Active|Tags|65561

Active   Client Client

Tags   HandleName                TDA       SDA        FDA   TBufD       TBytD

65561  7296672 Punt Rx ProtoSnoop  79821397  79821397   0  79821397   494316524

在65561前的s表示大量入向数据包导致FED handle被暂停或者被压垮(FEDhandle is suspended and overwhelmed). 如果s不消失,代表queue永久性的卡住了.

 第三步:转储发送到CPU的数据包

在show pds tag all 的输出中看到 handle是7296672.

在使用show pds client <handle> packet last sink命令之前,需要开启debug pds pktbuf-last.否则将看到以下输出:

3850-2#show pds client 7296672 packet last sink

% switch-2:pdsd:This command works in debug mode only. Enable debug using

"debug pds pktbuf-last" command

开启debug pds pktbuf-last后,将看到以下输出:

3850-2#show pds client 7296672 packet last sink

Dumping Packet(54528) # 0 of Length 60

-----------------------------------------

Meta-data

0000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................

0010 00 00 16 1d 00 00 00 00 00 00 00 00 55 5a 57 f0  ............UZW.

0020 00 00 00 00 fd 01 10 df 00 5b 70 00 00 10 43 00  .........[p...C.

0030 00 10 43 00 00 41 fd 00 00 41 fd 00 00 00 00 00  ..C..A...A......

0040 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................

0050 00 00 00 3c 00 00 00 00 00 01 00 19 00 00 00 00  ...<............

0060 01 01 b6 80 00 00 00 4f 00 00 00 00 00 00 00 00  .......O........

0070 01 04 d8 80 00 00 00 33 00 00 00 00 00 00 00 00  .......3........

0080 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................

0090 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................

00a0 00 00 00 00 00 00 00 02 00 00 00 00 00 00 00 00  ................

Data

0000 ff ff ff ff ff ff aa bb cc dd 00 00 08 06 00 01  ................

0010 08 00 06 04 00 01 aa bb cc dd 00 00 c0 a8 01 0a  ................

0020 ff ff ff ff ff ff c0 a8 01 14 00 01 02 03 04 05  ................

0030 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11              ............

Meta-data是被系统内部使用的,Data输出是真实数据包的信息. 以下命令将使用Meta-data 0070开始的前16bits.

* IIF=Interface ID Factory

3850-2#show platform port-asic ifm iif-id 0x0104d88000000033

Interface Table

Interface IIF-ID        : 0x0104d88000000033

Interface Name          : Gi2/0/20

Interface Block Pointer : 0x514d2f70

Interface State         : READY

Interface Stauts        : IFM-ADD-RCVD, FFM-ADD-RCVD

Interface Ref-Cnt       : 6

Interface Epoch         : 0

Interface Type          : ETHER

Port Type         : SWITCH PORT

Port Location     : LOCAL

Slot              : 2

Unit              : 20

Slot Unit         : 20

Acitve            : Y

SNMP IF Index     : 22

GPN               : 84

EC Channel        : 0

EC Index          : 0

ASIC              : 0

ASIC Port         : 14

Port LE Handle    : 0x514cd990

Non Zero Feature Ref Counts

FID : 48(AL_FID_L2_PM), Ref Count : 1

FID : 77(AL_FID_STATS), Ref Count : 1

FID : 51(AL_FID_L2_MATM), Ref Count : 1

FID : 13(AL_FID_SC), Ref Count : 1

FID : 26(AL_FID_QOS), Ref Count : 1

Sub block information

FID : 48(AL_FID_L2_PM), Private Data : 0x54072618

FID : 26(AL_FID_QOS), Private Data : 0x514d31b8

从以上输出可以看到ARP数据包来源于接口Gi2/0/20. 此时,如果关闭这个接口,将解决这个问题并降低CPU利用率.

第四步:使用FED tracing

在第3步讨论的方法的缺点是只可以解析列队中最后一个包,也许并不是真正导致CPU高的数据包.

有一个更好的排错方法是使用 FED tracing, 可以将FED送上CPU的数据包进行抓包.

=====

步骤:

=====

1/ 需要enable detail tracking, 才能抓包

3850-2#set trace control fed-punject-detail enable

2/ 调整抓包buffer. 按需调整detail tracing的buffer.默认buffer大小是32768.

3850-2#show mgmt-infra trace settings fed-punject-detail

One shot Trace Settings:

Buffer Name: fed-punject-detail

Default Size: 32768

Current Size: 32768

Traces Dropped due to internal error: No

Total Entries Written: 0

One shot mode: No

One shot and full: No

Disabled: False

可以通过以下命令修改buffer大小

3850-2#set trace control fed-punject-detail buffer-size <buffer size>

3850-2#set trace control fed-punject-detail buffer-size ?

<8192-67108864>  The new desired buffer size, in bytes

default          Reset trace buffer size to default

3/ 添加抓包filter. 你可以添加不同的filter,并且使用match all 或者match any来混合使用这些filter进行抓包.

3850-2#set trace fed-punject-detail direction rx filter_add <filter>

 

3850-2#set trace fed-punject-detail direction rx filter_add ?

cpu-queue  rxq 0..31

field      field

offset     offset

3850-2#set trace fed-punject-detail direction rx ?

Clear_all       Clear all debug configured

Dump_all        Dump all debug info: on

Dump_all_off    Dump all debug info: off

Filter_add      Add debug filter condition

Filter_clear    Clear a debug filter configured

Filter_disable  Disable configured filter condition(s)

Filter_enable   Enable configured filter condition(s)

Match_all       Match all configured filter conditions

Match_any       Match any configured filter condition

Show_all        Show all debug configured

在第二步案例分析中, 我们看到Queue16有大量数据包送上CPU, 所以需要查看这个queue,看看哪些数据包被送上CPU了.

使用以下命令去设置查看哪个cpu queue

3850-2#set trace fed-punject-detail direction rx filter_add cpu-queue <start queue> <end queue>

 

例如:

3850-2#set trace fed-punject-detail direction rx filter_add cpu-queue 16 16

使用match all 或者match any来混合使用已经定义了的filter来进行抓包

3850-2#set trace fed-punject-detail direction rx match_all

3850-2#set trace fed-punject-detail direction rx filter_enable

4/显示抓到的数据包

使用show mgmt-infra trace messages fed-punject-detail命令查看抓到的包.

3850-2#show mgmt-infra trace messages fed-punject-detail

[11/25/13 07:05:53.814 UTC 2eb0c9 5661]

00 00 00 00 00 4e 00 40 07 00 02 08 00 00 51 3b

00 00 00 00 00 01 00 00 03 00 00 00 00 00 00 01

00 00 00 00 20 00 00 0e 00 00 00 00 00 01 00 74

00 00 00 04 00 54 41 02 00 00 00 00 00 00 00 00

[11/25/13 07:05:53.814 UTC 2eb0ca 5661]

ff ff ff ff ff ff aa bb cc dd 00 00 08 06 00 01

08 00 06 04 00 01 aa bb cc dd 00 00 c0 a8 01 0a

ff ff ff ff ff ff c0 a8 01 14 00 01 02 03 04 05

06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 f6 b9 10 32

[11/25/13 07:05:53.814 UTC 2eb0cb 5661] Frame descriptors:

[11/25/13 07:05:53.814 UTC 2eb0cc 5661]

=========

fdFormat=0x4    systemTtl=0xe

loadBalHash1=0x8        loadBalHash2=0x8

spanSessionMap=0x0      forwardingMode=0x0

destModIndex=0x0        skipIdIndex=0x4

srcGpn=0x54     qosLabel=0x41

srcCos=0x0      ingressTranslatedVlan=0x3

bpdu=0x0        spanHistory=0x0

sgt=0x0 fpeFirstHeaderType=0x0

srcVlan=0x1     rcpServiceId=0x2

wccpSkip=0x0    srcPortLeIndex=0xe

cryptoProtocol=0x0      debugTagId=0x0

vrfId=0x0       saIndex=0x0

pendingAfdLabel=0x0     destClient=0x1

appId=0x0       finalStationIndex=0x74

decryptSuccess=0x0      encryptSuccess=0x0

rcpMiscResults=0x0      stackedFdPresent=0x0

spanDirection=0x0       egressRedirect=0x0

redirectIndex=0x0       exceptionLabel=0x0

destGpn=0x0     inlineFd=0x0

suppressRefPtrUpdate=0x0        suppressRewriteSideEfects=0x0

cmi2=0x0        currentRi=0x1

currentDi=0x513b        dropIpUnreachable=0x0

srcZoneId=0x0   srcAsicId=0x0

originalDi=0x0  originalRi=0x0

srcL3IfIndex=0x2        dstL3IfIndex=0x0

dstVlan=0x0     frameLength=0x40

fdCrc=0x7       tunnelSpokeId=0x0

 

=========

[11/25/13 07:05:53.814 UTC 2eb0cd 5661]

[11/25/13 07:05:53.814 UTC 2eb0ce 5661] PUNT PATH (fed_punject_rx_process_packet:

830):RX: Q: 16, Tag: 65561

[11/25/13 07:05:53.814 UTC 2eb0cf 5661] PUNT PATH (fed_punject_get_physical_iif:

579):RX: Physical IIF-id 0x104d88000000033

[11/25/13 07:05:53.814 UTC 2eb0d0 5661] PUNT PATH (fed_punject_get_src_l3if_index:

434):RX: L3 IIF-id 0x101b6800000004f

[11/25/13 07:05:53.814 UTC 2eb0d1 5661] PUNT PATH (fed_punject_fd_2_pds_md:478):

RX: l2_logical_if = 0x0

[11/25/13 07:05:53.814 UTC 2eb0d2 5661] PUNT PATH (fed_punject_get_source_cos:638):

RX: Source Cos 0

[11/25/13 07:05:53.814 UTC 2eb0d3 5661] PUNT PATH (fed_punject_get_vrf_id:653):

RX: VRF-id 0

[11/25/13 07:05:53.814 UTC 2eb0d4 5661] PUNT PATH (fed_punject_get_src_zoneid:667):

RX: Zone-id 0

[11/25/13 07:05:53.814 UTC 2eb0d5 5661] PUNT PATH (fed_punject_fd_2_pds_md:518):

RX: get_src_zoneid failed

[11/25/13 07:05:53.814 UTC 2eb0d6 5661] PUNT PATH (fed_punject_get_acl_log_direction:

695): RX: : Invalid CMI2

[11/25/13 07:05:53.814 UTC 2eb0d7 5661] PUNT PATH (fed_punject_fd_2_pds_md:541):RX:

get_acl_log_direction failed

[11/25/13 07:05:53.814 UTC 2eb0d8 5661] PUNT PATH (fed_punject_get_acl_full_direction:

724):RX: DI 0x513b ACL Full Direction 1

[11/25/13 07:05:53.814 UTC 2eb0d9 5661] PUNT PATH (fed_punject_get_source_sgt:446):

RX: Source SGT 0

[11/25/13 07:05:53.814 UTC 2eb0da 5661] PUNT PATH (fed_punject_get_first_header_type:680):

RX: FirstHeaderType 0

[11/25/13 07:05:53.814 UTC 2eb0db 5661] PUNT PATH (fed_punject_rx_process_packet:916):

RX: fed_punject_pds_send packet 0x1f00 to IOSd with tag 65561

[11/25/13 07:05:53.814 UTC 2eb0dc 5661] PUNT PATH (fed_punject_rx_process_packet:744):

RX: **** RX packet 0x2360 on qn 16, len 128 ****

[11/25/13 07:05:53.814 UTC 2eb0dd 5661]

buf_no 0 buf_len 128

 

<snip>

以上输出提供了足够信息,让我们知道数据包从哪里来 ,以及含有什么信息.

ff ff ff ff ff ff - 目的 MAC地址

aa bb cc dd 00 00 - 源 MAC地址

现在可以根据源MAC地址来找到相应的接口.

在log中, 也包含了非常有用的信息:

[11/25/13 07:05:53.814 UTC 2eb0ce 5661] PUNT PATH (fed_punject_rx_process_packet:

830):RX: Q: 16, Tag: 65561

[11/25/13 07:05:53.814 UTC 2eb0cf 5661] PUNT PATH (fed_punject_get_physical_iif:

579):RX: Physical IIF-id 0x104d88000000033

通过第一条log很容易看到数据包来自哪个queue和tag.

第二条log更有用, 因为它包含了源接口的IIF-ID, 可以使用以下命令找到源接口.

3850-2#show platform port-asic ifm iif-id 0x0104d88000000033

Interface Table

Interface IIF-ID        : 0x0104d88000000033

Interface Name          : Gi2/0/20

Interface Block Pointer : 0x514d2f70

Interface State         : READY

Interface Stauts        : IFM-ADD-RCVD, FFM-ADD-RCVD

Interface Ref-Cnt       : 6

Interface Epoch         : 0

Interface Type          : ETHER

Port Type         : SWITCH PORT

Port Location     : LOCAL

Slot              : 2

Unit              : 20

Slot Unit         : 20

Acitve            : Y

SNMP IF Index     : 22

GPN               : 84

EC Channel        : 0

EC Index          : 0

ASIC              : 0

ASIC Port         : 14

Port LE Handle    : 0x514cd990

Non Zero Feature Ref Counts

FID : 48(AL_FID_L2_PM), Ref Count : 1

FID : 77(AL_FID_STATS), Ref Count : 1

FID : 51(AL_FID_L2_MATM), Ref Count : 1

FID : 13(AL_FID_SC), Ref Count : 1

FID : 26(AL_FID_QOS), Ref Count : 1

Sub block information

FID : 48(AL_FID_L2_PM), Private Data : 0x54072618

FID : 26(AL_FID_QOS), Private Data : 0x514d31b8

 

 

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