透過UTD和URL過濾排除資料路徑處理故障
目錄
簡介
本檔案介紹如何在IOS® XE WAN邊緣路由器上排查統一威脅防禦(UTD)(也稱為Snort和統一資源定位器(URL)過濾)故障。
背景資訊
Snort是世界上部署最廣泛的入侵防禦系統(IPS)。自2013年以來，建立商業版Snort軟體的公司Sourcefire被思科收購。從16.10.1 IOS® XE SD-WAN軟體開始，UTD/URF過濾容器已增加到Cisco SD-WAN解決方案。
容器使用app-nav架構註冊到IOS®XE路由器。該過程的說明不在本檔案的範圍之內。
資料路徑高級檢視
在較高層級，資料路徑如下所示：
從LAN/WAN到容器
流量來自LAN端。由於IOS® XE知道容器處於正常狀態，因此它會將流量轉移到UTD容器。此轉移使用VirtualPortGroup1介面作為輸出介面，將封包封裝在通用路由封裝(GRE)通道中。
路由器使用原因：64 （服務引擎封包）執行「PUNT」動作，並將流量傳送到路由處理器(RP)。增加一個傳送報頭，並使用朝向容器「[internal0/0/svc_eng：0]」的內部輸出介面將資料包傳送到容器
在此階段，Snort會利用其前處理器和規則集。可以根據處理結果丟棄或轉發資料包。
從容器到LAN/WAN
假設流量不應被丟棄，則資料包會在UTD處理之後轉發迴路由器。它在Quantum Flow Processor (QFP)上顯示為來自Tunnel6000001。然後由路由器進行處理，並且必須（希望）路由到WAN介面。
容器控制IOS® XE資料路徑中UTD檢查的轉移結果。
例如，對於HTTPS流，前處理器有興趣檢視具有TLS協商的伺服器Hello/客戶端Hello資料包。然後，由於檢查TLS加密流量幾乎沒有價值，因此流量不會被重定向。
資料路徑深入分析
從Packet Tracer的角度來看，將看到這些操作集（192.168.16.254是Web客戶端）：
debug platform condition ipv4 192.168.16.254/32 both debug platform condition start debug platform packet-trace packet 256 fia-trace data-size 3000
從LAN或WAN端到容器的入口資料包
在此特定案例中，追蹤的封包來自LAN。從重定向的角度來看，如果流量來自LAN或WAN，則存在相關差異。
客戶端嘗試透過HTTPS訪問www.cisco.com
cedge6#show platform packet-trace packet 14
Packet: 14 CBUG ID: 3849209
Summary
Input : GigabitEthernet2
Output : internal0/0/svc_eng:0
State : PUNT 64 (Service Engine packet)
Timestamp
Start : 1196238208743284 ns (05/08/2019 10:50:36.836575 UTC)
Stop : 1196238208842625 ns (05/08/2019 10:50:36.836675 UTC)
Path Trace
Feature: IPV4(Input)
Input : GigabitEthernet2
Output : <unknown>
Source : 192.168.16.254
Destination : 203.0.113.67
Protocol : 6 (TCP)
SrcPort : 35568
DstPort : 443
Feature: DEBUG_COND_INPUT_PKT
Entry : Input - 0x8177c67c
Input : GigabitEthernet2
Output : <unknown>
Lapsed time : 2933 ns
<snip>
與條件匹配的流量在介面GigabitEthernet2上以入口進行跟蹤。
Feature: UTD Policy (First FIA)
Action : Divert
Input interface : GigabitEthernet2
Egress interface: GigabitEthernet3
Feature: OUTPUT_UTD_FIRST_INSPECT
Entry : Output - 0x817cc5b8
Input : GigabitEthernet2
Output : GigabitEthernet3
Lapsed time : 136260 ns
Feature: UTD Inspection
Action : Divert <<<<<<<<<<<<<<<<<<<<<<<<<<<<
Input interface : GigabitEthernet2
Egress interface: GigabitEthernet3
Feature: OUTPUT_UTD_FINAL_INSPECT
Entry : Output - 0x817cc5e8
Input : GigabitEthernet2
Output : GigabitEthernet3
Lapsed time : 43546 ns
<snip>
在輸出介面的輸出功能呼叫陣列(FIA)上，UTD FIA決定將此封包轉向容器。
Feature: IPV4_OUTPUT_LOOKUP_PROCESS_EXT
Entry : Output - 0x81781bb4
Input : GigabitEthernet2
Output : Tunnel6000001
<removed>
Feature: IPV4_OUTPUT_LOOKUP_PROCESS_EXT
Entry : Output - 0x81781bb4
Input : GigabitEthernet2
Output : Tunnel6000001
<removed>
Feature: IPV4_INPUT_LOOKUP_PROCESS_EXT
Entry : Output - 0x8177c698
Input : Tunnel6000001
Output : VirtualPortGroup1
Lapsed time : 880 ns
<snip>
封包會被置於預設的通道通道上600001並透過VPG1介面進行路由。在此階段，原始資料包採用GRE封裝。
Feature: OUTPUT_SERVICE_ENGINE
Entry : Output - 0x817c6b10
Input : Tunnel6000001
Output : internal0/0/svc_eng:0
Lapsed time : 15086 ns
<removed>
Feature: INTERNAL_TRANSMIT_PKT_EXT
Entry : Output - 0x8177c718
Input : Tunnel6000001
Output : internal0/0/svc_eng:0
Lapsed time : 43986 ns
資料包在內部傳輸到容器。
在路由器自身中越深入，流量到達路由處理器介面eth2上的內部VRF：
[cedge6:/]$ chvrf utd ifconfig
eth0 Link encap:Ethernet HWaddr 54:0e:00:0b:0c:02
inet6 addr: fe80::560e:ff:fe0b:c02/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1375101 errors:0 dropped:0 overruns:0 frame:0
TX packets:1366614 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:96520127 (92.0 MiB) TX bytes:96510792 (92.0 MiB)
eth1 Link encap:Ethernet HWaddr 00:1e:e6:61:6d:ba
inet addr:192.168.1.2 Bcast:192.168.1.3 Mask:255.255.255.252
inet6 addr: fe80::21e:e6ff:fe61:6dba/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:2000 Metric:1
RX packets:1069 errors:0 dropped:0 overruns:0 frame:0
TX packets:2001 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:235093 (229.5 KiB) TX bytes:193413 (188.8 KiB)
eth2 Link encap:Ethernet HWaddr 00:1e:e6:61:6d:b9
inet addr:192.0.2.2 Bcast:192.0.2.3 Mask:255.255.255.252
inet6 addr: fe80::21e:e6ff:fe61:6db9/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:2000 Metric:1
RX packets:2564233 errors:0 dropped:0 overruns:0 frame:0
TX packets:2564203 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:210051658 (200.3 MiB) TX bytes:301467970 (287.5 MiB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
Eth0是連線到IOSd進程的傳輸進程間通訊(TIPC)介面。OneP通道透過它來在IOSd和UTD容器之間來回傳遞配置和通知。
根據您關心的問題，「eth2 [容器介面]」橋接到「VPG1 [ 192.0.2.1/192.168.2.2 ]」是vManage推送到IOS-XE和容器的地址。
如果運行tcpdump，則會看到傳輸到容器的GRE封裝流量。GRE封裝包括VPATH報頭。
[cedge6:/]$ chvrf utd tcpdump -nNvvvXi eth2 not udp
tcpdump: listening on eth2, link-type EN10MB (Ethernet), capture size 262144 bytes
06:46:56.350725 IP (tos 0x0, ttl 255, id 35903, offset 0, flags [none], proto GRE (47), length 121)
192.0.2.1 > 192.0.2.2: GREv0, Flags [none], length 101
gre-proto-0x8921
0x0000: 4500 0079 8c3f 0000 ff2f ab12 c000 0201 E..y.?.../......
0x0010: c000 0202 0000 8921 4089 2102 0000 0000 .......!@.!.....
0x0020: 0000 0000 0300 0001 0000 0000 0000 0000 ................
0x0030: 0004 0800 e103 0004 0008 0000 0001 0000 ................
0x0040: 4500 0039 2542 4000 4011 ce40 c0a8 10fe E..9%B@.@..@....
0x0050: ad26 c864 8781 0035 0025 fe81 cfa8 0100 .&.d...5.%......
0x0060: 0001 0000 0000 0000 0377 7777 0363 6e6e .........www.cnn
0x0070: 0363 6f6d 0000 0100 01 .com.....
從容器到LAN或WAN端的入口資料包
在Snort處理之後（假設流量不會被丟棄），它會重新注入回QFP轉發路徑。
cedge6#show platform packet-trace packet 15 Packet: 15 CBUG ID: 3849210 Summary Input : Tunnel6000001 Output : GigabitEthernet3 State : FWD
通道600001來自容器的出口介面。
Feature: OUTPUT_UTD_FIRST_INSPECT_EXT
Entry : Output - 0x817cc5b8
Input : GigabitEthernet2
Output : GigabitEthernet3
Lapsed time : 2680 ns
Feature: UTD Inspection
Action : Reinject
Input interface : GigabitEthernet2
Egress interface: GigabitEthernet3
Feature: OUTPUT_UTD_FINAL_INSPECT_EXT
Entry : Output - 0x817cc5e8
Input : GigabitEthernet2
Output : GigabitEthernet3
Lapsed time : 12933 ns
由於流量已經過檢查，因此路由器知道這是重新注入。
Feature: NAT
Direction : IN to OUT
Action : Translate Source
Steps :
Match id : 1
Old Address : 192.168.16.254 35568
New Address : 172.16.16.254 05062
流量經過NAT處理並傳向Internet。
Feature: MARMOT_SPA_D_TRANSMIT_PKT
Entry : Output - 0x8177c838
Input : GigabitEthernet2
Output : GigabitEthernet3
Lapsed time : 91733 ns
UTD流日誌記錄與Packet-trace整合
IOS-XE 17.5.1增加了UTD流日誌記錄與packet-trace的整合，其中path-trace輸出將包括UTD判定。判定可為下列其中一項，例如：
- UTD決定阻止/告知Snort的資料包
- 允許/丟棄URLF
- 封鎖/允許AMP
對於沒有UTD判定資訊的資料包，不會記錄流日誌記錄資訊。另請注意，由於潛在的負面效能影響，沒有記錄IPS/IDS透過/允許判定。
要啟用流日誌記錄整合，請將CLI外掛模板與以下內容配合使用：
utd engine standard multi-tenancy
utd global
flow-logging all
不同裁決的輸出示例：
URL查詢超時：
show platform packet-trace pack all | sec Packet: | Feature: UTD Inspection
Packet: 31 CBUG ID: 12640
Feature: UTD Inspection
Action : Reinject
Input interface : GigabitEthernet2
Egress interface : GigabitEthernet3
Flow-Logging Information :
URLF Policy ID : 1
URLF Action : Allow(1)
URLF Reason : URL Lookup Timeout(8)
URLF信譽和判定允許：
Packet: 21 CBUG ID: 13859
Feature: UTD Inspection
Action : Reinject
Input interface : GigabitEthernet3
Egress interface : GigabitEthernet2
Flow-Logging Information :
URLF Policy ID : 1
URLF Action : Allow(1)
URLF Reason : No Policy Match(4)
URLF Category : News and Media(63)
URLF Reputation : 81
URLF信譽和判定區塊：
Packet: 26 CBUG ID: 15107
Feature: UTD Inspection
Action : Reinject
Input interface : GigabitEthernet3
Egress interface : GigabitEthernet2
Flow-Logging Information :
URLF Policy ID : 1
URLF Action : Block(2)
URLF Reason : Category/Reputation(3)
URLF Category : Social Network(14)
URLF Reputation : 81
先決條件：
檢查UTD版本是否與IOS XE相容
cedge7#sh utd eng sta ver
UTD Virtual-service Name: utd
IOS-XE Recommended UTD Version: 1.10.33_SV2.9.16.1_XEmain
IOS-XE Supported UTD Regex: ^1\.10\.([0-9]+)_SV(.*)_XEmain$
UTD Installed Version: 1.0.2_SV2.9.16.1_XE17.5 (UNSUPPORTED)
如果顯示「UNSUPPORTED」，則需要首先升級容器，然後再開始故障排除。
檢查容器中是否有有效的名稱伺服器配置
某些安全服務（如AMP和URLF）要求UTD容器能夠解析雲服務提供商的名稱，因此UTD容器必須具有有效的名稱伺服器配置。檢查系統shell下容器的resolv.conf檔案即可驗證這一點：
cedge:/harddisk/virtual-instance/utd/rootfs/etc]$ more resolv.conf
nameserver 208.67.222.222
nameserver 208.67.220.220
nameserver 8.8.8.8
問題1
根據設計，統一執行緒防禦必須使用直接網際網路訪問使用案例(DIA)進行完全配置。容器將嘗試解析api.bcti.brightcloud.com以查詢URL信譽和類別。在此範例中，即使套用正確的組態，也不會封鎖任何檢查的URL
疑難排解
請始終檢視容器日誌檔案。
cedge6#app-hosting move appid utd log to bootflash:
Successfully moved tracelog to bootflash:
iox_utd_R0-0_R0-0.18629_0.20190501005829.bin.gz
這會將記錄檔複製到快閃記憶體本身。
可以使用以下命令顯示日誌：
cedge6# more /compressed iox_utd_R0-0_R0-0.18629_0.20190501005829.bin.gz
顯示日誌會顯示：
2019-04-29 16:12:12 ERROR: Cannot resolve host api.bcti.brightcloud.com: Temporary failure in name resolution
2019-04-29 16:17:52 ERROR: Cannot resolve host api.bcti.brightcloud.com: Temporary failure in name resolution
2019-04-29 16:23:32 ERROR: Cannot resolve host api.bcti.brightcloud.com: Temporary failure in name resolution
2019-04-29 16:29:12 ERROR: Cannot resolve host api.bcti.brightcloud.com: Temporary failure in name resolution
2019-04-29 16:34:52 ERROR: Cannot resolve host api.bcti.brightcloud.com: Temporary failure in name resolution
2019-04-29 16:40:27 ERROR: Cannot resolve host api.bcti.brightcloud.com: Temporary failure in name resolution
預設情況下，vManage調配使用OpenDNS伺服器的容器[208.67.222.222和208.67.220.220]
根本原因
用於解析api.bcti.brightcloud.com的域名系統(DNS)流量被丟棄在容器和umbrella DNS伺服器之間的某個路徑中。請務必確保兩個DNS均可訪問。
問題2
在電腦和Internet資訊類別網站應被阻止的場景中，對www.cisco.com的http請求會被正確丟棄，而對HTTPS請求則不會。
疑難排解
如前所述，流量被傳送至容器。當此流封裝在GRE報頭中時，軟體將附加VPATH報頭。利用此報頭，系統允許向容器自身傳遞調試條件。 這表示UTD貨櫃可提供良好服務。
在本場景中，客戶端IP地址是192.168,16.254。對於來自我的客戶端的流量，讓我們排除容器自身的Snort處理故障。
debug platform condition ipv4 192.168.16.254/32 both
debug platform condition feature utd controlplane submode serviceplane-web-filtering level verbose
debug platform condition start
這組命令指示IOS-XE標籤來自或發往192.168.16.254的流量。這將允許透過VPATH報頭將調試與我標誌傳遞給容器
Snort僅調試特定流，而其它流則正常處理。
在此階段，您可以要求使用者觸發從客戶端到www.cisco.com的流量。
下一步是擷取記錄：
app-hosting move appid utd log to bootflash:
對於HTTP流量，snort HTTP前處理器在get請求中發現URL。
2019-04-26 13:04:27.773:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 39540, p->dst_port = 80
2019-04-26 13:04:27.793:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 80, p->dst_port = 39540
2019-04-26 13:04:27.794:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 39540, p->dst_port = 80
2019-04-26 13:04:27.794:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 39540, p->dst_port = 80
2019-04-26 13:04:27.794:(#1):SPP-URL-FILTERING got utmdata_p
2019-04-26 13:04:27.794:(#1):SPP-URL-FILTERING HTTP Callback, direction = 00000080
2019-04-26 13:04:27.795:(#1):SPP-URL-FILTERING White list regex match not enabled
2019-04-26 13:04:27.795:(#1):SPP-URL-FILTERING Black list regex match not enabled
2019-04-26 13:04:27.795:(#1):SPP-URL-FILTERING URL database Request: url_len = 12, msg overhead 12 url: www.cisco.com/ <<<<<<<
2019-04-26 13:04:27.795:(#1):SPP-URL-FILTERING Send to URL database: req_id=0x10480047
2019-04-26 13:04:27.795:(#1):SPP-URL-FILTERING Sent to URL database 24 bytes
2019-04-26 13:04:27.795:(#1):SPP-URL-FILTERING Send to URL database done, idx: 71, URL: www.cisco.com/
2019-04-26 13:04:27.795:(#1):SPP-URL-FILTERING Received from URL database 24 bytes
2019-04-26 13:04:27.816:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 80, p->dst_port = 39540
2019-04-26 13:04:27.816:(#1):SPP-URL-FILTERING Found UTMData at 0x007f8d9ee80878, action = 0000000a
2019-04-26 13:04:27.816:(#1):SPP-URL-FILTERING Utm_verdictProcess: vrf_id 1, category 0x63, score 81 <<<<<<<<<<<<<<<<<<<<<<<<<
2019-04-26 13:04:27.816:(#1):SPP-URL-FILTERING Category 0x3f <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
2019-04-26 13:04:27.816:(#1):SPP-URL-FILTERING index = 63, action = 1 <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
2019-04-26 13:04:27.816:(#1):SPP-URL-FILTERING Blocking category = 0x3f <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
對於https流量，已使用HTTPS前處理器從伺服器hello中提取目標DNS
2019-05-01 00:56:18.870:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 35322, p->dst_port = 443
2019-05-01 00:56:18.886:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 443, p->dst_port = 35322
2019-05-01 00:56:18.887:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 35322, p->dst_port = 443
2019-05-01 00:56:18.887:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 35322, p->dst_port = 443
2019-05-01 00:56:18.903:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 443, p->dst_port = 35322
2019-05-01 00:56:18.906:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 443, p->dst_port = 35322
2019-05-01 00:56:18.906:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 35322, p->dst_port = 443
2019-05-01 00:56:18.907:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 443, p->dst_port = 35322
2019-05-01 00:56:18.907:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 443, p->dst_port = 35322
2019-05-01 00:56:18.907:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 443, p->dst_port = 35322
2019-05-01 00:56:18.908:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 443, p->dst_port = 35322
2019-05-01 00:56:18.908:(#1):SPP-URL-FILTERING utm_sslLookupCallback
2019-05-01 00:56:18.908:(#1):SPP-URL-FILTERING got utmdata_p
2019-05-01 00:56:18.909:(#1):SPP-URL-FILTERING White list regex match not enabled
2019-05-01 00:56:18.909:(#1):SPP-URL-FILTERING Black list regex match not enabled
2019-05-01 00:56:18.909:(#1):SPP-URL-FILTERING URL database Request: url_len = 11, msg overhead 12 url: www.cisco.com <<<<<<<<
2019-05-01 00:56:18.909:(#1):SPP-URL-FILTERING Send to URL database: req_id=0x10130012
2019-05-01 00:56:18.909:(#1):SPP-URL-FILTERING Sent to URL database 23 bytes
2019-05-01 00:56:18.909:(#1):SPP-URL-FILTERING Send to URL database done, idx: 18, URL: www.cisco.com
2019-05-01 00:56:18.909:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 443, p->dst_port = 35322
2019-05-01 00:56:18.910:(#1):SPP-URL-FILTERING Found UTMData at 0x007f1d9c479640, action = 00000008
2019-05-01 00:56:18.910:(#1):SPP-URL-FILTERING Verdict very late, in queryig state 2, idx=18
2019-05-01 00:56:18.910:(#1):SPP-URL-FILTERING UTM preprocessor p->src_port = 443, p->dst_port = 35322
2019-05-01 00:56:18.910:(#1):SPP-URL-FILTERING Found UTMData at 0x007f1d9c479640, action = 00000009
2019-05-01 00:56:18.910:(#1):SPP-URL-FILTERING Verdict very late, in queryig state 2, idx=18 <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
2019-05-01 00:56:18.909:(#1):SPP-URL-FILTERING Received from URL database 24 bytes
此處您看不到正在觸發的阻止頁，因為軟體未報告Webroot查詢的結果。
根本原因
CSCvo77664 
「UTD URL filtering for category lookup is failed with webroot lookup failure」是關於軟體尚未對我們的URL裁決請求做出響應時，資料流被洩漏。
問題3
在此案例中，會間歇性捨棄URL-Filtering應允許的Web瀏覽工作階段（因其分類）。例如，即使允許類別「web search engine」，仍無法隨機訪問www.google.com。
疑難排解
步驟1：收集一般統計資料
cedge7#show utd engine standard statistics internal
*************Engine #1*************
<removed>
===============================================================================
HTTP Inspect - encodings (Note: stream-reassembled packets included): <<<<<<<<<< generic layer7 HTTP statistics
POST methods: 0
GET methods: 7
HTTP Request Headers extracted: 7
HTTP Request Cookies extracted: 0
Post parameters extracted: 0
HTTP response Headers extracted: 6
HTTP Response Cookies extracted: 0
Unicode: 0
Double unicode: 0
Non-ASCII representable: 0
Directory traversals: 0
Extra slashes ("//"): 0
Self-referencing paths ("./"): 0
HTTP Response Gzip packets extracted: 0
Gzip Compressed Data Processed: n/a
Gzip Decompressed Data Processed: n/a
Http/2 Rebuilt Packets: 0
Total packets processed: 13
<removed>
===============================================================================
SSL Preprocessor: <<<<<<<<<< generic layer7 SSL statistics
SSL packets decoded: 38
Client Hello: 8
Server Hello: 8
Certificate: 2
Server Done: 6
Client Key Exchange: 2
Server Key Exchange: 2
Change Cipher: 10
Finished: 0
Client Application: 2
Server Application: 11
Alert: 0
Unrecognized records: 11
Completed handshakes: 0
Bad handshakes: 0
Sessions ignored: 4
Detection disabled: 1
<removed>
UTM Preprocessor Statistics < URL filtering statistics including
---------------------------
URL Filter Requests Sent: 11
URL Filter Response Received: 5
Blacklist Hit Count: 0
Whitelist Hit Count: 0
Reputation Lookup Count: 5
Reputation Action Block: 0
Reputation Action Pass: 5
Reputation Action Default Pass: 0
Reputation Action Default Block: 0
Reputation Score None: 0
Reputation Score Out of Range: 0
Category Lookup Count: 5
Category Action Block: 0
Category Action Pass: 5
Category Action Default Pass: 0
Category None: 0
UTM Preprocessor Internal Statistics
------------------------------------
Total Packets Received: 193
SSL Packet Count: 4
Action Drop Flow: 0
Action Reset Session: 0
Action Block: 0
Action Pass: 85
Action Offload Session: 0
Invalid Action: 0
No UTM Tenant Persona: 0
No UTM Tenant Config: 0
URL Lookup Response Late: 4 <<<<< Explanation below
URL Lookup Response Very Late: 64 <<<<< Explanation below
URL Lookup Response Extremely Late: 2 <<<<< Explanation below
Response Does Not Match Session: 2 <<<<< Explanation below
No Response When Freeing Session: 1
First Packet Not From Initiator: 0
Fail Open Count: 0
Fail Close Count : 0
UTM Preprocessor Internal Global Statistics
-------------------------------------------
Domain Filter Whitelist Count: 0
utmdata Used Count: 11
utmdata Free Count: 11
utmdata Unavailable: 0
URL Filter Response Error: 0
No UTM Tenant Map: 0
No URL Filter Configuration : 0
Packet NULL Error : 0
URL Database Internal Statistics
--------------------------------
URL Database Not Ready: 0
Query Successful: 11
Query Successful from Cloud: 6 <<< 11 queries were succesful but 6 only are queried via brightcloud. 5 (11-6) queries are cached
Query Returned No Data: 0 <<<<<< errors
Query Bad Argument: 0 <<<<<< errors
Query Network Error: 0 <<<<<< errors
URL Database UTM disconnected: 0
URL Database request failed: 0
URL Database reconnect failed: 0
URL Database request blocked: 0
URL Database control msg response: 0
URL Database Error Response: 0
===============================================================================
Files processed: none
===============================================================================
- 「late request」-表示HTTP GET或HTTPS客戶端/伺服器證書[可從中提取SNI/DN以進行查詢。轉發延遲請求。
- 「非常晚請求」-表示某種型別的會話丟棄計數器，在該計數器中，流中的其他資料包將被丟棄，直到路由器收到來自Brightcloud的URL判定。換句話說，初始HTTP GET之後或SSL流程其餘部分的任何內容都將被丟棄，直到收到判定結果。
- 「極晚請求」-重設Brightcloud會話查詢時未提供判定結果。版本< 17.2.1的會話將在60秒後超時。從17.2.1開始，到Brightcloud的查詢會話將在2秒後超時。[透過CSCvr98723 UTD：兩秒後超時URL請求]
在此場景中，我們看到突出顯示不良情況的全局計數器。
步驟2：檢視應用程式日誌檔案
統一執行緒檢測軟體將在應用程式日誌檔案中記錄事件。
cedge6#app-hosting move appid utd log to bootflash:
Successfully moved tracelog to bootflash:
iox_utd_R0-0_R0-0.18629_0.20190501005829.bin.gz
該命令將提取容器應用程式日誌檔案並將其儲存到快閃記憶體中。
可以使用以下命令顯示日誌：
cedge6# more /compressed iox_utd_R0-0_R0-0.18629_0.20190501005829.bin.gz 顯示日誌會顯示：
.....
2020-04-14 17:47:57.504:(#1):SPP-URL-FILTERING txn_id miss match verdict txn_id 245 , utmdata txn_id 0
2020-04-14 17:47:57.504:(#1):SPP-URL-FILTERING txn_id miss match verdict txn_id 248 , utmdata txn_id 0
2020-04-14 17:47:57.504:(#1):SPP-URL-FILTERING txn_id miss match verdict txn_id 249 , utmdata txn_id 0
2020-04-14 17:47:57.504:(#1):SPP-URL-FILTERING txn_id miss match verdict txn_id 250 , utmdata txn_id 0
2020-04-14 17:47:57.660:(#1):SPP-URL-FILTERING txn_id miss match verdict txn_id 251 , utmdata txn_id 0
2020-04-14 17:47:57.660:(#1):SPP-URL-FILTERING txn_id miss match verdict txn_id 254 , utmdata txn_id 0
2020-04-14 17:47:57.660:(#1):SPP-URL-FILTERING txn_id miss match verdict txn_id 255 , utmdata txn_id 0
2020-04-14 17:48:05.725:(#1):SPP-URL-FILTERING txn_id miss match verdict txn_id 192 , utmdata txn_id 0
2020-04-14 17:48:37.629:(#1):SPP-URL-FILTERING txn_id miss match verdict txn_id 208 , utmdata txn_id 0
2020-04-14 17:49:55.421:(#1):SPP-URL-FILTERING txn_id miss match verdict txn_id 211 , utmdata txn_id 0
2020-04-14 17:51:40 ERROR: Cannot send to host api.bcti.brightcloud.com: Connection timed out
2020-04-14 17:52:21 ERROR: Cannot send to host api.bcti.brightcloud.com: Connection timed out
2020-04-14 17:52:21 ERROR: Cannot send to host api.bcti.brightcloud.com: Connection timed out
2020-04-14 17:53:56 ERROR: Cannot send to host api.bcti.brightcloud.com: Connection timed out
2020-04-14 17:54:28 ERROR: Cannot send to host api.bcti.brightcloud.com: Connection timed out
2020-04-14 17:54:29 ERROR: Cannot send to host api.bcti.brightcloud.com: Connection timed out
2020-04-14 17:54:37 ERROR: Cannot send to host api.bcti.brightcloud.com: Connection timed out
....
- 「錯誤：無法傳送到主機api.bcti.brightcloud.com」-表示到Brightcloud的查詢會話已超時[60秒< 17.2.1 / 2秒>= 17.2.1]。這是連線到Brightcloud連線錯誤的訊號。
為了演示問題，使用EPC（嵌入式資料包捕獲）可以直觀地顯示連線問題。
- 「SPP-URL-FILTERING txn_id miss match verdict」-此錯誤情況需要多一些解釋。Brightcloud查詢透過POST執行，其中查詢ID由路由器生成
問題4
在此場景中，IPS是UTD中唯一啟用的安全功能，並且客戶遇到了TCP應用的印表機通訊問題。
疑難排解
若要疑難排解此資料路徑問題，請先從發生問題的TCP主機擷取封包。捕獲顯示TCP三次握手成功，但帶有TCP資料的後續資料包似乎已被cEdge路由器丟棄。然後啟用packet-trace，顯示以下內容：
edge#show platform packet-trace summ
Pkt Input Output State Reason
0 Gi0/0/1 internal0/0/svc_eng:0 PUNT 64 (Service Engine packet)
1 Tu2000000001 Gi0/0/2 FWD
2 Gi0/0/2 internal0/0/svc_eng:0 PUNT 64 (Service Engine packet)
3 Tu2000000001 Gi0/0/1 FWD
4 Gi0/0/1 internal0/0/svc_eng:0 PUNT 64 (Service Engine packet)
5 Tu2000000001 Gi0/0/2 FWD
6 Gi0/0/1 internal0/0/svc_eng:0 PUNT 64 (Service Engine packet)
7 Tu2000000001 Gi0/0/2 FWD
8 Gi0/0/2 internal0/0/svc_eng:0 PUNT 64 (Service Engine packet)
9 Gi0/0/2 internal0/0/svc_eng:0 PUNT 64 (Service Engine packet)
上述輸出表明第8個和第9個資料包已轉移至UTD引擎，但它們未重新注入轉發路徑。檢查UTD引擎日誌記錄事件也不會發現任何Snort簽名丟棄。接下來檢查UTD內部統計資訊，其中會顯示由於TCP規範器導致的一些資料包丟棄：
edge#show utd engine standard statistics internal
<snip>
Normalizer drops:
OUTSIDE_PAWS: 0
AHEAD_PAWS: 0
NO_TIMESTAMP: 4
BAD_RST: 0
REPEAT_SYN: 0
WIN_TOO_BIG: 0
WIN_SHUT: 0
BAD_ACK: 0
DATA_CLOSE: 0
DATA_NO_FLAGS: 0
FIN_BEYOND: 0
根本原因
問題的根本原因是印表機上的TCP堆疊行為不當。在TCP三次握手期間協商Timestamp選項時，RFC7323表明TCP必須在每個非<RST>資料包中傳送TSopt選項。對資料包捕獲進行更仔細的檢查會發現，被丟棄的TCP資料包沒有啟用這些選項。透過IOS-XE UTD實施，Snort TCP規範器啟用了block選項，而與IPS或IDS無關。
參考資料
修訂記錄
| 修訂 | 發佈日期 | 意見 |
|---|---|---|
2.0 |
23-Feb-2022 |
增加了與packet-trace和utd btrace日誌檔案更改的流日誌記錄整合 |
1.0 |
10-Jan-2020 |
初始版本 |
意見