In Fujian's Quanzhou China Mobile 5G deployment (2023-04), sapp crashed repeatedly with the DTLS inspection plugin enabled; disabling sip/dtls/fw_dtls/fw_voip plugins stopped it. Root cause: DTLS parsing layer on an old, buggy version, with a full rewrite planned for v22.06 and DTLS inspection told to stay off meanwhile.
4.11日关闭sip,dtls,fw_dtls,fw_voip插件后不重启...福建现场的DTLS解析层版本较低（1.0.1）...DTLS插件正在重构，预计22.06版本提供重构后版本，当前版本建议暂时关闭该功能
Defense implications
- DTLS-based transports (WebRTC, e.g. Snowflake) faced a known-buggy, frequently-crashing DTLS inspection plugin in at least one domestic deployment as of April 2023; do not assume this persists in current versions without re-checking.
Related findings
An internal TSG operations/troubleshooting manual lays out TSG's full traffic pipeline (NIC -> mrzcpd/marsio capture driver -> sapp DPI engine -> firewall/proxy(KNI->TFE)/active-defense/WAN-NAT policy branches) and shows engineers using maat_redis_tool to pull the live Redis-synced blocking policy tables (TSG_SECURITY_COMPILE, TSG_OBJ_IP_ADDR, TSG_OBJ_APP_ID) and filter them by numeric policy/object ID to debug why a block rule isn't firing.
The internal 'MAAT网络流处理配置统一描述框架' engineering manual (v3.1.20, author 郑超, 2021) documents MAAT's Redis-synced rule-compilation framework and its RuleScan/Hyperscan-based pattern-matching engine (libmaatframe.so / librulescan), and records that RuleScan's fast-scan feature caused a production outage on 2019-03-19 and has been disabled ever since.
A dedicated internal "运营商前端分析团队" (Carrier Front-end Analysis Team) produces weekly, carrier-specific traffic-analysis reports explicitly titled "新疆移动流量分析报告" (Xinjiang Mobile Traffic Analysis Report) and "新疆联通流量分析报告" (Xinjiang Unicom Traffic Analysis Report), with instances dated from at least July 2022 through March 2024. One instance (Xinjiang Mobile, 2023-05-15) reports total carrier bandwidth of 4.4Tbps (1Tbps access bandwidth), 27.34PB of weekly throughput, 123 distinct identified application-layer protocols, and a section (4.1, pages 17+) explicitly tracking server IP/location for 28 named overseas apps (BBC, Discord, ESPN, Facebook, Gmail, Google, Hulu, Instagram, Netflix, Reddit, Skype, Telegram, Twitter, Uber, WhatsApp, Wikipedia, YouTube, Zoom, etc.).
A weekly "新疆移动流量分析报告" (Xinjiang Mobile Traffic Analysis Report), authored by the "运营商前端分析团队" (Carrier Front-End Analysis Team), directly ties the SNI/Server-IP overseas- APP report format to the China Mobile Xinjiang branch specifically, and states the pipeline identifies 126 distinct application-layer protocols including multi-layer tunnel nesting such as STUN.DTLS and STUN.RTP.RTCP.DTLS — i.e. it decomposes and classifies nested WebRTC-style transport stacks, not just top-level TLS/QUIC.
Side-by-side internal performance comparison across Xinjiang (China Mobile carrier deployment, hostname cmcc-xj-server1-sapp-244), Fujian (domestic), and Ethiopia (E21) explicitly references the same 'app_sketch_maat' diagnostic log format at all three sites, confirming the identical AppSketch app-fingerprinting stack is used for domestic Xinjiang surveillance and for the exported Ethiopia deployment.
Multiple domestic IDC traffic-monitoring reports rank "Freegate" (a well-known GFW-circumvention tool) as a distinct, named top-10 application by traffic volume alongside Bytedance/Tencent/Alibaba/Baidu, with peak 18.92 Gbps and average 5.9 Gbps in one 2022-07-07 report -- confirming Freegate has its own dedicated app-ID classifier tracked at carrier-comparable traffic scale, not merely a low-volume/rare signature.