Android users in China accessing google.com through circumvention tools report forced redirection to google.cn/m instead of the expected GFW block page. The thread investigates three possible mechanisms: GFW HTTP packet injection, Google's server-side geolocation redirect, or ISP-level interference—each implying a different interception layer.

The redirect from google.com to google.cn/m on proxied Android connections in China is ambiguous as to origin: it may represent GFW-side in-path HTTP redirect packet injection, or Google's server-side geo-redirect responding to signals (device locale, exit IP, or Accept-Language headers) that survive the proxy hop. The thread documents this as an unresolved mechanistic question requiring disambiguation.

Issue body / abstract detection

Chinese users accessing google.com on Android devices through circumvention proxies experience forced HTTP redirects to google.cn/m rather than the expected google.com destination. The behavior is observed specifically on proxied connections, suggesting either in-path HTTP redirect injection by the GFW or Google's own geo-targeting logic acting on IP or device signals that persist through the proxy.

Issue body / screenshot detection

Appending the /ncr (no-country-redirect) parameter to google.com requests successfully bypasses the forced redirect to google.cn/m for Chinese users on circumvention proxies. This workaround operates at the application layer and requires no changes to the underlying transport or proxy configuration.

Issue comments / abstract defense

The redirect behavior varies depending on which proxy type is used, indicating the interception is sensitive to how the proxy mediates the connection rather than being a blanket IP- or DNS-level block. This suggests the triggering condition is protocol- or flow-specific rather than purely destination-based.

Issue thread discussion evaluation

HTTP censorship blockpages in Iran fell into two distinct clusters distinguished by IP TTL values: type NTL1 (TTL 53–55) and type NTE1 (TTL 186–188); TCP RST injections targeting TLS and DNS-over-TCP exhibited the same two TTL ranges. The NTL1 injector was absent on June 11 but present on other days, leading the authors to conclude that an entire injector went offline rather than that a single injection pattern was selectively disabled.

2026-anon-insights-into-iranian §2.2.5 rst-injectionpacket-injectiondpi

Iran's censorship of refraction-networking proxies (Conjure via Psiphon) is not monolithic: different ISPs independently deploy different techniques and timelines. Over 800 million logged Conjure connections from July 2023–February 2025 across 10+ Iranian ASes show TCI (AS58224, ~33% of traffic) uses packet injection, while MCCI/Hamrah-e Avval (AS197207, ~22%) applies IP-based blocking, and some ASes (Parsonline AS16322, Shatel AS31549) show no proxy blocking at all.

2025-alaraj-iran-refraction §4 rst-injectionip-blockingpacket-injectiondpi

The GFI's HTTP and HTTPS filters are now stateful (requiring initial SYN packet with matching sequence numbers) and have been activated on all TCP ports—not only standard ports 80 and 443 as reported by prior studies. This is a significant departure from previous work that found stateless HTTP/HTTPS blocking limited to standard ports. The HTTP filter injects a 403 Forbidden blockpage (not RST packets as used by the GFW), while HTTPS injects a single RST+ACK packet. The GFI also exhibits TCP non-compliance (not requiring a full three-way handshake to trigger filtering), enabling outside-in measurement without in-country servers.

2025-tai-irblock §2.1, §3.2 dpirst-injectionpacket-injectionmiddlebox-interference

The GFI operates three distinct DNS/HTTP injectors with different fake IP addresses (10.10.34.34, 10.10.34.35, 10.10.34.36) and partially overlapping blocklists—mirroring the GFW's triplet-censor architecture. Injector 10.10.34.35 exhibits TTL reflection (injected response TTL = probe TTL − hop count), identical to the GFW. No IP exclusively receives injections from 10.10.34.34 (a smaller, selective component); the two primary injectors 10.10.34.35 and 10.10.34.36 handle the majority of censorship. Different injectors maintain distinct domain blocklists, meaning which domains a user sees as censored depends on routing through their AS.

2025-tai-irblock §5.4, Table 2 dns-poisoningpacket-injectiondpi

Since August 2023, Henan Province has operated its own TLS SNI-based and HTTP Host-based censorship middleboxes that inspect and block traffic exiting the province—a second filtering layer on top of the national GFW. The Henan Firewall is fingerprinted by a unique TCP RST+ACK injection carrying a fixed 10-byte payload (0x01 02 03 04 05 06 07 08 09 00), IP ID 0x0001, and an observed TTL of 58. Unlike the GFW, it injects resets only toward the client, performs no residual censorship, and requires no TCP handshake to trigger. Longitudinal testing (Nov 2023–Mar 2025, Tranco top 1M daily + 227M CZDS domains weekly) found the Henan Firewall blocked a cumulative 4.2 million domains—more than five times the GFW's cumulative blocklist—and at peak blocked ten times more domains than the GFW.

2025-wu-regional-censorship §4.4 / §5 sni-blockingdpipacket-injection

HTTP Request Smuggling—a web-security vulnerability that exploits CL/TE header parsing ambiguities between a front-end (censor) and back-end (web server)—can be systematically repurposed as a censorship circumvention technique. By hiding a censored Host in the body of a benign outer request, the censor parses only the uncensored outer request while the destination server processes both, successfully bypassing HTTP censorship in China (19 vectors), Iran (254 vectors), and Russia (all 2,015 vectors) from the evaluated vantage points.

2024-m-ller-turning §3 / §8 dpikeyword-filteringpacket-injection