As of June 2025, Iran blocks GitHub.com and Telegram but leaves the IP address of google.com reachable and Google Drive accessible. This selective blocking pattern created the operational window for Champa: because google.com is reachable, its AMP cache (cdn.ampproject.org) can be reached by fronting on that IP, then used to proxy connections to otherwise-blocked destinations.

Champa implements adaptive request-rate control: when the AMP cache returns an unexpected response (e.g., HTTP 302), the client halves its polling rate. Once the polling interval exceeds one second the client is considered fully rate-limited and must restart after a multi-hour cooldown. This mechanism keeps the client from burning through its allowance when cache responses degrade.

Troubleshooting section defense

Champa's AMP-cache tunnel delivers at most ~15 KB/s throughput before AMP rate-limiting activates. Sessions last approximately 15 minutes before the rate limit triggers; after that, users must stop the client and wait several hours before resuming.

Issue body (rate-limit description) evaluation

Because GitHub is blocked in Iran, Champa distributes binaries through three alternative channels: a Telegram bot (@getchampabot), Google Drive folders, and curl commands documented in the GitHub issue thread itself. The issue thread remains accessible via Google cache / AMP even when GitHub's domain is blocked, creating a bootstrapping loop.

Download section (§1) deployment

Champa routes connections by specifying an AMP cache URL (https://cdn.ampproject.org/) with google.com as the front domain, then uses the SOCKS5 proxy interface locally. The server's public key is hardcoded in the connection string, providing a fixed authentication token that prevents trivial impersonation of the proxy by a censor injecting a fake server response during active probing.

Setup section (§2) defense

The June 2025 Iran shutdown—carried out during the Iran-Israel war beginning ~June 19—did not use BGP route withdrawals as in 2019. Instead, authorities applied service-level restrictions at the national border: DNS poisoning of foreign destinations, protocol whitelisting permitting only pre-approved domestic services, and DPI to block circumvention-tool traffic. Iran's international traffic fell roughly 90% while the country's BGP routes remained advertised, making the shutdown invisible to BGP-based monitoring systems. OONI measurement volume, which totalled 121,333 in June 2025, collapsed to under 200 submissions on June 19-20.

2025-iran-shutdown-measurement Executive Summary / §2 dpidns-poisoningport-blockingip-blocking

Chinese users treat full proxy/VPN (Shadowsocks, V2Ray/Clash, commercial VPNs) as the '终极大杀器' (ultimate solution) for bypassing GitHub DNS poisoning, implying that lighter-weight DNS-only fixes fail in some network environments where the censor adds firewall-layer blocking beyond DNS.

2026-anon-6-github-dns §3 使用代理或 VPN dns-poisoningip-blocking

Rule-based proxy tools (Clash, Shadowsocks, V2Ray) are documented as the most reliable solution for accessing GitHub from China, with split-tunneling rules routing only GitHub traffic through the proxy while keeping domestic traffic on the direct path. Git command-line tools require explicit proxy configuration (git config --global http.proxy http://127.0.0.1:7890) to route clone/push operations, as they do not inherit system proxy settings automatically.

2026-anon-github-2026-6-dns §方法二 dns-poisoningip-blocking

The GFW blocks GitHub via DNS poisoning across at least four domains — github.com, assets-cdn.github.com, github.global.ssl.fastly.net, and raw.githubusercontent.com — causing connection timeouts and page-load failures for mainland China users. The block is persistent as of February 2026, affecting both browser access and command-line git operations.

2026-anon-github-2026-6-dns Introduction / §方法一 dns-poisoningip-blocking

Article 19 documents that Iran's National Information Network (NIN / SHOMA) was designed with explicit reference to China's Great Firewall as a model, with institutional mirroring: Iran's Supreme Council of Cyberspace parallels China's Cyberspace Administration of China, and both governments share a "cyber sovereignty" doctrine used to justify domestic content controls and cross-border technology transfer. The report frames Iran's filtering infrastructure as deliberately architected to replicate GFW capabilities, not as an independently developed system.

2026-article19-tightening-the-net §2, §3 dpisni-blockingdns-poisoningip-blockingbgp-hijackthrottling

Article 19 documents that Iran combines technical filtering with formal coercion of major foreign platforms (including Telegram, Instagram, and WhatsApp) to comply with content removal orders under threat of full blocking. The report notes that Iran's 2022 Women Life Freedom protests accelerated platform blocking when foreign operators refused compliance, demonstrating that the censorship system operates in two modes: coerce-and-allow for compliant platforms, block for non-compliant ones. Domain fronting via these platforms is therefore subject to sudden revocation if political conditions change.

2026-article19-tightening-the-net §6 ip-blockingdns-poisoningthrottling