[Iran] Advanced DPI is reassembling TCP fragments to extract SNI on VLESS/WS + CDN

As of June 2026, Iranian DPI blocking timescales are: CDN-fronted VLESS+WebSocket domains blocked within 24 hours; SSH dynamic port forwarding server IPs blocked within 8 hours; Reality and WireGuard connections blocked immediately (seconds) after handshake completion. This graduated timeline suggests separate fast-path (handshake-pattern) and slow-path (domain reputation / traffic accumulation) detection pipelines operating in parallel.

Issue body — combined observations evaluation dpisni-blockingip-blockingrst-injectiondns-poisoning ir

Iran's DPI blocks VLESS/WS traffic routed through Cloudflare CDN in full-strict TLS mode with regularly rotated clean Cloudflare IPs, demonstrating that CDN-fronted traffic is not opaque to the censor and that IP-layer evasion (using clean CDN IPs) is insufficient when the SNI is fingerprinted.

Description detection dpisni-blockingip-blocking ir

Iran's DPI infrastructure performs full TCP reassembly and stateful inspection on the fly, nullifying TCP fragmentation (10–30 byte fragments with 10–20ms delays) applied to VLESS+WebSocket behind Cloudflare CDN in full-strict mode. Domains are blocked within 24 hours despite the CDN layer and rotation of clean Cloudflare IPs. Fragmentation was applied to the first 5 packets and verified correct on the client side with tcpdump; the setup used port 443 with a randomized WebSocket path.

Issue body — Description / The Issue detection dpisni-blockingtraffic-shape ir

Iran's censor deploys a two-stage blocking response within 24 hours of domain exposure: DNS hijacking that resolves blocked domains to 10.10.34.34, combined with RST floods when clients connect directly to Cloudflare IPs using the blocked SNI. Both mechanisms activate independently, so DNS-resistant clients are still terminated at the TCP layer.

Issue body — The Issue detection dns-poisoningrst-injectionsni-blocking ir

The Reality protocol triggers immediate RST flood responses from Iranian ISP infrastructure at the completion of the TLS handshake, suggesting Iranian DPI has developed a fingerprint or active-probe response specifically targeting Reality's TLS handshake forwarding mechanism as of June 2026.

Issue body — Other Observations §2 detection dpirst-injectiontls-fingerprintactive-probing ir

Domains on VLESS+WebSocket behind Cloudflare are blocked in Iran even when they have no configured DNS A record and the root domain was never used — indicating Iran blocklists domain names extracted from SNI in reassembled TCP streams rather than requiring prior DNS query evidence.

Issue body — The Issue detection sni-blockingdpi ir

Iranian DPI exhibits stateful connection tracking with 'cooling-off' enforcement periods on flagged flows and is synchronized across multiple ISPs, suggesting centralized or coordinated blocking infrastructure. Port 443 receives particularly aggressive inspection, and the DPI performs behavioral analysis of upload/download traffic ratios to identify proxy usage, enabling SSH-based proxy server IPs to be fully blocked within 8 hours.

Issue body and thread summary (Jun 10, 2026) detection dpiport-blockingtraffic-shapeml-classifier ir

Community members propose a two-hop architecture as a potential mitigation for Iran's current DPI upgrade: a first-hop server inside Iran's whitelisted datacenter ranges (where outbound traffic faces lighter inspection) proxying to a foreign exit node, with Reality masquerading as a legitimate Iranian organization's domain. The architecture's effectiveness under active TCP reassembly and handshake probing is explicitly unverified.

Issue body — Description defense active-probingip-blocking ir

WireGuard connections are blackholed by Iranian infrastructure immediately after the initial WireGuard handshake completes — clients stop receiving server packets — indicating the Iranian DPI identifies WireGuard by its distinct UDP handshake pattern and applies IP-level blocking at that point.

Issue body — Other Observations §3 detection dpiip-blocking ir