Apps Script's response body cap is ~50 MiB. tunnel-node had a TCP_DRAIN_MAX_BYTES = 16 MiB per-session cap to stay under it, but multiple sessions in the same batch each contributed up to 16 MiB raw, summing past 50 MiB on busy VPS — N≥4 concurrent sessions × 16 MiB → ≥64 MiB raw → ≥85 MiB after base64. Steam updates and other CDN-served large downloads hit this exactly: `EOF while parsing a string at line 1 column 52428630` from the client and the session aborts mid-stream. Fix: new BATCH_RESPONSE_BUDGET = 32 MiB total-batch cap. Drain loop tracks remaining budget across sessions and stops one short of the cliff. drain_now() now takes max_bytes; effective cap = min(budget, TCP_DRAIN_MAX_BYTES). Sessions deferred this batch keep their buffered data — no data loss, they drain on the next poll. Single-op-path callers and existing tests pass usize::MAX (no extra constraint, original TCP_DRAIN_MAX_BYTES still enforced). New regression test `drain_now_respects_caller_budget_below_per_session_cap` covers the new behavior. Tests: 197 lib + 36 tunnel-node (was 35) all green. UI release build green. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Tunnel Node
Persian / فارسی: README.fa.md
HTTP tunnel bridge server for MasterHttpRelayVPN "full" mode. Bridges HTTP tunnel requests (from Apps Script) to real TCP connections.
Architecture
Phone → mhrv-rs → [domain-fronted TLS] → Apps Script → [HTTP] → Tunnel Node → [real TCP] → Internet
The tunnel node manages persistent TCP and UDP sessions. TCP sessions are real TCP connections to a destination server; UDP sessions are connected UDP sockets to one destination host:port. Data flows through a JSON protocol:
- connect — open TCP to host:port, return session ID
- data — write client data, return server response
- udp_open — open UDP to host:port, optionally send the first datagram
- udp_data — send one UDP datagram, or poll for returned datagrams when
dis omitted - close — tear down session
- batch — process multiple ops in one HTTP request (reduces round trips)
Deployment
Cloud Run
cd tunnel-node
gcloud run deploy tunnel-node \
--source . \
--region us-central1 \
--allow-unauthenticated \
--set-env-vars TUNNEL_AUTH_KEY=$(openssl rand -hex 24) \
--memory 256Mi \
--cpu 1 \
--max-instances 1
Docker — prebuilt image (any VPS)
The fastest path. Pull a prebuilt image and run it; no Rust toolchain needed on the VPS.
# Generate a strong secret. Save it — you'll paste the same value into CodeFull.gs.
SECRET=$(openssl rand -hex 24)
echo "Your TUNNEL_AUTH_KEY: $SECRET"
# Pull + run.
docker run -d \
--name mhrv-tunnel \
--restart unless-stopped \
-p 8080:8080 \
-e TUNNEL_AUTH_KEY="$SECRET" \
ghcr.io/therealaleph/mhrv-tunnel-node:latest
The :latest tag tracks the most recent release. To pin a specific version (recommended for production), use ghcr.io/therealaleph/mhrv-tunnel-node:v1.5.0 (or whatever release you're on). Image is available for linux/amd64 and linux/arm64.
docker-compose.yml if you prefer:
services:
tunnel:
image: ghcr.io/therealaleph/mhrv-tunnel-node:latest
restart: unless-stopped
ports:
- "8080:8080"
environment:
TUNNEL_AUTH_KEY: ${TUNNEL_AUTH_KEY}
Then TUNNEL_AUTH_KEY=your-secret docker compose up -d.
Docker — build from source
If you'd rather build the image yourself (or add custom changes):
cd tunnel-node
docker build -t tunnel-node .
docker run -p 8080:8080 -e TUNNEL_AUTH_KEY=your-secret tunnel-node
Direct binary
cd tunnel-node
cargo build --release
TUNNEL_AUTH_KEY=your-secret PORT=8080 ./target/release/tunnel-node
Environment Variables
| Variable | Required | Default | Description |
|---|---|---|---|
TUNNEL_AUTH_KEY |
Yes | changeme |
Shared secret — must match TUNNEL_AUTH_KEY in CodeFull.gs |
PORT |
No | 8080 |
Listen port (Cloud Run sets this automatically) |
Protocol
Single op: POST /tunnel
{"k":"auth","op":"connect","host":"example.com","port":443}
{"k":"auth","op":"data","sid":"uuid","data":"base64"}
{"k":"auth","op":"close","sid":"uuid"}
Batch: POST /tunnel/batch
{
"k": "auth",
"ops": [
{"op":"data","sid":"uuid1","d":"base64"},
{"op":"udp_data","sid":"uuid2","d":"base64"},
{"op":"close","sid":"uuid3"}
]
}
→ {"r": [{...}, {...}, {...}]}
Health check: GET /health → ok
Performance: deployment count and pipeline depth
The mhrv-rs client runs a pipelined batch multiplexer in full mode. Each Apps Script round-trip takes ~2s, so the client fires multiple batch requests concurrently — the pipeline depth equals the number of configured script deployment IDs (minimum 2, no upper cap).
More deployments = more concurrent batches hitting the tunnel-node = lower per-session latency. With 6 deployments, a new batch arrives every ~0.3s instead of every 2s.
The tunnel-node itself is stateless per-request (sessions are keyed by UUID), so it handles concurrent batches naturally. For best results, deploy 3–12 Apps Script instances across separate Google accounts and list all their deployment IDs in the client config.