feat(ant-devnet): opt-in LAN / external-devnet mode (--host / --evm-network / --serve-port) by Nic-dorman · Pull Request #174 · WithAutonomi/ant-node

Nic-dorman · 2026-07-13T16:09:32Z

What

Adds a LAN / external-devnet scenario to the existing ant-devnet harness so a devnet can be tested from another device — a phone, an iOS simulator, or a second machine — rather than only from the host box. Three opt-in flags, all default off:

Flag	Effect
`--host <ipv4>`	Bind `0.0.0.0` and advertise this LAN IP in the manifest's bootstrap addresses, so other LAN devices can connect.
`--evm-network arbitrum-sepolia`	Verify payments against the real deployed Arbitrum Sepolia contracts (no local Anvil, empty wallet key) — exercises the external-signer payment flow.
`--serve-port <port>`	Serve the manifest over a small read-only HTTP API (`GET /api/devnet-manifest.json` + `/api/info`) so devices fetch it instead of copying files.

# unchanged default behavior (single machine, local Anvil)
ant-devnet --preset small --enable-evm

# LAN devnet backed by Arbitrum Sepolia, manifest served over HTTP
ant-devnet --preset small --host 192.168.1.100 --evm-network arbitrum-sepolia --serve-port 8088

Why here

ant-devnet is already the maintained local-devnet tool; this is a focused enhancement to it, not a new binary or module — no new dependencies (the manifest server is hand-rolled HTTP/1.1). It's the node half of enabling on-device testing of the mobile SDK; the client half already shipped in the Autonomi mobile FFI.

Backward compatibility / blast radius

Opt-in and default-off. No --host → advertise_ip = None → .local(true) + 127.0.0.1 bootstrap addresses, byte-identical to today.
Confined to the harness. Only the ant-devnet binary and the Devnet/DevnetConfig type change. The real node binary (ant-node) and the wire protocol are untouched, and nothing here is on the production node path — so deployed testnets are unaffected.
Minor API note: adds one field to the public DevnetConfig (advertise_ip: Option<Ipv4Addr>). It's covered by the Default impl, so ..Default::default() construction is unaffected; only a struct-literal build without ..Default::default() would need the new field.

Tests

cli.rs: LAN flags default to None (backward-compat contract); parse into the expected typed values; non-IPv4 --host is rejected.
devnet.rs: DevnetConfig::default().advertise_ip is None.
cargo fmt --all --check clean; strict clippy gates (-D clippy::panic/unwrap_used/expect_used) pass; release build green.

Proven end-to-end out-of-band: a physical Android device completed a full paid upload + byte-perfect download round-trip against a Sepolia-backed LAN devnet launched with these flags.

🤖 Generated with Claude Code

Extends the ant-devnet harness so a devnet can be reached from another device on the LAN (phone, simulator, second machine). All three flags are opt-in and default off — omitting them reproduces today's loopback-only behavior exactly. - --host <ipv4>: bind 0.0.0.0 and advertise the given LAN IP in the manifest bootstrap addresses (adds DevnetConfig::advertise_ip, default None → .local(true) + 127.0.0.1, unchanged). - --evm-network arbitrum-sepolia: verify payments against the real deployed Arbitrum Sepolia contracts (no local Anvil, empty wallet key) — exercises the external-signer payment flow. - --serve-port <port>: read-only manifest HTTP API (GET /api/devnet-manifest.json + /api/info); hand-rolled HTTP/1.1, no new dependencies. Node code and the wire protocol are untouched — only the ant-devnet binary and the Devnet harness change. Adds CLI parse tests + a default-config test. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Copilot

Pull request overview

Adds opt-in LAN/external-devnet capabilities to the existing ant-devnet harness so a devnet can be accessed from other devices, including (a) advertising a LAN IPv4 in bootstrap addresses, (b) verifying payments against a real external EVM network, and (c) optionally serving the devnet manifest via a minimal HTTP API.

Changes:

Extend DevnetConfig with advertise_ip: Option<Ipv4Addr> and use it for bootstrap address construction and local/loopback binding behavior.
Add CLI flags --host, --evm-network, and --serve-port and wire them into devnet startup.
Implement a small read-only HTTP endpoint for serving the manifest and a derived /api/info payload.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
src/devnet.rs	Adds `advertise_ip` to devnet config, uses it to generate bootstrap MultiAddrs and toggles `.local(...)`, plus a backward-compat test.
src/bin/ant-devnet/main.rs	Wires new CLI options into devnet config, adds external EVM network selection, and introduces a tiny manifest HTTP server.
src/bin/ant-devnet/cli.rs	Defines the new CLI flags and adds parsing/backward-compat tests.

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-    // Start Anvil and deploy contracts if EVM is enabled
-    let evm_info = if cli.enable_evm {
+    config.advertise_ip = cli.host;


+fn local_ip_guess() -> String {
+    std::net::UdpSocket::bind("0.0.0.0:0")
+        .and_then(|s| {
+            s.connect("1.1.1.1:80")?;
+            Ok(s.local_addr()?.ip().to_string())
+        })
+        .unwrap_or_else(|_| "127.0.0.1".to_string())
+}


+                let req = String::from_utf8_lossy(&buf[..n]);
+                let raw = req.split_whitespace().nth(1).unwrap_or("/");
+                let path = raw.split('?').next().unwrap_or("/").trim_end_matches('/');
+                let (status, body) = match path {
+                    "/api/devnet-manifest.json" => ("200 OK", manifest.as_str()),
+                    "/api/info" => ("200 OK", info.as_str()),
+                    "" | "/api" => (
+                        "200 OK",
+                        "{\"service\":\"ant-devnet manifest API\",\
+                         \"endpoints\":[\"/api/devnet-manifest.json\",\"/api/info\"]}",
+                    ),
+                    _ => ("404 Not Found", "{\"error\":\"not found\"}"),
+                };


+    /// (`--enable-evm`).
+    #[arg(long)]
+    pub evm_network: Option<String>,


…many_lines CI runs clippy with -D warnings and the workspace enables clippy::pedantic, so the expanded main() tripped too_many_lines (121/100). Extract the EVM-backing resolution into resolve_evm_info; behavior unchanged, main() back to ~85 lines. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Copilot

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

+    let info = serde_json::json!({
+        "host_ip": host_ip,
+        "manifest_url": format!("http://{host_ip}:{port}/api/devnet-manifest.json"),
+        "node_count": manifest.node_count as u64,
+        "bootstrap": serde_json::to_value(&manifest.bootstrap).unwrap_or(serde_json::Value::Null),
+        "evm": evm_block,
+    });


+        for stream in listener.incoming() {
+            let Ok(mut stream) = stream else { continue };
+            let manifest = manifest_json.clone();
+            let info = info_json.clone();
+            std::thread::spawn(move || {


…EVM flags, read timeout Automated-review follow-ups on the manifest HTTP API + CLI: - Reject a loopback/unspecified --host early (would stamp unreachable bootstrap addresses into the manifest). - Manifest API now enforces GET and returns 405 for other methods. - --evm-network and --enable-evm are mutually exclusive at the clap level. - Cap the manifest-server handler with a 5s socket read timeout so a slow/idle client can't tie up a thread (listener binds 0.0.0.0). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Nic-dorman · 2026-07-13T17:09:31Z

Addressed the review feedback in 96ab80a:

--host validation — a loopback/unspecified --host is now rejected early with a clear error (it would otherwise stamp unreachable bootstrap addresses into the manifest).
GET enforcement — the manifest API now returns 405 for any method other than GET.
--evm-network / --enable-evm — made mutually exclusive at the clap level (conflicts_with).
Manifest server read timeout — handler sockets get a 5s read timeout so a slow/idle client can't tie up a thread (the listener binds 0.0.0.0).

Not changed, with rationale:

local_ip_guess() returning IPv6 — the socket binds 0.0.0.0 (IPv4) and connects to an IPv4 address, so local_addr() is always IPv4; it can't return an IPv6 literal here.
host_ip use-after-move — this compiles as written (green build on all three OSes); json!/format! don't consume host_ip the way the comment suggests.

fmt + clippy (-D warnings) + tests green.

Copilot

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

+    if let Some(port) = cli.serve_port {
+        serve_manifest_api(port, cli.host, &manifest, json.clone())?;
+    }


+    #[arg(long)]
+    pub serve_port: Option<u16>,


+    std::thread::spawn(move || {
+        use std::io::{Read, Write};
+        for stream in listener.incoming() {
+            let Ok(mut stream) = stream else { continue };
+            // Cap how long a slow/idle client can hold a handler thread — the
+            // listener binds 0.0.0.0, so an unbounded blocking read is a trivial
+            // resource-exhaustion vector.
+            let _ = stream.set_read_timeout(Some(std::time::Duration::from_secs(5)));
+            let manifest = manifest_json.clone();
+            let info = info_json.clone();
+            std::thread::spawn(move || {


dirvine

Reviewed current head 96ab80aaa2fbee966a00e83c08b30c36fda32677 with a multi-reviewer pass and local runtime checks.

Verdict: changes requested before merge. The latest commit fixes loopback/unspecified --host, GET-only handling, conflicting EVM flags, and idle-read timeout. Two functional issues remain:

src/bin/ant-devnet/main.rs:260-267 — --serve-port bind failure is swallowed. spawn_manifest_server only warns and returns, then serve_manifest_api returns Ok(()) and the CLI reports Devnet running. I reproduced this with an occupied port on the current head: the process logged failed to bind ... Address already in use, then continued successfully. Please bind synchronously and propagate the error.
src/bin/ant-devnet/cli.rs:84-85 / main.rs:237,261 — port 0 is accepted but advertised as :0. The OS actually selected port 49241 in my current-head run, while the log and /api/info construction retained port 0. Either reject zero or return/use listener.local_addr().

Also worth fixing in this pass:

--serve-port without --host binds 0.0.0.0 and publishes a LAN-looking API URL, but the served manifest still contains loopback bootstrap addresses. Require --host, or bind/report loopback when it is absent.
The five-second timeout bounds idle connection lifetime, but the server still creates an unbounded OS thread per connection. A small concurrency cap/inline handler would remove the remaining burst-exhaustion path.
--host now rejects loopback/unspecified addresses, but multicast and broadcast values remain accepted and are not usable bootstrap destinations.
Current ant-cli does not infer Sepolia from the manifest alone; users need --evm-network arbitrum-sepolia (or local to consume the manifest's custom RPC/contracts). This is not necessarily a blocker for the mobile flow, but should be documented unless the manifest schema gains an explicit network/chain ID.

Local verification on the current head:

cargo test --bin ant-devnet — 3 passed
cargo test default_config_has_no_advertise_ip --lib — 1 passed
strict cargo clippy --bin ant-devnet --all-features — passed
runtime occupied-port and port-zero cases reproduced as above

The reported Android paid upload/download result was not independently reproduced during this review.

@dirvine

… hardening @dirvine review + Copilot follow-ups on the manifest API: - Bind the manifest listener synchronously in serve_manifest_api and propagate the error, so a bind failure (e.g. port in use) fails the run instead of the devnet reporting 'running' without its API. - Reject --serve-port 0 at the parser (range 1..) — it would otherwise bind an ephemeral port while /api/info advertises ':0'. - --serve-port now requires --host (the API publishes a LAN URL; a loopback-only devnet would be misleading/unsafe). - Handle manifest-API connections inline in the single server thread instead of spawning an unbounded thread per connection (kept the 5s read timeout). - Also reject multicast/broadcast --host, not just loopback/unspecified. - Propagate the bootstrap serialization error in /api/info instead of silently substituting null. Adds serve_port_requires_host + serve_port_rejects_zero CLI tests. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Nic-dorman · 2026-07-13T17:29:30Z

Thanks @dirvine — addressed in 998493d.

Blockers:

Swallowed bind failure — serve_manifest_api now binds the listener synchronously and propagates the error via ?, so an occupied port fails the run instead of the devnet reporting running without its API.
--serve-port 0 — rejected at the parser (value_parser = value_parser!(u16).range(1..)), so :0 can't be advertised. (ant-devnet --host … --serve-port 0 → error: invalid value '0' … 0 is not in 1..=65535.)

Also fixed this pass:

--serve-port without --host — --serve-port now requires = "host" at the clap level, so it can't publish a LAN URL over a loopback-only devnet.
Unbounded thread-per-connection — the server now handles connections inline in its single thread (no per-connection thread), keeping the 5s read timeout. Payloads are tiny and a devnet serves a handful of devices, so serial handling bounds resource use with no burst-exhaustion path.
Multicast/broadcast --host — the early validation now also rejects is_multicast() / is_broadcast(), not just loopback/unspecified.
Bootstrap serialization — /api/info now propagates the serde_json::to_value(&bootstrap) error instead of substituting null.

Not changed here (documentation / follow-up):

ant-cli can't infer Sepolia from the manifest alone — correct: the manifest's evm block carries rpc_url/token/vault but no network identifier, so consumers pass --evm-network arbitrum-sepolia (or local to use the manifest's custom RPC/contracts). This is a manifest-schema matter rather than an ant-devnet behavior; the cleanest fix is adding an explicit chain_id to the manifest evm block so clients can infer it. That touches the shared manifest schema (and its FFI consumers), so I'd propose it as a separate follow-up rather than fold it in here — happy to open that if you agree.

Local: cargo fmt --check, strict clippy -D warnings, and cargo test --bin ant-devnet (5 passed) all green; the occupied-port, port-0, serve-port-without-host, and multicast-host cases verified by hand.

Copilot

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

+    // Optional read-only HTTP API so LAN devices fetch the manifest instead of
+    // copying files (GET /api/devnet-manifest.json + /api/info).
+    if let Some(port) = cli.serve_port {
+        serve_manifest_api(port, cli.host, &manifest, json.clone())?;
+    }


+    // Bind synchronously so a failure (e.g. the port is already in use)
+    // propagates to the caller instead of the devnet silently coming up
+    // without its manifest API.
+    let listener = std::net::TcpListener::bind(("0.0.0.0", port)).map_err(|e| {
+        color_eyre::eyre::eyre!("failed to bind manifest API on 0.0.0.0:{port}: {e}")
+    })?;
+    ant_node::logging::info!(
+        "manifest API on http://0.0.0.0:{port}/api/devnet-manifest.json (+ /api/info)"
+    );
+    spawn_manifest_server(listener, manifest_json, info_json);


dirvine

Re-reviewed current head 998493dd8a13f842ec2b16d00ffa51fa31240916 against the previous reviewed head.

The previous blockers are addressed:

manifest-listener bind errors now propagate;
port zero and --serve-port without --host are rejected;
loopback/unspecified/multicast/broadcast hosts are rejected;
unbounded per-connection threads are removed;
bootstrap serialisation errors propagate.

Local/runtime verification:

cargo test --bin ant-devnet — 5 passed
cargo test default_config_has_no_advertise_ip --lib — passed
strict clippy and build — passed
occupied-port case now exits with the expected bind error
normal GET succeeds and invalid host classes are rejected

Recommendation: approve once the remaining platform CI tests pass. No remaining blocker was found for the stated opt-in trusted-LAN devnet scope. The single-read HTTP parser, process-scoped detached listener, intentional DevnetConfig field addition, and possible data-directory residue on a post-start error are non-blocking limitations here.

At review time, format, clippy, documentation, all three builds, no-logging tests and security audit are green. Ubuntu/macOS/Windows test jobs remain in progress.

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feat(devnet): add loopback_only flag for LAN testnet support #84

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feat(ant-devnet): opt-in LAN / external-devnet mode (--host / --evm-network / --serve-port)#174

feat(ant-devnet): opt-in LAN / external-devnet mode (--host / --evm-network / --serve-port)#174
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Nic-dorman commented Jul 13, 2026

What

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Backward compatibility / blast radius

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