host: add --net and --net-allow CLI flags to hyperlight-unikraft and pyhl

Signed-off-by: danbugs <danilochiarlone@gmail.com>

Author: danbugs

examples/networking-py/Justfile

@@ -16,19 +16,19 @@ image       := "networking-py-hyperlight"
 
 # Run HTTP GET test (raw sockets)
 run-get:
-    hyperlight-unikraft {{kernel}} --initrd {{initrd}} --memory {{memory}} -- /http_get.py
+    hyperlight-unikraft {{kernel}} --initrd {{initrd}} --memory {{memory}} --net -- /http_get.py
 
 # Run HTTP GET test (urllib — high-level stdlib)
 run-urllib:
-    hyperlight-unikraft {{kernel}} --initrd {{initrd}} --memory {{memory}} -- /urllib_get.py
+    hyperlight-unikraft {{kernel}} --initrd {{initrd}} --memory {{memory}} --net -- /urllib_get.py
 
 # Run HTTPS (TLS) test
 run-https:
-    hyperlight-unikraft {{kernel}} --initrd {{initrd}} --memory {{memory}} -- /https_test.py
+    hyperlight-unikraft {{kernel}} --initrd {{initrd}} --memory {{memory}} --net -- /https_test.py
 
 # Run echo server
 run-echo:
-    hyperlight-unikraft {{kernel}} --initrd {{initrd}} --memory {{memory}} -- /echo_server.py
+    hyperlight-unikraft {{kernel}} --initrd {{initrd}} --memory {{memory}} --net -- /echo_server.py
 
 # Build rootfs via Docker (cross-platform)
 rootfs:

host/src/bin/pyhl.rs

@@ -26,7 +26,7 @@ use hyperlight_unikraft::pyhl::{
     copy_replace, discover_source_artifacts, extract_from_ghcr, GHCR_INITRD_IMAGE,
     GHCR_KERNEL_IMAGE,
 };
-use hyperlight_unikraft::{Preopen, Sandbox};
+use hyperlight_unikraft::{AllowList, NetworkPolicy, Preopen, Sandbox};
 use std::fs;
 use std::path::{Path, PathBuf};
 use std::time::Instant;
@@ -37,6 +37,16 @@ fn parse_mount(spec: &str) -> Result<Preopen> {
     Preopen::parse_cli(spec).map_err(|e| anyhow!("invalid --mount {:?}: {}", spec, e))
 }
 
+fn build_network_policy(net: bool, net_allow: &[String]) -> Result<Option<NetworkPolicy>> {
+    if !net_allow.is_empty() {
+        Ok(Some(NetworkPolicy::AllowList(AllowList::from_hosts(net_allow)?)))
+    } else if net {
+        Ok(Some(NetworkPolicy::AllowAll))
+    } else {
+        Ok(None)
+    }
+}
+
 /// Keep in sync with `py_initialize_once` in examples/python-agent-driver/
 /// hl_pydriver.c. These modules are imported during `pyhl setup`'s warmup
 /// so they're already in `sys.modules` in every `pyhl run` invocation —
@@ -145,6 +155,15 @@ struct SetupArgs {
     /// given to `setup`.
     #[arg(long = "mount", value_name = "HOST[:GUEST]")]
     mounts: Vec<String>,
+
+    /// Enable guest networking.
+    #[arg(long)]
+    net: bool,
+
+    /// Restrict guest networking to the listed hosts/IPs.
+    /// Implies --net. Repeatable.
+    #[arg(long = "net-allow", value_name = "HOST_OR_IP")]
+    net_allow: Vec<String>,
 }
 
 #[derive(Args)]
@@ -172,6 +191,15 @@ struct RunArgs {
     #[arg(long = "mount", value_name = "HOST[:GUEST]")]
     mounts: Vec<String>,
 
+    /// Enable guest networking.
+    #[arg(long)]
+    net: bool,
+
+    /// Restrict guest networking to the listed hosts/IPs.
+    /// Implies --net. Repeatable.
+    #[arg(long = "net-allow", value_name = "HOST_OR_IP")]
+    net_allow: Vec<String>,
+
     /// Print evolve/warmup/per-run timing to stderr. Off by default so the
     /// user's script output is clean.
     #[arg(short = 'v', long = "verbose")]
@@ -329,6 +357,7 @@ fn cmd_setup(args: SetupArgs) -> Result<()> {
         .iter()
         .map(|m| parse_mount(m))
         .collect::<Result<_>>()?;
+    let network = build_network_policy(args.net, &args.net_allow)?;
 
     eprintln!("pyhl: warming up Python and persisting snapshot…");
     let t_warm = Instant::now();
@@ -339,6 +368,9 @@ fn cmd_setup(args: SetupArgs) -> Result<()> {
         for p in &setup_preopens {
             builder = builder.preopen(p.clone());
         }
+        if let Some(ref policy) = network {
+            builder = builder.network(policy.clone());
+        }
         let mut sbox = builder.build()?;
         sbox.restore()?;
         let _: () = sbox.call_named("run", "pass".to_string())?;
@@ -463,17 +495,22 @@ fn cmd_run(args: RunArgs) -> Result<()> {
         .iter()
         .map(|m| parse_mount(m))
         .collect::<Result<_>>()?;
+    let network = build_network_policy(args.net, &args.net_allow)?;
 
     let initrd = home.join(INITRD_FILE);
 
     let t_load = Instant::now();
-    let mut sandbox = if initrd.is_file() {
-        Sandbox::from_snapshot_file_with_initrd(&snapshot, &run_preopens, &initrd)?
-    } else if run_preopens.is_empty() {
-        Sandbox::from_snapshot_file(&snapshot)?
+    let initrd_ref = if initrd.is_file() {
+        Some(initrd.as_path())
     } else {
-        Sandbox::from_snapshot_file_with(&snapshot, &run_preopens)?
+        None
     };
+    let mut sandbox = Sandbox::from_snapshot_file_configured(
+        &snapshot,
+        &run_preopens,
+        initrd_ref,
+        network.as_ref(),
+    )?;
     if args.verbose {
         eprintln!(
             "[pyhl] load_snapshot={:.1}ms",

host/src/main.rs

@@ -8,7 +8,7 @@
 
 use anyhow::Result;
 use clap::Parser;
-use hyperlight_unikraft::{parse_memory, Preopen, Sandbox};
+use hyperlight_unikraft::{parse_memory, AllowList, NetworkPolicy, Preopen, Sandbox};
 use std::path::PathBuf;
 
 #[derive(Parser, Debug)]
@@ -57,6 +57,17 @@ struct Args {
     #[arg(long, value_name = "HOST[:GUEST]")]
     mount: Vec<String>,
 
+    /// Enable guest networking. Without this flag, the guest has no
+    /// network access.
+    #[arg(long)]
+    net: bool,
+
+    /// Restrict guest networking to the listed hosts/IPs.
+    /// Implies --net. Hostnames are resolved at sandbox creation time.
+    /// Repeatable: `--net-allow api.github.com --net-allow 10.0.0.1`.
+    #[arg(long = "net-allow", value_name = "HOST_OR_IP")]
+    net_allow: Vec<String>,
+
     /// Run the application N additional times via snapshot/restore + call.
     /// The first run always happens. --repeat=2 means 3 total runs.
     #[arg(long, default_value = "0")]
@@ -152,6 +163,14 @@ fn main() -> Result<()> {
         None => args.app_args.clone(),
     };
 
+    let network = if !args.net_allow.is_empty() {
+        Some(NetworkPolicy::AllowList(AllowList::from_hosts(&args.net_allow)?))
+    } else if args.net {
+        Some(NetworkPolicy::AllowAll)
+    } else {
+        None
+    };
+
     let mut builder = Sandbox::builder(&args.kernel)
         .args(app_args)
         .heap_size(heap_size)
@@ -162,6 +181,9 @@ fn main() -> Result<()> {
     for p in preopens {
         builder = builder.preopen(p);
     }
+    if let Some(policy) = network {
+        builder = builder.network(policy);
+    }
     if args.enable_tools {
         builder = builder.tool("echo", Ok);
     }