Added a way to enable host-only networking through tart using --net-host (#32)

* Added a way to enable host-only networking through tart using SOFTNET_NET_TYPE=host

* Removed env variable and moved to Enum instead of str

* Fixed defaults & restricted publicity of host

* Fixed usage of NetType

.cirrus.yml

@@ -4,17 +4,18 @@ env:
 task:
   name: Build
   macos_instance:
-    image: ghcr.io/cirruslabs/macos-monterey-xcode:14
+    image: ghcr.io/cirruslabs/macos-sonoma-xcode:latest
   install_rust_script:
     - curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+    - rustup target add x86_64-apple-darwin
   build_script:
-    - cargo build
+    - cargo build --target aarch64-apple-darwin --target x86_64-apple-darwin
 
 task:
   name: Release
   only_if: $CIRRUS_TAG != ''
   macos_instance:
-    image: ghcr.io/cirruslabs/macos-monterey-xcode:14
+    image: ghcr.io/cirruslabs/macos-sonoma-xcode:latest
   env:
     GITHUB_TOKEN: ENCRYPTED[!98ace8259c6024da912c14d5a3c5c6aac186890a8d4819fad78f3e0c41a4e0cd3a2537dd6e91493952fb056fa434be7c!]
     GORELEASER_KEY: ENCRYPTED[!9b80b6ef684ceaf40edd4c7af93014ee156c8aba7e6e5795f41c482729887b5c31f36b651491d790f1f668670888d9fd!]
@@ -23,13 +24,14 @@ task:
     SENTRY_AUTH_TOKEN: ENCRYPTED[!c16a5cf7da5f856b4bc2f21fe8cb7aa2a6c981f851c094ed4d3025fd02ea59a58a86cee8b193a69a1fc20fa217e56ac3!]
   install_rust_script:
     - curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+    - rustup target add x86_64-apple-darwin
   install_script:
     - brew install go goreleaser/tap/goreleaser-pro getsentry/tools/sentry-cli
   build_script:
-    - cargo build --profile release-with-debug
+    - cargo build --target aarch64-apple-darwin --target x86_64-apple-darwin --profile release-with-debug
   release_script: goreleaser
   upload_sentry_debug_files_script:
-    - cd target/release-with-debug/
+    - cd target/aarch64-apple-darwin/release-with-debug/
     # Generate and upload symbols
     - dsymutil softnet
     - sentry-cli debug-files upload -o $SENTRY_ORG -p $SENTRY_PROJECT softnet.dSYM/

.gitignore

@@ -1 +1,3 @@
+/.idea
+/dist
 /target

.goreleaser.yml

@@ -1,29 +1,27 @@
 project_name: softnet
 
 builds:
-  - builder: prebuilt
+  - id: softnet
+    builder: prebuilt
+    goamd64: [v1]
     goos:
       - darwin
     goarch:
       - arm64
+      - amd64
     prebuilt:
-      path: "target/release-with-debug/softnet"
+      path: 'target/{{- if eq .Arch "arm64" }}aarch64{{- else }}x86_64{{ end }}-apple-darwin/release-with-debug/softnet'
 
 archives:
-  - id: binary
-    format: binary
-    name_template: "{{ .ProjectName }}"
   - id: regular
-    name_template: "{{ .ProjectName }}"
+    name_template: "{{ .ProjectName }}-{{ .Arch }}"
 
 release:
   prerelease: auto
 
 brews:
   - name: softnet
-    ids:
-      - regular
-    tap:
+    repository:
       owner: cirruslabs
       name: homebrew-cli
     caveats: See the Github repository for more information

Cargo.lock

@@ -970,9 +970,9 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.51"
+version = "1.0.66"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5d727cae5b39d21da60fa540906919ad737832fe0b1c165da3a34d6548c849d6"
+checksum = "18fb31db3f9bddb2ea821cde30a9f70117e3f119938b5ee630b7403aa6e2ead9"
 dependencies = [
  "unicode-ident",
 ]
@@ -1351,7 +1351,7 @@ dependencies = [
  "sentry-anyhow",
  "smoltcp",
  "system-configuration",
- "users",
+ "uzers",
  "vmnet",
 ]
 
@@ -1634,16 +1634,6 @@ dependencies = [
  "serde",
 ]
 
-[[package]]
-name = "users"
-version = "0.11.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "24cc0f6d6f267b73e5a2cadf007ba8f9bc39c6a6f9666f8cf25ea809a153b032"
-dependencies = [
- "libc",
- "log",
-]
-
 [[package]]
 name = "uuid"
 version = "1.3.0"
@@ -1654,6 +1644,16 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "uzers"
+version = "0.11.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76d283dc7e8c901e79e32d077866eaf599156cbf427fffa8289aecc52c5c3f63"
+dependencies = [
+ "libc",
+ "log",
+]
+
 [[package]]
 name = "vcpkg"
 version = "0.2.15"

Cargo.toml

@@ -22,7 +22,7 @@ mac_address = "1.1.3"
 privdrop = "0.5.2"
 anyhow = { version = "1.0.66", features = ["backtrace"] }
 ip_network = "0.4.1"
-users = "0.11.0"
+uzers = "0.11.3"
 system-configuration = "0.5.0"
 num_enum = "0.5.7"
 sentry = { version = "0.29.1", features = ["debug-images"] }

README.md

@@ -1,13 +1,14 @@
 # Softnet
 
 Softnet is a software networking for [Tart](https://github.com/cirruslabs/tart) which provides better network isolation and alleviates DHCP shortage on production systems.
+Please check out [this blog post](https://cirrus-ci.org/blog/2022/07/07/isolating-network-between-tarts-macos-virtual-machines/) for backstory.
 
 ## Working model
 
 Softnet solves two problems:
 
 1. VM network isolation
-  * [`VZNATNetworkDeviceAttachment`](https://developer.apple.com/documentation/virtualization/vznatnetworkdeviceattachment) (the default networking in Tart) enables [vmnet's bridge isolation](https://developer.apple.com/documentation/vmnet/vmnet_enable_isolation_key) by default and prevents cross-VM traffic, however it's still possible for any VM to spoof the host's ARP-table and capture other VMs traffic, for example
+  * [`VZNATNetworkDeviceAttachment`](https://developer.apple.com/documentation/virtualization/vznatnetworkdeviceattachment) (the default networking in Tart) enables [vmnet's bridge isolation](https://developer.apple.com/documentation/vmnet/vmnet_enable_isolation_key) by default and prevents cross-VM traffic, however it's still possible for any VM to spoof the host's ARP-table and capture other VMs traffic
 2. DHCP exhaustion
   * macOS built-in DHCP-server allocates a `/24` subnet with 86400 seconds lease time by default, which only allows for ~253 VMs a day (or 1 VM every ~6 minutes) to be spawned without causing a denial-of-service, which is pretty limiting for CI services like Cirrus CI
 
@@ -30,4 +31,4 @@ For proper functioning, Softnet binary requires two things:
 
 ## Running
 
-Softnet is started and managed automatically by Tart if `--with-softnet` flag is present when calling `tart run`.
+Softnet is started and managed automatically by Tart if `--net-softnet` flag is provided when calling `tart run`.

lib/host.rs

@@ -1,3 +1,4 @@
+use clap::ArgEnum;
 use anyhow::{anyhow, Context, Result};
 use std::net::Ipv4Addr;
 use std::os::unix::io::{AsRawFd, RawFd};
@@ -8,6 +9,18 @@ use vmnet::mode::Mode;
 use vmnet::parameters::{Parameter, ParameterKind};
 use vmnet::{Events, Options};
 
+#[derive(ArgEnum, Clone, Debug)]
+pub enum NetType {
+    /// Shared network
+    ///
+    /// Uses NAT-translation to give guests access to the global network
+    Nat,
+    /// Host network
+    ///
+    /// Guests will be able to talk only to the host without access to global network
+    Host,
+}
+
 pub struct Host {
     interface: vmnet::Interface,
     new_packets_rx: UnixDatagram,
@@ -18,10 +31,13 @@ pub struct Host {
 }
 
 impl Host {
-    pub fn new() -> Result<Host> {
-        // Initialize a vmnet.framework NAT interface with isolation enabled
+    pub fn new(vm_net_type: NetType) -> Result<Host> {
+        // Initialize a vmnet.framework NAT or Host interface with isolation enabled
         let mut interface = vmnet::Interface::new(
-            Mode::Shared(Default::default()),
+            match vm_net_type {
+                NetType::Nat => Mode::Shared(Default::default()),
+                NetType::Host => Mode::Host(Default::default()),
+            },
             Options {
                 enable_isolation: Some(true),
                 ..Default::default()

lib/mod.rs

@@ -1,5 +1,6 @@
 mod dhcp_snooper;
 mod host;
+pub use host::NetType;
 mod poller;
 pub mod proxy;
 mod vm;

lib/proxy/mod.rs

@@ -4,6 +4,7 @@ mod vm;
 
 use crate::dhcp_snooper::DhcpSnooper;
 use crate::host::Host;
+use crate::host::NetType;
 use crate::poller::Poller;
 use crate::vm::VM;
 use anyhow::Result;
@@ -22,9 +23,9 @@ pub struct Proxy {
 }
 
 impl Proxy {
-    pub fn new(vm_fd: RawFd, vm_mac_address: MacAddress) -> Result<Proxy> {
+    pub fn new(vm_fd: RawFd, vm_mac_address: MacAddress, vm_net_type: NetType) -> Result<Proxy> {
         let vm = VM::new(vm_fd)?;
-        let host = Host::new()?;
+        let host = Host::new(vm_net_type)?;
         let poller = Poller::new(vm.as_raw_fd(), host.as_raw_fd())?;
 
         Ok(Proxy {

src/main.rs

@@ -2,6 +2,7 @@ use anyhow::{anyhow, Context};
 use clap::Parser;
 use nix::sys::signal::{signal, SigHandler, Signal};
 use privdrop::PrivDrop;
+use softnet::NetType;
 use softnet::proxy::Proxy;
 use std::borrow::Cow;
 use std::env;
@@ -15,7 +16,7 @@ use system_configuration::core_foundation::number::CFNumber;
 use system_configuration::core_foundation::string::CFString;
 use system_configuration::preferences::SCPreferences;
 use system_configuration::sys::preferences::{SCPreferencesCommitChanges, SCPreferencesSetValue};
-use users::{get_current_groupname, get_current_username, get_effective_uid};
+use uzers::{get_current_groupname, get_current_username, get_effective_uid};
 
 #[derive(Parser, Debug)]
 struct Args {
@@ -28,6 +29,9 @@ struct Args {
     #[clap(long, help = "MAC address to enforce for the VM")]
     vm_mac_address: mac_address::MacAddress,
 
+    #[clap(long, arg_enum, help = "type of network to use for the VM", default_value_t=NetType::Nat)]
+    vm_net_type: NetType,
+
     #[clap(
         long,
         help = "set bootpd(8) lease time to this value (in seconds) before starting the VM",
@@ -140,7 +144,7 @@ fn try_main() -> anyhow::Result<()> {
     set_bootpd_lease_time(args.bootpd_lease_time);
 
     // Initialize the proxy while still having the root privileges
-    let mut proxy = Proxy::new(args.vm_fd as RawFd, args.vm_mac_address)
+    let mut proxy = Proxy::new(args.vm_fd as RawFd, args.vm_mac_address, args.vm_net_type)
         .context("failed to initialize proxy")?;
 
     // Drop effective privileges to the user