tests: Add vmnet-helper tests

Signed-off-by: Matej Hrica <mhrica@redhat.com>

Author: mtjhrc

tests/test_cases/src/net_config.rs

@@ -104,7 +104,7 @@ pub fn add_default_route(gateway: [u8; 4]) -> nix::Result<()> {
     rt.rt_dst = make_sockaddr_in([0, 0, 0, 0]);
     rt.rt_gateway = make_sockaddr_in(gateway);
     rt.rt_genmask = make_sockaddr_in([0, 0, 0, 0]);
-    rt.rt_flags = (libc::RTF_UP | libc::RTF_GATEWAY) as u16;
+    rt.rt_flags = libc::RTF_UP | libc::RTF_GATEWAY;
 
     let ret = unsafe { libc::ioctl(sock.as_raw_fd(), libc::SIOCADDRT as _, &rt) };
     if ret < 0 {

tests/test_cases/src/test_net/mod.rs

@@ -99,10 +99,8 @@ impl TestNet {
             #[cfg(feature = "guest")]
             netmask: [255, 255, 255, 0],
             #[cfg(feature = "guest")]
-            gateway: Some([192, 168, 105, 1]),
-            // HACK: hardcoded host LAN IP for testing; guest needs a default
-            // route via the vmnet gateway (192.168.105.1) to reach it.
-            tcp_tester: TcpTester::new(9003, [10, 42, 0, 115].into()),
+            gateway: None,
+            tcp_tester: TcpTester::new(9003, [192, 168, 105, 1].into()),
             #[cfg(feature = "host")]
             should_run: vmnet_helper::should_run,
             #[cfg(feature = "host")]
@@ -175,8 +173,7 @@ mod guest {
                 .expect("Failed to configure eth0");
 
             if let Some(gw) = self.gateway {
-                crate::net_config::add_default_route(gw)
-                    .expect("Failed to add default route");
+                crate::net_config::add_default_route(gw).expect("Failed to add default route");
             }
 
             self.tcp_tester.run_client();

tests/test_cases/src/test_net/vmnet_helper.rs

@@ -1,7 +1,6 @@
 //! vmnet-helper backend for virtio-net test (macOS only)
 
 use crate::{krun_call, ShouldRun, TestSetup};
-use krun_sys::COMPAT_NET_FEATURES;
 use nix::libc;
 use std::ffi::CString;
 use std::io::{BufRead, BufReader, Read};
@@ -187,6 +186,26 @@ fn start_vmnet_helper(log_path: &std::path::Path) -> std::io::Result<VmnetConfig
     let mac = parse_mac(mac_str)
         .ok_or_else(|| std::io::Error::other(format!("invalid MAC address: {mac_str}")))?;
 
+    // Increase socket buffer sizes so libkrun's Unixgram backend (which uses
+    // the fd path and does NOT set these) can batch frames without drops.
+    let buf_size: libc::c_int = 7 * 1024 * 1024;
+    unsafe {
+        libc::setsockopt(
+            our_fd,
+            libc::SOL_SOCKET,
+            libc::SO_SNDBUF,
+            &buf_size as *const _ as *const libc::c_void,
+            std::mem::size_of_val(&buf_size) as libc::socklen_t,
+        );
+        libc::setsockopt(
+            our_fd,
+            libc::SOL_SOCKET,
+            libc::SO_RCVBUF,
+            &buf_size as *const _ as *const libc::c_void,
+            std::mem::size_of_val(&buf_size) as libc::socklen_t,
+        );
+    }
+
     Ok(VmnetConfig { fd: our_fd, mac })
 }
 
@@ -218,8 +237,8 @@ pub(crate) fn setup_backend(ctx: u32, test_setup: &TestSetup) -> anyhow::Result<
             std::ptr::null(),
             config.fd,
             config.mac.as_mut_ptr(),
-            COMPAT_NET_FEATURES,
-            0, // no VFKIT flag - vmnet-helper uses raw datagrams
+            0, // no offloading - vmnet-helper uses raw ethernet frames
+            0, // no VFKIT flag
         ))?;
     }
     Ok(())