libnyanpasu/clash-nyanpasu · warning

flushing the system DNS cache is not supported on this platf

Error message

flushing the system DNS cache is not supported on this platform

What it means

flush_system_dns_cache is a platform-gated helper that shells out to OS tools to clear the OS DNS resolver cache. On unsupported platforms (anything that is neither Windows nor macOS) the #[cfg] fallback deliberately aborts with this bail instead of attempting a command, because there is no portable way to flush DNS. Callers must treat DNS-cache flushing as a best-effort, platform-dependent capability.

Source

Thrown at backend/tauri/src/client/system_dns.rs:53

        .status()
        .context("failed to request permission to flush the Windows DNS cache")?;

    ensure_success(status, "ipconfig /flushdns")
}

#[cfg(target_os = "macos")]
fn flush_system_dns_cache() -> anyhow::Result<()> {
    let status = std::process::Command::new("/usr/bin/osascript")
        .args(["-e", MACOS_SCRIPT])
        .status()
        .context("failed to request permission to flush the macOS DNS cache")?;

    ensure_success(status, "macOS DNS cache flush")
}

#[cfg(not(any(target_os = "windows", target_os = "macos")))]
fn flush_system_dns_cache() -> anyhow::Result<()> {
    anyhow::bail!("flushing the system DNS cache is not supported on this platform")
}

#[cfg(any(target_os = "windows", target_os = "macos"))]
fn ensure_success(status: std::process::ExitStatus, operation: &str) -> anyhow::Result<()> {
    if status.success() {
        Ok(())
    } else {
        anyhow::bail!("{operation} failed with status {status}")
    }
}

#[cfg(test)]
#[derive(Debug, Default)]
pub struct NoopSystemDnsCache;

#[cfg(test)]
impl SystemDnsCache for NoopSystemDnsCache {
    fn flush(&self) -> anyhow::Result<()> {

View on GitHub (pinned to f7dbce2997)

Solutions

1. Guard the call behind a cfg(all(windows, target_os = "macos")) check or an is_supported() predicate and skip flushing on other platforms
2. Log the failure as a warning and continue the calling flow (DNS flush is best-effort, not required for proxy correctness)
3. Optionally extend support by implementing Linux flush (e.g. resolvectl flush-caches) behind a new cfg arm

Example fix

// before
flush_system_dns_cache()?;
// after
#[cfg(any(target_os = "windows", target_os = "macos"))]
if let Err(e) = flush_system_dns_cache() {
    log::warn!("DNS cache flush skipped: {e}");
}

fn can_flush_dns() -> bool {
    cfg!(any(target_os = "windows", target_os = "macos"))
}

fn dns_flush_supported() -> bool {
    cfg!(any(target_os = "windows", target_os = "macos"))
}

match flush_system_dns_cache() {
    Err(e) if e.to_string().contains("not supported") => log::info!("DNS flush unsupported; skipping"),
    other => other?,
}

When it happens

Trigger: Calling flush_system_dns_cache() on a Linux/BSD or any non-Windows/non-macOS target; the cfg-gated stub compiles to an unconditional bail, so every call on such a platform fails immediately.

Common situations: Running nyanpasu on Linux and toggling system proxy/TUN in a flow that also tries to flush DNS; CI builds targeting unsupported platforms; distro-specific expectations that DNS can be flushed via systemd-resolved (not implemented here).

Understand the failure class

Background: "unsupported platform" / "not supported on this platform" errors: what they mean and how to fix them — this error's family across 47 libraries.

Related errors

• unimplemented!()
• IPC server is already initialized
• application actor call timed out
• clash config actor reply dropped
• clash config actor call timed out

AI-assisted analysis of libnyanpasu/clash-nyanpasu@f7dbce2997 (2026-09-08). Data as JSON: /api/errors/128032ec02c988dd. Report an issue: GitHub.