{"record":{"id":"0238ce8b64d27d2b","repo":"zeroclaw-labs/zeroclaw","slug":"failed-to-resolve-host-host-0238ce","errorCode":null,"errorMessage":"Failed to resolve host '{host}'","messagePattern":"Failed to resolve host '(.+?)'","errorType":"exception","errorClass":"anyhow::Error","httpStatus":null,"severity":"error","filePath":"crates/zeroclaw-tools/src/http_request.rs","lineNumber":768,"sourceCode":"}\n\nfn extract_port(url: &str) -> anyhow::Result<u16> {\n    let parsed = reqwest::Url::parse(url)\n        .map_err(|e| anyhow::Error::msg(format!(\"Invalid URL format: {e}\")))?;\n\n    parsed\n        .port_or_known_default()\n        .ok_or_else(|| anyhow::Error::msg(\"URL must include a valid port\"))\n}\n\nasync fn resolve_host_for_request(host: String, port: u16) -> anyhow::Result<Vec<SocketAddr>> {\n    let addrs = tokio::net::lookup_host((host.as_str(), port))\n        .await\n        .map_err(|e| anyhow::Error::msg(format!(\"Failed to resolve host '{host}': {e}\")))?\n        .collect::<Vec<_>>();\n\n    if addrs.is_empty() {\n        anyhow::bail!(\"Failed to resolve host '{host}'\");\n    }\n\n    Ok(addrs)\n}\n\nfn validate_resolved_ips_for_ssrf(\n    host: &str,\n    private_resolution_allowed: bool,\n    ips: &[std::net::IpAddr],\n    nat64_prefixes: &[domain_guard::Nat64Prefix],\n) -> anyhow::Result<()> {\n    if private_resolution_allowed {\n        domain_guard::validate_resolved_ips_exclude_metadata(host, ips, nat64_prefixes)\n    } else {\n        domain_guard::validate_resolved_ips_are_public(host, ips, nat64_prefixes)\n    }\n}\n","sourceCodeStart":750,"sourceCodeEnd":786,"githubUrl":"https://github.com/zeroclaw-labs/zeroclaw/blob/88bb9c8533fc57ed7a03e36ca7c9ed2bf8336dcc/crates/zeroclaw-tools/src/http_request.rs#L750-L786","documentation":"resolve_host_for_request performs the DNS lookup for the http_request tool via tokio::net::lookup_host and treats two outcomes as failures: the lookup returns an error (surfaced as \"Failed to resolve host '{host}': {e}\"), or it succeeds but yields zero addresses, which produces this exact message. The empty-success case is a defensive guard: the resolved IP list feeds SSRF validation, and an empty list would silently skip that check, so the request aborts instead. It almost always indicates a broken resolver environment rather than a bad hostname.","triggerScenarios":"An http_request call to a host whose getaddrinfo-style lookup completes successfully but returns no addresses: minimal/musl containers with a stripped /etc/nsswitch.conf, resolvers that answer with zero A/AAAA records, transient states while systemd-resolved or a VPN DNS proxy is starting, or search-domain configurations where the queried name matches nothing.","commonSituations":"Distroless or Alpine-based containers without the dns module in nsswitch.conf, Docker/Kubernetes pods during network setup, hosts with an unreachable or flapping DNS server, and CI runners where /etc/resolv.conf points at a resolver that returns empty answers.","solutions":["Run 'getent hosts <host>' and 'dig <host> @<resolver>' in the same environment (same container/pod) to confirm the resolver actually returns records.","Inspect /etc/nsswitch.conf and /etc/resolv.conf; in minimal images ensure the 'dns' source is present and the nameserver is reachable.","Retry after network/DNS setup settles — empty answers during resolver startup are transient.","If relying on search domains, pass the fully qualified name instead of the short name."],"exampleFix":null,"handlingStrategy":"retry","validationCode":"// Pre-flight the same lookup the tool performs:\nasync fn resolvable(host: &str, port: u16) -> bool {\n    tokio::net::lookup_host((host, port)).await.map(|it| it.count() > 0).unwrap_or(false)\n}","typeGuard":null,"tryCatchPattern":"for attempt in 0..3 {\n    match http_request_tool(url.clone()).await {\n        Ok(res) => break Ok(res),\n        Err(e) if e.to_string().starts_with(\"Failed to resolve host\") && attempt < 2 => {\n            tokio::time::sleep(Duration::from_millis(500 * (attempt + 1))).await;\n        }\n        Err(e) => break Err(e),\n    }\n}","preventionTips":["Verify container images ship a working /etc/nsswitch.conf (with the dns source) and a reachable nameserver in /etc/resolv.conf.","Use fully qualified names instead of relying on search domains.","Treat empty-resolution as environment breakage: diagnose with 'getent hosts <host>' in the same pod before blaming the URL."],"tags":["dns","network","http-request","environment","rust"],"backgroundTag":"dns-resolution-failed","analyzedSha":"88bb9c8533fc57ed7a03e36ca7c9ed2bf8336dcc","analyzedAt":"2026-08-23T01:07:41.857Z","schemaVersion":2},"datasetVersion":"2026-08-23T08:06:27.607Z"}