isPlainHostName alone sends every single-label name direct
info
isPlainHostName(host) is true for any name without a dot, including a mistyped public name. The user then gets a local resolver error instead of the proxy's block page. Fine as a performance short-cut, weak as the only definition of "internal".
Why it matters
Single-label names are resolved through the client’s search list, so intranet becomes
intranet.corp.example; that is why the DIRECT short-cut works. But googl or wiki typed
without a suffix are also plain names and go DIRECT, where they fail at the resolver instead
of reaching the proxy’s error page and logs. In environments that want all failures visible
on the proxy, pair isPlainHostName with an explicit list of known short names or rely on
dnsDomainIs(host, ".corp.example") for the internal definition.
How to fix
Keep isPlainHostName as a fast path only if a resolver-side failure for typos is acceptable; otherwise list the known short names explicitly.
Examples
Bad
function FindProxyForURL(url, host) {
if (isPlainHostName(host)) {
return "DIRECT";
}
return "PROXY proxy.corp.example:8080";
}
Good
var shortNames = ["intranet", "wiki", "print"];
function FindProxyForURL(url, host) {
if (shortNames.indexOf(host) >= 0 || dnsDomainIs(host, ".corp.example")) {
return "DIRECT";
}
return "PROXY proxy.corp.example:8080";
}
Related rules
- DNS-dependent rule placed before string rules PAC-P005
- *.local routed direct PAC-B007