73 lines
1.9 KiB
TypeScript
73 lines
1.9 KiB
TypeScript
// Copyright 2023 Signal Messenger, LLC
|
|
// SPDX-License-Identifier: AGPL-3.0-only
|
|
|
|
import {
|
|
lookup as nativeLookup,
|
|
resolve4,
|
|
resolve6,
|
|
getServers,
|
|
setServers,
|
|
} from 'dns';
|
|
import type { LookupOneOptions } from 'dns';
|
|
|
|
import * as log from '../logging/log';
|
|
import * as Errors from '../types/errors';
|
|
import { strictAssert } from './assert';
|
|
|
|
const ORIGINAL_SERVERS = getServers();
|
|
const FALLBACK_SERVERS = ['1.1.1.1'];
|
|
|
|
export function lookupWithFallback(
|
|
hostname: string,
|
|
opts: LookupOneOptions,
|
|
callback: (
|
|
err: NodeJS.ErrnoException | null,
|
|
address: string,
|
|
family: number
|
|
) => void
|
|
): void {
|
|
// Node.js support various signatures, but we only support one.
|
|
strictAssert(typeof opts === 'object', 'missing options');
|
|
strictAssert(Boolean(opts.all) !== true, 'options.all is not supported');
|
|
strictAssert(typeof callback === 'function', 'missing callback');
|
|
|
|
nativeLookup(hostname, opts, (err, ...nativeArgs) => {
|
|
if (!err) {
|
|
return callback(err, ...nativeArgs);
|
|
}
|
|
|
|
const family = opts.family === 6 ? 6 : 4;
|
|
|
|
log.error(
|
|
`lookup: failed for ${hostname}, error: ${Errors.toLogFormat(err)}. ` +
|
|
`Retrying with c-ares (IPv${family})`
|
|
);
|
|
const onRecords = (
|
|
fallbackErr: NodeJS.ErrnoException | null,
|
|
records: Array<string>
|
|
): void => {
|
|
setServers(ORIGINAL_SERVERS);
|
|
if (fallbackErr) {
|
|
return callback(fallbackErr, '', 0);
|
|
}
|
|
|
|
if (!Array.isArray(records) || records.length === 0) {
|
|
return callback(
|
|
new Error(`No DNS records returned for: ${hostname}`),
|
|
'',
|
|
0
|
|
);
|
|
}
|
|
|
|
const index = Math.floor(Math.random() * records.length);
|
|
callback(null, records[index], family);
|
|
};
|
|
|
|
setServers(FALLBACK_SERVERS);
|
|
if (family === 4) {
|
|
resolve4(hostname, onRecords);
|
|
} else {
|
|
resolve6(hostname, onRecords);
|
|
}
|
|
});
|
|
}
|