| // Copyright 2022 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| package net |
| |
| import ( |
| "os" |
| "sync/atomic" |
| "time" |
| ) |
| |
| var ( |
| defaultNS = []string{"127.0.0.1:53", "[::1]:53"} |
| getHostname = os.Hostname // variable for testing |
| ) |
| |
| type dnsConfig struct { |
| servers []string // server addresses (in host:port form) to use |
| search []string // rooted suffixes to append to local name |
| ndots int // number of dots in name to trigger absolute lookup |
| timeout time.Duration // wait before giving up on a query, including retries |
| attempts int // lost packets before giving up on server |
| rotate bool // round robin among servers |
| unknownOpt bool // anything unknown was encountered |
| lookup []string // OpenBSD top-level database "lookup" order |
| err error // any error that occurs during open of resolv.conf |
| mtime time.Time // time of resolv.conf modification |
| soffset uint32 // used by serverOffset |
| singleRequest bool // use sequential A and AAAA queries instead of parallel queries |
| useTCP bool // force usage of TCP for DNS resolutions |
| } |
| |
| // serverOffset returns an offset that can be used to determine |
| // indices of servers in c.servers when making queries. |
| // When the rotate option is enabled, this offset increases. |
| // Otherwise it is always 0. |
| func (c *dnsConfig) serverOffset() uint32 { |
| if c.rotate { |
| return atomic.AddUint32(&c.soffset, 1) - 1 // return 0 to start |
| } |
| return 0 |
| } |