golang dnsconfig 代码
文件路径：/src/net/dnsconfig.go
/ 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
}