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net: append ":53" to DNS servers when reading resolv.conf

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Avoids generating some redundant garbage from re-concatenating the
same string for every DNS query.

benchmark                                      old allocs     new allocs     delta
BenchmarkGoLookupIP-32                         156            154            -1.28%
BenchmarkGoLookupIPNoSuchHost-32               456            446            -2.19%
BenchmarkGoLookupIPWithBrokenNameServer-32     577            564            -2.25%

benchmark                                      old bytes     new bytes     delta
BenchmarkGoLookupIP-32                         10873         10824         -0.45%
BenchmarkGoLookupIPNoSuchHost-32               43303         43140         -0.38%
BenchmarkGoLookupIPWithBrokenNameServer-32     46824         46616         -0.44%

Update #15473.

Change-Id: I3b0173dfedf31bd08eaea1069968b416850864a1
Reviewed-on: https://go-review.googlesource.com/22556
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Matthew Dempsky 2016-04-28 11:15:44 -07:00
parent 2cc27a7de9
commit 4d9bda51ff
4 changed files with 10 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
src/net/dnsclient_unix.go
View File

@ -190,7 +190,6 @@ func tryOneName(ctx context.Context, cfg *dnsConfig, name string, qtype uint16)
var lastErr error
for i := 0; i < cfg.attempts; i++ {
for _, server := range cfg.servers {
server = JoinHostPort(server, "53")
msg, err := exchange(ctx, server, name, qtype)
if err != nil {
lastErr = &DNSError{

4
src/net/dnsclient_unix_test.go
View File

@ -221,7 +221,7 @@ var updateResolvConfTests = []struct {
{
name: "golang.org",
lines: []string{"nameserver 8.8.8.8"},
servers: []string{"8.8.8.8"},
servers: []string{"8.8.8.8:53"},
},
{
name: "",
@ -231,7 +231,7 @@ var updateResolvConfTests = []struct {
{
name: "www.example.com",
lines: []string{"nameserver 8.8.4.4"},
servers: []string{"8.8.4.4"},
servers: []string{"8.8.4.4:53"},
},
}

8
src/net/dnsconfig_unix.go
View File

@ -14,12 +14,12 @@ import (
)
var (
defaultNS = []string{"127.0.0.1", "::1"}
defaultNS = []string{"127.0.0.1:53", "[::1]:53"}
getHostname = os.Hostname // variable for testing
)
type dnsConfig struct {
servers []string // servers to use
servers []string // server addresses (in host:port form) to use
search []string // 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
@ -70,9 +70,9 @@ func dnsReadConfig(filename string) *dnsConfig {
// just an IP address. Otherwise we need DNS
// to look it up.
if parseIPv4(f[1]) != nil {
conf.servers = append(conf.servers, f[1])
conf.servers = append(conf.servers, JoinHostPort(f[1], "53"))
} else if ip, _ := parseIPv6(f[1], true); ip != nil {
conf.servers = append(conf.servers, f[1])
conf.servers = append(conf.servers, JoinHostPort(f[1], "53"))
}
}

8
src/net/dnsconfig_unix_test.go
View File

@ -21,7 +21,7 @@ var dnsReadConfigTests = []struct {
{
name: "testdata/resolv.conf",
want: &dnsConfig{
servers: []string{"8.8.8.8", "2001:4860:4860::8888", "fe80::1%lo0"},
servers: []string{"8.8.8.8:53", "[2001:4860:4860::8888]:53", "[fe80::1%lo0]:53"},
search: []string{"localdomain"},
ndots: 5,
timeout: 10 * time.Second,
@ -33,7 +33,7 @@ var dnsReadConfigTests = []struct {
{
name: "testdata/domain-resolv.conf",
want: &dnsConfig{
servers: []string{"8.8.8.8"},
servers: []string{"8.8.8.8:53"},
search: []string{"localdomain"},
ndots: 1,
timeout: 5 * time.Second,
@ -43,7 +43,7 @@ var dnsReadConfigTests = []struct {
{
name: "testdata/search-resolv.conf",
want: &dnsConfig{
servers: []string{"8.8.8.8"},
servers: []string{"8.8.8.8:53"},
search: []string{"test", "invalid"},
ndots: 1,
timeout: 5 * time.Second,
@ -67,7 +67,7 @@ var dnsReadConfigTests = []struct {
timeout: 5 * time.Second,
attempts: 2,
lookup: []string{"file", "bind"},
servers: []string{"169.254.169.254", "10.240.0.1"},
servers: []string{"169.254.169.254:53", "10.240.0.1:53"},
search: []string{"c.symbolic-datum-552.internal."},
},
},