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net: clear /etc/hosts cache on fs.ErrNotExist and fs.ErrPermission errors 

This was also the cause of my issues in CL 455275

Before:
root@arch:~/aa# $(time sleep 5 && mv /etc/hosts /tmp/hosts) &
[1] 2214
root@arch:~/aa# go run main.go
[232.223.232.123] <nil>
[232.223.232.123] <nil>
[232.223.232.123] <nil>
[232.223.232.123] <nil>
[232.223.232.123] <nil>
[232.223.232.123] <nil>
(....)

After:
root@arch:~/aa# $(time sleep 5 && mv /etc/hosts /tmp/hosts) &
[1] 2284
root@arch:~/aa# go run main.go
[232.223.232.123] <nil>
[232.223.232.123] <nil>
[232.223.232.123] <nil>
[232.223.232.123] <nil>
[232.223.232.123] <nil>
[] lookup sth on 127.0.0.53:53: server misbehaving
[] lookup sth on 127.0.0.53:53: server misbehaving

Change-Id: I3090fd8f3105db8c2d7c3bf5afe7b18ebca61cda
GitHub-Last-Rev: cb0dac6448
GitHub-Pull-Request: golang/go#59963
Reviewed-on: https://go-review.googlesource.com/c/go/+/492555
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Run-TryBot: Mateusz Poliwczak <mpoliwczak34@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
This commit is contained in:
Mateusz Poliwczak 2023-05-11 11:54:28 +00:00 committed by Gopher Robot
parent 42023d6f52
commit 7db6d8a29d
1 changed files with 44 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

81
src/net/hosts.go
View File

@ -5,7 +5,9 @@
package net
import (
"errors"
"internal/bytealg"
"io/fs"
"net/netip"
"sync"
"time"
@ -63,48 +65,54 @@ func readHosts() {
hs := make(map[string]byName)
is := make(map[string][]string)
var file *file
if file, _ = open(hp); file == nil {
return
file, err := open(hp)
if err != nil {
if !errors.Is(err, fs.ErrNotExist) && !errors.Is(err, fs.ErrPermission) {
return
}
}
for line, ok := file.readLine(); ok; line, ok = file.readLine() {
if i := bytealg.IndexByteString(line, '#'); i >= 0 {
// Discard comments.
line = line[0:i]
}
f := getFields(line)
if len(f) < 2 {
continue
}
addr := parseLiteralIP(f[0])
if addr == "" {
continue
}
var canonical string
for i := 1; i < len(f); i++ {
name := absDomainName(f[i])
h := []byte(f[i])
lowerASCIIBytes(h)
key := absDomainName(string(h))
if i == 1 {
canonical = key
if file != nil {
defer file.close()
for line, ok := file.readLine(); ok; line, ok = file.readLine() {
if i := bytealg.IndexByteString(line, '#'); i >= 0 {
// Discard comments.
line = line[0:i]
}
is[addr] = append(is[addr], name)
if v, ok := hs[key]; ok {
hs[key] = byName{
addrs: append(v.addrs, addr),
canonicalName: v.canonicalName,
}
f := getFields(line)
if len(f) < 2 {
continue
}
addr := parseLiteralIP(f[0])
if addr == "" {
continue
}
hs[key] = byName{
addrs: []string{addr},
canonicalName: canonical,
var canonical string
for i := 1; i < len(f); i++ {
name := absDomainName(f[i])
h := []byte(f[i])
lowerASCIIBytes(h)
key := absDomainName(string(h))
if i == 1 {
canonical = key
}
is[addr] = append(is[addr], name)
if v, ok := hs[key]; ok {
hs[key] = byName{
addrs: append(v.addrs, addr),
canonicalName: v.canonicalName,
}
continue
}
hs[key] = byName{
addrs: []string{addr},
canonicalName: canonical,
}
}
}
}
@ -115,7 +123,6 @@ func readHosts() {
hosts.byAddr = is
hosts.mtime = mtime
hosts.size = size
file.close()
}
// lookupStaticHost looks up the addresses and the canonical name for the given host from /etc/hosts.