diff options
Diffstat (limited to 'vendor/github.com/docker/libnetwork/resolvconf')
| -rw-r--r-- | vendor/github.com/docker/libnetwork/resolvconf/resolvconf.go | 51 |
1 files changed, 41 insertions, 10 deletions
diff --git a/vendor/github.com/docker/libnetwork/resolvconf/resolvconf.go b/vendor/github.com/docker/libnetwork/resolvconf/resolvconf.go index 5cb251b13..946bb8712 100644 --- a/vendor/github.com/docker/libnetwork/resolvconf/resolvconf.go +++ b/vendor/github.com/docker/libnetwork/resolvconf/resolvconf.go @@ -14,6 +14,45 @@ import ( "github.com/sirupsen/logrus" ) +const ( + // defaultPath is the default path to the resolv.conf that contains information to resolve DNS. See Path(). + defaultPath = "/etc/resolv.conf" + // alternatePath is a path different from defaultPath, that may be used to resolve DNS. See Path(). + alternatePath = "/run/systemd/resolve/resolv.conf" +) + +var ( + detectSystemdResolvConfOnce sync.Once + pathAfterSystemdDetection = defaultPath +) + +// Path returns the path to the resolv.conf file that libnetwork should use. +// +// When /etc/resolv.conf contains 127.0.0.53 as the only nameserver, then +// it is assumed systemd-resolved manages DNS. Because inside the container 127.0.0.53 +// is not a valid DNS server, Path() returns /run/systemd/resolve/resolv.conf +// which is the resolv.conf that systemd-resolved generates and manages. +// Otherwise Path() returns /etc/resolv.conf. +// +// Errors are silenced as they will inevitably resurface at future open/read calls. +// +// More information at https://www.freedesktop.org/software/systemd/man/systemd-resolved.service.html#/etc/resolv.conf +func Path() string { + detectSystemdResolvConfOnce.Do(func() { + candidateResolvConf, err := ioutil.ReadFile(defaultPath) + if err != nil { + // silencing error as it will resurface at next calls trying to read defaultPath + return + } + ns := GetNameservers(candidateResolvConf, types.IP) + if len(ns) == 1 && ns[0] == "127.0.0.53" { + pathAfterSystemdDetection = alternatePath + logrus.Infof("detected 127.0.0.53 nameserver, assuming systemd-resolved, so using resolv.conf: %s", alternatePath) + } + }) + return pathAfterSystemdDetection +} + var ( // Note: the default IPv4 & IPv6 resolvers are set to Google's Public DNS defaultIPv4Dns = []string{"nameserver 8.8.8.8", "nameserver 8.8.4.4"} @@ -50,15 +89,7 @@ type File struct { // Get returns the contents of /etc/resolv.conf and its hash func Get() (*File, error) { - resolv, err := ioutil.ReadFile("/etc/resolv.conf") - if err != nil { - return nil, err - } - hash, err := ioutils.HashData(bytes.NewReader(resolv)) - if err != nil { - return nil, err - } - return &File{Content: resolv, Hash: hash}, nil + return GetSpecific(Path()) } // GetSpecific returns the contents of the user specified resolv.conf file and its hash @@ -81,7 +112,7 @@ func GetIfChanged() (*File, error) { lastModified.Lock() defer lastModified.Unlock() - resolv, err := ioutil.ReadFile("/etc/resolv.conf") + resolv, err := ioutil.ReadFile(Path()) if err != nil { return nil, err } |