github.com/coreos/mantle@v0.13.0/system/hostname.go (about)

     1  // Copyright 2015 CoreOS, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package system
    16  
    17  import (
    18  	"net"
    19  	"os"
    20  	"strings"
    21  )
    22  
    23  // FullHostname is a best effort attempt to resolve the canonical FQDN of
    24  // the host. On failure it will fall back to a reasonable looking default
    25  // such as 'localhost.' or 'hostname.invalid.'
    26  func FullHostname() string {
    27  	hostname, err := os.Hostname()
    28  	if err != nil || hostname == "localhost" || hostname == "(none)" {
    29  		return "localhost."
    30  	}
    31  	fullname, err := net.LookupCNAME(hostname)
    32  	if err != nil {
    33  		fullname = hostname
    34  		if !strings.Contains(fullname, ".") {
    35  			fullname += ".invalid."
    36  		}
    37  	}
    38  	return fullname
    39  }