net: LookupAddr adds trailing dots to entries from /etc/hosts

[rsc]

Here is a program:

package main

import (
    "fmt"
    "net"
)

func main() {
    fmt.Println(net.LookupAddr("127.0.0.1"))
}

When run, it prints:

$ go run /tmp/x.go
[localhost.] <nil>

This is incorrect, given this /etc/hosts:

$ cat /etc/hosts
##
# Host Database
#
# localhost is used to configure the loopback interface
# when the system is booting.  Do not change this entry.
##
127.0.0.1   localhost
255.255.255.255 broadcasthost
::1             localhost 

Names obtained from the DNS system are rooted and have a trailing dot. Names obtained from /etc/hosts should not.

This is a partial regression from Go 1.5 and should be fixed for Go 1.6.

It looks like Go 1.5 was inconsistent based on what routines were being used:

$ GODEBUG=netdns=go go1.5 run /tmp/x.go
[localhost] <nil>
$ GODEBUG=netdns=cgo go1.5 run /tmp/x.go
[localhost.] <nil>

and now netdns=go has been changed to match netdns=cgo:

$ GODEBUG=netdns=go go run /tmp/x.go
[localhost.] <nil>
$ GODEBUG=netdns=cgo go run /tmp/x.go
[localhost.] <nil>

I'm not sure that's the right fix.

[gopherbot]

CL https://golang.org/cl/18384 mentions this issue.

[gopherbot]

CL https://golang.org/cl/18559 mentions this issue.