collector: Implement uname collector for FreeBSD (#1239)

* collector: Implement uname collector for FreeBSD

Signed-off-by: David O'Rourke <david.orourke@gmail.com>

collector/uname_freebsd.go

@@ -0,0 +1,57 @@
+// Copyright 2019 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !nouname
+
+package collector
+
+import (
+	"bytes"
+	"strings"
+
+	"golang.org/x/sys/unix"
+)
+
+func getUname() (uname, error) {
+	var utsname unix.Utsname
+	if err := unix.Uname(&utsname); err != nil {
+		return uname{}, err
+	}
+
+	// We do a little bit of work here to emulate what happens in the Linux
+	// uname calls since FreeBSD uname doesn't have a Domainname.
+	nodename := string(utsname.Nodename[:bytes.IndexByte(utsname.Nodename[:], 0)])
+	split := strings.SplitN(nodename, ".", 2)
+
+	// We'll always have at least a single element in the array. We assume this
+	// is the hostname.
+	hostname := split[0]
+
+	// If we have more than one element, we assume this is the domainname.
+	// Otherwise leave it to "(none)" like Linux.
+	domainname := "(none)"
+	if len(split) > 1 {
+		domainname = split[1]
+	}
+
+	output := uname{
+		SysName:    string(utsname.Sysname[:bytes.IndexByte(utsname.Sysname[:], 0)]),
+		Release:    string(utsname.Release[:bytes.IndexByte(utsname.Release[:], 0)]),
+		Version:    string(utsname.Version[:bytes.IndexByte(utsname.Version[:], 0)]),
+		Machine:    string(utsname.Machine[:bytes.IndexByte(utsname.Machine[:], 0)]),
+		NodeName:   hostname,
+		DomainName: domainname,
+	}
+
+	return output, nil
+}