moving cgo to shared and adding nocgo fallback

providers/darwin/host_darwin.go

@@ -20,13 +20,11 @@
 
 package darwin
 
-import "C"
 import (
 	"errors"
 	"fmt"
 	"os"
 	"time"
-	"unsafe"
 
 	"github.com/joeshaw/multierror"
 
@@ -217,7 +215,7 @@ func (r *reader) hostname(h *host) {
 }
 
 func (r *reader) fqdn(h *host) {
-	fqdn, err := fqdnC()
+	fqdn, err := shared.FQDN()
 	if err != nil {
 		r.addErr(fmt.Errorf("could not get linux FQDN: %w", err))
 		return
@@ -226,34 +224,6 @@ func (r *reader) fqdn(h *host) {
 	h.info.FQDN = fqdn
 }
 
-func fqdnC() (string, error) {
-	// Another option could be reading:
-	// - /proc/sys/kernel/hostname
-	// - /proc/sys/kernel/domainname
-	const buffSize = 64
-	buff := make([]byte, buffSize)
-	size := C.size_t(buffSize)
-	cString := C.CString(string(buff))
-	defer C.free(unsafe.Pointer(cString))
-
-	_, errno := C.gethostname(cString, size)
-	if errno != nil {
-		return "", fmt.Errorf("syscall gethostname errored: %v", errno)
-	}
-	var hostname string = C.GoString(cString)
-
-	_, errno = C.getdomainname(cString, size)
-	if errno != nil {
-		return "", fmt.Errorf("syscall getdomainname errored: %v", errno)
-	}
-	var domain string = C.GoString(cString)
-	if domain == "" || domain == "(none)" { // mimicking 'hostname -f' behaviour
-		domain = "lan"
-	}
-
-	return fmt.Sprintf("%s.%s", hostname, domain), nil
-}
-
 func (r *reader) network(h *host) {
 	ips, macs, err := shared.Network()
 	if r.addErr(err) {

providers/linux/host_linux.go

@@ -17,18 +17,13 @@
 
 package linux
 
-// #include <unistd.h>
-// #include <stdlib.h>
-import "C"
-
 import (
 	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
 	"path/filepath"
 	"time"
-	"unsafe"
 
 	"github.com/joeshaw/multierror"
 	"github.com/prometheus/procfs"
@@ -218,7 +213,7 @@ func (r *reader) hostname(h *host) {
 }
 
 func (r *reader) fqdn(h *host) {
-	fqdn, err := fqdnC()
+	fqdn, err := shared.FQDN()
 	if err != nil {
 		r.addErr(fmt.Errorf("could not get linux FQDN: %w", err))
 		return
@@ -227,34 +222,6 @@ func (r *reader) fqdn(h *host) {
 	h.info.FQDN = fqdn
 }
 
-func fqdnC() (string, error) {
-	// Another option could be reading:
-	// - /proc/sys/kernel/hostname
-	// - /proc/sys/kernel/domainname
-	const buffSize = 64
-	buff := make([]byte, buffSize)
-	size := C.size_t(buffSize)
-	cString := C.CString(string(buff))
-	defer C.free(unsafe.Pointer(cString))
-
-	_, errno := C.gethostname(cString, size)
-	if errno != nil {
-		return "", fmt.Errorf("syscall gethostname errored: %v", errno)
-	}
-	var hostname string = C.GoString(cString)
-
-	_, errno = C.getdomainname(cString, size)
-	if errno != nil {
-		return "", fmt.Errorf("syscall getdomainname errored: %v", errno)
-	}
-	var domain string = C.GoString(cString)
-	if domain == "" || domain == "(none)" { // mimicking 'hostname -f' behaviour
-		domain = "lan"
-	}
-
-	return fmt.Sprintf("%s.%s", hostname, domain), nil
-}
-
 func (r *reader) network(h *host) {
 	ips, macs, err := shared.Network()
 	if r.addErr(err) {

providers/shared/host_fqdn_cgo_unix.go

@@ -0,0 +1,58 @@
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you 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.
+
+//go:build cgo
+
+package shared
+
+// #include <unistd.h>
+// #include <stdlib.h>
+import "C"
+import (
+	"fmt"
+	"unsafe"
+)
+
+func FQDN() (string, error) {
+	// Another option could be reading:
+	// - /proc/sys/kernel/hostname
+	// - /proc/sys/kernel/domainname
+	// perhaps not valid for darwin
+
+	const buffSize = 64
+	buff := make([]byte, buffSize)
+	size := C.size_t(buffSize)
+	cString := C.CString(string(buff))
+	defer C.free(unsafe.Pointer(cString))
+
+	_, errno := C.gethostname(cString, size)
+	if errno != nil {
+		return "", fmt.Errorf("syscall gethostname errored: %v", errno)
+	}
+	var hostname string = C.GoString(cString)
+
+	_, errno = C.getdomainname(cString, size)
+	if errno != nil {
+		return "", fmt.Errorf("syscall getdomainname errored: %v", errno)
+	}
+	var domain string = C.GoString(cString)
+	if domain == "" || domain == "(none)" { // mimicking 'hostname -f' behaviour
+		domain = "lan"
+	}
+
+	return fmt.Sprintf("%s.%s", hostname, domain), nil
+}

providers/shared/host_fqdn_nocgo_linux.go

@@ -0,0 +1,29 @@
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you 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.
+
+//go:build !cgo
+
+package shared
+
+import "C"
+import (
+	"os"
+)
+
+func FQDN() (string, error) {
+	return os.Hostname()
+}