allow to choose hostname and FQDN to be lowercased or not

providers.LowercaseHostname and providers.SetLowerHostname allow to control hostname case sensitivity

This addresses the behavior change introduced in v1.11.0 and reverted in v1.14.1. By default, hostnames are not lowercased.

.changelog/236.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+Allow to choose hostname and FQDN to be lowercased or not
+```

providers/aix/host_aix_ppc64.go

@@ -34,9 +34,11 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"strings"
 	"time"
 
 	"github.com/elastic/go-sysinfo/internal/registry"
+	"github.com/elastic/go-sysinfo/providers"
 	"github.com/elastic/go-sysinfo/providers/shared"
 	"github.com/elastic/go-sysinfo/types"
 )
@@ -190,6 +192,10 @@ func (r *reader) hostname(h *host) {
 	if r.addErr(err) {
 		return
 	}
+
+	if providers.LowercaseHostname() {
+		v = strings.ToLower(v)
+	}
 	h.info.Hostname = v
 }
 

providers/darwin/host_darwin.go

@@ -24,9 +24,11 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"strings"
 	"time"
 
 	"github.com/elastic/go-sysinfo/internal/registry"
+	"github.com/elastic/go-sysinfo/providers"
 	"github.com/elastic/go-sysinfo/providers/shared"
 	"github.com/elastic/go-sysinfo/types"
 )
@@ -225,6 +227,10 @@ func (r *reader) hostname(h *host) {
 	if r.addErr(err) {
 		return
 	}
+
+	if providers.LowercaseHostname() {
+		v = strings.ToLower(v)
+	}
 	h.info.Hostname = v
 }
 

providers/doc.go

@@ -0,0 +1,30 @@
+// 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.
+
+// Package providers
+//
+// # Hostname Behavior
+//
+// Starting from version v1.11.0, the host provider started automatically
+// lowercasing hostnames. This behavior was reverted in v1.14.1.
+//
+// To provide flexibility and allow users to control this behavior, the
+// `LowercaseHostname` and `SetLowerHostname` functions were added.
+//
+// By default, hostnames are not lowercased. If you require hostnames to be
+// lowercased, explicitly set this using `SetLowerHostname(true)`.
+package providers

providers/linux/host_linux.go

@@ -23,11 +23,13 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 	"time"
 
 	"github.com/prometheus/procfs"
 
 	"github.com/elastic/go-sysinfo/internal/registry"
+	"github.com/elastic/go-sysinfo/providers"
 	"github.com/elastic/go-sysinfo/providers/shared"
 	"github.com/elastic/go-sysinfo/types"
 )
@@ -176,7 +178,8 @@ func newHost(fs procFS) (*host, error) {
 }
 
 type reader struct {
-	errs []error
+	errs          []error
+	lowerHostname bool
 }
 
 func (r *reader) addErr(err error) bool {
@@ -233,6 +236,10 @@ func (r *reader) hostname(h *host) {
 	if r.addErr(err) {
 		return
 	}
+
+	if providers.LowercaseHostname() {
+		v = strings.ToLower(v)
+	}
 	h.info.Hostname = v
 }
 

providers/lowerhostname.go

@@ -0,0 +1,34 @@
+// 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.
+
+package providers
+
+import "sync/atomic"
+
+var lowerHostname atomic.Bool
+
+// LowercaseHostname returns if the hostname should be lowercased or not.
+func LowercaseHostname() bool {
+	return lowerHostname.Load()
+}
+
+// SetLowerHostname instruct the host provider to lowercase the hostname.
+// The LowercaseHostname and SetLowerHostname exist as a fix to allow the user
+// to choose or not this behaviour introduced on v1.11.0 and reverted on v1.14.1.
+func SetLowerHostname(lower bool) {
+	lowerHostname.Store(lower)
+}

providers/shared/fqdn.go

@@ -25,6 +25,8 @@ import (
 	"net"
 	"os"
 	"strings"
+
+	"github.com/elastic/go-sysinfo/providers"
 )
 
 // FQDNWithContext attempts to lookup the host's fully-qualified domain name and returns it.
@@ -67,6 +69,10 @@ func fqdn(ctx context.Context, hostname string) (string, error) {
 	if cname != "" {
 		cname = strings.TrimSuffix(cname, ".")
 
+		if providers.LowercaseHostname() {
+			return strings.ToLower(cname), nil
+		}
+
 		// Go might lowercase the cname "for convenience". Therefore, if cname
 		// is the same as hostname, return hostname as is.
 		// See https://github.com/golang/go/blob/go1.22.5/src/net/hosts.go#L38

providers/shared/fqdn_test.go

@@ -26,14 +26,22 @@ import (
 	"time"
 
 	"github.com/stretchr/testify/require"
+
+	"github.com/elastic/go-sysinfo/providers"
 )
 
 func TestFQDN(t *testing.T) {
+	lowercaseHostname := providers.LowercaseHostname()
+	defer func() {
+		providers.SetLowerHostname(lowercaseHostname)
+	}()
+
 	tests := map[string]struct {
-		osHostname       string
-		expectedFQDN     string
-		expectedErrRegex string
-		timeout          time.Duration
+		lowercaseHostname bool
+		osHostname        string
+		expectedFQDN      string
+		expectedErrRegex  string
+		timeout           time.Duration
 	}{
 		// This test case depends on network, particularly DNS,
 		// being available. If it starts to fail often enough
@@ -59,6 +67,12 @@ func TestFQDN(t *testing.T) {
 			expectedFQDN:     "eLaSTic.co",
 			expectedErrRegex: "",
 		},
+		"long_mixed_case_hostname_lowercaseHostname": {
+			lowercaseHostname: true,
+			osHostname:        "eLaSTic.co",
+			expectedFQDN:      "elastic.co",
+			expectedErrRegex:  "",
+		},
 		"nonexistent_timeout": {
 			osHostname:       "foobarbaz",
 			expectedFQDN:     "",
@@ -77,6 +91,7 @@ func TestFQDN(t *testing.T) {
 			ctx, cancel := context.WithTimeout(context.Background(), timeout)
 			defer cancel()
 
+			providers.SetLowerHostname(test.lowercaseHostname)
 			actualFQDN, err := fqdn(ctx, test.osHostname)
 			require.Equal(t, test.expectedFQDN, actualFQDN)
 

providers/windows/host_windows.go

@@ -28,9 +28,10 @@ import (
 
 	stdwindows "golang.org/x/sys/windows"
 
-	windows "github.com/elastic/go-windows"
+	"github.com/elastic/go-windows"
 
 	"github.com/elastic/go-sysinfo/internal/registry"
+	"github.com/elastic/go-sysinfo/providers"
 	"github.com/elastic/go-sysinfo/providers/shared"
 	"github.com/elastic/go-sysinfo/types"
 )
@@ -161,6 +162,10 @@ func (r *reader) hostname(h *host) {
 	if r.addErr(err) {
 		return
 	}
+
+	if providers.LowercaseHostname() {
+		v = strings.ToLower(v)
+	}
 	h.info.Hostname = v
 }