[feature] Initial Prometheus metrics implementation (#2334)

* feat: Initial OTEL metrics

* docs: add metrics documentation

* fix: metrics endpoint conditional check

* feat: metrics endpoint basic auth

* fix: make metrics-auth-enabled default false

* fix: go fmt helpers.gen.go

* fix: add metric-related env vars to envparsing.sh

* fix: metrics docs

* fix: metrics related stuff in envparsing.sh

* fix: metrics docs

* chore: metrics docs wording

* fix: metrics stuff in envparsing?

* bump otel versions

---------

Co-authored-by: Tsuribori <user@acertaindebian>
Co-authored-by: Tsuribori <none@example.org>
Co-authored-by: tsmethurst <tobi.smethurst@protonmail.com>

vendor/github.com/prometheus/procfs/net_wireless.go

@@ -0,0 +1,182 @@
+// Copyright 2023 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.
+
+package procfs
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+
+	"github.com/prometheus/procfs/internal/util"
+)
+
+// Wireless models the content of /proc/net/wireless.
+type Wireless struct {
+	Name string
+
+	// Status is the current 4-digit hex value status of the interface.
+	Status uint64
+
+	// QualityLink is the link quality.
+	QualityLink int
+
+	// QualityLevel is the signal gain (dBm).
+	QualityLevel int
+
+	// QualityNoise is the signal noise baseline (dBm).
+	QualityNoise int
+
+	// DiscardedNwid is the number of discarded packets with wrong nwid/essid.
+	DiscardedNwid int
+
+	// DiscardedCrypt is the number of discarded packets with wrong code/decode (WEP).
+	DiscardedCrypt int
+
+	// DiscardedFrag is the number of discarded packets that can't perform MAC reassembly.
+	DiscardedFrag int
+
+	// DiscardedRetry is the number of discarded packets that reached max MAC retries.
+	DiscardedRetry int
+
+	// DiscardedMisc is the number of discarded packets for other reasons.
+	DiscardedMisc int
+
+	// MissedBeacon is the number of missed beacons/superframe.
+	MissedBeacon int
+}
+
+// Wireless returns kernel wireless statistics.
+func (fs FS) Wireless() ([]*Wireless, error) {
+	b, err := util.ReadFileNoStat(fs.proc.Path("net/wireless"))
+	if err != nil {
+		return nil, err
+	}
+
+	m, err := parseWireless(bytes.NewReader(b))
+	if err != nil {
+		return nil, fmt.Errorf("%s: wireless: %w", ErrFileParse, err)
+	}
+
+	return m, nil
+}
+
+// parseWireless parses the contents of /proc/net/wireless.
+/*
+Inter-| sta-|   Quality        |   Discarded packets               | Missed | WE
+face | tus | link level noise |  nwid  crypt   frag  retry   misc | beacon | 22
+ eth1: 0000    5.  -256.  -10.       0      1      0     3      0        0
+ eth2: 0000    5.  -256.  -20.       0      2      0     4      0        0
+*/
+func parseWireless(r io.Reader) ([]*Wireless, error) {
+	var (
+		interfaces []*Wireless
+		scanner    = bufio.NewScanner(r)
+	)
+
+	for n := 0; scanner.Scan(); n++ {
+		// Skip the 2 header lines.
+		if n < 2 {
+			continue
+		}
+
+		line := scanner.Text()
+
+		parts := strings.Split(line, ":")
+		if len(parts) != 2 {
+			return nil, fmt.Errorf("%w: expected 2 parts after splitting line by ':', got %d for line %q", ErrFileParse, len(parts), line)
+		}
+
+		name := strings.TrimSpace(parts[0])
+		stats := strings.Fields(parts[1])
+
+		if len(stats) < 10 {
+			return nil, fmt.Errorf("%w: invalid number of fields in line %d, expected 10+, got %d: %q", ErrFileParse, n, len(stats), line)
+		}
+
+		status, err := strconv.ParseUint(stats[0], 16, 16)
+		if err != nil {
+			return nil, fmt.Errorf("%w: invalid status in line %d: %q", ErrFileParse, n, line)
+		}
+
+		qlink, err := strconv.Atoi(strings.TrimSuffix(stats[1], "."))
+		if err != nil {
+			return nil, fmt.Errorf("%s: parse Quality:link as integer %q: %w", ErrFileParse, qlink, err)
+		}
+
+		qlevel, err := strconv.Atoi(strings.TrimSuffix(stats[2], "."))
+		if err != nil {
+			return nil, fmt.Errorf("%s: Quality:level as integer %q: %w", ErrFileParse, qlevel, err)
+		}
+
+		qnoise, err := strconv.Atoi(strings.TrimSuffix(stats[3], "."))
+		if err != nil {
+			return nil, fmt.Errorf("%s: Quality:noise as integer %q: %w", ErrFileParse, qnoise, err)
+		}
+
+		dnwid, err := strconv.Atoi(stats[4])
+		if err != nil {
+			return nil, fmt.Errorf("%s: Discarded:nwid as integer %q: %w", ErrFileParse, dnwid, err)
+		}
+
+		dcrypt, err := strconv.Atoi(stats[5])
+		if err != nil {
+			return nil, fmt.Errorf("%s: Discarded:crypt as integer %q: %w", ErrFileParse, dcrypt, err)
+		}
+
+		dfrag, err := strconv.Atoi(stats[6])
+		if err != nil {
+			return nil, fmt.Errorf("%s: Discarded:frag as integer %q: %w", ErrFileParse, dfrag, err)
+		}
+
+		dretry, err := strconv.Atoi(stats[7])
+		if err != nil {
+			return nil, fmt.Errorf("%s: Discarded:retry as integer %q: %w", ErrFileParse, dretry, err)
+		}
+
+		dmisc, err := strconv.Atoi(stats[8])
+		if err != nil {
+			return nil, fmt.Errorf("%s: Discarded:misc as integer %q: %w", ErrFileParse, dmisc, err)
+		}
+
+		mbeacon, err := strconv.Atoi(stats[9])
+		if err != nil {
+			return nil, fmt.Errorf("%s: Missed:beacon as integer %q: %w", ErrFileParse, mbeacon, err)
+		}
+
+		w := &Wireless{
+			Name:           name,
+			Status:         status,
+			QualityLink:    qlink,
+			QualityLevel:   qlevel,
+			QualityNoise:   qnoise,
+			DiscardedNwid:  dnwid,
+			DiscardedCrypt: dcrypt,
+			DiscardedFrag:  dfrag,
+			DiscardedRetry: dretry,
+			DiscardedMisc:  dmisc,
+			MissedBeacon:   mbeacon,
+		}
+
+		interfaces = append(interfaces, w)
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, fmt.Errorf("%s: Failed to scan /proc/net/wireless: %w", ErrFileRead, err)
+	}
+
+	return interfaces, nil
+}