[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>

1 files changed, 116 insertions, 0 deletions

diff --git a/vendor/github.com/prometheus/procfs/arp.go b/vendor/github.com/prometheus/procfs/arp.go
new file mode 100644
index 000000000..28783e2dd
--- /dev/null
+++ b/vendor/github.com/prometheus/procfs/arp.go
@@ -0,0 +1,116 @@
+// 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.
+
+package procfs
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"strconv"
+	"strings"
+)
+
+// Learned from include/uapi/linux/if_arp.h.
+const (
+	// completed entry (ha valid).
+	ATFComplete = 0x02
+	// permanent entry.
+	ATFPermanent = 0x04
+	// Publish entry.
+	ATFPublish = 0x08
+	// Has requested trailers.
+	ATFUseTrailers = 0x10
+	// Obsoleted: Want to use a netmask (only for proxy entries).
+	ATFNetmask = 0x20
+	// Don't answer this addresses.
+	ATFDontPublish = 0x40
+)
+
+// ARPEntry contains a single row of the columnar data represented in
+// /proc/net/arp.
+type ARPEntry struct {
+	// IP address
+	IPAddr net.IP
+	// MAC address
+	HWAddr net.HardwareAddr
+	// Name of the device
+	Device string
+	// Flags
+	Flags byte
+}
+
+// GatherARPEntries retrieves all the ARP entries, parse the relevant columns,
+// and then return a slice of ARPEntry's.
+func (fs FS) GatherARPEntries() ([]ARPEntry, error) {
+	data, err := os.ReadFile(fs.proc.Path("net/arp"))
+	if err != nil {
+		return nil, fmt.Errorf("%s: error reading arp %s: %w", ErrFileRead, fs.proc.Path("net/arp"), err)
+	}
+
+	return parseARPEntries(data)
+}
+
+func parseARPEntries(data []byte) ([]ARPEntry, error) {
+	lines := strings.Split(string(data), "\n")
+	entries := make([]ARPEntry, 0)
+	var err error
+	const (
+		expectedDataWidth   = 6
+		expectedHeaderWidth = 9
+	)
+	for _, line := range lines {
+		columns := strings.Fields(line)
+		width := len(columns)
+
+		if width == expectedHeaderWidth || width == 0 {
+			continue
+		} else if width == expectedDataWidth {
+			entry, err := parseARPEntry(columns)
+			if err != nil {
+				return []ARPEntry{}, fmt.Errorf("%s: Failed to parse ARP entry: %v: %w", ErrFileParse, entry, err)
+			}
+			entries = append(entries, entry)
+		} else {
+			return []ARPEntry{}, fmt.Errorf("%s: %d columns found, but expected %d: %w", ErrFileParse, width, expectedDataWidth, err)
+		}
+
+	}
+
+	return entries, err
+}
+
+func parseARPEntry(columns []string) (ARPEntry, error) {
+	entry := ARPEntry{Device: columns[5]}
+	ip := net.ParseIP(columns[0])
+	entry.IPAddr = ip
+
+	if mac, err := net.ParseMAC(columns[3]); err == nil {
+		entry.HWAddr = mac
+	} else {
+		return ARPEntry{}, err
+	}
+
+	if flags, err := strconv.ParseUint(columns[2], 0, 8); err == nil {
+		entry.Flags = byte(flags)
+	} else {
+		return ARPEntry{}, err
+	}
+
+	return entry, nil
+}
+
+// IsComplete returns true if ARP entry is marked with complete flag.
+func (entry *ARPEntry) IsComplete() bool {
+	return entry.Flags&ATFComplete != 0
+}