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// 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
}
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