106 lines
2.2 KiB
Go
106 lines
2.2 KiB
Go
//go:build !windows
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package deploy
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import (
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"bufio"
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"net"
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"os"
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"os/exec"
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"strings"
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)
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// arpHosts returns IPv4 hosts in the ARP cache on the local subnets.
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// On Linux it reads /proc/net/arp; on macOS/BSD it falls back to running
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// `arp -n`. Returns nil if nothing useful is found (caller does full scan).
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func arpHosts() []string {
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hosts := arpFromProc()
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if len(hosts) == 0 {
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hosts = arpFromCmd()
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}
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return hosts
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}
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// arpFromProc parses Linux's /proc/net/arp.
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// Format: IP address HW type Flags HW address Mask Device
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func arpFromProc() []string {
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f, err := os.Open("/proc/net/arp")
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if err != nil {
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return nil
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}
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defer f.Close()
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local := getLocalIPs()
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subnets := make(map[string]bool)
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for _, ip := range local {
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subnets[getSubnet(ip)] = true
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}
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var hosts []string
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seen := make(map[string]bool)
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scanner := bufio.NewScanner(f)
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for scanner.Scan() {
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fields := strings.Fields(scanner.Text())
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if len(fields) < 4 {
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continue // skip header
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}
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ip := net.ParseIP(fields[0])
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if ip == nil || ip.To4() == nil {
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continue
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}
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// Flags = 0x0 means incomplete — skip
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if fields[2] == "0x0" {
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continue
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}
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ipStr := ip.To4().String()
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sub := getSubnet(ipStr)
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if !subnets[sub] || seen[ipStr] {
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continue
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}
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seen[ipStr] = true
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hosts = append(hosts, ipStr)
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}
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_ = scanner.Err()
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return hosts
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}
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// arpFromCmd runs `arp -n` for macOS/BSD where /proc/net/arp doesn't exist.
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func arpFromCmd() []string {
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raw, err := exec.Command("arp", "-n").Output()
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if err != nil {
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return nil
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}
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out := string(raw)
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local := getLocalIPs()
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subnets := make(map[string]bool)
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for _, ip := range local {
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subnets[getSubnet(ip)] = true
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}
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var hosts []string
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seen := make(map[string]bool)
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for _, line := range strings.Split(out, "\n") {
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fields := strings.Fields(line)
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if len(fields) < 2 {
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continue
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}
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ip := net.ParseIP(fields[0])
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if ip == nil || ip.To4() == nil || ip.IsLoopback() {
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continue
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}
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// arp -n marks incomplete entries as "(incomplete)"
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if strings.Contains(line, "incomplete") {
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continue
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}
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ipStr := ip.To4().String()
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sub := getSubnet(ipStr)
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if !subnets[sub] || seen[ipStr] {
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continue
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}
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seen[ipStr] = true
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hosts = append(hosts, ipStr)
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}
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return hosts
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}
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