52 lines
1.2 KiB
Go
52 lines
1.2 KiB
Go
//go:build windows
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package deploy
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import (
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"net"
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"os/exec"
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"strings"
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)
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// arpHosts returns the list of IPv4 hosts currently in the OS ARP cache
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// that share a subnet with one of our local interfaces. These are machines
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// that have recently communicated on the LAN — a far smaller and more
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// targeted set than a blind /24 sweep.
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//
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// Falls back to nil (caller will do a full scan) on any error.
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func arpHosts() []string {
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out, err := exec.Command("arp", "-a").Output()
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if err != nil {
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return nil
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}
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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(string(out), "\n") {
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line = strings.TrimSpace(line)
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// arp -a lines look like:
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// 192.168.1.1 00-11-22-33-44-55 dynamic
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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() || ip.IsMulticast() {
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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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