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src/modules/discovery/scanners/arp.scanner.ts

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+import { exec } from 'node:child_process';
+import { promisify } from 'node:util';
+import { env } from '@/config/env';
+import type { DiscoveryResult, DiscoveryTarget, Scanner } from '../types';
+
+const execAsync = promisify(exec);
+
+/**
+ * Lit la table ARP locale via `ip neigh` (Linux) ou `arp -a` (fallback).
+ * Ne scanne pas activement : retourne ce que le kernel a déjà vu.
+ * Pour forcer la résolution, il faut ping-sweeper d'abord (voir discovery.service).
+ */
+export const arpScanner: Scanner = {
+  kind: 'arp',
+  label: 'Table ARP locale',
+  enabled: env.DISCOVERY_ENABLE_ARP,
+
+  async run(_target: DiscoveryTarget): Promise<DiscoveryResult[]> {
+    const { stdout } = await execAsync('ip neigh show').catch(() => ({ stdout: '' }));
+    if (stdout) return parseIpNeigh(stdout);
+
+    const { stdout: arpOut } = await execAsync('arp -a').catch(() => ({ stdout: '' }));
+    return parseArpA(arpOut);
+  },
+};
+
+function parseIpNeigh(output: string): DiscoveryResult[] {
+  // Exemple : 192.168.1.10 dev eth0 lladdr aa:bb:cc:dd:ee:ff REACHABLE
+  return output
+    .split('\n')
+    .map((line) => line.trim())
+    .filter(Boolean)
+    .map((line) => {
+      const ipMatch = line.match(/^(\d{1,3}(?:\.\d{1,3}){3})/);
+      const macMatch = line.match(/lladdr\s+([0-9a-fA-F:]{17})/);
+      if (!ipMatch) return null;
+      return {
+        ipAddress: ipMatch[1],
+        macAddress: macMatch?.[1],
+      } satisfies DiscoveryResult;
+    })
+    .filter((r): r is DiscoveryResult => r !== null);
+}
+
+function parseArpA(output: string): DiscoveryResult[] {
+  // Exemple : ? (192.168.1.10) at aa:bb:cc:dd:ee:ff [ether] on eth0
+  return output
+    .split('\n')
+    .map((line) => line.trim())
+    .filter(Boolean)
+    .map((line) => {
+      const ipMatch = line.match(/\((\d{1,3}(?:\.\d{1,3}){3})\)/);
+      const macMatch = line.match(/([0-9a-fA-F]{2}(:[0-9a-fA-F]{2}){5})/);
+      if (!ipMatch) return null;
+      return {
+        ipAddress: ipMatch[1],
+        macAddress: macMatch?.[1],
+      } satisfies DiscoveryResult;
+    })
+    .filter((r): r is DiscoveryResult => r !== null);
+}