From 90f60d2f650a417a8ffd002d2cfa22605941069f Mon Sep 17 00:00:00 2001
From: Andreas Kling <awesomekling@gmail.com>
Date: Tue, 12 Mar 2019 00:56:33 +0100
Subject: Kernel: Cache MAC<->IP mappings (from ARP responses) seen on the
 wire.

---
 Kernel/NetworkTask.cpp | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

(limited to 'Kernel/NetworkTask.cpp')

diff --git a/Kernel/NetworkTask.cpp b/Kernel/NetworkTask.cpp
index 867266d855..e8a5404bb4 100644
--- a/Kernel/NetworkTask.cpp
+++ b/Kernel/NetworkTask.cpp
@@ -3,10 +3,19 @@
 #include <Kernel/ARPPacket.h>
 #include <Kernel/Process.h>
 #include <Kernel/EtherType.h>
+#include <AK/Lock.h>
 
 static void handle_arp(const EthernetFrameHeader&, int frame_size);
 static void handle_ipv4(const EthernetFrameHeader&, int frame_size);
 
+Lockable<HashMap<IPv4Address, MACAddress>>& arp_table()
+{
+    static Lockable<HashMap<IPv4Address, MACAddress>>* the;
+    if (!the)
+        the = new Lockable<HashMap<IPv4Address, MACAddress>>;
+    return *the;
+}
+
 void NetworkTask_main()
 {
     auto* e1000_ptr = E1000NetworkAdapter::the();
@@ -59,7 +68,7 @@ void handle_arp(const EthernetFrameHeader& eth, int frame_size)
         kprintf("handle_arp: Frame too small (%d, need %d)\n", frame_size, minimum_arp_frame_size);
         return;
     }
-    const ARPPacket& packet = *static_cast<const ARPPacket*>(eth.payload());
+    auto& packet = *static_cast<const ARPPacket*>(eth.payload());
     if (packet.hardware_type() != 1 || packet.hardware_address_length() != sizeof(MACAddress)) {
         kprintf("handle_arp: Hardware type not ethernet (%w, len=%u)\n",
             packet.hardware_type(),
@@ -104,6 +113,20 @@ void handle_arp(const EthernetFrameHeader& eth, int frame_size)
 
             e1000.send(packet.sender_hardware_address(), response);
         }
+        return;
+    }
+
+    if (packet.operation() == 2) {
+        // Someone has this IPv4 address. I guess we can try to remember that.
+        // FIXME: Protect against ARP spamming.
+        // FIXME: Support static ARP table entries.
+        LOCKER(arp_table().lock());
+        arp_table().resource().set(packet.sender_protocol_address(), packet.sender_hardware_address());
+
+        kprintf("ARP table (%d entries):\n", arp_table().resource().size());
+        for (auto& it : arp_table().resource()) {
+            kprintf("%s :: %s\n", it.value.to_string().characters(), it.key.to_string().characters());
+        }
     }
 }
 
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