4 files changed, 16 insertions, 4 deletions
diff --git a/Kernel/FileSystem/ProcFS.cpp b/Kernel/FileSystem/ProcFS.cpp
index 95e5d220ea..140834484d 100644
--- a/Kernel/FileSystem/ProcFS.cpp
+++ b/Kernel/FileSystem/ProcFS.cpp
@@ -345,6 +345,7 @@ Optional<KBuffer> procfs$net_adapters(InodeIdentifier)
         obj.add("packets_out", adapter.packets_out());
         obj.add("bytes_out", adapter.bytes_out());
         obj.add("link_up", adapter.link_up());
+        obj.add("mtu", adapter.mtu());
     });
     array.finish();
     return builder.build();
diff --git a/Kernel/Net/LoopbackAdapter.cpp b/Kernel/Net/LoopbackAdapter.cpp
index 7e5c44adb0..f304c7680b 100644
--- a/Kernel/Net/LoopbackAdapter.cpp
+++ b/Kernel/Net/LoopbackAdapter.cpp
@@ -11,6 +11,7 @@ LoopbackAdapter& LoopbackAdapter::the()
 LoopbackAdapter::LoopbackAdapter()
 {
     set_interface_name("loop");
+    set_mtu(65536);
 }
 
 LoopbackAdapter::~LoopbackAdapter()
diff --git a/Kernel/Net/NetworkAdapter.cpp b/Kernel/Net/NetworkAdapter.cpp
index b1617109b4..f20a963966 100644
--- a/Kernel/Net/NetworkAdapter.cpp
+++ b/Kernel/Net/NetworkAdapter.cpp
@@ -70,8 +70,14 @@ void NetworkAdapter::send(const MACAddress& destination, const ARPPacket& packet
 
 void NetworkAdapter::send_ipv4(const MACAddress& destination_mac, const IPv4Address& destination_ipv4, IPv4Protocol protocol, const u8* payload, size_t payload_size, u8 ttl)
 {
-    size_t size_in_bytes = sizeof(EthernetFrameHeader) + sizeof(IPv4Packet) + payload_size;
-    auto buffer = ByteBuffer::create_zeroed(size_in_bytes);
+    size_t ipv4_packet_size = sizeof(IPv4Packet) + payload_size;
+    if (ipv4_packet_size > mtu()) {
+        // FIXME: Implement IP fragmentation.
+        ASSERT_NOT_REACHED();
+    }
+
+    size_t ethernet_frame_size = sizeof(EthernetFrameHeader) + sizeof(IPv4Packet) + payload_size;
+    auto buffer = ByteBuffer::create_zeroed(ethernet_frame_size);
     auto& eth = *(EthernetFrameHeader*)buffer.data();
     eth.set_source(mac_address());
     eth.set_destination(destination_mac);
@@ -87,9 +93,9 @@ void NetworkAdapter::send_ipv4(const MACAddress& destination_mac, const IPv4Addr
     ipv4.set_ttl(ttl);
     ipv4.set_checksum(ipv4.compute_checksum());
     m_packets_out++;
-    m_bytes_out += size_in_bytes;
+    m_bytes_out += ethernet_frame_size;
     memcpy(ipv4.payload(), payload, payload_size);
-    send_raw((const u8*)&eth, size_in_bytes);
+    send_raw((const u8*)&eth, ethernet_frame_size);
 }
 
 void NetworkAdapter::did_receive(const u8* data, int length)
diff --git a/Kernel/Net/NetworkAdapter.h b/Kernel/Net/NetworkAdapter.h
index f1270ef552..b776121a20 100644
--- a/Kernel/Net/NetworkAdapter.h
+++ b/Kernel/Net/NetworkAdapter.h
@@ -41,6 +41,9 @@ public:
 
     bool has_queued_packets() const { return !m_packet_queue.is_empty(); }
 
+    u32 mtu() const { return m_mtu; }
+    void set_mtu(u32 mtu) { m_mtu = mtu; }
+
     u32 packets_in() const { return m_packets_in; }
     u32 bytes_in() const { return m_bytes_in; }
     u32 packets_out() const { return m_packets_out; }
@@ -66,4 +69,5 @@ private:
     u32 m_bytes_in { 0 };
     u32 m_packets_out { 0 };
     u32 m_bytes_out { 0 };
+    u32 m_mtu { 1500 };
 };