ladybird/Kernel/Net/LoopbackAdapter.cpp
Idan Horowitz 743a9e9ebf Kernel: Stop including the ethernet header in LoopbackAdapter's mtu
The networking subsystem currently assumes all adapters are Ethernet
adapters, including the LoopbackAdapter, so all packets are pre-pended
with an Ethernet Frame header. Since the MTU must not include any
overhead added by the data-link (Ethernet in this case) or physical
layers, we need to subtract it from the MTU.

This fixes a kernel panic which occurs when sending a packet that is at
least 65523 bytes long through the loopback adapter, which results in
the kernel "receiving" a packet which is larger than the support MTU
out the other end. (As the actual final size was increased by the
addition of the ethernet frame header)
2023-11-25 16:34:38 +01:00

40 lines
1.2 KiB
C++

/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Singleton.h>
#include <Kernel/Net/LoopbackAdapter.h>
namespace Kernel {
static bool s_loopback_initialized = false;
ErrorOr<NonnullRefPtr<LoopbackAdapter>> LoopbackAdapter::try_create()
{
return TRY(adopt_nonnull_ref_or_enomem(new (nothrow) LoopbackAdapter("loop"sv)));
}
LoopbackAdapter::LoopbackAdapter(StringView interface_name)
: NetworkAdapter(interface_name)
{
VERIFY(!s_loopback_initialized);
s_loopback_initialized = true;
// The networking subsystem currently assumes all adapters are Ethernet adapters, including the LoopbackAdapter,
// so all packets are pre-pended with an Ethernet Frame header. Since the MTU must not include any overhead added
// by the data-link (Ethernet in this case) or physical layers, we need to subtract it from the MTU.
set_mtu(65536 - sizeof(EthernetFrameHeader));
set_mac_address({ 19, 85, 2, 9, 0x55, 0xaa });
}
LoopbackAdapter::~LoopbackAdapter() = default;
void LoopbackAdapter::send_raw(ReadonlyBytes payload)
{
dbgln_if(LOOPBACK_DEBUG, "LoopbackAdapter: Sending {} byte(s) to myself.", payload.size());
did_receive(payload);
}
}