From ddb7641b056ba71bfcdc649d668f54c4efacc324 Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Mon, 29 Jun 2026 00:26:10 +0300
Subject: [PATCH] Kernel: Support hardware checksum offload on E1000 receive

---
 .../kernel/Networking/E1000/Definitions.h     | 30 +++++++++++++
 kernel/kernel/Networking/E1000/E1000.cpp      | 44 +++++++++++++++----
 2 files changed, 65 insertions(+), 9 deletions(-)

diff --git a/kernel/include/kernel/Networking/E1000/Definitions.h b/kernel/include/kernel/Networking/E1000/Definitions.h
index 68dfc2d6..5c3bbfec 100644
--- a/kernel/include/kernel/Networking/E1000/Definitions.h
+++ b/kernel/include/kernel/Networking/E1000/Definitions.h
@@ -29,6 +29,7 @@ namespace Kernel
 		REG_TDLEN	= 0x3808,
 		REG_TDH		= 0x3810,
 		REG_TDT		= 0x3818,
+		REG_RXCSUM	= 0x5000,
 		REG_MTA		= 0x5200,
 	};
 
@@ -167,6 +168,15 @@ namespace Kernel
 		RCTL_BSIZE_16384	= (0b01 << 16) | RCTL_BSEX,
 	};
 
+	enum E1000_RXCSUM : uint32_t
+	{
+		RXSUM_IPOFLD  = 1 << 8,
+		RXSUM_TUOFLD  = 1 << 9,
+		RXSUM_CRCOFLD = 1 << 11,
+		RXSUM_IPPCE   = 1 << 12,
+		RXSUM_PCSD    = 1 << 13,
+	};
+
 	enum E1000_CMD : uint8_t
 	{
 		CMD_EOP		= 1 << 0,
@@ -178,6 +188,26 @@ namespace Kernel
 		CMD_IDE		= 1 << 7,
 	};
 
+	enum E1000_RX_STS : uint8_t
+	{
+		RX_STS_IPCS  = 1 << 6,
+		RX_STS_TCPCS = 1 << 5,
+		RX_STS_UDPCS = 1 << 5,
+		RX_STS_EOP   = 1 << 1,
+		RX_STS_DD    = 1 << 0,
+	};
+
+	enum E1000_RX_ERR : uint8_t
+	{
+		RX_ERR_RXE  = 1 << 7,
+		RX_ERR_IPE  = 1 << 6,
+		RX_ERR_TCPE = 1 << 5,
+		RX_ERR_CXE  = 1 << 4,
+		RX_ERR_SEQ  = 1 << 2,
+		RX_ERR_SE   = 1 << 1,
+		RX_ERR_CE   = 1 << 0,
+	};
+
 	struct e1000_rx_desc
 	{
 		uint64_t addr;
diff --git a/kernel/kernel/Networking/E1000/E1000.cpp b/kernel/kernel/Networking/E1000/E1000.cpp
index 636387ed..479e8838 100644
--- a/kernel/kernel/Networking/E1000/E1000.cpp
+++ b/kernel/kernel/Networking/E1000/E1000.cpp
@@ -202,6 +202,8 @@ namespace Kernel
 		rctrl |= RCTL_BSIZE_8192;
 		write32(REG_RCTL, rctrl);
 
+		write32(REG_RXCSUM, RXSUM_IPOFLD | RXSUM_TUOFLD);
+
 		return {};
 	}
 
@@ -330,20 +332,44 @@ namespace Kernel
 			for (;;)
 			{
 				auto& descriptor = reinterpret_cast<volatile e1000_rx_desc*>(m_rx_descriptor_region->vaddr())[rx_current];
-				if (!(descriptor.status & 1))
+
+				const auto status = descriptor.status;
+				if (!(status & RX_STS_DD))
 					break;
-				ASSERT(descriptor.length <= E1000_RX_BUFFER_SIZE);
 
-				dprintln_if(DEBUG_E1000, "got {} bytes", (uint16_t)descriptor.length);
+				const auto errors = descriptor.errors;
+				if (!(status & RX_STS_EOP))
+					dwarnln("multi descriptor packet??");
+				else if (errors & (RX_ERR_CE | RX_ERR_SE | RX_ERR_RXE))
+					dwarnln("descriptor error {2h}", errors);
+				else if ((status & RX_STS_IPCS) && (errors & RX_ERR_IPE))
+					dwarnln("IPv4 checksum error");
+				else if ((status & RX_STS_TCPCS) && (errors & RX_ERR_TCPE))
+					dwarnln("TCP checkum error");
+				else if ((status & RX_STS_UDPCS) && (errors & RX_ERR_TCPE))
+					dwarnln("UDP checksum error");
+				else
+				{
+					m_rx_lock.unlock(InterruptState::Enabled);
 
-				m_rx_lock.unlock(InterruptState::Enabled);
+					const uint32_t packet_length = descriptor.length;
+					ASSERT(packet_length <= E1000_RX_BUFFER_SIZE);
 
-				NetworkManager::get().on_receive(*this, BAN::ConstByteSpan {
-					reinterpret_cast<const uint8_t*>(m_rx_buffer_region->vaddr() + rx_current * E1000_RX_BUFFER_SIZE),
-					descriptor.length
-				}, 0);
+					dprintln_if(DEBUG_E1000, "got {} bytes", packet_length);
 
-				m_rx_lock.lock();
+					uint32_t validated_cksums = 0;
+					if ((status & RX_STS_IPCS) && !(errors & RX_ERR_IPE))
+						validated_cksums |= CKSUM_IPV4;
+					if ((status & RX_STS_TCPCS) && !(errors & RX_ERR_TCPE))
+						validated_cksums |= CKSUM_TCP;
+					if ((status & RX_STS_UDPCS) && !(errors & RX_ERR_TCPE))
+						validated_cksums |= CKSUM_UDP;
+
+					const uint8_t* packet_data = reinterpret_cast<const uint8_t*>(m_rx_buffer_region->vaddr() + rx_current * E1000_RX_BUFFER_SIZE);
+					NetworkManager::get().on_receive(*this, BAN::ConstByteSpan { packet_data, packet_length }, validated_cksums);
+
+					m_rx_lock.lock();
+				}
 
 				descriptor.status = 0;