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Kernel: Send Fragmented IPv4 packets if payload size > mtu

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This adds IPv4 fragmentation, so now we can send huuuuuuge packets
properly.
This commit is contained in:
AnotherTest 2020-04-02 05:57:49 +04:30 committed by Andreas Kling
parent 592f218151
commit b3d7c5d9de
Notes: sideshowbarker 2024-07-19 07:59:46 +09:00 
Author: https://github.com/alimpfard
Commit: https://github.com/SerenityOS/serenity/commit/b3d7c5d9de3
Pull-request: https://github.com/SerenityOS/serenity/pull/1574
Reviewed-by: https://github.com/awesomekling
3 changed files with 70 additions and 2 deletions
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28
Kernel/Net/IPv4.h
View File

@ -40,6 +40,11 @@ enum class IPv4Protocol : u16 {
UDP = 17,
};
enum class IPv4PacketFlags : u16 {
DontFragment = 0x4000,
MoreFragments = 0x2000,
};
NetworkOrdered<u16> internet_checksum(const void*, size_t);
class [[gnu::packed]] IPv4Packet
@ -75,6 +80,28 @@ public:
void* payload() { return this + 1; }
const void* payload() const { return this + 1; }
u16 flags_and_fragment() const { return m_flags_and_fragment; }
u16 fragment_offset() const { return ((u16)m_flags_and_fragment & 0x2fff); }
u16 flags() const { return (((u16)m_flags_and_fragment) & (((u16)IPv4PacketFlags::MoreFragments) | ((u16)IPv4PacketFlags::DontFragment))); }
void set_has_more_fragments(bool more_fragments)
{
if (more_fragments)
m_flags_and_fragment = (u16)m_flags_and_fragment | ((u16)IPv4PacketFlags::MoreFragments);
else
m_flags_and_fragment = (u16)m_flags_and_fragment & ((u16)IPv4PacketFlags::MoreFragments);
}
void set_fragment_offset(u16 offset)
{
m_flags_and_fragment = flags() | (offset & 0x2fff);
}
bool is_a_fragment() const
{
// either has More-Fragments set, or has a fragment offset
return (((u16)m_flags_and_fragment) & ((u16)IPv4PacketFlags::MoreFragments)) || ((u16)m_flags_and_fragment & 0x2fff);
}
u16 payload_size() const { return m_length - sizeof(IPv4Packet); }
NetworkOrdered<u16> compute_checksum() const
@ -97,6 +124,7 @@ private:
};
static_assert(sizeof(IPv4Packet) == 20);
const LogStream& operator<<(const LogStream& stream, const IPv4Packet& packet);
inline NetworkOrdered<u16> internet_checksum(const void* ptr, size_t count)
{

43
Kernel/Net/NetworkAdapter.cpp
View File

@ -32,6 +32,7 @@
#include <Kernel/Net/EthernetFrameHeader.h>
#include <Kernel/Net/LoopbackAdapter.h>
#include <Kernel/Net/NetworkAdapter.h>
#include <Kernel/Random.h>
#include <LibBareMetal/StdLib.h>
namespace Kernel {
@ -103,8 +104,8 @@ void NetworkAdapter::send_ipv4(const MACAddress& destination_mac, const IPv4Addr
{
size_t ipv4_packet_size = sizeof(IPv4Packet) + payload_size;
if (ipv4_packet_size > mtu()) {
// FIXME: Implement IP fragmentation.
ASSERT_NOT_REACHED();
send_ipv4_fragmented(destination_mac, destination_ipv4, protocol, payload, payload_size, ttl);
return;
}
size_t ethernet_frame_size = sizeof(EthernetFrameHeader) + sizeof(IPv4Packet) + payload_size;
@ -129,6 +130,44 @@ void NetworkAdapter::send_ipv4(const MACAddress& destination_mac, const IPv4Addr
send_raw((const u8*)&eth, ethernet_frame_size);
}
void NetworkAdapter::send_ipv4_fragmented(const MACAddress& destination_mac, const IPv4Address& destination_ipv4, IPv4Protocol protocol, const u8* payload, size_t payload_size, u8 ttl)
{
// packets must be split on the 64-bit boundary
auto packet_boundary_size = (mtu() - sizeof(IPv4Packet) - sizeof(EthernetFrameHeader)) & 0xfffffff8;
auto fragment_block_count = (payload_size + packet_boundary_size) / packet_boundary_size;
auto last_block_size = payload_size - packet_boundary_size * (fragment_block_count - 1);
auto number_of_blocks_in_fragment = packet_boundary_size / 8;
auto identification = get_good_random<u16>();
size_t ethernet_frame_size = mtu();
for (size_t packet_index = 0; packet_index < fragment_block_count; ++packet_index) {
auto is_last_block = packet_index + 1 == fragment_block_count;
auto packet_payload_size = is_last_block ? last_block_size : packet_boundary_size;
auto buffer = ByteBuffer::create_zeroed(ethernet_frame_size);
auto& eth = *(EthernetFrameHeader*)buffer.data();
eth.set_source(mac_address());
eth.set_destination(destination_mac);
eth.set_ether_type(EtherType::IPv4);
auto& ipv4 = *(IPv4Packet*)eth.payload();
ipv4.set_version(4);
ipv4.set_internet_header_length(5);
ipv4.set_source(ipv4_address());
ipv4.set_destination(destination_ipv4);
ipv4.set_protocol((u8)protocol);
ipv4.set_length(sizeof(IPv4Packet) + packet_payload_size);
ipv4.set_has_more_fragments(!is_last_block);
ipv4.set_ident(identification);
ipv4.set_ttl(ttl);
ipv4.set_fragment_offset(packet_index * number_of_blocks_in_fragment);
ipv4.set_checksum(ipv4.compute_checksum());
m_packets_out++;
m_bytes_out += ethernet_frame_size;
memcpy(ipv4.payload(), payload + packet_index * packet_boundary_size, packet_payload_size);
send_raw((const u8*)&eth, ethernet_frame_size);
}
}
void NetworkAdapter::did_receive(const u8* data, size_t length)
{
InterruptDisabler disabler;

1
Kernel/Net/NetworkAdapter.h
View File

@ -64,6 +64,7 @@ public:
void send(const MACAddress&, const ARPPacket&);
void send_ipv4(const MACAddress&, const IPv4Address&, IPv4Protocol, const u8* payload, size_t payload_size, u8 ttl);
void send_ipv4_fragmented(const MACAddress&, const IPv4Address&, IPv4Protocol, const u8* payload, size_t payload_size, u8 ttl);
size_t dequeue_packet(u8* buffer, size_t buffer_size);