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Kernel: Rework TCP window size reporting 

We now report actually available window size when sending packets. If
the available window size grows significantly we send an ACK to reflect
this to the remote.
This commit is contained in:
Bananymous 2026-02-23 19:42:29 +02:00
parent 1ac20251cf
commit 666a7bb826
2 changed files with 34 additions and 18 deletions
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2
kernel/include/kernel/Networking/TCPSocket.h
View File

@ -167,6 +167,8 @@ namespace Kernel
State m_next_state { State::Closed };
uint8_t m_next_flags { 0 };
size_t m_last_sent_window_size { 0 };
Thread* m_thread { nullptr };
// TODO: actually support these

50
kernel/kernel/Networking/TCPSocket.cpp
View File

@ -28,6 +28,7 @@ namespace Kernel
BAN::ErrorOr<BAN::RefPtr<TCPSocket>> TCPSocket::create(NetworkLayer& network_layer, const Info& info)
{
auto socket = TRY(BAN::RefPtr<TCPSocket>::create(network_layer, info));
socket->m_last_sent_window_size = s_recv_window_buffer_size;
socket->m_recv_window.buffer = TRY(VirtualRange::create_to_vaddr_range(
PageTable::kernel(),
KERNEL_OFFSET,
@ -241,6 +242,16 @@ namespace Kernel
memmove(recv_buffer, recv_buffer + nrecv, m_recv_window.data_size);
}
const bool should_update_window_size =
(m_last_sent_window_size == 0) ||
(m_recv_window.data_size == 0) ||
(m_last_sent_window_size + PAGE_SIZE < m_recv_window.buffer->size() - m_recv_window.data_size);
if (m_next_flags == 0 && should_update_window_size)
{
m_next_flags = ACK;
m_thread_blocker.unblock();
}
return total_recv;
}
@ -502,12 +513,14 @@ namespace Kernel
memset(&header, 0, sizeof(TCPHeader));
memset(header.options, TCPOption::End, m_tcp_options_bytes);
m_last_sent_window_size = m_recv_window.buffer->size() - m_recv_window.data_size;
header.src_port = bound_port();
header.dst_port = dst_port;
header.seq_number = m_send_window.current_seq + m_send_window.has_ghost_byte;
header.ack_number = m_recv_window.start_seq + m_recv_window.data_size + m_recv_window.has_ghost_byte;
header.data_offset = (sizeof(TCPHeader) + m_tcp_options_bytes) / sizeof(uint32_t);
header.window_size = BAN::Math::min<size_t>(0xFFFF, m_recv_window.buffer->size() >> m_recv_window.scale_shift);
header.window_size = BAN::Math::min<size_t>(0xFFFF, m_last_sent_window_size >> m_recv_window.scale_shift);
header.flags = m_next_flags;
if (header.flags & FIN)
m_send_window.has_ghost_byte = true;
@ -730,27 +743,28 @@ namespace Kernel
m_send_window.current_ack = header.ack_number;
auto payload = buffer.slice(header.data_offset * sizeof(uint32_t));
if (payload.size() > 0)
if (payload.size() > 0 && m_recv_window.data_size < m_recv_window.buffer->size())
{
if (m_recv_window.data_size + payload.size() > m_recv_window.buffer->size())
dprintln_if(DEBUG_TCP, "Cannot fit received bytes to window, waiting for retransmission");
else
const size_t nrecv = BAN::Math::min(payload.size(), m_recv_window.buffer->size() - m_recv_window.data_size);
auto* buffer = reinterpret_cast<uint8_t*>(m_recv_window.buffer->vaddr());
memcpy(buffer + m_recv_window.data_size, payload.data(), nrecv);
m_recv_window.data_size += nrecv;
epoll_notify(EPOLLIN);
dprintln_if(DEBUG_TCP, "Received {} bytes", nrecv);
if (m_next_flags == 0)
{
auto* buffer = reinterpret_cast<uint8_t*>(m_recv_window.buffer->vaddr());
memcpy(buffer + m_recv_window.data_size, payload.data(), payload.size());
m_recv_window.data_size += payload.size();
epoll_notify(EPOLLIN);
dprintln_if(DEBUG_TCP, "Received {} bytes", payload.size());
if (m_next_flags == 0)
{
m_next_flags = ACK;
m_next_state = m_state;
}
m_next_flags = ACK;
m_next_state = m_state;
}
}
// make sure zero window is reported
if (m_next_flags == 0 && m_last_sent_window_size > 0 && m_recv_window.data_size == m_recv_window.buffer->size())
m_next_flags = ACK;
}
if (!hungup_before && has_hungup_impl())