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Kernel: Implement outgoing TCP retransmission and better ACK handling

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This approach is a bit naiive - whenever we send a packet out, we
check to see if there are any other packets we should try to send.
This works well enough for a busy connection but not very well for a
quiet one. Ideally we would check for not-acked packets on some kind
of timer, and use the length of this not-acked list as feedback to
throttle the writes coming from userspace.
This commit is contained in:
Conrad Pankoff 2019-09-08 17:38:08 +10:00 • committed by Andreas Kling
parent b8e3c7ef01
commit 117d8db2a2
3 changed files with 90 additions and 28 deletions
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97
Kernel/Net/TCPSocket.cpp
View file

@ -138,9 +138,6 @@ int TCPSocket::protocol_send(const void* data, int data_length)
void TCPSocket::send_tcp_packet(u16 flags, const void* payload, int payload_size)
{
auto routing_decision = route_to(peer_address(), local_address());
ASSERT(!routing_decision.is_zero());
auto buffer = ByteBuffer::create_zeroed(sizeof(TCPPacket) + payload_size);
auto& tcp_packet = *(TCPPacket*)(buffer.pointer());
ASSERT(local_port());
@ -162,29 +159,87 @@ void TCPSocket::send_tcp_packet(u16 flags, const void* payload, int payload_size
memcpy(tcp_packet.payload(), payload, payload_size);
tcp_packet.set_checksum(compute_tcp_checksum(local_address(), peer_address(), tcp_packet, payload_size));
#ifdef TCP_SOCKET_DEBUG
kprintf("sending tcp packet from %s:%u to %s:%u with (%s%s%s%s) seq_no=%u, ack_no=%u\n",
local_address().to_string().characters(),
local_port(),
peer_address().to_string().characters(),
peer_port(),
tcp_packet.has_syn() ? "SYN " : "",
tcp_packet.has_ack() ? "ACK " : "",
tcp_packet.has_fin() ? "FIN " : "",
tcp_packet.has_rst() ? "RST " : "",
tcp_packet.sequence_number(),
tcp_packet.ack_number());
#endif
routing_decision.adapter->send_ipv4(routing_decision.next_hop, peer_address(), IPv4Protocol::TCP, buffer.data(), buffer.size());
m_packets_out++;
m_bytes_out += buffer.size();
if (tcp_packet.has_syn() || payload_size > 0) {
m_not_acked.append({ m_sequence_number, buffer, 0, {} });
send_outgoing_packets();
} else {
auto routing_decision = route_to(peer_address(), local_address());
ASSERT(!routing_decision.is_zero());
routing_decision.adapter->send_ipv4(
routing_decision.next_hop, peer_address(), IPv4Protocol::TCP,
buffer.data(), buffer.size());
m_packets_out++;
m_bytes_out += buffer.size();
}
}
void TCPSocket::record_incoming_data(int size)
void TCPSocket::send_outgoing_packets()
{
auto routing_decision = route_to(peer_address(), local_address());
ASSERT(!routing_decision.is_zero());
auto now = kgettimeofday();
for (auto& packet : m_not_acked) {
if (now.tv_sec <= packet.tx_time.tv_sec)
continue;
packet.tx_time = now;
packet.tx_counter++;
#ifdef TCP_SOCKET_DEBUG
auto& tcp_packet = *(TCPPacket*)(packet.buffer.pointer());
kprintf("sending tcp packet from %s:%u to %s:%u with (%s%s%s%s) seq_no=%u, ack_no=%u, tx_counter=%u\n",
local_address().to_string().characters(),
local_port(),
peer_address().to_string().characters(),
peer_port(),
tcp_packet.has_syn() ? "SYN " : "",
tcp_packet.has_ack() ? "ACK " : "",
tcp_packet.has_fin() ? "FIN " : "",
tcp_packet.has_rst() ? "RST " : "",
tcp_packet.sequence_number(),
tcp_packet.ack_number(),
packet.tx_counter);
#endif
routing_decision.adapter->send_ipv4(
routing_decision.next_hop, peer_address(), IPv4Protocol::TCP,
packet.buffer.data(), packet.buffer.size());
m_packets_out++;
m_bytes_out += packet.buffer.size();
}
}
void TCPSocket::receive_tcp_packet(const TCPPacket& packet, u16 size)
{
if (packet.has_ack()) {
u32 ack_number = packet.ack_number();
dbg() << "TCPSocket: receive_tcp_packet: " << ack_number;
int removed = 0;
while (!m_not_acked.is_empty()) {
auto& packet = m_not_acked.first();
dbg() << "TCPSocket: iterate: " << packet.ack_number;
if (packet.ack_number <= ack_number) {
m_not_acked.take_first();
removed++;
} else {
break;
}
}
dbg() << "TCPSocket: receive_tcp_packet acknowledged " << removed << " packets";
}
m_packets_in++;
m_bytes_in += size;
m_bytes_in += packet.header_size() + size;
}
NetworkOrdered<u16> TCPSocket::compute_tcp_checksum(const IPv4Address& source, const IPv4Address& destination, const TCPPacket& packet, u16 payload_size)