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Kernel: Coalesce TCP ACKs

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Previously we'd send a TCP ACK for each TCP packet we received. This
changes NetworkTask so that we send fewer TCP ACKs.
This commit is contained in:
Gunnar Beutner 2021-05-12 09:14:37 +02:00 • committed by Andreas Kling
parent ffc6b714b0
commit af59f64bc0
3 changed files with 81 additions and 8 deletions
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28
Kernel/Net/TCPSocket.cpp
View file

@ -167,6 +167,13 @@ KResultOr<size_t> TCPSocket::protocol_send(const UserOrKernelBuffer& data, size_
return data_length;
}
KResult TCPSocket::send_ack(bool allow_duplicate)
{
if (!allow_duplicate && m_last_ack_number_sent == m_ack_number)
return KSuccess;
return send_tcp_packet(TCPFlags::ACK);
}
KResult TCPSocket::send_tcp_packet(u16 flags, const UserOrKernelBuffer* payload, size_t payload_size)
{
const bool has_mss_option = flags == TCPFlags::SYN;
@ -183,8 +190,11 @@ KResult TCPSocket::send_tcp_packet(u16 flags, const UserOrKernelBuffer* payload,
tcp_packet.set_data_offset(header_size / sizeof(u32));
tcp_packet.set_flags(flags);
if (flags & TCPFlags::ACK)
if (flags & TCPFlags::ACK) {
m_last_ack_number_sent = m_ack_number;
m_last_ack_sent_time = kgettimeofday();
tcp_packet.set_ack_number(m_ack_number);
}
if (payload && !payload->read(tcp_packet.payload(), payload_size))
return EFAULT;
@ -308,6 +318,22 @@ void TCPSocket::receive_tcp_packet(const TCPPacket& packet, u16 size)
m_bytes_in += packet.header_size() + size;
}
bool TCPSocket::should_delay_next_ack() const
{
// FIXME: We don't know the MSS here so make a reasonable guess.
const size_t mss = 1500;
// RFC 1122 says we should send an ACK for every two full-sized segments.
if (m_ack_number >= m_last_ack_number_sent + 2 * mss)
return false;
// RFC 1122 says we should not delay ACKs for more than 500 milliseconds.
if (kgettimeofday() >= m_last_ack_sent_time + Time::from_milliseconds(500))
return false;
return true;
}
NetworkOrdered<u16> TCPSocket::compute_tcp_checksum(const IPv4Address& source, const IPv4Address& destination, const TCPPacket& packet, u16 payload_size)
{
struct [[gnu::packed]] PseudoHeader {