From a0c1d0eafd1ef1ada3b588ea205e5bc37ae0d8d9 Mon Sep 17 00:00:00 2001 From: Christoph Paasch Date: Thu, 14 May 2020 08:53:03 -0700 Subject: mptcp: Use 32-bit DATA_ACK when possible RFC8684 allows to send 32-bit DATA_ACKs as long as the peer is not sending 64-bit data-sequence numbers. The 64-bit DSN is only there for extreme scenarios when a very high throughput subflow is combined with a long-RTT subflow such that the high-throughput subflow wraps around the 32-bit sequence number space within an RTT of the high-RTT subflow. It is thus a rare scenario and we should try to use the 32-bit DATA_ACK instead as long as possible. It allows to reduce the TCP-option overhead by 4 bytes, thus makes space for an additional SACK-block. It also makes tcpdumps much easier to read when the DSN and DATA_ACK are both either 32 or 64-bit. Signed-off-by: Christoph Paasch Reviewed-by: Matthieu Baerts Signed-off-by: David S. Miller --- net/mptcp/protocol.h | 1 + 1 file changed, 1 insertion(+) (limited to 'net/mptcp/protocol.h') diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index e4ca6320ce76..f5adca93e8fb 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -290,6 +290,7 @@ struct mptcp_subflow_context { data_avail : 1, rx_eof : 1, data_fin_tx_enable : 1, + use_64bit_ack : 1, /* Set when we received a 64-bit DSN */ can_ack : 1; /* only after processing the remote a key */ u64 data_fin_tx_seq; u32 remote_nonce; -- cgit v1.2.3