The number of bytes that the kernel believes the client TCP stack is using for its maximum segment size (MSS) sending parameter. It is based on the largest packet size previously received on the same connection.
client.socket.tcpi_rcv_mss is primarily used to govern
the rate of ACK generation by the TCP stack when implementing the
delayed ACK algorithm. The value of
client.socket.tcpi_rcv_mss will change
over the lifetime of the connection as new data is received. Its value can also
provide limited insight into how efficiently the client was able to
use its TCP send channel.