iptables -A INPUT -p tcp -m tcp --tcp-flags PSH,ACK PSH,ACK -m length --length 52 -m state --state ESTABLISHED -j DROP

unwanted packet: destination=192.168.0.111  source=192.168.0.100    TCP length=72   [TCP Retransmission] 38111→61578 [PSH, ACK] Seq=1 Ack=15 Win=14720 Len=18

needed packet: destination=192.168.0.111    source=192.168.0.100    TCP length=76   [TCP Retransmission] 38111→61595 [PSH, ACK] Seq=589 Ack=1 Win=136 Len=22