The receive window size consists of two values: a
fixed maximum (/proc/sys/net/core/rmem_max:
mucking with changing of values is not suggested unless you know you need to and you know what you are doing) and the current size
which is flexibly based on the amount of data not yet received from the sender. The latter, basically a countdown of bytes not received yet, is advertised in ACKs as a 16-bit window value. Sloppy AWK but on the server this should more or less show the window settings it advertises to clients:
Code:
tcpdump -n -nn -N -i [ethernet_device_name] 'tcp[tcpflags] & (tcp-syn|tcp-ack) == tcp-ack'|awk '{if($10 = "win") print $5,$11}'
