Fetching the TCP RTT in Linux

Question

I need to fetch the RTT for TCP flow. I have looked into the proc file system but not able to get the RTT value of TCP .If any one having any idea regarding it that, in whic

Answer 1

It also possible to print the cached rtts (and rttvar, cwnd) for previous destinations using the ip command:

sudo ip tcp_metrics

Answer 2

You can so this using tcpprobe (inserts a hook into the tcp_recv processing path using kprobe and records the state of a TCP connection in response to incoming packets).

Explained here: Extract TCP round trip time (RTT) estimations on linux

Answer 3

Maybe the ss (socket statistics) util available in the iproute utils can help you with this.

# ss -i 'src 1.1.1.1:1234 and dst 2.2.2.2:1234'
State      Recv-Q Send-Q                         Local Address:Port                             Peer Address:Port
ESTAB      0      0                              1.1.1.1:1234                                   2.2.2.2:1234
    reno wscale:2,7 rto:3380 rtt:855/602.5 ato:40 ssthresh:2 send 27.3Kbps rcv_space:5840

If you want more information what the rtt field is i think it is best to take a look at ss.c.