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On Linux/Mac/Windows, is it possible to access the TCP timestamp and/or RTT in user space of a connected TCP socket? I'm referring to the TCP timestamp and associated RTT calculation enabled by RFC 1323. Obviously, I could utilize a raw socket, but the socket would neither be connected or capable of sending TCP packets on Windows (post XP Update 3, I believe).

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2 Answers2

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I want to append more information.

For iOS/MacOSX, I found another method which is very similar with Linux tcp_info. It's struct tcp_connection_info. You can find it in the usr/include/netinet/tcp.h of the iOS/MacOSX xcode sdk. You can use it as the following: 

int length = sizeof(struct tcp_connection_info);  
getsockopt(socket_fd, IPPROTO_TCP, TCP_CONNECTION_INFO, (void *)info, (socklen_t *)&length);

I tested it on iOS 10.2.

Jay Zhang
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On Windows (EstatsType = TcpConnectionEstatsFineRtt):
GetPerTcp6ConnectionEStats
GetPerTcpConnectionEStats

On Linux (tcp_info.tcpi_rtt):
Measuring TCP Congestion Windows (getsockopt)

On Mac (xtcpcb64.t_srtt):
sysctl TCPCTL_PCBLIST to acquire the xtcpcb64 struct

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  • `GetPerTcpConnectionEStats` on Windows is possible but requires Administator access to enable the Extended Statistics in the first place, unlike Linux and OSX, unfortunately. – qris Aug 19 '17 at 21:01