NAME

tcpsso — set a socket option on a TCP endpoint

SYNOPSIS

DESCRIPTION

The tcpsso command applies a level level socket option with name optname and value optval on a TCP endpoint from the command line.

TCP endpoints in the SYN_RCVD state can only be handled by tcpsso if their prior state was SYN_SENT.

[level] can be specified as a non-negative number or a symbolic name like SOL_SOCKET, IPPROTO_IP, IPPROTO_IPV6, or IPPROTO_TCP. If not specified, tcpsso deduces the level from optname, if provided as a symbolic name. If that is not the case, IPPROTO_TCP is used.

optname can be specified as a non-negative number or a symbolic name like SO_DEBUG, IP_TOS, IPV6_TCLASS, TCP_LOG, TCP_CONGESTION, or TCP_FUNCTION_BLK.

optval can be an integer value, which will be converted to a binary value and passed as an int value. If it cannot be parsed as an integer value, it will be processed as a string. If the optname is TCP_FUNCTION_BLK then optval is converted to a struct tcp_function_set.

If -i id is specified then tcpsso will apply the socket option to the TCP endpoint with the inp_gencnt provided as id. The inp_gencnt for existing TCP endpoints can be determined by using sockstat(1).

If -a is specified then tcpsso will apply the socket option to all TCP endpoints subject to the above state restrictions.

If -C cc-algo is specified then tcpsso will apply the socket option to all TCP endpoints using the TCP congestion control algorithm cc-algo and subject to the above state restrictions.

If -S stack is specified then tcpsso will apply the socket option to all TCP endpoints using the TCP stack stack and subject to the above state restrictions.

If -s state is specified then tcpsso will apply the socket option to all TCP endpoints being in the state state. state is one of CLOSED, LISTEN, SYN_SENT, SYN_RCVD, ESTABLISHED, CLOSE_WAIT, FIN_WAIT_1, CLOSING, LAST_ACK, FIN_WAIT_2, or TIME_WAIT. Using SYN_RCVD only applies to TCP endpoints in the state SYN_RCVD if their prior state was SYN_SENT.

If multiple of -C cc-algo, -S stack, and -s state are specified, tcpsso will apply the socket option to all TCP endpoints using the congestion control algorithm cc-algo, being in the state state, and using the TCP stack stack, if specified.

If none of the -a, -C, -S, or -s options are specified then the option -i must be specified.

EXIT STATUS

The tcpsso utility exits 0 on success, and >0 if an error occurs.

EXAMPLES

To diagnose a problem with a particular TCP connection to sshd(8), first determine its inp_gencnt using sockstat(1):

# sockstat -4 -c -i -p 22 -P tcp -q
root     sshd       827   4  tcp4 \
	192.168.1.1:22        192.168.1.2:53736     435

Then, use the following command to enable Black Box Logging on it:

# tcpsso -i 435 TCP_LOG 4

To switch all TCP endpoints from using the freebsd stack to the RACK stack use:

# tcpsso -S freebsd TCP_FUNCTION_BLK rack

Switch all TCP endpoints in the LISTEN state to the RACK stack by using:

# tcpsso -s LISTEN TCP_FUNCTION_BLK rack

The following command will set the congestion control module of all TCP endpoints currently using cubic as its congestion control algorithm to the congestion control algorithm newreno:

# tcpsso -C cubic TCP_CONGESTION newreno

SEE ALSO

sockstat(1), setsockopt(2), tcp(4), tcp_functions(9)

HISTORY

The tcpsso command first appeared in FreeBSD 14.

AUTHORS

Michael Tuexen <tuexen@FreeBSD.org>