SETFIB(2)                 FreeBSD System Calls Manual                SETFIB(2)

NAME

     setfib - set the default FIB (routing table) for the calling process

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <sys/socket.h>

     int
     setfib(int fib);

DESCRIPTION

     The setfib() system call sets the associated FIB (routing table) for all
     sockets opened subsequent to the call, to be that of the argument fib.
     The fib argument must be greater than or equal to 0 and less than the
     current system maximum which may be retrieved by the net.fibs sysctl.
     The system maximum is set in the kernel configuration file with

           options ROUTETABLES=N

     or in /boot/loader.conf or /etc/sysctl.conf with

           net.fibs="N"

     where N is an integer smaller than 65536.  Note that the number of FIBs
     may be increased after booting, but cannot be reduced.

     The maximum of 65536 is due to the implementation storing the FIB number
     in a 16-bit field in the mbuf(9) packet header, however it is not
     suggested that one use such a large number as memory is allocated for
     every FIB regardless of whether it is used, and there are places where
     all FIBs are iterated over.

     The default FIB of the process will be applied to all protocol families
     that support multiple FIBs, and ignored by those that do not.  The
     default FIB for a process may be overridden for a socket with the use of
     the SO_SETFIB socket option.

RETURN VALUES

     The setfib() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.

ERRORS

     The setfib() system call will fail and no action will be taken and return
     EINVAL if the fib argument is greater than the current system maximum.

SEE ALSO

     setfib(1), setsockopt(2)

STANDARDS

     The setfib() system call is a FreeBSD extension however similar
     extensions have been added to many other Unix style kernels.

HISTORY

     The setfib() function appeared in FreeBSD 7.1.

FreeBSD 15.1-STABLE-HBSD       January 10, 2025                      SETFIB(2)