trusty (9) rtalloc_fib.9freebsd.gz

NAME

     rtalloc1_fib, rtalloc_ign_fib, rtalloc_fib — look up a route in the kernel routing table

SYNOPSIS

     #include <sys/types.h>
     #include <sys/socket.h>
     #include <net/route.h>

     struct rtentry *
     rtalloc1_fib(struct sockaddr *dst, int report, u_long flags, u_int fibnum);

     void
     rtalloc_fib(struct route *ro, u_int fibnum);

     void
     rtalloc_ign_fib(struct route *ro, u_long flags, u_int fibnum);

     RTFREE_LOCKED(struct rt_entry *rt);

     RTFREE(struct rt_entry *rt);

     RT_LOCK(struct rt_entry *rt);

     RT_UNLOCK(struct rt_entry *rt);

     RT_ADDREF(struct rt_entry *rt);

     RT_REMREF(struct rt_entry *rt);

     RO_RTFREE(struct route *ro);

     void
     rtfree(struct rt_entry *rt);

     struct rtentry *
     rtalloc1(struct sockaddr *dst, int report, u_long flags);

     void
     rtalloc(struct route *ro);

     void
     rtalloc_ign(struct route *ro, u_long flags);

     options RADIX_MPATH

DESCRIPTION

     The kernel uses a radix tree structure to manage routes for the networking subsystem.  If compiled with
     options RADIX_MPATH kernel may maintain several independent forwarding information databases (FIBs).  The
     rtalloc() family of routines is used by protocols to query these structures for a route corresponding to a
     particular end-node address, and to cause certain protocol- and interface-specific actions to take place.

     The rtalloc1_fib() function is the most general form of rtalloc(), and all of the other forms are
     implemented as calls to it.  It takes a struct sockaddr * directly as the dst argument.  The second
     argument, report, controls whether the routing sockets are notified when a lookup fails.  The third
     argument, flags, is a combination of the following values:

           RTF_RNH_LOCKED indicates that the radix tree lock is already held

     The last argument fibnum specifies number of forwarding information database (FIB) on which the lookup
     should be performed.  In case of success the rtalloc1_fib() function returns a pointer to a locked struct
     rtentry with an additional reference.

     The rtalloc_fib() is the most simple variant.  Its main argument is ro, a pointer to a struct route, which
     is defined as follows:

           struct route {
                   struct rtentry *ro_rt;
                   struct llentry *ro_lle;
                   struct sockaddr ro_dst;
           };

     Thus, this function can only be used for address families which are smaller than the default struct
     sockaddr.  Before calling rtalloc_fib() for the first time, callers should ensure that unused bits of the
     structure are set to zero.  The second argument fibnum is FIB number.  In case of success of the
     rtalloc_fib() the ro_rt points to a valid and unlocked rtentry(9), which has an additional reference put on
     it, freeing which is responsibility of the caller.  On subsequent calls, rtalloc_fib() returns without
     performing a lookup if ro->ro_rt is non-null and the RTF_UP flag is set in the rtentry's rt_flags field.

     The rtalloc_ign_fib() function is the same as the rtalloc_fib(), but there is additional flags argument,
     which is same as in rtalloc1_fib().

     The RTFREE_LOCKED() macro is used to unref and possibly free a locked routing entry with one our reference,
     for example previously allocated by rtalloc1_fib().

     The RTFREE() macro is used to unref and possibly free an unlocked route entries with one our reference, for
     example previously allocated by rtalloc_fib() or rtalloc_ign_fib().

     Both RTFREE_LOCKED() and RTFREE() macros decrement the reference count on the routing table entry, and
     proceed with actual freeing if the reference count has reached zero.

     The RT_LOCK() macro is used to lock a routing table entry.

     The RT_UNLOCK() macro is used to unlock a routing table entry.

     The RT_ADDREF() macro increments the reference count on a previously locked route entry.  It should be used
     whenever a reference to an rtentry(9) is going to be stored outside the routing table.

     The RT_REMREF() macro decrements the reference count on a previously locked route entry.  Its usage is
     contrary to RT_ADDREF().

     The RO_RTFREE() macro is used to free route entry that is referenced by struct route.  At certain
     circumstances the latter may not hold a reference on rtentry, and RO_RTFREE() treats such routes correctly.

     The rtfree() function does the actual free of the routing table entry, and shouldn't be called directly by
     facilities, that just perform routing table lookups.

LEGACY INTERFACE

     Prior to introduction of multiple routing tables functions did not require the u_int fibnum argument.
     Legacy rtalloc1(), rtalloc() and rtalloc_ign() functions are kept for compatibility, and are equivalent to
     calling new interface with fibnum argument equal to 0, which implies default forwarding table.

RETURN VALUES

     The rtalloc1_fib() function returns a pointer to a locked routing-table entry if it succeeds, otherwise a
     null pointer.  The rtalloc_fib() and rtalloc_ign_fib() functions do not return a value, but they fill in
     the *ro_rt member of the *ro argument with a pointer to an unlocked routing-table entry if they succeed,
     otherwise a null pointer.  In a case of success all functions put a reference on the routing-table entry,
     freeing of which is responsibility of the caller.  Lack of a route should in most cases be translated to
     the errno(2) value EHOSTUNREACH.

SEE ALSO

     route(4), rtentry(9)

HISTORY

     The rtalloc facility first appeared in 4.2BSD, although with much different internals.  The rtalloc_ign()
     function and the flags argument to rtalloc1() first appeared in FreeBSD 2.0.  Routing table locking was
     introduced in FreeBSD 5.2.  Multiple routing tables were introduced in FreeBSD 8.0.

AUTHORS

     The original version of this manual page was written by Garrett Wollman.  It was significantly updated by
     Gleb Smirnoff.