FreeBSD/Linux Kernel Cross Reference
sys/netinet/in_rmx.c

     /*
      * Copyright 1994, 1995 Massachusetts Institute of Technology
      *
      * Permission to use, copy, modify, and distribute this software and
      * its documentation for any purpose and without fee is hereby
      * granted, provided that both the above copyright notice and this
      * permission notice appear in all copies, that both the above
      * copyright notice and this permission notice appear in all
      * supporting documentation, and that the name of M.I.T. not be used
     * in advertising or publicity pertaining to distribution of the
     * software without specific, written prior permission.  M.I.T. makes
     * no representations about the suitability of this software for any
     * purpose.  It is provided "as is" without express or implied
     * warranty.
     *
     * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''.  M.I.T. DISCLAIMS
     * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
     * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
     * SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
     * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
     * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     * $FreeBSD: releng/5.1/sys/netinet/in_rmx.c 110656 2003-02-10 22:01:34Z hsu $
     */
    
    /*
     * This code does two things necessary for the enhanced TCP metrics to
     * function in a useful manner:
     *  1) It marks all non-host routes as `cloning', thus ensuring that
     *     every actual reference to such a route actually gets turned
     *     into a reference to a host route to the specific destination
     *     requested.
     *  2) When such routes lose all their references, it arranges for them
     *     to be deleted in some random collection of circumstances, so that
     *     a large quantity of stale routing data is not kept in kernel memory
     *     indefinitely.  See in_rtqtimo() below for the exact mechanism.
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/kernel.h>
    #include <sys/sysctl.h>
    #include <sys/socket.h>
    #include <sys/mbuf.h>
    #include <sys/syslog.h>
    
    #include <net/if.h>
    #include <net/route.h>
    #include <netinet/in.h>
    #include <netinet/in_var.h>
    #include <netinet/ip_var.h>
    
    extern int      in_inithead(void **head, int off);
    
    #define RTPRF_OURS              RTF_PROTO3      /* set on routes we manage */
    
    /*
     * Do what we need to do when inserting a route.
     */
    static struct radix_node *
    in_addroute(void *v_arg, void *n_arg, struct radix_node_head *head,
                struct radix_node *treenodes)
    {
            struct rtentry *rt = (struct rtentry *)treenodes;
            struct sockaddr_in *sin = (struct sockaddr_in *)rt_key(rt);
            struct radix_node *ret;
    
            /*
             * For IP, all unicast non-host routes are automatically cloning.
             */
            if (IN_MULTICAST(ntohl(sin->sin_addr.s_addr)))
                    rt->rt_flags |= RTF_MULTICAST;
    
            if (!(rt->rt_flags & (RTF_HOST | RTF_CLONING | RTF_MULTICAST)))
                    rt->rt_flags |= RTF_PRCLONING;
    
            /*
             * A little bit of help for both IP output and input:
             *   For host routes, we make sure that RTF_BROADCAST
             *   is set for anything that looks like a broadcast address.
             *   This way, we can avoid an expensive call to in_broadcast()
             *   in ip_output() most of the time (because the route passed
             *   to ip_output() is almost always a host route).
             *
             *   We also do the same for local addresses, with the thought
             *   that this might one day be used to speed up ip_input().
             *
             * We also mark routes to multicast addresses as such, because
             * it's easy to do and might be useful (but this is much more
             * dubious since it's so easy to inspect the address).  (This
             * is done above.)
             */
            if (rt->rt_flags & RTF_HOST) {
                   if (in_broadcast(sin->sin_addr, rt->rt_ifp)) {
                           rt->rt_flags |= RTF_BROADCAST;
                   } else if (satosin(rt->rt_ifa->ifa_addr)->sin_addr.s_addr ==
                       sin->sin_addr.s_addr) {
                           rt->rt_flags |= RTF_LOCAL;
                   }
           }
   
           if (!rt->rt_rmx.rmx_mtu && !(rt->rt_rmx.rmx_locks & RTV_MTU) &&
               rt->rt_ifp)
                   rt->rt_rmx.rmx_mtu = rt->rt_ifp->if_mtu;
   
           ret = rn_addroute(v_arg, n_arg, head, treenodes);
           if (ret == NULL && rt->rt_flags & RTF_HOST) {
                   struct rtentry *rt2;
                   /*
                    * We are trying to add a host route, but can't.
                    * Find out if it is because of an
                    * ARP entry and delete it if so.
                    */
                   rt2 = rtalloc1((struct sockaddr *)sin, 0,
                                   RTF_CLONING | RTF_PRCLONING);
                   if (rt2) {
                           if (rt2->rt_flags & RTF_LLINFO &&
                               rt2->rt_flags & RTF_HOST &&
                               rt2->rt_gateway &&
                               rt2->rt_gateway->sa_family == AF_LINK) {
                                   rtrequest(RTM_DELETE,
                                             (struct sockaddr *)rt_key(rt2),
                                             rt2->rt_gateway, rt_mask(rt2),
                                             rt2->rt_flags, 0);
                                   ret = rn_addroute(v_arg, n_arg, head,
                                                     treenodes);
                           }
                           RTFREE(rt2);
                   }
           }
   
           /*
            * If the new route created successfully, and we are forwarding,
            * and there is a cached route, free it.  Otherwise, we may end
            * up using the wrong route.
            */
           if (ret != NULL && ipforwarding && ipforward_rt.ro_rt) {
                   RTFREE(ipforward_rt.ro_rt);
                   ipforward_rt.ro_rt = 0;
           }
   
           return ret;
   }
   
   /*
    * This code is the inverse of in_clsroute: on first reference, if we
    * were managing the route, stop doing so and set the expiration timer
    * back off again.
    */
   static struct radix_node *
   in_matroute(void *v_arg, struct radix_node_head *head)
   {
           struct radix_node *rn = rn_match(v_arg, head);
           struct rtentry *rt = (struct rtentry *)rn;
   
           if (rt && rt->rt_refcnt == 0) {         /* this is first reference */
                   if (rt->rt_flags & RTPRF_OURS) {
                           rt->rt_flags &= ~RTPRF_OURS;
                           rt->rt_rmx.rmx_expire = 0;
                   }
           }
           return rn;
   }
   
   static int rtq_reallyold = 60*60;               /* one hour is "really old" */
   SYSCTL_INT(_net_inet_ip, IPCTL_RTEXPIRE, rtexpire, CTLFLAG_RW,
       &rtq_reallyold, 0, "Default expiration time on dynamically learned routes");
   
   static int rtq_minreallyold = 10;  /* never automatically crank down to less */
   SYSCTL_INT(_net_inet_ip, IPCTL_RTMINEXPIRE, rtminexpire, CTLFLAG_RW,
       &rtq_minreallyold, 0,
       "Minimum time to attempt to hold onto dynamically learned routes");
   
   static int rtq_toomany = 128;           /* 128 cached routes is "too many" */
   SYSCTL_INT(_net_inet_ip, IPCTL_RTMAXCACHE, rtmaxcache, CTLFLAG_RW,
       &rtq_toomany, 0, "Upper limit on dynamically learned routes");
   
   /*
    * On last reference drop, mark the route as belong to us so that it can be
    * timed out.
    */
   static void
   in_clsroute(struct radix_node *rn, struct radix_node_head *head)
   {
           struct rtentry *rt = (struct rtentry *)rn;
   
           if (!(rt->rt_flags & RTF_UP))
                   return;                 /* prophylactic measures */
   
           if ((rt->rt_flags & (RTF_LLINFO | RTF_HOST)) != RTF_HOST)
                   return;
   
           if ((rt->rt_flags & (RTF_WASCLONED | RTPRF_OURS)) != RTF_WASCLONED)
                   return;
   
           /*
            * If rtq_reallyold is 0, just delete the route without
            * waiting for a timeout cycle to kill it.
            */
           if (rtq_reallyold != 0) {
                   rt->rt_flags |= RTPRF_OURS;
                   rt->rt_rmx.rmx_expire = time_second + rtq_reallyold;
           } else {
                   rtrequest(RTM_DELETE,
                             (struct sockaddr *)rt_key(rt),
                             rt->rt_gateway, rt_mask(rt),
                             rt->rt_flags, 0);
           }
   }
   
   struct rtqk_arg {
           struct radix_node_head *rnh;
           int draining;
           int killed;
           int found;
           int updating;
           time_t nextstop;
   };
   
   /*
    * Get rid of old routes.  When draining, this deletes everything, even when
    * the timeout is not expired yet.  When updating, this makes sure that
    * nothing has a timeout longer than the current value of rtq_reallyold.
    */
   static int
   in_rtqkill(struct radix_node *rn, void *rock)
   {
           struct rtqk_arg *ap = rock;
           struct rtentry *rt = (struct rtentry *)rn;
           int err;
   
           if (rt->rt_flags & RTPRF_OURS) {
                   ap->found++;
   
                   if (ap->draining || rt->rt_rmx.rmx_expire <= time_second) {
                           if (rt->rt_refcnt > 0)
                                   panic("rtqkill route really not free");
   
                           err = rtrequest(RTM_DELETE,
                                           (struct sockaddr *)rt_key(rt),
                                           rt->rt_gateway, rt_mask(rt),
                                           rt->rt_flags, 0);
                           if (err) {
                                   log(LOG_WARNING, "in_rtqkill: error %d\n", err);
                           } else {
                                   ap->killed++;
                           }
                   } else {
                           if (ap->updating &&
                               (rt->rt_rmx.rmx_expire - time_second >
                                rtq_reallyold)) {
                                   rt->rt_rmx.rmx_expire =
                                       time_second + rtq_reallyold;
                           }
                           ap->nextstop = lmin(ap->nextstop,
                                               rt->rt_rmx.rmx_expire);
                   }
           }
   
           return 0;
   }
   
   #define RTQ_TIMEOUT     60*10   /* run no less than once every ten minutes */
   static int rtq_timeout = RTQ_TIMEOUT;
   
   static void
   in_rtqtimo(void *rock)
   {
           struct radix_node_head *rnh = rock;
           struct rtqk_arg arg;
           struct timeval atv;
           static time_t last_adjusted_timeout = 0;
           int s;
   
           arg.found = arg.killed = 0;
           arg.rnh = rnh;
           arg.nextstop = time_second + rtq_timeout;
           arg.draining = arg.updating = 0;
           s = splnet();
           RADIX_NODE_HEAD_LOCK(rnh);
           rnh->rnh_walktree(rnh, in_rtqkill, &arg);
           RADIX_NODE_HEAD_UNLOCK(rnh);
           splx(s);
   
           /*
            * Attempt to be somewhat dynamic about this:
            * If there are ``too many'' routes sitting around taking up space,
            * then crank down the timeout, and see if we can't make some more
            * go away.  However, we make sure that we will never adjust more
            * than once in rtq_timeout seconds, to keep from cranking down too
            * hard.
            */
           if ((arg.found - arg.killed > rtq_toomany) &&
               (time_second - last_adjusted_timeout >= rtq_timeout) &&
               rtq_reallyold > rtq_minreallyold) {
                   rtq_reallyold = 2 * rtq_reallyold / 3;
                   if (rtq_reallyold < rtq_minreallyold) {
                           rtq_reallyold = rtq_minreallyold;
                   }
   
                   last_adjusted_timeout = time_second;
   #ifdef DIAGNOSTIC
                   log(LOG_DEBUG, "in_rtqtimo: adjusted rtq_reallyold to %d\n",
                       rtq_reallyold);
   #endif
                   arg.found = arg.killed = 0;
                   arg.updating = 1;
                   s = splnet();
                   RADIX_NODE_HEAD_LOCK(rnh);
                   rnh->rnh_walktree(rnh, in_rtqkill, &arg);
                   RADIX_NODE_HEAD_UNLOCK(rnh);
                   splx(s);
           }
   
           atv.tv_usec = 0;
           atv.tv_sec = arg.nextstop - time_second;
           timeout(in_rtqtimo, rock, tvtohz(&atv));
   }
   
   void
   in_rtqdrain(void)
   {
           struct radix_node_head *rnh = rt_tables[AF_INET];
           struct rtqk_arg arg;
           int s;
           arg.found = arg.killed = 0;
           arg.rnh = rnh;
           arg.nextstop = 0;
           arg.draining = 1;
           arg.updating = 0;
           s = splnet();
           RADIX_NODE_HEAD_LOCK(rnh);
           rnh->rnh_walktree(rnh, in_rtqkill, &arg);
           RADIX_NODE_HEAD_UNLOCK(rnh);
           splx(s);
   }
   
   /*
    * Initialize our routing tree.
    */
   int
   in_inithead(void **head, int off)
   {
           struct radix_node_head *rnh;
   
           if (!rn_inithead(head, off))
                   return 0;
   
           if (head != (void **)&rt_tables[AF_INET])       /* BOGUS! */
                   return 1;       /* only do this for the real routing table */
   
           rnh = *head;
           rnh->rnh_addaddr = in_addroute;
           rnh->rnh_matchaddr = in_matroute;
           rnh->rnh_close = in_clsroute;
           in_rtqtimo(rnh);        /* kick off timeout first time */
           return 1;
   }
   
   /*
    * This zaps old routes when the interface goes down or interface
    * address is deleted.  In the latter case, it deletes static routes
    * that point to this address.  If we don't do this, we may end up
    * using the old address in the future.  The ones we always want to
    * get rid of are things like ARP entries, since the user might down
    * the interface, walk over to a completely different network, and
    * plug back in.
    */
   struct in_ifadown_arg {
           struct radix_node_head *rnh;
           struct ifaddr *ifa;
           int del;
   };
   
   static int
   in_ifadownkill(struct radix_node *rn, void *xap)
   {
           struct in_ifadown_arg *ap = xap;
           struct rtentry *rt = (struct rtentry *)rn;
           int err;
   
           if (rt->rt_ifa == ap->ifa &&
               (ap->del || !(rt->rt_flags & RTF_STATIC))) {
                   /*
                    * We need to disable the automatic prune that happens
                    * in this case in rtrequest() because it will blow
                    * away the pointers that rn_walktree() needs in order
                    * continue our descent.  We will end up deleting all
                    * the routes that rtrequest() would have in any case,
                    * so that behavior is not needed there.
                    */
                   rt->rt_flags &= ~(RTF_CLONING | RTF_PRCLONING);
                   err = rtrequest(RTM_DELETE, (struct sockaddr *)rt_key(rt),
                                   rt->rt_gateway, rt_mask(rt), rt->rt_flags, 0);
                   if (err) {
                           log(LOG_WARNING, "in_ifadownkill: error %d\n", err);
                   }
           }
           return 0;
   }
   
   int
   in_ifadown(struct ifaddr *ifa, int delete)
   {
           struct in_ifadown_arg arg;
           struct radix_node_head *rnh;
   
           if (ifa->ifa_addr->sa_family != AF_INET)
                   return 1;
   
           arg.rnh = rnh = rt_tables[AF_INET];
           arg.ifa = ifa;
           arg.del = delete;
           RADIX_NODE_HEAD_LOCK(rnh);
           rnh->rnh_walktree(rnh, in_ifadownkill, &arg);
           RADIX_NODE_HEAD_UNLOCK(rnh);
           ifa->ifa_flags &= ~IFA_ROUTE;
           return 0;
   }

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