The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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

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    1 /*-
    2  * Copyright 1994, 1995 Massachusetts Institute of Technology
    3  *
    4  * Permission to use, copy, modify, and distribute this software and
    5  * its documentation for any purpose and without fee is hereby
    6  * granted, provided that both the above copyright notice and this
    7  * permission notice appear in all copies, that both the above
    8  * copyright notice and this permission notice appear in all
    9  * supporting documentation, and that the name of M.I.T. not be used
   10  * in advertising or publicity pertaining to distribution of the
   11  * software without specific, written prior permission.  M.I.T. makes
   12  * no representations about the suitability of this software for any
   13  * purpose.  It is provided "as is" without express or implied
   14  * warranty.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''.  M.I.T. DISCLAIMS
   17  * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
   18  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
   19  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
   20  * SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   23  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   25  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   26  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  */
   29 
   30 /*
   31  * This code does two things necessary for the enhanced TCP metrics to
   32  * function in a useful manner:
   33  *  1) It marks all non-host routes as `cloning', thus ensuring that
   34  *     every actual reference to such a route actually gets turned
   35  *     into a reference to a host route to the specific destination
   36  *     requested.
   37  *  2) When such routes lose all their references, it arranges for them
   38  *     to be deleted in some random collection of circumstances, so that
   39  *     a large quantity of stale routing data is not kept in kernel memory
   40  *     indefinitely.  See in_rtqtimo() below for the exact mechanism.
   41  */
   42 
   43 #include <sys/cdefs.h>
   44 __FBSDID("$FreeBSD$");
   45 
   46 #include <sys/param.h>
   47 #include <sys/systm.h>
   48 #include <sys/kernel.h>
   49 #include <sys/sysctl.h>
   50 #include <sys/socket.h>
   51 #include <sys/mbuf.h>
   52 #include <sys/syslog.h>
   53 #include <sys/callout.h>
   54 
   55 #include <net/if.h>
   56 #include <net/route.h>
   57 #include <netinet/in.h>
   58 #include <netinet/in_var.h>
   59 #include <netinet/ip_var.h>
   60 
   61 extern int      in_inithead(void **head, int off);
   62 
   63 #define RTPRF_OURS              RTF_PROTO3      /* set on routes we manage */
   64 
   65 /*
   66  * Do what we need to do when inserting a route.
   67  */
   68 static struct radix_node *
   69 in_addroute(void *v_arg, void *n_arg, struct radix_node_head *head,
   70     struct radix_node *treenodes)
   71 {
   72         struct rtentry *rt = (struct rtentry *)treenodes;
   73         struct sockaddr_in *sin = (struct sockaddr_in *)rt_key(rt);
   74         struct radix_node *ret;
   75 
   76         /*
   77          * A little bit of help for both IP output and input:
   78          *   For host routes, we make sure that RTF_BROADCAST
   79          *   is set for anything that looks like a broadcast address.
   80          *   This way, we can avoid an expensive call to in_broadcast()
   81          *   in ip_output() most of the time (because the route passed
   82          *   to ip_output() is almost always a host route).
   83          *
   84          *   We also do the same for local addresses, with the thought
   85          *   that this might one day be used to speed up ip_input().
   86          *
   87          * We also mark routes to multicast addresses as such, because
   88          * it's easy to do and might be useful (but this is much more
   89          * dubious since it's so easy to inspect the address).
   90          */
   91         if (rt->rt_flags & RTF_HOST) {
   92                 if (in_broadcast(sin->sin_addr, rt->rt_ifp)) {
   93                         rt->rt_flags |= RTF_BROADCAST;
   94                 } else if (satosin(rt->rt_ifa->ifa_addr)->sin_addr.s_addr ==
   95                     sin->sin_addr.s_addr) {
   96                         rt->rt_flags |= RTF_LOCAL;
   97                 }
   98         }
   99         if (IN_MULTICAST(ntohl(sin->sin_addr.s_addr)))
  100                 rt->rt_flags |= RTF_MULTICAST;
  101 
  102         if (!rt->rt_rmx.rmx_mtu && rt->rt_ifp)
  103                 rt->rt_rmx.rmx_mtu = rt->rt_ifp->if_mtu;
  104 
  105         ret = rn_addroute(v_arg, n_arg, head, treenodes);
  106         if (ret == NULL && rt->rt_flags & RTF_HOST) {
  107                 struct rtentry *rt2;
  108                 /*
  109                  * We are trying to add a host route, but can't.
  110                  * Find out if it is because of an
  111                  * ARP entry and delete it if so.
  112                  */
  113                 rt2 = rtalloc1((struct sockaddr *)sin, 0, RTF_CLONING);
  114                 if (rt2) {
  115                         if (rt2->rt_flags & RTF_LLINFO &&
  116                             rt2->rt_flags & RTF_HOST &&
  117                             rt2->rt_gateway &&
  118                             rt2->rt_gateway->sa_family == AF_LINK) {
  119                                 rtexpunge(rt2);
  120                                 RTFREE_LOCKED(rt2);
  121                                 ret = rn_addroute(v_arg, n_arg, head,
  122                                                   treenodes);
  123                         } else
  124                                 RTFREE_LOCKED(rt2);
  125                 }
  126         }
  127 
  128         return ret;
  129 }
  130 
  131 /*
  132  * This code is the inverse of in_clsroute: on first reference, if we
  133  * were managing the route, stop doing so and set the expiration timer
  134  * back off again.
  135  */
  136 static struct radix_node *
  137 in_matroute(void *v_arg, struct radix_node_head *head)
  138 {
  139         struct radix_node *rn = rn_match(v_arg, head);
  140         struct rtentry *rt = (struct rtentry *)rn;
  141 
  142         /*XXX locking? */
  143         if (rt && rt->rt_refcnt == 0) {         /* this is first reference */
  144                 if (rt->rt_flags & RTPRF_OURS) {
  145                         rt->rt_flags &= ~RTPRF_OURS;
  146                         rt->rt_rmx.rmx_expire = 0;
  147                 }
  148         }
  149         return rn;
  150 }
  151 
  152 static int rtq_reallyold = 60*60;               /* one hour is "really old" */
  153 SYSCTL_INT(_net_inet_ip, IPCTL_RTEXPIRE, rtexpire, CTLFLAG_RW,
  154     &rtq_reallyold, 0, "Default expiration time on dynamically learned routes");
  155 
  156 static int rtq_minreallyold = 10;  /* never automatically crank down to less */
  157 SYSCTL_INT(_net_inet_ip, IPCTL_RTMINEXPIRE, rtminexpire, CTLFLAG_RW,
  158     &rtq_minreallyold, 0,
  159     "Minimum time to attempt to hold onto dynamically learned routes");
  160 
  161 static int rtq_toomany = 128;           /* 128 cached routes is "too many" */
  162 SYSCTL_INT(_net_inet_ip, IPCTL_RTMAXCACHE, rtmaxcache, CTLFLAG_RW,
  163     &rtq_toomany, 0, "Upper limit on dynamically learned routes");
  164 
  165 /*
  166  * On last reference drop, mark the route as belong to us so that it can be
  167  * timed out.
  168  */
  169 static void
  170 in_clsroute(struct radix_node *rn, struct radix_node_head *head)
  171 {
  172         struct rtentry *rt = (struct rtentry *)rn;
  173 
  174         RT_LOCK_ASSERT(rt);
  175 
  176         if (!(rt->rt_flags & RTF_UP))
  177                 return;                 /* prophylactic measures */
  178 
  179         if ((rt->rt_flags & (RTF_LLINFO | RTF_HOST)) != RTF_HOST)
  180                 return;
  181 
  182         if (rt->rt_flags & RTPRF_OURS)
  183                 return;
  184 
  185         if (!(rt->rt_flags & (RTF_WASCLONED | RTF_DYNAMIC)))
  186                 return;
  187 
  188         /*
  189          * If rtq_reallyold is 0, just delete the route without
  190          * waiting for a timeout cycle to kill it.
  191          */
  192         if (rtq_reallyold != 0) {
  193                 rt->rt_flags |= RTPRF_OURS;
  194                 rt->rt_rmx.rmx_expire = time_uptime + rtq_reallyold;
  195         } else {
  196                 rtexpunge(rt);
  197         }
  198 }
  199 
  200 struct rtqk_arg {
  201         struct radix_node_head *rnh;
  202         int draining;
  203         int killed;
  204         int found;
  205         int updating;
  206         time_t nextstop;
  207 };
  208 
  209 /*
  210  * Get rid of old routes.  When draining, this deletes everything, even when
  211  * the timeout is not expired yet.  When updating, this makes sure that
  212  * nothing has a timeout longer than the current value of rtq_reallyold.
  213  */
  214 static int
  215 in_rtqkill(struct radix_node *rn, void *rock)
  216 {
  217         struct rtqk_arg *ap = rock;
  218         struct rtentry *rt = (struct rtentry *)rn;
  219         int err;
  220 
  221         if (rt->rt_flags & RTPRF_OURS) {
  222                 ap->found++;
  223 
  224                 if (ap->draining || rt->rt_rmx.rmx_expire <= time_uptime) {
  225                         if (rt->rt_refcnt > 0)
  226                                 panic("rtqkill route really not free");
  227 
  228                         err = rtrequest(RTM_DELETE,
  229                                         (struct sockaddr *)rt_key(rt),
  230                                         rt->rt_gateway, rt_mask(rt),
  231                                         rt->rt_flags, 0);
  232                         if (err) {
  233                                 log(LOG_WARNING, "in_rtqkill: error %d\n", err);
  234                         } else {
  235                                 ap->killed++;
  236                         }
  237                 } else {
  238                         if (ap->updating &&
  239                             (rt->rt_rmx.rmx_expire - time_uptime >
  240                              rtq_reallyold)) {
  241                                 rt->rt_rmx.rmx_expire =
  242                                     time_uptime + rtq_reallyold;
  243                         }
  244                         ap->nextstop = lmin(ap->nextstop,
  245                                             rt->rt_rmx.rmx_expire);
  246                 }
  247         }
  248 
  249         return 0;
  250 }
  251 
  252 #define RTQ_TIMEOUT     60*10   /* run no less than once every ten minutes */
  253 static int rtq_timeout = RTQ_TIMEOUT;
  254 static struct callout rtq_timer;
  255 
  256 static void
  257 in_rtqtimo(void *rock)
  258 {
  259         struct radix_node_head *rnh = rock;
  260         struct rtqk_arg arg;
  261         struct timeval atv;
  262         static time_t last_adjusted_timeout = 0;
  263 
  264         arg.found = arg.killed = 0;
  265         arg.rnh = rnh;
  266         arg.nextstop = time_uptime + rtq_timeout;
  267         arg.draining = arg.updating = 0;
  268         RADIX_NODE_HEAD_LOCK(rnh);
  269         rnh->rnh_walktree(rnh, in_rtqkill, &arg);
  270         RADIX_NODE_HEAD_UNLOCK(rnh);
  271 
  272         /*
  273          * Attempt to be somewhat dynamic about this:
  274          * If there are ``too many'' routes sitting around taking up space,
  275          * then crank down the timeout, and see if we can't make some more
  276          * go away.  However, we make sure that we will never adjust more
  277          * than once in rtq_timeout seconds, to keep from cranking down too
  278          * hard.
  279          */
  280         if ((arg.found - arg.killed > rtq_toomany) &&
  281             (time_uptime - last_adjusted_timeout >= rtq_timeout) &&
  282             rtq_reallyold > rtq_minreallyold) {
  283                 rtq_reallyold = 2 * rtq_reallyold / 3;
  284                 if (rtq_reallyold < rtq_minreallyold) {
  285                         rtq_reallyold = rtq_minreallyold;
  286                 }
  287 
  288                 last_adjusted_timeout = time_uptime;
  289 #ifdef DIAGNOSTIC
  290                 log(LOG_DEBUG, "in_rtqtimo: adjusted rtq_reallyold to %d\n",
  291                     rtq_reallyold);
  292 #endif
  293                 arg.found = arg.killed = 0;
  294                 arg.updating = 1;
  295                 RADIX_NODE_HEAD_LOCK(rnh);
  296                 rnh->rnh_walktree(rnh, in_rtqkill, &arg);
  297                 RADIX_NODE_HEAD_UNLOCK(rnh);
  298         }
  299 
  300         atv.tv_usec = 0;
  301         atv.tv_sec = arg.nextstop - time_uptime;
  302         callout_reset(&rtq_timer, tvtohz(&atv), in_rtqtimo, rock);
  303 }
  304 
  305 void
  306 in_rtqdrain(void)
  307 {
  308         struct radix_node_head *rnh = rt_tables[AF_INET];
  309         struct rtqk_arg arg;
  310 
  311         arg.found = arg.killed = 0;
  312         arg.rnh = rnh;
  313         arg.nextstop = 0;
  314         arg.draining = 1;
  315         arg.updating = 0;
  316         RADIX_NODE_HEAD_LOCK(rnh);
  317         rnh->rnh_walktree(rnh, in_rtqkill, &arg);
  318         RADIX_NODE_HEAD_UNLOCK(rnh);
  319 }
  320 
  321 /*
  322  * Initialize our routing tree.
  323  */
  324 int
  325 in_inithead(void **head, int off)
  326 {
  327         struct radix_node_head *rnh;
  328 
  329         if (!rn_inithead(head, off))
  330                 return 0;
  331 
  332         if (head != (void **)&rt_tables[AF_INET])       /* BOGUS! */
  333                 return 1;       /* only do this for the real routing table */
  334 
  335         rnh = *head;
  336         rnh->rnh_addaddr = in_addroute;
  337         rnh->rnh_matchaddr = in_matroute;
  338         rnh->rnh_close = in_clsroute;
  339         callout_init(&rtq_timer, CALLOUT_MPSAFE);
  340         in_rtqtimo(rnh);        /* kick off timeout first time */
  341         return 1;
  342 }
  343 
  344 /*
  345  * This zaps old routes when the interface goes down or interface
  346  * address is deleted.  In the latter case, it deletes static routes
  347  * that point to this address.  If we don't do this, we may end up
  348  * using the old address in the future.  The ones we always want to
  349  * get rid of are things like ARP entries, since the user might down
  350  * the interface, walk over to a completely different network, and
  351  * plug back in.
  352  */
  353 struct in_ifadown_arg {
  354         struct radix_node_head *rnh;
  355         struct ifaddr *ifa;
  356         int del;
  357 };
  358 
  359 static int
  360 in_ifadownkill(struct radix_node *rn, void *xap)
  361 {
  362         struct in_ifadown_arg *ap = xap;
  363         struct rtentry *rt = (struct rtentry *)rn;
  364 
  365         RT_LOCK(rt);
  366         if (rt->rt_ifa == ap->ifa &&
  367             (ap->del || !(rt->rt_flags & RTF_STATIC))) {
  368                 /*
  369                  * We need to disable the automatic prune that happens
  370                  * in this case in rtrequest() because it will blow
  371                  * away the pointers that rn_walktree() needs in order
  372                  * continue our descent.  We will end up deleting all
  373                  * the routes that rtrequest() would have in any case,
  374                  * so that behavior is not needed there.
  375                  */
  376                 rt->rt_flags &= ~RTF_CLONING;
  377                 rtexpunge(rt);
  378         }
  379         RT_UNLOCK(rt);
  380         return 0;
  381 }
  382 
  383 int
  384 in_ifadown(struct ifaddr *ifa, int delete)
  385 {
  386         struct in_ifadown_arg arg;
  387         struct radix_node_head *rnh;
  388 
  389         if (ifa->ifa_addr->sa_family != AF_INET)
  390                 return 1;
  391 
  392         arg.rnh = rnh = rt_tables[AF_INET];
  393         arg.ifa = ifa;
  394         arg.del = delete;
  395         RADIX_NODE_HEAD_LOCK(rnh);
  396         rnh->rnh_walktree(rnh, in_ifadownkill, &arg);
  397         RADIX_NODE_HEAD_UNLOCK(rnh);
  398         ifa->ifa_flags &= ~IFA_ROUTE;           /* XXXlocking? */
  399         return 0;
  400 }

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