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461 lines
11 KiB
C
461 lines
11 KiB
C
/*
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* ntp_restrict.c - find out what restrictions this host is running under
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif
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#include <stdio.h>
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#include <sys/types.h>
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#include "ntpd.h"
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#include "ntp_if.h"
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#include "ntp_stdlib.h"
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/*
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* This code keeps a simple address-and-mask list of hosts we want
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* to place restrictions on (or remove them from). The restrictions
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* are implemented as a set of flags which tell you what the host
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* can't do. There is a subroutine entry to return the flags. The
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* list is kept sorted to reduce the average number of comparisons
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* and make sure you get the set of restrictions most specific to
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* the address.
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*
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* The algorithm is that, when looking up a host, it is first assumed
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* that the default set of restrictions will apply. It then searches
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* down through the list. Whenever it finds a match it adopts the match's
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* flags instead. When you hit the point where the sorted address is
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* greater than the target, you return with the last set of flags you
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* found. Because of the ordering of the list, the most specific match
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* will provide the final set of flags.
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*
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* This was originally intended to restrict you from sync'ing to your
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* own broadcasts when you are doing that, by restricting yourself
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* from your own interfaces. It was also thought it would sometimes
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* be useful to keep a misbehaving host or two from abusing your primary
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* clock. It has been expanded, however, to suit the needs of those
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* with more restrictive access policies.
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*/
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/*
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* Memory allocation parameters. We allocate INITRESLIST entries
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* initially, and add INCRESLIST entries to the free list whenever
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* we run out.
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*/
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#define INITRESLIST 10
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#define INCRESLIST 5
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/*
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* The restriction list
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*/
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struct restrictlist *restrictlist;
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static int restrictcount; /* count of entries in the restriction list */
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/*
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* The free list and associated counters. Also some uninteresting
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* stat counters.
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*/
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static struct restrictlist *resfree;
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static int numresfree; /* number of structures on free list */
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static u_long res_calls;
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static u_long res_found;
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static u_long res_not_found;
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/* static u_long res_timereset; */
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/*
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* Parameters of the RES_LIMITED restriction option.
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* client_limit is the number of hosts allowed per source net
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* client_limit_period is the number of seconds after which an entry
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* is no longer considered for client limit determination
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*/
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u_long client_limit;
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u_long client_limit_period;
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/*
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* count number of restriction entries referring to RES_LIMITED
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* controls activation/deactivation of monitoring
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* (with respect to RES_LIMITED control)
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*/
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static u_long res_limited_refcnt;
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/*
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* Our initial allocation of list entries.
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*/
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static struct restrictlist resinit[INITRESLIST];
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/*
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* init_restrict - initialize the restriction data structures
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*/
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void
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init_restrict(void)
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{
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register int i;
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char bp[80];
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/*
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* Zero the list and put all but one on the free list
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*/
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resfree = 0;
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memset((char *)resinit, 0, sizeof resinit);
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for (i = 1; i < INITRESLIST; i++) {
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resinit[i].next = resfree;
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resfree = &resinit[i];
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}
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numresfree = INITRESLIST-1;
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/*
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* Put the remaining item at the head of the
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* list as our default entry. Everything in here
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* should be zero for now.
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*/
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resinit[0].addr = htonl(INADDR_ANY);
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resinit[0].mask = 0;
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restrictlist = &resinit[0];
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restrictcount = 1;
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/*
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* fix up stat counters
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*/
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res_calls = 0;
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res_found = 0;
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res_not_found = 0;
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/* res_timereset = 0; */
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/*
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* set default values for RES_LIMIT functionality
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*/
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client_limit = 3;
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client_limit_period = 3600;
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res_limited_refcnt = 0;
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sprintf(bp, "client_limit=%ld", client_limit);
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set_sys_var(bp, strlen(bp)+1, RO);
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sprintf(bp, "client_limit_period=%ld", client_limit_period);
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set_sys_var(bp, strlen(bp)+1, RO);
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}
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/*
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* restrictions - return restrictions for this host
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*/
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int
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restrictions(
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struct sockaddr_in *srcadr
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)
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{
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register struct restrictlist *rl;
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register struct restrictlist *match;
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register u_int32 hostaddr;
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register int isntpport;
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res_calls++;
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/*
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* We need the host address in host order. Also need to know
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* whether this is from the ntp port or not.
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*/
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hostaddr = SRCADR(srcadr);
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isntpport = (SRCPORT(srcadr) == NTP_PORT);
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/*
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* Ignore any packets with a multicast source address
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* (this should be done early in the receive process, later!)
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*/
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if (IN_CLASSD(ntohl(srcadr->sin_addr.s_addr)))
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return (int)RES_IGNORE;
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/*
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* Set match to first entry, which is default entry. Work our
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* way down from there.
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*/
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match = restrictlist;
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for (rl = match->next; rl != 0 && rl->addr <= hostaddr; rl = rl->next)
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if ((hostaddr & rl->mask) == rl->addr) {
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if ((rl->mflags & RESM_NTPONLY) && !isntpport)
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continue;
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match = rl;
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}
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match->count++;
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if (match == restrictlist)
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res_not_found++;
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else
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res_found++;
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/*
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* The following implements limiting the number of clients
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* accepted from a given network. The notion of "same network"
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* is determined by the mask and addr fields of the restrict
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* list entry. The monitor mechanism has to be enabled for
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* collecting info on current clients.
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*
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* The policy is as follows:
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* - take the list of clients recorded
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* from the given "network" seen within the last
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* client_limit_period seconds
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* - if there are at most client_limit entries:
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* --> access allowed
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* - otherwise sort by time first seen
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* - current client among the first client_limit seen
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* hosts?
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* if yes: access allowed
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* else: eccess denied
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*/
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if (match->flags & RES_LIMITED) {
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int lcnt;
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struct mon_data *md, *this_client;
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#ifdef DEBUG
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if (debug > 2)
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printf("limited clients check: %ld clients, period %ld seconds, net is 0x%lX\n",
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client_limit, client_limit_period,
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(u_long)netof(hostaddr));
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#endif /*DEBUG*/
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if (mon_enabled == MON_OFF) {
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#ifdef DEBUG
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if (debug > 4)
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printf("no limit - monitoring is off\n");
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#endif
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return (int)(match->flags & ~RES_LIMITED);
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}
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/*
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* How nice, MRU list provides our current client as the
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* first entry in the list.
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* Monitoring was verified to be active above, thus we
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* know an entry for our client must exist, or some
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* brain dead set the memory limit for mon entries to ZERO!!!
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*/
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this_client = mon_mru_list.mru_next;
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for (md = mon_fifo_list.fifo_next,lcnt = 0;
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md != &mon_fifo_list;
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md = md->fifo_next) {
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if ((current_time - md->lasttime)
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> client_limit_period) {
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#ifdef DEBUG
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if (debug > 5)
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printf("checking: %s: ignore: too old: %ld\n",
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numtoa(md->rmtadr),
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current_time - md->lasttime);
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#endif
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continue;
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}
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if (md->mode == MODE_BROADCAST ||
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md->mode == MODE_CONTROL ||
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md->mode == MODE_PRIVATE) {
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#ifdef DEBUG
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if (debug > 5)
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printf("checking: %s: ignore mode %d\n",
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numtoa(md->rmtadr),
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md->mode);
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#endif
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continue;
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}
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if (netof(md->rmtadr) !=
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netof(hostaddr)) {
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#ifdef DEBUG
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if (debug > 5)
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printf("checking: %s: different net 0x%lX\n",
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numtoa(md->rmtadr),
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(u_long)netof(md->rmtadr));
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#endif
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continue;
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}
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lcnt++;
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if (lcnt > (int) client_limit ||
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md->rmtadr == hostaddr) {
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#ifdef DEBUG
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if (debug > 5)
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printf("considering %s: found host\n",
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numtoa(md->rmtadr));
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#endif
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break;
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}
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#ifdef DEBUG
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else {
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if (debug > 5)
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printf("considering %s: same net\n",
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numtoa(md->rmtadr));
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}
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#endif
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}
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#ifdef DEBUG
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if (debug > 4)
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printf("this one is rank %d in list, limit is %lu: %s\n",
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lcnt, client_limit,
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(lcnt <= (int) client_limit) ? "ALLOW" : "REJECT");
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#endif
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if (lcnt <= (int) client_limit) {
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this_client->lastdrop = 0;
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return (int)(match->flags & ~RES_LIMITED);
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} else {
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this_client->lastdrop = current_time;
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}
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}
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return (int)match->flags;
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}
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/*
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* hack_restrict - add/subtract/manipulate entries on the restrict list
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*/
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void
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hack_restrict(
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int op,
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struct sockaddr_in *resaddr,
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struct sockaddr_in *resmask,
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int mflags,
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int flags
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)
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{
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register u_int32 addr;
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register u_int32 mask;
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register struct restrictlist *rl;
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register struct restrictlist *rlprev;
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int i;
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/*
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* Get address and mask in host byte order
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*/
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addr = SRCADR(resaddr);
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mask = SRCADR(resmask);
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addr &= mask; /* make sure low bits are zero */
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/*
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* If this is the default address, point at first on list. Else
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* go searching for it.
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*/
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if (addr == htonl(INADDR_ANY)) {
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rlprev = 0;
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rl = restrictlist;
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} else {
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rlprev = restrictlist;
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rl = rlprev->next;
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while (rl != 0) {
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if (rl->addr > addr) {
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rl = 0;
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break;
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} else if (rl->addr == addr) {
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if (rl->mask == mask) {
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if ((mflags & RESM_NTPONLY)
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== (rl->mflags & RESM_NTPONLY))
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break; /* exact match */
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if (!(mflags & RESM_NTPONLY)) {
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/*
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* No flag fits before flag
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*/
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rl = 0;
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break;
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}
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/* continue on */
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} else if (rl->mask > mask) {
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rl = 0;
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break;
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}
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}
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rlprev = rl;
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rl = rl->next;
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}
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}
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/*
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* In case the above wasn't clear :-), either rl now points
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* at the entry this call refers to, or rl is zero and rlprev
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* points to the entry prior to where this one should go in
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* the sort.
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*/
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/*
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* Switch based on operation
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*/
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switch (op) {
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case RESTRICT_FLAGS:
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/*
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* Here we add bits to the flags. If this is a new
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* restriction add it.
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*/
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if (rl == 0) {
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if (numresfree == 0) {
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rl = (struct restrictlist *) emalloc(
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INCRESLIST*sizeof(struct restrictlist));
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memset((char *)rl, 0,
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INCRESLIST*sizeof(struct restrictlist));
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for (i = 0; i < INCRESLIST; i++) {
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rl->next = resfree;
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resfree = rl;
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rl++;
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}
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numresfree = INCRESLIST;
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}
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rl = resfree;
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resfree = rl->next;
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numresfree--;
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rl->addr = addr;
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rl->mask = mask;
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rl->mflags = (u_short)mflags;
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rl->next = rlprev->next;
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rlprev->next = rl;
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restrictcount++;
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}
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if ((rl->flags ^ (u_short)flags) & RES_LIMITED) {
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res_limited_refcnt++;
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mon_start(MON_RES); /* ensure data gets collected */
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}
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rl->flags |= (u_short)flags;
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break;
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case RESTRICT_UNFLAG:
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/*
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* Remove some bits from the flags. If we didn't
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* find this one, just return.
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*/
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if (rl != 0) {
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if ((rl->flags ^ (u_short)flags) & RES_LIMITED) {
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res_limited_refcnt--;
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if (res_limited_refcnt == 0)
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mon_stop(MON_RES);
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}
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rl->flags &= (u_short)~flags;
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}
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break;
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case RESTRICT_REMOVE:
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/*
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* Remove an entry from the table entirely if we found one.
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* Don't remove the default entry and don't remove an
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* interface entry.
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*/
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if (rl != 0
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&& rl->addr != htonl(INADDR_ANY)
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&& !(rl->mflags & RESM_INTERFACE)) {
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rlprev->next = rl->next;
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restrictcount--;
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if (rl->flags & RES_LIMITED) {
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res_limited_refcnt--;
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if (res_limited_refcnt == 0)
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mon_stop(MON_RES);
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}
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memset((char *)rl, 0, sizeof(struct restrictlist));
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rl->next = resfree;
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resfree = rl;
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numresfree++;
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}
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break;
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default:
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/* Oh, well */
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break;
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}
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/* done! */
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}
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