/*
* mon_reclaim_entry - Remove an entry from the MRU list and from the
* hash array, then zero-initialize it. Indirectly
* decrements mru_entries.
* The entry is prepared to be reused. Before return, in
* remove_from_hash(), mru_entries is decremented. It is the caller's
* responsibility to increment it again.
*/
static inline void
mon_reclaim_entry(
mon_entry *m
)
{
DEBUG_INSIST(NULL != m);
UNLINK_DLIST(m, mru);
remove_from_hash(m);
ZERO(*m);
}
/*
* mon_clearinterface -- remove mru entries referring to a local address
* which is going away.
*/
void
mon_clearinterface(
endpt *lcladr
)
{
mon_entry *mon;
/* iterate mon over mon_mru_list */
ITER_DLIST_BEGIN(mon_mru_list, mon, mru, mon_entry)
if (mon->lcladr == lcladr) {
/* remove from mru list */
UNLINK_DLIST(mon, mru);
/* remove from hash list, adjust mru_entries */
remove_from_hash(mon);
/* put on free list */
mon_free_entry(mon);
}
ITER_DLIST_END()
}
/*
* freesymkey - common code to remove a symkey and recycle its entry.
*/
static void
freesymkey(
symkey * sk,
symkey ** bucket
)
{
symkey * unlinked;
if (sk->secret != NULL) {
memset(sk->secret, '\0', sk->secretsize);
free(sk->secret);
}
UNLINK_SLIST(unlinked, *bucket, sk, hlink, symkey);
DEBUG_ENSURE(sk == unlinked);
UNLINK_DLIST(sk, llink);
memset((char *)sk + offsetof(symkey, symkey_payload), '\0',
sizeof(*sk) - offsetof(symkey, symkey_payload));
LINK_SLIST(authfreekeys, sk, llink.f);
authnumkeys--;
authnumfreekeys++;
}
/*
* ntp_monitor - record stats about this packet
*
* Returns supplied restriction flags, with RES_LIMITED and RES_KOD
* cleared unless the packet should not be responded to normally
* (RES_LIMITED) and possibly should trigger a KoD response (RES_KOD).
* The returned flags are saved in the MRU entry, so that it reflects
* whether the last packet from that source triggered rate limiting,
* and if so, possible KoD response. This implies you can not tell
* whether a given address is eligible for rate limiting/KoD from the
* monlist restrict bits, only whether or not the last packet triggered
* such responses. ntpdc -c reslist lets you see whether RES_LIMITED
* or RES_KOD is lit for a particular address before ntp_monitor()'s
* typical dousing.
*/
u_short
ntp_monitor(
struct recvbuf *rbufp,
u_short flags
)
{
l_fp interval_fp;
struct pkt * pkt;
mon_entry * mon;
mon_entry * oldest;
int oldest_age;
u_int hash;
u_short restrict_mask;
u_char mode;
u_char version;
int interval;
int head; /* headway increment */
int leak; /* new headway */
int limit; /* average threshold */
REQUIRE(rbufp != NULL);
if (mon_enabled == MON_OFF)
return ~(RES_LIMITED | RES_KOD) & flags;
pkt = &rbufp->recv_pkt;
hash = MON_HASH(&rbufp->recv_srcadr);
mode = PKT_MODE(pkt->li_vn_mode);
version = PKT_VERSION(pkt->li_vn_mode);
mon = mon_hash[hash];
/*
* We keep track of all traffic for a given IP in one entry,
* otherwise cron'ed ntpdate or similar evades RES_LIMITED.
*/
for (; mon != NULL; mon = mon->hash_next)
if (SOCK_EQ(&mon->rmtadr, &rbufp->recv_srcadr))
break;
if (mon != NULL) {
interval_fp = rbufp->recv_time;
L_SUB(&interval_fp, &mon->last);
/* add one-half second to round up */
L_ADDUF(&interval_fp, 0x80000000);
interval = interval_fp.l_i;
mon->last = rbufp->recv_time;
NSRCPORT(&mon->rmtadr) = NSRCPORT(&rbufp->recv_srcadr);
mon->count++;
restrict_mask = flags;
mon->vn_mode = VN_MODE(version, mode);
/* Shuffle to the head of the MRU list. */
UNLINK_DLIST(mon, mru);
LINK_DLIST(mon_mru_list, mon, mru);
/*
* At this point the most recent arrival is first in the
* MRU list. Decrease the counter by the headway, but
* not less than zero.
*/
mon->leak -= interval;
mon->leak = max(0, mon->leak);
head = 1 << ntp_minpoll;
leak = mon->leak + head;
limit = NTP_SHIFT * head;
DPRINTF(2, ("MRU: interval %d headway %d limit %d\n",
interval, leak, limit));
/*
* If the minimum and average thresholds are not
* exceeded, douse the RES_LIMITED and RES_KOD bits and
* increase the counter by the headway increment. Note
* that we give a 1-s grace for the minimum threshold
* and a 2-s grace for the headway increment. If one or
* both thresholds are exceeded and the old counter is
* less than the average threshold, set the counter to
* the average threshold plus the increment and leave
* the RES_LIMITED and RES_KOD bits lit. Otherwise,
* leave the counter alone and douse the RES_KOD bit.
* This rate-limits the KoDs to no less than the average
* headway.
*/
if (interval + 1 >= ntp_minpkt && leak < limit) {
mon->leak = leak - 2;
restrict_mask &= ~(RES_LIMITED | RES_KOD);
} else if (mon->leak < limit)
mon->leak = limit + head;
else
restrict_mask &= ~RES_KOD;
mon->flags = restrict_mask;
return mon->flags;
}
/*
* If we got here, this is the first we've heard of this
* guy. Get him some memory, either from the free list
* or from the tail of the MRU list.
*
* The following ntp.conf "mru" knobs come into play determining
* the depth (or count) of the MRU list:
* - mru_mindepth ("mru mindepth") is a floor beneath which
* entries are kept without regard to their age. The
* default is 600 which matches the longtime implementation
* limit on the total number of entries.
* - mru_maxage ("mru maxage") is a ceiling on the age in
* seconds of entries. Entries older than this are
* reclaimed once mon_mindepth is exceeded. 64s default.
* Note that entries older than this can easily survive
* as they are reclaimed only as needed.
* - mru_maxdepth ("mru maxdepth") is a hard limit on the
* number of entries.
* - "mru maxmem" sets mru_maxdepth to the number of entries
* which fit in the given number of kilobytes. The default is
* 1024, or 1 megabyte.
* - mru_initalloc ("mru initalloc" sets the count of the
* initial allocation of MRU entries.
* - "mru initmem" sets mru_initalloc in units of kilobytes.
* The default is 4.
* - mru_incalloc ("mru incalloc" sets the number of entries to
* allocate on-demand each time the free list is empty.
* - "mru incmem" sets mru_incalloc in units of kilobytes.
* The default is 4.
* Whichever of "mru maxmem" or "mru maxdepth" occurs last in
* ntp.conf controls. Similarly for "mru initalloc" and "mru
* initmem", and for "mru incalloc" and "mru incmem".
*/
if (mru_entries < mru_mindepth) {
if (NULL == mon_free)
mon_getmoremem();
UNLINK_HEAD_SLIST(mon, mon_free, hash_next);
} else {
oldest = TAIL_DLIST(mon_mru_list, mru);
oldest_age = 0; /* silence uninit warning */
if (oldest != NULL) {
interval_fp = rbufp->recv_time;
L_SUB(&interval_fp, &oldest->last);
/* add one-half second to round up */
L_ADDUF(&interval_fp, 0x80000000);
oldest_age = interval_fp.l_i;
}
/* note -1 is legal for mru_maxage (disables) */
if (oldest != NULL && mru_maxage < oldest_age) {
mon_reclaim_entry(oldest);
mon = oldest;
} else if (mon_free != NULL || mru_alloc <
mru_maxdepth) {
if (NULL == mon_free)
mon_getmoremem();
UNLINK_HEAD_SLIST(mon, mon_free, hash_next);
/* Preempt from the MRU list if old enough. */
} else if (ntp_random() / (2. * FRAC) >
(double)oldest_age / mon_age) {
return ~(RES_LIMITED | RES_KOD) & flags;
} else {
mon_reclaim_entry(oldest);
mon = oldest;
}
}
INSIST(mon != NULL);
/*
* Got one, initialize it
*/
mru_entries++;
mru_peakentries = max(mru_peakentries, mru_entries);
mon->last = rbufp->recv_time;
mon->first = mon->last;
mon->count = 1;
mon->flags = ~(RES_LIMITED | RES_KOD) & flags;
mon->leak = 0;
memcpy(&mon->rmtadr, &rbufp->recv_srcadr, sizeof(mon->rmtadr));
mon->vn_mode = VN_MODE(version, mode);
mon->lcladr = rbufp->dstadr;
mon->cast_flags = (u_char)(((rbufp->dstadr->flags &
INT_MCASTOPEN) && rbufp->fd == mon->lcladr->fd) ? MDF_MCAST
: rbufp->fd == mon->lcladr->bfd ? MDF_BCAST : MDF_UCAST);
/*
* Drop him into front of the hash table. Also put him on top of
* the MRU list.
*/
LINK_SLIST(mon_hash[hash], mon, hash_next);
LINK_DLIST(mon_mru_list, mon, mru);
return mon->flags;
}
