ntp_peer.c

网络时间协议NTP 源码 版本v4.2.0b 该源码用于linux平台下

/*
 * ntp_peer.c - management of data maintained for peer associations
 */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <sys/types.h>

#include "ntpd.h"
#include "ntp_stdlib.h"
#include <ntp_random.h>
#ifdef OPENSSL
#include "openssl/rand.h"
#endif /* OPENSSL */

/*
 *                  Table of valid association combinations
 *                  ---------------------------------------
 *
 *                             packet->mode
 * peer->mode      | UNSPEC  ACTIVE PASSIVE  CLIENT  SERVER  BCAST
 * ----------      | ---------------------------------------------
 * NO_PEER         |   e       1       0       1       1       1
 * ACTIVE          |   e       1       1       0       0       0
 * PASSIVE         |   e       1       e       0       0       0
 * CLIENT          |   e       0       0       0       1       1
 * SERVER          |   e       0       0       0       0       0
 * BCAST	   |   e       0       0       0       0       0
 * BCLIENT         |   e       0       0       0       e       1
 *
 * One point to note here: a packet in BCAST mode can potentially match
 * a peer in CLIENT mode, but we that is a special case and we check for
 * that early in the decision process.  This avoids having to keep track
 * of what kind of associations are possible etc...  We actually
 * circumvent that problem by requiring that the first b(m)roadcast
 * received after the change back to BCLIENT mode sets the clock.
 */
#define AM_MODES	7	/* number of rows and columns */
#define NO_PEER		0	/* action when no peer is found */

int AM[AM_MODES][AM_MODES] = {
/*	{ UNSPEC,   ACTIVE,     PASSIVE,    CLIENT,     SERVER,     BCAST } */

/*NONE*/{ AM_ERR, AM_NEWPASS, AM_NOMATCH, AM_FXMIT,   AM_MANYCAST, AM_NEWBCL},

/*A*/	{ AM_ERR, AM_PROCPKT, AM_PROCPKT, AM_NOMATCH, AM_NOMATCH,  AM_NOMATCH},

/*P*/	{ AM_ERR, AM_PROCPKT, AM_ERR,     AM_NOMATCH, AM_NOMATCH,  AM_NOMATCH},

/*C*/	{ AM_ERR, AM_NOMATCH, AM_NOMATCH, AM_NOMATCH, AM_PROCPKT,  AM_POSSBCL},

/*S*/	{ AM_ERR, AM_NOMATCH, AM_NOMATCH, AM_NOMATCH, AM_NOMATCH,  AM_NOMATCH},

/*BCST*/{ AM_ERR, AM_NOMATCH, AM_NOMATCH, AM_NOMATCH, AM_NOMATCH,  AM_NOMATCH},

/*BCL*/ { AM_ERR, AM_NOMATCH, AM_NOMATCH, AM_NOMATCH, AM_NOMATCH,  AM_PROCPKT},
};

#define MATCH_ASSOC(x,y)	AM[(x)][(y)]

/*
 * These routines manage the allocation of memory to peer structures
 * and the maintenance of the peer hash table. The two main entry
 * points are findpeer(), which looks for matching peer sturctures in
 * the peer list, newpeer(), which allocates a new peer structure and
 * adds it to the list, and unpeer(), which demobilizes the association
 * and deallocates the structure.
 */
/*
 * Peer hash tables
 */
struct peer *peer_hash[NTP_HASH_SIZE];	/* peer hash table */
int peer_hash_count[NTP_HASH_SIZE];	/* peers in each bucket */
struct peer *assoc_hash[NTP_HASH_SIZE];	/* association ID hash table */
int assoc_hash_count[NTP_HASH_SIZE];	/* peers in each bucket */
static struct peer *peer_free;		/* peer structures free list */
int peer_free_count;			/* count of free structures */

/*
 * Association ID.  We initialize this value randomly, then assign a new
 * value every time the peer structure is incremented.
 */
static associd_t current_association_ID; /* association ID */

/*
 * Memory allocation watermarks.
 */
#define	INIT_PEER_ALLOC		15	/* initialize for 15 peers */
#define	INC_PEER_ALLOC		5	/* when run out, add 5 more */

/*
 * Miscellaneous statistic counters which may be queried.
 */
u_long peer_timereset;			/* time stat counters zeroed */
u_long findpeer_calls;			/* calls to findpeer */
u_long assocpeer_calls;			/* calls to findpeerbyassoc */
u_long peer_allocations;		/* allocations from free list */
u_long peer_demobilizations;		/* structs freed to free list */
int total_peer_structs;			/* peer structs */
int peer_associations;			/* mobilized associations */
int peer_preempt;			/* preemptable associations */
static struct peer init_peer_alloc[INIT_PEER_ALLOC]; /* init alloc */

static	void	getmorepeermem	P((void));

/*
 * init_peer - initialize peer data structures and counters
 *
 * N.B. We use the random number routine in here. It had better be
 * initialized prior to getting here.
 */
void
init_peer(void)
{
	register int i;

	/*
	 * Clear hash table and counters.
	 */
	for (i = 0; i < NTP_HASH_SIZE; i++) {
		peer_hash[i] = 0;
		peer_hash_count[i] = 0;
		assoc_hash[i] = 0;
		assoc_hash_count[i] = 0;
	}

	/*
	 * Clear stat counters
	 */
	findpeer_calls = peer_allocations = 0;
	assocpeer_calls = peer_demobilizations = 0;

	/*
	 * Initialize peer memory.
	 */
	peer_free = 0;
	for (i = 0; i < INIT_PEER_ALLOC; i++) {
		init_peer_alloc[i].next = peer_free;
		peer_free = &init_peer_alloc[i];
	}
	total_peer_structs = INIT_PEER_ALLOC;
	peer_free_count = INIT_PEER_ALLOC;

	/*
	 * Initialize our first association ID
	 */
	while ((current_association_ID = ntp_random() & 0xffff) == 0);
}


/*
 * getmorepeermem - add more peer structures to the free list
 */
static void
getmorepeermem(void)
{
	register int i;
	register struct peer *peer;

	peer = (struct peer *)emalloc(INC_PEER_ALLOC *
	    sizeof(struct peer));
	for (i = 0; i < INC_PEER_ALLOC; i++) {
		peer->next = peer_free;
		peer_free = peer;
		peer++;
	}

	total_peer_structs += INC_PEER_ALLOC;
	peer_free_count += INC_PEER_ALLOC;
}


/*
 * findexistingpeer - return a pointer to a peer in the hash table
 */
struct peer *
findexistingpeer(
	struct sockaddr_storage *addr,
	struct peer *start_peer,
	int mode
	)
{
	register struct peer *peer;

	/*
	 * start_peer is included so we can locate instances of the
	 * same peer through different interfaces in the hash table.
	 */
	if (start_peer == 0)
		peer = peer_hash[NTP_HASH_ADDR(addr)];
	else
		peer = start_peer->next;
	
	while (peer != 0) {
		if (SOCKCMP(addr, &peer->srcadr)
		    && NSRCPORT(addr) == NSRCPORT(&peer->srcadr)) {
			if (mode == -1)
				return (peer);
			else if (peer->hmode == mode)
				break;
		}
		peer = peer->next;
	}
	return (peer);
}


/*
 * findpeer - find and return a peer in the hash table.
 */
struct peer *
findpeer(
	struct sockaddr_storage *srcadr,
	struct interface *dstadr,
	int	pkt_mode,
	int	*action
	)
{
	register struct peer *peer;
	int hash;

	findpeer_calls++;
	hash = NTP_HASH_ADDR(srcadr);
	for (peer = peer_hash[hash]; peer != NULL; peer = peer->next) {
		if (SOCKCMP(srcadr, &peer->srcadr) &&
		    NSRCPORT(srcadr) == NSRCPORT(&peer->srcadr)) {

			/*
			 * if the association matching rules determine
			 * that this is not a valid combination, then
			 * look for the next valid peer association.
			 */
			*action = MATCH_ASSOC(peer->hmode, pkt_mode);

			/*
			 * if an error was returned, exit back right
			 * here.
			 */
			if (*action == AM_ERR)
				return ((struct peer *)0);

			/*
			 * if a match is found, we stop our search.
			 */
			if (*action != AM_NOMATCH)
				break;
		}
	}

	/*
	 * If no matching association is found
	 */
	if (peer == 0) {
		*action = MATCH_ASSOC(NO_PEER, pkt_mode);
		return ((struct peer *)0);
	}
	peer->dstadr = dstadr;
	return (peer);
}

/*
 * findpeerbyassocid - find and return a peer using his association ID
 */
struct peer *
findpeerbyassoc(
	u_int assoc
	)
{
	register struct peer *peer;
	int hash;

	assocpeer_calls++;

	hash = assoc & NTP_HASH_MASK;
	for (peer = assoc_hash[hash]; peer != 0; peer =
	    peer->ass_next) {
		if (assoc == peer->associd)
		    return (peer);
	}
	return (NULL);
}


/*
 * clear_all - flush all time values for all associations
 */
void
clear_all(void)
{
	struct peer *peer, *next_peer;
	int n;

	/*
	 * This routine is called when the clock is stepped, and so all
	 * previously saved time values are untrusted.
	 */
	for (n = 0; n < NTP_HASH_SIZE; n++) {
		for (peer = peer_hash[n]; peer != 0; peer = next_peer) {
			next_peer = peer->next;
			if (!(peer->cast_flags & (MDF_ACAST | MDF_MCAST |
			    MDF_BCAST))) {
				peer->hpoll = peer->minpoll;
				peer_clear(peer, "STEP");
			}
		}
	}
#ifdef DEBUG
	if (debug)
		printf("clear_all: at %lu\n", current_time);
#endif
}


/*
 * unpeer - remove peer structure from hash table and free structure
 */
void
unpeer(
	struct peer *peer_to_remove
	)
{
	int hash;
#ifdef OPENSSL
	char	statstr[NTP_MAXSTRLEN]; /* statistics for filegen */

	if (peer_to_remove->flags & FLAG_SKEY) {
		sprintf(statstr, "unpeer %d flash %x reach %03o flags %04x",
		    peer_to_remove->associd, peer_to_remove->flash,
		    peer_to_remove->reach, peer_to_remove->flags);
		record_crypto_stats(&peer_to_remove->srcadr, statstr);
#ifdef DEBUG
		if (debug)
			printf("peer: %s\n", statstr);
#endif
	}
#endif /* OPENSSL */
#ifdef DEBUG
	if (debug)
		printf("demobilize %u %d %d\n", peer_to_remove->associd,
		    peer_associations, peer_preempt);
#endif
	hash = NTP_HASH_ADDR(&peer_to_remove->srcadr);
	peer_hash_count[hash]--;
	peer_demobilizations++;
	peer_associations--;
	if (peer_to_remove->flags & FLAG_PREEMPT)
		peer_preempt--;
#ifdef REFCLOCK
	/*
	 * If this peer is actually a clock, shut it down first
	 */
	if (peer_to_remove->flags & FLAG_REFCLOCK)
		refclock_unpeer(peer_to_remove);
#endif
	peer_to_remove->action = 0;	/* disable timeout actions */
	if (peer_hash[hash] == peer_to_remove)
		peer_hash[hash] = peer_to_remove->next;
	else {
		register struct peer *peer;

		peer = peer_hash[hash];
		while (peer != 0 && peer->next != peer_to_remove)
		    peer = peer->next;
		
		if (peer == 0) {
			peer_hash_count[hash]++;
			msyslog(LOG_ERR, "peer struct for %s not in table!",
				stoa(&peer->srcadr));
		} else {
			peer->next = peer_to_remove->next;
		}
	}

	/*
	 * Remove him from the association hash as well.
	 */
	hash = peer_to_remove->associd & NTP_HASH_MASK;
	assoc_hash_count[hash]--;
	if (assoc_hash[hash] == peer_to_remove)
		assoc_hash[hash] = peer_to_remove->ass_next;
	else {
		register struct peer *peer;

		peer = assoc_hash[hash];
		while (peer != 0 && peer->ass_next != peer_to_remove)
		    peer = peer->ass_next;
		
		if (peer == 0) {
			assoc_hash_count[hash]++;
			msyslog(LOG_ERR,
				"peer struct for %s not in association table!",
				stoa(&peer->srcadr));
		} else {
			peer->ass_next = peer_to_remove->ass_next;
		}
	}
	peer_to_remove->next = peer_free;
	peer_free = peer_to_remove;
	peer_free_count++;
}


/*
 * peer_config - configure a new association
 */
struct peer *
peer_config(
	struct sockaddr_storage *srcadr,
	struct interface *dstadr,
	int hmode,
	int version,
	int minpoll,
	int maxpoll,
	u_int flags,
	int ttl,
	keyid_t key,
	u_char *keystr
	)
{
	register struct peer *peer;
	u_char cast_flags;

	/*
	 * First search from the beginning for an association with given
	 * remote address and mode. If an interface is given, search
	 * from there to find the association which matches that
	 * destination.
	 */
	peer = findexistingpeer(srcadr, (struct peer *)0, hmode);
	if (dstadr != 0) {
		while (peer != 0) {
			if (peer->dstadr == dstadr)
				break;
			peer = findexistingpeer(srcadr, peer, hmode);
		}
	}

	/*