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ip_flow.c revision 1.48
      1 /*	$NetBSD: ip_flow.c,v 1.48 2007/08/20 19:42:34 dyoung Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1998 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by the 3am Software Foundry ("3am").  It was developed by Matt Thomas.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *	This product includes software developed by the NetBSD
     21  *	Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/cdefs.h>
     40 __KERNEL_RCSID(0, "$NetBSD: ip_flow.c,v 1.48 2007/08/20 19:42:34 dyoung Exp $");
     41 
     42 #include <sys/param.h>
     43 #include <sys/systm.h>
     44 #include <sys/malloc.h>
     45 #include <sys/mbuf.h>
     46 #include <sys/domain.h>
     47 #include <sys/protosw.h>
     48 #include <sys/socket.h>
     49 #include <sys/socketvar.h>
     50 #include <sys/errno.h>
     51 #include <sys/time.h>
     52 #include <sys/kernel.h>
     53 #include <sys/pool.h>
     54 #include <sys/sysctl.h>
     55 
     56 #include <net/if.h>
     57 #include <net/if_dl.h>
     58 #include <net/route.h>
     59 #include <net/pfil.h>
     60 
     61 #include <netinet/in.h>
     62 #include <netinet/in_systm.h>
     63 #include <netinet/ip.h>
     64 #include <netinet/in_pcb.h>
     65 #include <netinet/in_var.h>
     66 #include <netinet/ip_var.h>
     67 
     68 /*
     69  * Similar code is very well commented in netinet6/ip6_flow.c
     70  */
     71 
     72 POOL_INIT(ipflow_pool, sizeof(struct ipflow), 0, 0, 0, "ipflowpl", NULL,
     73     IPL_NET);
     74 
     75 LIST_HEAD(ipflowhead, ipflow);
     76 
     77 #define	IPFLOW_TIMER		(5 * PR_SLOWHZ)
     78 #define	IPFLOW_DEFAULT_HASHSIZE	(1 << IPFLOW_HASHBITS)
     79 
     80 static struct ipflowhead *ipflowtable = NULL;
     81 static struct ipflowhead ipflowlist;
     82 static int ipflow_inuse;
     83 
     84 #define	IPFLOW_INSERT(bucket, ipf) \
     85 do { \
     86 	LIST_INSERT_HEAD((bucket), (ipf), ipf_hash); \
     87 	LIST_INSERT_HEAD(&ipflowlist, (ipf), ipf_list); \
     88 } while (/*CONSTCOND*/ 0)
     89 
     90 #define	IPFLOW_REMOVE(ipf) \
     91 do { \
     92 	LIST_REMOVE((ipf), ipf_hash); \
     93 	LIST_REMOVE((ipf), ipf_list); \
     94 } while (/*CONSTCOND*/ 0)
     95 
     96 #ifndef IPFLOW_MAX
     97 #define	IPFLOW_MAX		256
     98 #endif
     99 int ip_maxflows = IPFLOW_MAX;
    100 int ip_hashsize = IPFLOW_DEFAULT_HASHSIZE;
    101 
    102 static size_t
    103 ipflow_hash(struct ip *ip)
    104 {
    105 	size_t hash = ip->ip_tos;
    106 	size_t idx;
    107 
    108 	for (idx = 0; idx < 32; idx += IPFLOW_HASHBITS) {
    109 		hash += (ip->ip_dst.s_addr >> (32 - idx)) +
    110 		    (ip->ip_src.s_addr >> idx);
    111 	}
    112 
    113 	return hash & (ip_hashsize-1);
    114 }
    115 
    116 static struct ipflow *
    117 ipflow_lookup(struct ip *ip)
    118 {
    119 	size_t hash;
    120 	struct ipflow *ipf;
    121 
    122 	hash = ipflow_hash(ip);
    123 
    124 	LIST_FOREACH(ipf, &ipflowtable[hash], ipf_hash) {
    125 		if (ip->ip_dst.s_addr == ipf->ipf_dst.s_addr
    126 		    && ip->ip_src.s_addr == ipf->ipf_src.s_addr
    127 		    && ip->ip_tos == ipf->ipf_tos)
    128 			break;
    129 	}
    130 	return ipf;
    131 }
    132 
    133 int
    134 ipflow_init(int table_size)
    135 {
    136 	struct ipflowhead *new_table;
    137 	size_t i;
    138 
    139 	new_table = (struct ipflowhead *)malloc(sizeof(struct ipflowhead) *
    140 	    table_size, M_RTABLE, M_NOWAIT);
    141 
    142 	if (new_table == NULL)
    143 		return 1;
    144 
    145 	if (ipflowtable != NULL)
    146 		free(ipflowtable, M_RTABLE);
    147 
    148 	ipflowtable = new_table;
    149 	ip_hashsize = table_size;
    150 
    151 	LIST_INIT(&ipflowlist);
    152 	for (i = 0; i < ip_hashsize; i++)
    153 		LIST_INIT(&ipflowtable[i]);
    154 
    155 	return 0;
    156 }
    157 
    158 int
    159 ipflow_fastforward(struct mbuf *m)
    160 {
    161 	struct ip *ip, ip_store;
    162 	struct ipflow *ipf;
    163 	struct rtentry *rt;
    164 	const struct sockaddr *dst;
    165 	int error;
    166 	int iplen;
    167 
    168 	/*
    169 	 * Are we forwarding packets?  Big enough for an IP packet?
    170 	 */
    171 	if (!ipforwarding || ipflow_inuse == 0 || m->m_len < sizeof(struct ip))
    172 		return 0;
    173 
    174 	/*
    175 	 * Was packet received as a link-level multicast or broadcast?
    176 	 * If so, don't try to fast forward..
    177 	 */
    178 	if ((m->m_flags & (M_BCAST|M_MCAST)) != 0)
    179 		return 0;
    180 
    181 	/*
    182 	 * IP header with no option and valid version and length
    183 	 */
    184 	if (IP_HDR_ALIGNED_P(mtod(m, void *)))
    185 		ip = mtod(m, struct ip *);
    186 	else {
    187 		memcpy(&ip_store, mtod(m, void *), sizeof(ip_store));
    188 		ip = &ip_store;
    189 	}
    190 	iplen = ntohs(ip->ip_len);
    191 	if (ip->ip_v != IPVERSION || ip->ip_hl != (sizeof(struct ip) >> 2) ||
    192 	    iplen < sizeof(struct ip) || iplen > m->m_pkthdr.len)
    193 		return 0;
    194 	/*
    195 	 * Find a flow.
    196 	 */
    197 	if ((ipf = ipflow_lookup(ip)) == NULL)
    198 		return 0;
    199 
    200 	/*
    201 	 * Verify the IP header checksum.
    202 	 */
    203 	switch (m->m_pkthdr.csum_flags &
    204 		((m->m_pkthdr.rcvif->if_csum_flags_rx & M_CSUM_IPv4) |
    205 		 M_CSUM_IPv4_BAD)) {
    206 	case M_CSUM_IPv4|M_CSUM_IPv4_BAD:
    207 		return (0);
    208 
    209 	case M_CSUM_IPv4:
    210 		/* Checksum was okay. */
    211 		break;
    212 
    213 	default:
    214 		/* Must compute it ourselves. */
    215 		if (in_cksum(m, sizeof(struct ip)) != 0)
    216 			return (0);
    217 		break;
    218 	}
    219 
    220 	/*
    221 	 * Route and interface still up?
    222 	 */
    223 	if (rtcache_down(&ipf->ipf_ro) || (rt = ipf->ipf_ro.ro_rt) == NULL ||
    224 	    (rt->rt_ifp->if_flags & IFF_UP) == 0)
    225 		return 0;
    226 
    227 	/*
    228 	 * Packet size OK?  TTL?
    229 	 */
    230 	if (m->m_pkthdr.len > rt->rt_ifp->if_mtu || ip->ip_ttl <= IPTTLDEC)
    231 		return 0;
    232 
    233 	/*
    234 	 * Clear any in-bound checksum flags for this packet.
    235 	 */
    236 	m->m_pkthdr.csum_flags = 0;
    237 
    238 	/*
    239 	 * Everything checks out and so we can forward this packet.
    240 	 * Modify the TTL and incrementally change the checksum.
    241 	 *
    242 	 * This method of adding the checksum works on either endian CPU.
    243 	 * If htons() is inlined, all the arithmetic is folded; otherwise
    244 	 * the htons()s are combined by CSE due to the const attribute.
    245 	 *
    246 	 * Don't bother using HW checksumming here -- the incremental
    247 	 * update is pretty fast.
    248 	 */
    249 	ip->ip_ttl -= IPTTLDEC;
    250 	if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8))
    251 		ip->ip_sum -= ~htons(IPTTLDEC << 8);
    252 	else
    253 		ip->ip_sum += htons(IPTTLDEC << 8);
    254 
    255 	/*
    256 	 * Done modifying the header; copy it back, if necessary.
    257 	 */
    258 	if (IP_HDR_ALIGNED_P(mtod(m, void *)) == 0)
    259 		memcpy(mtod(m, void *), &ip_store, sizeof(ip_store));
    260 
    261 	/*
    262 	 * Trim the packet in case it's too long..
    263 	 */
    264 	if (m->m_pkthdr.len > iplen) {
    265 		if (m->m_len == m->m_pkthdr.len) {
    266 			m->m_len = iplen;
    267 			m->m_pkthdr.len = iplen;
    268 		} else
    269 			m_adj(m, iplen - m->m_pkthdr.len);
    270 	}
    271 
    272 	/*
    273 	 * Send the packet on it's way.  All we can get back is ENOBUFS
    274 	 */
    275 	ipf->ipf_uses++;
    276 	PRT_SLOW_ARM(ipf->ipf_timer, IPFLOW_TIMER);
    277 
    278 	if (rt->rt_flags & RTF_GATEWAY)
    279 		dst = rt->rt_gateway;
    280 	else
    281 		dst = rtcache_getdst(&ipf->ipf_ro);
    282 
    283 	if ((error = (*rt->rt_ifp->if_output)(rt->rt_ifp, m, dst, rt)) != 0) {
    284 		if (error == ENOBUFS)
    285 			ipf->ipf_dropped++;
    286 		else
    287 			ipf->ipf_errors++;
    288 	}
    289 	return 1;
    290 }
    291 
    292 static void
    294 ipflow_addstats(struct ipflow *ipf)
    295 {
    296 	if (!rtcache_down(&ipf->ipf_ro) && ipf->ipf_ro.ro_rt != NULL)
    297 		ipf->ipf_ro.ro_rt->rt_use += ipf->ipf_uses;
    298 	ipstat.ips_cantforward += ipf->ipf_errors + ipf->ipf_dropped;
    299 	ipstat.ips_total += ipf->ipf_uses;
    300 	ipstat.ips_forward += ipf->ipf_uses;
    301 	ipstat.ips_fastforward += ipf->ipf_uses;
    302 }
    303 
    304 static void
    305 ipflow_free(struct ipflow *ipf)
    306 {
    307 	int s;
    308 	/*
    309 	 * Remove the flow from the hash table (at elevated IPL).
    310 	 * Once it's off the list, we can deal with it at normal
    311 	 * network IPL.
    312 	 */
    313 	s = splnet();
    314 	IPFLOW_REMOVE(ipf);
    315 	splx(s);
    316 	ipflow_addstats(ipf);
    317 	rtcache_free(&ipf->ipf_ro);
    318 	ipflow_inuse--;
    319 	s = splnet();
    320 	pool_put(&ipflow_pool, ipf);
    321 	splx(s);
    322 }
    323 
    324 struct ipflow *
    325 ipflow_reap(int just_one)
    326 {
    327 	while (just_one || ipflow_inuse > ip_maxflows) {
    328 		struct ipflow *ipf, *maybe_ipf = NULL;
    329 		int s;
    330 
    331 		ipf = LIST_FIRST(&ipflowlist);
    332 		while (ipf != NULL) {
    333 			/*
    334 			 * If this no longer points to a valid route
    335 			 * reclaim it.
    336 			 */
    337 			if (rtcache_down(&ipf->ipf_ro) ||
    338 			    ipf->ipf_ro.ro_rt == NULL)
    339 				goto done;
    340 			/*
    341 			 * choose the one that's been least recently
    342 			 * used or has had the least uses in the
    343 			 * last 1.5 intervals.
    344 			 */
    345 			if (maybe_ipf == NULL ||
    346 			    ipf->ipf_timer < maybe_ipf->ipf_timer ||
    347 			    (ipf->ipf_timer == maybe_ipf->ipf_timer &&
    348 			     ipf->ipf_last_uses + ipf->ipf_uses <
    349 			         maybe_ipf->ipf_last_uses +
    350 			         maybe_ipf->ipf_uses))
    351 				maybe_ipf = ipf;
    352 			ipf = LIST_NEXT(ipf, ipf_list);
    353 		}
    354 		ipf = maybe_ipf;
    355 	    done:
    356 		/*
    357 		 * Remove the entry from the flow table.
    358 		 */
    359 		s = splnet();
    360 		IPFLOW_REMOVE(ipf);
    361 		splx(s);
    362 		ipflow_addstats(ipf);
    363 		rtcache_free(&ipf->ipf_ro);
    364 		if (just_one)
    365 			return ipf;
    366 		pool_put(&ipflow_pool, ipf);
    367 		ipflow_inuse--;
    368 	}
    369 	return NULL;
    370 }
    371 
    372 void
    373 ipflow_slowtimo(void)
    374 {
    375 	struct ipflow *ipf, *next_ipf;
    376 
    377 	for (ipf = LIST_FIRST(&ipflowlist); ipf != NULL; ipf = next_ipf) {
    378 		next_ipf = LIST_NEXT(ipf, ipf_list);
    379 		if (PRT_SLOW_ISEXPIRED(ipf->ipf_timer) ||
    380 		    rtcache_down(&ipf->ipf_ro) || ipf->ipf_ro.ro_rt == NULL) {
    381 			ipflow_free(ipf);
    382 		} else {
    383 			ipf->ipf_last_uses = ipf->ipf_uses;
    384 			ipf->ipf_ro.ro_rt->rt_use += ipf->ipf_uses;
    385 			ipstat.ips_total += ipf->ipf_uses;
    386 			ipstat.ips_forward += ipf->ipf_uses;
    387 			ipstat.ips_fastforward += ipf->ipf_uses;
    388 			ipf->ipf_uses = 0;
    389 		}
    390 	}
    391 }
    392 
    393 void
    394 ipflow_create(const struct route *ro, struct mbuf *m)
    395 {
    396 	struct ip *const ip = mtod(m, struct ip *);
    397 	struct ipflow *ipf;
    398 	size_t hash;
    399 	int s;
    400 
    401 	/*
    402 	 * Don't create cache entries for ICMP messages.
    403 	 */
    404 	if (ip_maxflows == 0 || ip->ip_p == IPPROTO_ICMP)
    405 		return;
    406 	/*
    407 	 * See if an existing flow struct exists.  If so remove it from it's
    408 	 * list and free the old route.  If not, try to malloc a new one
    409 	 * (if we aren't at our limit).
    410 	 */
    411 	ipf = ipflow_lookup(ip);
    412 	if (ipf == NULL) {
    413 		if (ipflow_inuse >= ip_maxflows) {
    414 			ipf = ipflow_reap(1);
    415 		} else {
    416 			s = splnet();
    417 			ipf = pool_get(&ipflow_pool, PR_NOWAIT);
    418 			splx(s);
    419 			if (ipf == NULL)
    420 				return;
    421 			ipflow_inuse++;
    422 		}
    423 		memset(ipf, 0, sizeof(*ipf));
    424 	} else {
    425 		s = splnet();
    426 		IPFLOW_REMOVE(ipf);
    427 		splx(s);
    428 		ipflow_addstats(ipf);
    429 		rtcache_free(&ipf->ipf_ro);
    430 		ipf->ipf_uses = ipf->ipf_last_uses = 0;
    431 		ipf->ipf_errors = ipf->ipf_dropped = 0;
    432 	}
    433 
    434 	/*
    435 	 * Fill in the updated information.
    436 	 */
    437 	rtcache_copy(&ipf->ipf_ro, ro);
    438 	ipf->ipf_dst = ip->ip_dst;
    439 	ipf->ipf_src = ip->ip_src;
    440 	ipf->ipf_tos = ip->ip_tos;
    441 	PRT_SLOW_ARM(ipf->ipf_timer, IPFLOW_TIMER);
    442 	ipf->ipf_start = time_uptime;
    443 	/*
    444 	 * Insert into the approriate bucket of the flow table.
    445 	 */
    446 	hash = ipflow_hash(ip);
    447 	s = splnet();
    448 	IPFLOW_INSERT(&ipflowtable[hash], ipf);
    449 	splx(s);
    450 }
    451 
    452 int
    453 ipflow_invalidate_all(int new_size)
    454 {
    455 	struct ipflow *ipf, *next_ipf;
    456 	int s, error;
    457 
    458 	error = 0;
    459 	s = splnet();
    460 	for (ipf = LIST_FIRST(&ipflowlist); ipf != NULL; ipf = next_ipf) {
    461 		next_ipf = LIST_NEXT(ipf, ipf_list);
    462 		ipflow_free(ipf);
    463 	}
    464 
    465 	if (new_size)
    466 		error = ipflow_init(new_size);
    467 	splx(s);
    468 
    469 	return error;
    470 }
    471