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

     /*-
      * Copyright (c) 2015 Gleb Smirnoff <glebius@FreeBSD.org>
      * Copyright (c) 2015 Adrian Chadd <adrian@FreeBSD.org>
      * Copyright (c) 1982, 1986, 1988, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)ip_input.c  8.2 (Berkeley) 1/4/94
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/11.0/sys/netinet/ip_reass.c 281541 2015-04-15 00:57:21Z adrian $");
    
    #include "opt_rss.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/eventhandler.h>
    #include <sys/hash.h>
    #include <sys/mbuf.h>
    #include <sys/malloc.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/sysctl.h>
    
    #include <net/rss_config.h>
    #include <net/netisr.h>
    #include <net/vnet.h>
    
    #include <netinet/in.h>
    #include <netinet/ip.h>
    #include <netinet/ip_var.h>
    #include <netinet/in_rss.h>
    #ifdef MAC
    #include <security/mac/mac_framework.h>
    #endif
    
    SYSCTL_DECL(_net_inet_ip);
    
    /*
     * Reassembly headers are stored in hash buckets.
     */
    #define IPREASS_NHASH_LOG2      6
    #define IPREASS_NHASH           (1 << IPREASS_NHASH_LOG2)
    #define IPREASS_HMASK           (IPREASS_NHASH - 1)
    
    struct ipqbucket {
            TAILQ_HEAD(ipqhead, ipq) head;
            struct mtx               lock;
    };
    
    static VNET_DEFINE(struct ipqbucket, ipq[IPREASS_NHASH]);
    #define V_ipq           VNET(ipq)
    static VNET_DEFINE(uint32_t, ipq_hashseed);
    #define V_ipq_hashseed   VNET(ipq_hashseed)
    
    #define IPQ_LOCK(i)     mtx_lock(&V_ipq[i].lock)
    #define IPQ_TRYLOCK(i)  mtx_trylock(&V_ipq[i].lock)
    #define IPQ_UNLOCK(i)   mtx_unlock(&V_ipq[i].lock)
    #define IPQ_LOCK_ASSERT(i)      mtx_assert(&V_ipq[i].lock, MA_OWNED)
    
    void            ipreass_init(void);
    void            ipreass_drain(void);
    void            ipreass_slowtimo(void);
    #ifdef VIMAGE
    void            ipreass_destroy(void);
    #endif
    static int      sysctl_maxfragpackets(SYSCTL_HANDLER_ARGS);
    static void     ipreass_zone_change(void *);
    static void     ipreass_drain_tomax(void);
    static void     ipq_free(struct ipqhead *, struct ipq *);
    static struct ipq * ipq_reuse(int);
    
    static inline void
    ipq_timeout(struct ipqhead *head, struct ipq *fp)
    {
   
           IPSTAT_ADD(ips_fragtimeout, fp->ipq_nfrags);
           ipq_free(head, fp);
   }
   
   static inline void
   ipq_drop(struct ipqhead *head, struct ipq *fp)
   {
   
           IPSTAT_ADD(ips_fragdropped, fp->ipq_nfrags);
           ipq_free(head, fp);
   }
   
   static VNET_DEFINE(uma_zone_t, ipq_zone);
   #define V_ipq_zone      VNET(ipq_zone)
   SYSCTL_PROC(_net_inet_ip, OID_AUTO, maxfragpackets, CTLFLAG_VNET |
       CTLTYPE_INT | CTLFLAG_RW, NULL, 0, sysctl_maxfragpackets, "I",
       "Maximum number of IPv4 fragment reassembly queue entries");
   SYSCTL_UMA_CUR(_net_inet_ip, OID_AUTO, fragpackets, CTLFLAG_VNET,
       &VNET_NAME(ipq_zone),
       "Current number of IPv4 fragment reassembly queue entries");
   
   static VNET_DEFINE(int, noreass);
   #define V_noreass       VNET(noreass)
   
   static VNET_DEFINE(int, maxfragsperpacket);
   #define V_maxfragsperpacket     VNET(maxfragsperpacket)
   SYSCTL_INT(_net_inet_ip, OID_AUTO, maxfragsperpacket, CTLFLAG_VNET | CTLFLAG_RW,
       &VNET_NAME(maxfragsperpacket), 0,
       "Maximum number of IPv4 fragments allowed per packet");
   
   /*
    * Take incoming datagram fragment and try to reassemble it into
    * whole datagram.  If the argument is the first fragment or one
    * in between the function will return NULL and store the mbuf
    * in the fragment chain.  If the argument is the last fragment
    * the packet will be reassembled and the pointer to the new
    * mbuf returned for further processing.  Only m_tags attached
    * to the first packet/fragment are preserved.
    * The IP header is *NOT* adjusted out of iplen.
    */
   #define M_IP_FRAG       M_PROTO9
   struct mbuf *
   ip_reass(struct mbuf *m)
   {
           struct ip *ip;
           struct mbuf *p, *q, *nq, *t;
           struct ipq *fp;
           struct ipqhead *head;
           int i, hlen, next;
           u_int8_t ecn, ecn0;
           uint32_t hash;
   #ifdef  RSS
           uint32_t rss_hash, rss_type;
   #endif
   
           /*
            * If no reassembling or maxfragsperpacket are 0,
            * never accept fragments.
            */
           if (V_noreass == 1 || V_maxfragsperpacket == 0) {
                   IPSTAT_INC(ips_fragments);
                   IPSTAT_INC(ips_fragdropped);
                   m_freem(m);
                   return (NULL);
           }
   
           ip = mtod(m, struct ip *);
           hlen = ip->ip_hl << 2;
   
           /*
            * Adjust ip_len to not reflect header,
            * convert offset of this to bytes.
            */
           ip->ip_len = htons(ntohs(ip->ip_len) - hlen);
           if (ip->ip_off & htons(IP_MF)) {
                   /*
                    * Make sure that fragments have a data length
                    * that's a non-zero multiple of 8 bytes.
                    */
                   if (ip->ip_len == htons(0) || (ntohs(ip->ip_len) & 0x7) != 0) {
                           IPSTAT_INC(ips_toosmall); /* XXX */
                           IPSTAT_INC(ips_fragdropped);
                           m_freem(m);
                           return (NULL);
                   }
                   m->m_flags |= M_IP_FRAG;
           } else
                   m->m_flags &= ~M_IP_FRAG;
           ip->ip_off = htons(ntohs(ip->ip_off) << 3);
   
           /*
            * Attempt reassembly; if it succeeds, proceed.
            * ip_reass() will return a different mbuf.
            */
           IPSTAT_INC(ips_fragments);
           m->m_pkthdr.PH_loc.ptr = ip;
   
           /*
            * Presence of header sizes in mbufs
            * would confuse code below.
            */
           m->m_data += hlen;
           m->m_len -= hlen;
   
           hash = ip->ip_src.s_addr ^ ip->ip_id;
           hash = jenkins_hash32(&hash, 1, V_ipq_hashseed) & IPREASS_HMASK;
           head = &V_ipq[hash].head;
           IPQ_LOCK(hash);
   
           /*
            * Look for queue of fragments
            * of this datagram.
            */
           TAILQ_FOREACH(fp, head, ipq_list)
                   if (ip->ip_id == fp->ipq_id &&
                       ip->ip_src.s_addr == fp->ipq_src.s_addr &&
                       ip->ip_dst.s_addr == fp->ipq_dst.s_addr &&
   #ifdef MAC
                       mac_ipq_match(m, fp) &&
   #endif
                       ip->ip_p == fp->ipq_p)
                           break;
           /*
            * If first fragment to arrive, create a reassembly queue.
            */
           if (fp == NULL) {
                   fp = uma_zalloc(V_ipq_zone, M_NOWAIT);
                   if (fp == NULL)
                           fp = ipq_reuse(hash);
   #ifdef MAC
                   if (mac_ipq_init(fp, M_NOWAIT) != 0) {
                           uma_zfree(V_ipq_zone, fp);
                           fp = NULL;
                           goto dropfrag;
                   }
                   mac_ipq_create(m, fp);
   #endif
                   TAILQ_INSERT_HEAD(head, fp, ipq_list);
                   fp->ipq_nfrags = 1;
                   fp->ipq_ttl = IPFRAGTTL;
                   fp->ipq_p = ip->ip_p;
                   fp->ipq_id = ip->ip_id;
                   fp->ipq_src = ip->ip_src;
                   fp->ipq_dst = ip->ip_dst;
                   fp->ipq_frags = m;
                   m->m_nextpkt = NULL;
                   goto done;
           } else {
                   fp->ipq_nfrags++;
   #ifdef MAC
                   mac_ipq_update(m, fp);
   #endif
           }
   
   #define GETIP(m)        ((struct ip*)((m)->m_pkthdr.PH_loc.ptr))
   
           /*
            * Handle ECN by comparing this segment with the first one;
            * if CE is set, do not lose CE.
            * drop if CE and not-ECT are mixed for the same packet.
            */
           ecn = ip->ip_tos & IPTOS_ECN_MASK;
           ecn0 = GETIP(fp->ipq_frags)->ip_tos & IPTOS_ECN_MASK;
           if (ecn == IPTOS_ECN_CE) {
                   if (ecn0 == IPTOS_ECN_NOTECT)
                           goto dropfrag;
                   if (ecn0 != IPTOS_ECN_CE)
                           GETIP(fp->ipq_frags)->ip_tos |= IPTOS_ECN_CE;
           }
           if (ecn == IPTOS_ECN_NOTECT && ecn0 != IPTOS_ECN_NOTECT)
                   goto dropfrag;
   
           /*
            * Find a segment which begins after this one does.
            */
           for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt)
                   if (ntohs(GETIP(q)->ip_off) > ntohs(ip->ip_off))
                           break;
   
           /*
            * If there is a preceding segment, it may provide some of
            * our data already.  If so, drop the data from the incoming
            * segment.  If it provides all of our data, drop us, otherwise
            * stick new segment in the proper place.
            *
            * If some of the data is dropped from the preceding
            * segment, then it's checksum is invalidated.
            */
           if (p) {
                   i = ntohs(GETIP(p)->ip_off) + ntohs(GETIP(p)->ip_len) -
                       ntohs(ip->ip_off);
                   if (i > 0) {
                           if (i >= ntohs(ip->ip_len))
                                   goto dropfrag;
                           m_adj(m, i);
                           m->m_pkthdr.csum_flags = 0;
                           ip->ip_off = htons(ntohs(ip->ip_off) + i);
                           ip->ip_len = htons(ntohs(ip->ip_len) - i);
                   }
                   m->m_nextpkt = p->m_nextpkt;
                   p->m_nextpkt = m;
           } else {
                   m->m_nextpkt = fp->ipq_frags;
                   fp->ipq_frags = m;
           }
   
           /*
            * While we overlap succeeding segments trim them or,
            * if they are completely covered, dequeue them.
            */
           for (; q != NULL && ntohs(ip->ip_off) + ntohs(ip->ip_len) >
               ntohs(GETIP(q)->ip_off); q = nq) {
                   i = (ntohs(ip->ip_off) + ntohs(ip->ip_len)) -
                       ntohs(GETIP(q)->ip_off);
                   if (i < ntohs(GETIP(q)->ip_len)) {
                           GETIP(q)->ip_len = htons(ntohs(GETIP(q)->ip_len) - i);
                           GETIP(q)->ip_off = htons(ntohs(GETIP(q)->ip_off) + i);
                           m_adj(q, i);
                           q->m_pkthdr.csum_flags = 0;
                           break;
                   }
                   nq = q->m_nextpkt;
                   m->m_nextpkt = nq;
                   IPSTAT_INC(ips_fragdropped);
                   fp->ipq_nfrags--;
                   m_freem(q);
           }
   
           /*
            * Check for complete reassembly and perform frag per packet
            * limiting.
            *
            * Frag limiting is performed here so that the nth frag has
            * a chance to complete the packet before we drop the packet.
            * As a result, n+1 frags are actually allowed per packet, but
            * only n will ever be stored. (n = maxfragsperpacket.)
            *
            */
           next = 0;
           for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt) {
                   if (ntohs(GETIP(q)->ip_off) != next) {
                           if (fp->ipq_nfrags > V_maxfragsperpacket)
                                   ipq_drop(head, fp);
                           goto done;
                   }
                   next += ntohs(GETIP(q)->ip_len);
           }
           /* Make sure the last packet didn't have the IP_MF flag */
           if (p->m_flags & M_IP_FRAG) {
                   if (fp->ipq_nfrags > V_maxfragsperpacket)
                           ipq_drop(head, fp);
                   goto done;
           }
   
           /*
            * Reassembly is complete.  Make sure the packet is a sane size.
            */
           q = fp->ipq_frags;
           ip = GETIP(q);
           if (next + (ip->ip_hl << 2) > IP_MAXPACKET) {
                   IPSTAT_INC(ips_toolong);
                   ipq_drop(head, fp);
                   goto done;
           }
   
           /*
            * Concatenate fragments.
            */
           m = q;
           t = m->m_next;
           m->m_next = NULL;
           m_cat(m, t);
           nq = q->m_nextpkt;
           q->m_nextpkt = NULL;
           for (q = nq; q != NULL; q = nq) {
                   nq = q->m_nextpkt;
                   q->m_nextpkt = NULL;
                   m->m_pkthdr.csum_flags &= q->m_pkthdr.csum_flags;
                   m->m_pkthdr.csum_data += q->m_pkthdr.csum_data;
                   m_cat(m, q);
           }
           /*
            * In order to do checksumming faster we do 'end-around carry' here
            * (and not in for{} loop), though it implies we are not going to
            * reassemble more than 64k fragments.
            */
           while (m->m_pkthdr.csum_data & 0xffff0000)
                   m->m_pkthdr.csum_data = (m->m_pkthdr.csum_data & 0xffff) +
                       (m->m_pkthdr.csum_data >> 16);
   #ifdef MAC
           mac_ipq_reassemble(fp, m);
           mac_ipq_destroy(fp);
   #endif
   
           /*
            * Create header for new ip packet by modifying header of first
            * packet;  dequeue and discard fragment reassembly header.
            * Make header visible.
            */
           ip->ip_len = htons((ip->ip_hl << 2) + next);
           ip->ip_src = fp->ipq_src;
           ip->ip_dst = fp->ipq_dst;
           TAILQ_REMOVE(head, fp, ipq_list);
           uma_zfree(V_ipq_zone, fp);
           m->m_len += (ip->ip_hl << 2);
           m->m_data -= (ip->ip_hl << 2);
           /* some debugging cruft by sklower, below, will go away soon */
           if (m->m_flags & M_PKTHDR)      /* XXX this should be done elsewhere */
                   m_fixhdr(m);
           IPSTAT_INC(ips_reassembled);
           IPQ_UNLOCK(hash);
   
   #ifdef  RSS
           /*
            * Query the RSS layer for the flowid / flowtype for the
            * mbuf payload.
            *
            * For now, just assume we have to calculate a new one.
            * Later on we should check to see if the assigned flowid matches
            * what RSS wants for the given IP protocol and if so, just keep it.
            *
            * We then queue into the relevant netisr so it can be dispatched
            * to the correct CPU.
            *
            * Note - this may return 1, which means the flowid in the mbuf
            * is correct for the configured RSS hash types and can be used.
            */
           if (rss_mbuf_software_hash_v4(m, 0, &rss_hash, &rss_type) == 0) {
                   m->m_pkthdr.flowid = rss_hash;
                   M_HASHTYPE_SET(m, rss_type);
           }
   
           /*
            * Queue/dispatch for reprocessing.
            *
            * Note: this is much slower than just handling the frame in the
            * current receive context.  It's likely worth investigating
            * why this is.
            */
           netisr_dispatch(NETISR_IP_DIRECT, m);
           return (NULL);
   #endif
   
           /* Handle in-line */
           return (m);
   
   dropfrag:
           IPSTAT_INC(ips_fragdropped);
           if (fp != NULL)
                   fp->ipq_nfrags--;
           m_freem(m);
   done:
           IPQ_UNLOCK(hash);
           return (NULL);
   
   #undef GETIP
   }
   
   /*
    * Initialize IP reassembly structures.
    */
   void
   ipreass_init(void)
   {
   
           for (int i = 0; i < IPREASS_NHASH; i++) {
                   TAILQ_INIT(&V_ipq[i].head);
                   mtx_init(&V_ipq[i].lock, "IP reassembly", NULL,
                       MTX_DEF | MTX_DUPOK);
           }
           V_ipq_hashseed = arc4random();
           V_maxfragsperpacket = 16;
           V_ipq_zone = uma_zcreate("ipq", sizeof(struct ipq), NULL, NULL, NULL,
               NULL, UMA_ALIGN_PTR, 0);
           uma_zone_set_max(V_ipq_zone, nmbclusters / 32);
   
           if (IS_DEFAULT_VNET(curvnet))
                   EVENTHANDLER_REGISTER(nmbclusters_change, ipreass_zone_change,
                       NULL, EVENTHANDLER_PRI_ANY);
   }
   
   /*
    * If a timer expires on a reassembly queue, discard it.
    */
   void
   ipreass_slowtimo(void)
   {
           struct ipq *fp, *tmp;
   
           for (int i = 0; i < IPREASS_NHASH; i++) {
                   IPQ_LOCK(i);
                   TAILQ_FOREACH_SAFE(fp, &V_ipq[i].head, ipq_list, tmp)
                   if (--fp->ipq_ttl == 0)
                                   ipq_timeout(&V_ipq[i].head, fp);
                   IPQ_UNLOCK(i);
           }
   }
   
   /*
    * Drain off all datagram fragments.
    */
   void
   ipreass_drain(void)
   {
   
           for (int i = 0; i < IPREASS_NHASH; i++) {
                   IPQ_LOCK(i);
                   while(!TAILQ_EMPTY(&V_ipq[i].head))
                           ipq_drop(&V_ipq[i].head, TAILQ_FIRST(&V_ipq[i].head));
                   IPQ_UNLOCK(i);
           }
   }
   
   #ifdef VIMAGE
   /*
    * Destroy IP reassembly structures.
    */
   void
   ipreass_destroy(void)
   {
   
           ipreass_drain();
           uma_zdestroy(V_ipq_zone);
           for (int i = 0; i < IPREASS_NHASH; i++)
                   mtx_destroy(&V_ipq[i].lock);
   }
   #endif
   
   /*
    * After maxnipq has been updated, propagate the change to UMA.  The UMA zone
    * max has slightly different semantics than the sysctl, for historical
    * reasons.
    */
   static void
   ipreass_drain_tomax(void)
   {
           int target;
   
           /*
            * If we are over the maximum number of fragments,
            * drain off enough to get down to the new limit,
            * stripping off last elements on queues.  Every
            * run we strip the oldest element from each bucket.
            */
           target = uma_zone_get_max(V_ipq_zone);
           while (uma_zone_get_cur(V_ipq_zone) > target) {
                   struct ipq *fp;
   
                   for (int i = 0; i < IPREASS_NHASH; i++) {
                           IPQ_LOCK(i);
                           fp = TAILQ_LAST(&V_ipq[i].head, ipqhead);
                           if (fp != NULL)
                                   ipq_timeout(&V_ipq[i].head, fp);
                           IPQ_UNLOCK(i);
                   }
           }
   }
   
   static void
   ipreass_zone_change(void *tag)
   {
   
           uma_zone_set_max(V_ipq_zone, nmbclusters / 32);
           ipreass_drain_tomax();
   }
   
   /*
    * Change the limit on the UMA zone, or disable the fragment allocation
    * at all.  Since 0 and -1 is a special values here, we need our own handler,
    * instead of sysctl_handle_uma_zone_max().
    */
   static int
   sysctl_maxfragpackets(SYSCTL_HANDLER_ARGS)
   {
           int error, max;
   
           if (V_noreass == 0) {
                   max = uma_zone_get_max(V_ipq_zone);
                   if (max == 0)
                           max = -1;
           } else 
                   max = 0;
           error = sysctl_handle_int(oidp, &max, 0, req);
           if (error || !req->newptr)
                   return (error);
           if (max > 0) {
                   /*
                    * XXXRW: Might be a good idea to sanity check the argument
                    * and place an extreme upper bound.
                    */
                   max = uma_zone_set_max(V_ipq_zone, max);
                   ipreass_drain_tomax();
                   V_noreass = 0;
           } else if (max == 0) {
                   V_noreass = 1;
                   ipreass_drain();
           } else if (max == -1) {
                   V_noreass = 0;
                   uma_zone_set_max(V_ipq_zone, 0);
           } else
                   return (EINVAL);
           return (0);
   }
   
   /*
    * Seek for old fragment queue header that can be reused.  Try to
    * reuse a header from currently locked hash bucket.
    */
   static struct ipq *
   ipq_reuse(int start)
   {
           struct ipq *fp;
           int i;
   
           IPQ_LOCK_ASSERT(start);
   
           for (i = start;; i++) {
                   if (i == IPREASS_NHASH)
                           i = 0;
                   if (i != start && IPQ_TRYLOCK(i) == 0)
                           continue;
                   fp = TAILQ_LAST(&V_ipq[i].head, ipqhead);
                   if (fp) {
                           struct mbuf *m;
   
                           IPSTAT_ADD(ips_fragtimeout, fp->ipq_nfrags);
                           while (fp->ipq_frags) {
                                   m = fp->ipq_frags;
                                   fp->ipq_frags = m->m_nextpkt;
                                   m_freem(m);
                           }
                           TAILQ_REMOVE(&V_ipq[i].head, fp, ipq_list);
                           if (i != start)
                                   IPQ_UNLOCK(i);
                           IPQ_LOCK_ASSERT(start);
                           return (fp);
                   }
                   if (i != start)
                           IPQ_UNLOCK(i);
           }
   }
   
   /*
    * Free a fragment reassembly header and all associated datagrams.
    */
   static void
   ipq_free(struct ipqhead *fhp, struct ipq *fp)
   {
           struct mbuf *q;
   
           while (fp->ipq_frags) {
                   q = fp->ipq_frags;
                   fp->ipq_frags = q->m_nextpkt;
                   m_freem(q);
           }
           TAILQ_REMOVE(fhp, fp, ipq_list);
           uma_zfree(V_ipq_zone, fp);
   }

Cache object: c7561a270b9b8b9c2a31916f8fb3cc38