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

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2010-2011 Juniper Networks, Inc.
      * All rights reserved.
      *
      * This software was developed by Robert N. M. Watson under contract
      * to Juniper Networks, Inc.
      *
     * 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.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
     */
    
    #include <sys/cdefs.h>
    
    __FBSDID("$FreeBSD: releng/12.0/sys/netinet/in_pcbgroup.c 335093 2018-06-13 23:19:54Z mmacy $");
    
    #include "opt_inet6.h"
    #include "opt_rss.h"
    
    #include <sys/param.h>
    #include <sys/lock.h>
    #include <sys/malloc.h>
    #include <sys/mbuf.h>
    #include <sys/mutex.h>
    #include <sys/smp.h>
    #include <sys/socket.h>
    #include <sys/socketvar.h>
    
    #include <net/rss_config.h>
    
    #include <netinet/in.h>
    
    #include <netinet/in_pcb.h>
    #include <netinet/in_rss.h>
    #ifdef INET6
    #include <netinet6/in6_pcb.h>
    #endif /* INET6 */
    
    /*
     * pcbgroups, or "connection groups" are based on Willman, Rixner, and Cox's
     * 2006 USENIX paper, "An Evaluation of Network Stack Parallelization
     * Strategies in Modern Operating Systems".  This implementation differs
     * significantly from that described in the paper, in that it attempts to
     * introduce not just notions of affinity for connections and distribute work
     * so as to reduce lock contention, but also align those notions with
     * hardware work distribution strategies such as RSS.  In this construction,
     * connection groups supplement, rather than replace, existing reservation
     * tables for protocol 4-tuples, offering CPU-affine lookup tables with
     * minimal cache line migration and lock contention during steady state
     * operation.
     *
     * Hardware-offloaded checksums are often inefficient in software -- for
     * example, Toeplitz, specified by RSS, introduced a significant overhead if
     * performed during per-packge processing.  It is therefore desirable to fall
     * back on traditional reservation table lookups without affinity where
     * hardware-offloaded checksums aren't available, such as for traffic over
     * non-RSS interfaces.
     *
     * Internet protocols, such as UDP and TCP, register to use connection groups
     * by providing an ipi_hashfields value other than IPI_HASHFIELDS_NONE; this
     * indicates to the connection group code whether a 2-tuple or 4-tuple is
     * used as an argument to hashes that assign a connection to a particular
     * group.  This must be aligned with any hardware offloaded distribution
     * model, such as RSS or similar approaches taken in embedded network boards.
     * Wildcard sockets require special handling, as in Willman 2006, and are
     * shared between connection groups -- while being protected by group-local
     * locks.  This means that connection establishment and teardown can be
     * signficantly more expensive than without connection groups, but that
     * steady-state processing can be significantly faster.
     *
     * When RSS is used, certain connection group parameters, such as the number
     * of groups, are provided by the RSS implementation, found in in_rss.c.
     * Otherwise, in_pcbgroup.c selects possible sensible parameters
     * corresponding to the degree of parallelism exposed by netisr.
     *
     * Most of the implementation of connection groups is in this file; however,
     * connection group lookup is implemented in in_pcb.c alongside reservation
     * table lookups -- see in_pcblookup_group().
     *
     * TODO:
    *
    * Implement dynamic rebalancing of buckets with connection groups; when
    * load is unevenly distributed, search for more optimal balancing on
    * demand.  This might require scaling up the number of connection groups
    * by <<1.
    *
    * Provide an IP 2-tuple or 4-tuple netisr m2cpu handler based on connection
    * groups for ip_input and ip6_input, allowing non-offloaded work
    * distribution.
    *
    * Expose effective CPU affinity of connections to userspace using socket
    * options.
    *
    * Investigate per-connection affinity overrides based on socket options; an
    * option could be set, certainly resulting in work being distributed
    * differently in software, and possibly propagated to supporting hardware
    * with TCAMs or hardware hash tables.  This might require connections to
    * exist in more than one connection group at a time.
    *
    * Hook netisr thread reconfiguration events, and propagate those to RSS so
    * that rebalancing can occur when the thread pool grows or shrinks.
    *
    * Expose per-pcbgroup statistics to userspace monitoring tools such as
    * netstat, in order to allow better debugging and profiling.
    */
   
   void
   in_pcbgroup_init(struct inpcbinfo *pcbinfo, u_int hashfields,
       int hash_nelements)
   {
           struct inpcbgroup *pcbgroup;
           u_int numpcbgroups, pgn;
   
           /*
            * Only enable connection groups for a protocol if it has been
            * specifically requested.
            */
           if (hashfields == IPI_HASHFIELDS_NONE)
                   return;
   
           /*
            * Connection groups are about multi-processor load distribution,
            * lock contention, and connection CPU affinity.  As such, no point
            * in turning them on for a uniprocessor machine, it only wastes
            * memory.
            */
           if (mp_ncpus == 1)
                   return;
   
   #ifdef RSS
           /*
            * If we're using RSS, then RSS determines the number of connection
            * groups to use: one connection group per RSS bucket.  If for some
            * reason RSS isn't able to provide a number of buckets, disable
            * connection groups entirely.
            *
            * XXXRW: Can this ever happen?
            */
           numpcbgroups = rss_getnumbuckets();
           if (numpcbgroups == 0)
                   return;
   #else
           /*
            * Otherwise, we'll just use one per CPU for now.  If we decide to
            * do dynamic rebalancing a la RSS, we'll need similar logic here.
            */
           numpcbgroups = mp_ncpus;
   #endif
   
           pcbinfo->ipi_hashfields = hashfields;
           pcbinfo->ipi_pcbgroups = malloc(numpcbgroups *
               sizeof(*pcbinfo->ipi_pcbgroups), M_PCB, M_WAITOK | M_ZERO);
           pcbinfo->ipi_npcbgroups = numpcbgroups;
           pcbinfo->ipi_wildbase = hashinit(hash_nelements, M_PCB,
               &pcbinfo->ipi_wildmask);
           for (pgn = 0; pgn < pcbinfo->ipi_npcbgroups; pgn++) {
                   pcbgroup = &pcbinfo->ipi_pcbgroups[pgn];
                   pcbgroup->ipg_hashbase = hashinit(hash_nelements, M_PCB,
                       &pcbgroup->ipg_hashmask);
                   INP_GROUP_LOCK_INIT(pcbgroup, "pcbgroup");
   
                   /*
                    * Initialise notional affinity of the pcbgroup -- for RSS,
                    * we want the same notion of affinity as NICs to be used.  In
                    * the non-RSS case, just round robin for the time being.
                    *
                    * XXXRW: The notion of a bucket to CPU mapping is common at
                    * both pcbgroup and RSS layers -- does that mean that we
                    * should migrate it all from RSS to here, and just leave RSS
                    * responsible only for providing hashing and mapping funtions?
                    */
   #ifdef RSS
                   pcbgroup->ipg_cpu = rss_getcpu(pgn);
   #else
                   pcbgroup->ipg_cpu = (pgn % mp_ncpus);
   #endif
           }
   }
   
   void
   in_pcbgroup_destroy(struct inpcbinfo *pcbinfo)
   {
           struct inpcbgroup *pcbgroup;
           u_int pgn;
   
           if (pcbinfo->ipi_npcbgroups == 0)
                   return;
   
           for (pgn = 0; pgn < pcbinfo->ipi_npcbgroups; pgn++) {
                   pcbgroup = &pcbinfo->ipi_pcbgroups[pgn];
                   KASSERT(CK_LIST_EMPTY(pcbinfo->ipi_listhead),
                       ("in_pcbinfo_destroy: listhead not empty"));
                   INP_GROUP_LOCK_DESTROY(pcbgroup);
                   hashdestroy(pcbgroup->ipg_hashbase, M_PCB,
                       pcbgroup->ipg_hashmask);
           }
           hashdestroy(pcbinfo->ipi_wildbase, M_PCB, pcbinfo->ipi_wildmask);
           free(pcbinfo->ipi_pcbgroups, M_PCB);
           pcbinfo->ipi_pcbgroups = NULL;
           pcbinfo->ipi_npcbgroups = 0;
           pcbinfo->ipi_hashfields = 0;
   }
   
   /*
    * Given a hash of whatever the covered tuple might be, return a pcbgroup
    * index.  Where RSS is supported, try to align bucket selection with RSS CPU
    * affinity strategy.
    */
   static __inline u_int
   in_pcbgroup_getbucket(struct inpcbinfo *pcbinfo, uint32_t hash)
   {
   
   #ifdef RSS
           return (rss_getbucket(hash));
   #else
           return (hash % pcbinfo->ipi_npcbgroups);
   #endif
   }
   
   /*
    * Map a (hashtype, hash) tuple into a connection group, or NULL if the hash
    * information is insufficient to identify the pcbgroup.  This might occur if
    * a TCP packet turns up with a 2-tuple hash, or if an RSS hash is present but
    * RSS is not compiled into the kernel.
    */
   struct inpcbgroup *
   in_pcbgroup_byhash(struct inpcbinfo *pcbinfo, u_int hashtype, uint32_t hash)
   {
   
   #ifdef RSS
           if ((pcbinfo->ipi_hashfields == IPI_HASHFIELDS_4TUPLE &&
               hashtype == M_HASHTYPE_RSS_TCP_IPV4) ||
               (pcbinfo->ipi_hashfields == IPI_HASHFIELDS_4TUPLE &&
               hashtype == M_HASHTYPE_RSS_UDP_IPV4) ||
               (pcbinfo->ipi_hashfields == IPI_HASHFIELDS_2TUPLE &&
               hashtype == M_HASHTYPE_RSS_IPV4))
                   return (&pcbinfo->ipi_pcbgroups[
                       in_pcbgroup_getbucket(pcbinfo, hash)]);
   #endif
           return (NULL);
   }
   
   static struct inpcbgroup *
   in_pcbgroup_bymbuf(struct inpcbinfo *pcbinfo, struct mbuf *m)
   {
   
           return (in_pcbgroup_byhash(pcbinfo, M_HASHTYPE_GET(m),
               m->m_pkthdr.flowid));
   }
   
   struct inpcbgroup *
   in_pcbgroup_bytuple(struct inpcbinfo *pcbinfo, struct in_addr laddr,
       u_short lport, struct in_addr faddr, u_short fport)
   {
           uint32_t hash;
   
           /*
            * RSS note: we pass foreign addr/port as source, and local addr/port
            * as destination, as we want to align with what the hardware is
            * doing.
            */
           switch (pcbinfo->ipi_hashfields) {
           case IPI_HASHFIELDS_4TUPLE:
   #ifdef RSS
                   hash = rss_hash_ip4_4tuple(faddr, fport, laddr, lport);
   #else
                   hash = faddr.s_addr ^ fport;
   #endif
                   break;
   
           case IPI_HASHFIELDS_2TUPLE:
   #ifdef RSS
                   hash = rss_hash_ip4_2tuple(faddr, laddr);
   #else
                   hash = faddr.s_addr ^ laddr.s_addr;
   #endif
                   break;
   
           default:
                   hash = 0;
           }
           return (&pcbinfo->ipi_pcbgroups[in_pcbgroup_getbucket(pcbinfo,
               hash)]);
   }
   
   struct inpcbgroup *
   in_pcbgroup_byinpcb(struct inpcb *inp)
   {
   #ifdef  RSS
           /*
            * Listen sockets with INP_RSS_BUCKET_SET set have a pre-determined
            * RSS bucket and thus we should use this pcbgroup, rather than
            * using a tuple or hash.
            *
            * XXX should verify that there's actually pcbgroups and inp_rss_listen_bucket
            * fits in that!
            */
           if (inp->inp_flags2 & INP_RSS_BUCKET_SET)
                   return (&inp->inp_pcbinfo->ipi_pcbgroups[inp->inp_rss_listen_bucket]);
   #endif
   
           return (in_pcbgroup_bytuple(inp->inp_pcbinfo, inp->inp_laddr,
               inp->inp_lport, inp->inp_faddr, inp->inp_fport));
   }
   
   static void
   in_pcbwild_add(struct inpcb *inp)
   {
           struct inpcbinfo *pcbinfo;
           struct inpcbhead *head;
           u_int pgn;
   
           INP_WLOCK_ASSERT(inp);
           KASSERT(!(inp->inp_flags2 & INP_PCBGROUPWILD),
               ("%s: is wild",__func__));
   
           pcbinfo = inp->inp_pcbinfo;
           for (pgn = 0; pgn < pcbinfo->ipi_npcbgroups; pgn++)
                   INP_GROUP_LOCK(&pcbinfo->ipi_pcbgroups[pgn]);
           head = &pcbinfo->ipi_wildbase[INP_PCBHASH(INADDR_ANY, inp->inp_lport,
               0, pcbinfo->ipi_wildmask)];
           CK_LIST_INSERT_HEAD(head, inp, inp_pcbgroup_wild);
           inp->inp_flags2 |= INP_PCBGROUPWILD;
           for (pgn = 0; pgn < pcbinfo->ipi_npcbgroups; pgn++)
                   INP_GROUP_UNLOCK(&pcbinfo->ipi_pcbgroups[pgn]);
   }
   
   static void
   in_pcbwild_remove(struct inpcb *inp)
   {
           struct inpcbinfo *pcbinfo;
           u_int pgn;
   
           INP_WLOCK_ASSERT(inp);
           KASSERT((inp->inp_flags2 & INP_PCBGROUPWILD),
               ("%s: not wild", __func__));
   
           pcbinfo = inp->inp_pcbinfo;
           for (pgn = 0; pgn < pcbinfo->ipi_npcbgroups; pgn++)
                   INP_GROUP_LOCK(&pcbinfo->ipi_pcbgroups[pgn]);
           CK_LIST_REMOVE(inp, inp_pcbgroup_wild);
           for (pgn = 0; pgn < pcbinfo->ipi_npcbgroups; pgn++)
                   INP_GROUP_UNLOCK(&pcbinfo->ipi_pcbgroups[pgn]);
           inp->inp_flags2 &= ~INP_PCBGROUPWILD;
   }
   
   static __inline int
   in_pcbwild_needed(struct inpcb *inp)
   {
   #ifdef  RSS
           /*
            * If it's a listen socket and INP_RSS_BUCKET_SET is set,
            * it's a wildcard socket _but_ it's in a specific pcbgroup.
            * Thus we don't treat it as a pcbwild inp.
            */
           if (inp->inp_flags2 & INP_RSS_BUCKET_SET)
                   return (0);
   #endif
   
   #ifdef INET6
           if (inp->inp_vflag & INP_IPV6)
                   return (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_faddr));
           else
   #endif
                   return (inp->inp_faddr.s_addr == htonl(INADDR_ANY));
   }
   
   static void
   in_pcbwild_update_internal(struct inpcb *inp)
   {
           int wildcard_needed;
   
           wildcard_needed = in_pcbwild_needed(inp);
           if (wildcard_needed && !(inp->inp_flags2 & INP_PCBGROUPWILD))
                   in_pcbwild_add(inp);
           else if (!wildcard_needed && (inp->inp_flags2 & INP_PCBGROUPWILD))
                   in_pcbwild_remove(inp);
   }
   
   /*
    * Update the pcbgroup of an inpcb, which might include removing an old
    * pcbgroup reference and/or adding a new one.  Wildcard processing is not
    * performed here, although ideally we'll never install a pcbgroup for a
    * wildcard inpcb (asserted below).
    */
   static void
   in_pcbgroup_update_internal(struct inpcbinfo *pcbinfo,
       struct inpcbgroup *newpcbgroup, struct inpcb *inp)
   {
           struct inpcbgroup *oldpcbgroup;
           struct inpcbhead *pcbhash;
           uint32_t hashkey_faddr;
   
           INP_WLOCK_ASSERT(inp);
   
           oldpcbgroup = inp->inp_pcbgroup;
           if (oldpcbgroup != NULL && oldpcbgroup != newpcbgroup) {
                   INP_GROUP_LOCK(oldpcbgroup);
                   CK_LIST_REMOVE(inp, inp_pcbgrouphash);
                   inp->inp_pcbgroup = NULL;
                   INP_GROUP_UNLOCK(oldpcbgroup);
           }
           if (newpcbgroup != NULL && oldpcbgroup != newpcbgroup) {
   #ifdef INET6
                   if (inp->inp_vflag & INP_IPV6)
                           hashkey_faddr = INP6_PCBHASHKEY(&inp->in6p_faddr);
                   else
   #endif
                           hashkey_faddr = inp->inp_faddr.s_addr;
                   INP_GROUP_LOCK(newpcbgroup);
                   /*
                    * If the inp is an RSS bucket wildcard entry, ensure
                    * that the PCB hash is calculated correctly.
                    *
                    * The wildcard hash calculation differs from the
                    * non-wildcard definition.  The source address is
                    * INADDR_ANY and the far port is 0.
                    */
                   if (inp->inp_flags2 & INP_RSS_BUCKET_SET) {
                           pcbhash = &newpcbgroup->ipg_hashbase[
                               INP_PCBHASH(INADDR_ANY, inp->inp_lport, 0,
                               newpcbgroup->ipg_hashmask)];
                   } else {
                           pcbhash = &newpcbgroup->ipg_hashbase[
                               INP_PCBHASH(hashkey_faddr, inp->inp_lport,
                               inp->inp_fport,
                               newpcbgroup->ipg_hashmask)];
                   }
                   CK_LIST_INSERT_HEAD(pcbhash, inp, inp_pcbgrouphash);
                   inp->inp_pcbgroup = newpcbgroup;
                   INP_GROUP_UNLOCK(newpcbgroup);
           }
   
           KASSERT(!(newpcbgroup != NULL && in_pcbwild_needed(inp)),
               ("%s: pcbgroup and wildcard!", __func__));
   }
   
   /*
    * Two update paths: one in which the 4-tuple on an inpcb has been updated
    * and therefore connection groups may need to change (or a wildcard entry
    * may needed to be installed), and another in which the 4-tuple has been
    * set as a result of a packet received, in which case we may be able to use
    * the hash on the mbuf to avoid doing a software hash calculation for RSS.
    *
    * In each case: first, let the wildcard code have a go at placing it as a
    * wildcard socket.  If it was a wildcard, or if the connection has been
    * dropped, then no pcbgroup is required (so potentially clear it);
    * otherwise, calculate and update the pcbgroup for the inpcb.
    */
   void
   in_pcbgroup_update(struct inpcb *inp)
   {
           struct inpcbinfo *pcbinfo;
           struct inpcbgroup *newpcbgroup;
   
           INP_WLOCK_ASSERT(inp);
   
           pcbinfo = inp->inp_pcbinfo;
           if (!in_pcbgroup_enabled(pcbinfo))
                   return;
   
           in_pcbwild_update_internal(inp);
           if (!(inp->inp_flags2 & INP_PCBGROUPWILD) &&
               !(inp->inp_flags & INP_DROPPED)) {
   #ifdef INET6
                   if (inp->inp_vflag & INP_IPV6)
                           newpcbgroup = in6_pcbgroup_byinpcb(inp);
                   else
   #endif
                           newpcbgroup = in_pcbgroup_byinpcb(inp);
           } else
                   newpcbgroup = NULL;
           in_pcbgroup_update_internal(pcbinfo, newpcbgroup, inp);
   }
   
   void
   in_pcbgroup_update_mbuf(struct inpcb *inp, struct mbuf *m)
   {
           struct inpcbinfo *pcbinfo;
           struct inpcbgroup *newpcbgroup;
   
           INP_WLOCK_ASSERT(inp);
   
           pcbinfo = inp->inp_pcbinfo;
           if (!in_pcbgroup_enabled(pcbinfo))
                   return;
   
           /*
            * Possibly should assert !INP_PCBGROUPWILD rather than testing for
            * it; presumably this function should never be called for anything
            * other than non-wildcard socket?
            */
           in_pcbwild_update_internal(inp);
           if (!(inp->inp_flags2 & INP_PCBGROUPWILD) &&
               !(inp->inp_flags & INP_DROPPED)) {
                   newpcbgroup = in_pcbgroup_bymbuf(pcbinfo, m);
   #ifdef INET6
                   if (inp->inp_vflag & INP_IPV6) {
                           if (newpcbgroup == NULL)
                                   newpcbgroup = in6_pcbgroup_byinpcb(inp);
                   } else {
   #endif
                           if (newpcbgroup == NULL)
                                   newpcbgroup = in_pcbgroup_byinpcb(inp);
   #ifdef INET6
                   }
   #endif
           } else
                   newpcbgroup = NULL;
           in_pcbgroup_update_internal(pcbinfo, newpcbgroup, inp);
   }
   
   /*
    * Remove pcbgroup entry and optional pcbgroup wildcard entry for this inpcb.
    */
   void
   in_pcbgroup_remove(struct inpcb *inp)
   {
           struct inpcbgroup *pcbgroup;
   
           INP_WLOCK_ASSERT(inp);
   
           if (!in_pcbgroup_enabled(inp->inp_pcbinfo))
                   return;
   
           if (inp->inp_flags2 & INP_PCBGROUPWILD)
                   in_pcbwild_remove(inp);
   
           pcbgroup = inp->inp_pcbgroup;
           if (pcbgroup != NULL) {
                   INP_GROUP_LOCK(pcbgroup);
                   CK_LIST_REMOVE(inp, inp_pcbgrouphash);
                   inp->inp_pcbgroup = NULL;
                   INP_GROUP_UNLOCK(pcbgroup);
           }
   }
   
   /*
    * Query whether or not it is appropriate to use pcbgroups to look up inpcbs
    * for a protocol.
    */
   int
   in_pcbgroup_enabled(struct inpcbinfo *pcbinfo)
   {
   
           return (pcbinfo->ipi_npcbgroups > 0);
   }

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