FreeBSD/Linux Kernel Cross Reference
sys/net/route/nhgrp_ctl.c

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2020 Alexander V. Chernikov
      *
      * 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.
     *
     * $FreeBSD$
     */
    #include "opt_inet.h"
    #include "opt_route.h"
    
    #include <sys/cdefs.h>
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/lock.h>
    #include <sys/rmlock.h>
    #include <sys/malloc.h>
    #include <sys/mbuf.h>
    #include <sys/refcount.h>
    #include <sys/socket.h>
    #include <sys/sysctl.h>
    #include <sys/kernel.h>
    #include <sys/epoch.h>
    
    #include <net/if.h>
    #include <net/if_var.h>
    #include <net/if_private.h>
    #include <net/route.h>
    #include <net/route/route_ctl.h>
    #include <net/route/route_var.h>
    #include <net/vnet.h>
    
    #include <netinet/in.h>
    #include <netinet/in_var.h>
    #include <netinet/in_fib.h>
    
    #include <net/route/nhop_utils.h>
    #include <net/route/nhop.h>
    #include <net/route/nhop_var.h>
    #include <net/route/nhgrp_var.h>
    
    #define DEBUG_MOD_NAME  nhgrp_ctl
    #define DEBUG_MAX_LEVEL LOG_DEBUG
    #include <net/route/route_debug.h>
    _DECLARE_DEBUG(LOG_INFO);
    
    /*
     * This file contains the supporting functions for creating multipath groups
     *  and compiling their dataplane parts.
     */
    
    /* MPF_MULTIPATH must be the same as NHF_MULTIPATH for nhop selection to work */
    _Static_assert(MPF_MULTIPATH == NHF_MULTIPATH,
        "MPF_MULTIPATH must be the same as NHF_MULTIPATH");
    /* Offset and size of flags field has to be the same for nhop/nhop groups */
    CHK_STRUCT_FIELD_GENERIC(struct nhop_object, nh_flags, struct nhgrp_object, nhg_flags);
    /* Cap multipath to 64, as the larger values would break rib_cmd_info bmasks */
    CTASSERT(RIB_MAX_MPATH_WIDTH <= 64);
    
    static int wn_cmp_idx(const void *a, const void *b);
    static void sort_weightened_nhops(struct weightened_nhop *wn, int num_nhops);
    
    static struct nhgrp_priv *get_nhgrp(struct nh_control *ctl,
        struct weightened_nhop *wn, int num_nhops, uint32_t uidx, int *perror);
    static void destroy_nhgrp(struct nhgrp_priv *nhg_priv);
    static void destroy_nhgrp_epoch(epoch_context_t ctx);
    static void free_nhgrp_nhops(struct nhgrp_priv *nhg_priv);
    
    static int
    wn_cmp_idx(const void *a, const void *b)
    {
            const struct weightened_nhop *w_a = a;
            const struct weightened_nhop *w_b = b;
            uint32_t a_idx = w_a->nh->nh_priv->nh_idx;
            uint32_t b_idx = w_b->nh->nh_priv->nh_idx;
    
            if (a_idx < b_idx)
                    return (-1);
            else if (a_idx > b_idx)
                   return (1);
           else
                   return (0);
   }
   
   /*
    * Perform in-place sorting for array of nexthops in @wn.
    * Sort by nexthop index ascending.
    */
   static void
   sort_weightened_nhops(struct weightened_nhop *wn, int num_nhops)
   {
   
           qsort(wn, num_nhops, sizeof(struct weightened_nhop), wn_cmp_idx);
   }
   
   /*
    * In order to determine the minimum weight difference in the array
    * of weights, create a sorted array of weights, using spare "storage"
    * field in the `struct weightened_nhop`.
    * Assume weights to be (mostly) the same and use insertion sort to
    * make it sorted.
    */
   static void
   sort_weightened_nhops_weights(struct weightened_nhop *wn, int num_items)
   {
           wn[0].storage = wn[0].weight;
           for (int i = 1, j = 0; i < num_items; i++) {
                   uint32_t weight = wn[i].weight; // read from 'weight' as it's not reordered
                   /* Move all weights > weight 1 position right */
                   for (j = i - 1; j >= 0 && wn[j].storage > weight; j--)
                           wn[j + 1].storage = wn[j].storage;
                   wn[j + 1].storage = weight;
           }
   }
   
   /*
    * Calculate minimum number of slots required to fit the existing
    * set of weights in the common use case where weights are "easily"
    * comparable.
    * Assumes @wn is sorted by weight ascending and each weight is > 0.
    * Returns number of slots or 0 if precise calculation failed.
    *
    * Some examples:
    * note: (i, X) pair means (nhop=i, weight=X):
    * (1, 1) (2, 2) -> 3 slots [1, 2, 2]
    * (1, 100), (2, 200) -> 3 slots [1, 2, 2]
    * (1, 100), (2, 200), (3, 400) -> 7 slots [1, 2, 2, 3, 3, 3]
    */
   static uint32_t
   calc_min_mpath_slots_fast(struct weightened_nhop *wn, size_t num_items,
       uint64_t *ptotal)
   {
           uint32_t i, last, xmin;
           uint64_t total = 0;
   
           // Get sorted array of weights in .storage field
           sort_weightened_nhops_weights(wn, num_items);
   
           last = 0;
           xmin = wn[0].storage;
           for (i = 0; i < num_items; i++) {
                   total += wn[i].storage;
                   if ((wn[i].storage != last) &&
                       ((wn[i].storage - last < xmin) || xmin == 0)) {
                           xmin = wn[i].storage - last;
                   }
                   last = wn[i].storage;
           }
           *ptotal = total;
           /* xmin is the minimum unit of desired capacity */
           if ((total % xmin) != 0)
                   return (0);
           for (i = 0; i < num_items; i++) {
                   if ((wn[i].weight % xmin) != 0)
                           return (0);
           }
   
           return ((uint32_t)(total / xmin));
   }
   
   /*
    * Calculate minimum number of slots required to fit the existing
    * set of weights while maintaining weight coefficients.
    *
    * Assume @wn is sorted by weight ascending and each weight is > 0.
    *
    * Tries to find simple precise solution first and falls back to
    *  RIB_MAX_MPATH_WIDTH in case of any failure.
    */
   static uint32_t
   calc_min_mpath_slots(struct weightened_nhop *wn, size_t num_items)
   {
           uint32_t v;
           uint64_t total;
   
           v = calc_min_mpath_slots_fast(wn, num_items, &total);
           if (total == 0)
                   return (0);
           if ((v == 0) || (v > RIB_MAX_MPATH_WIDTH))
                   v = RIB_MAX_MPATH_WIDTH;
   
           return (v);
   }
   
   /*
    * Nexthop group data consists of
    * 1) dataplane part, with nhgrp_object as a header followed by an
    *   arbitrary number of nexthop pointers.
    * 2) control plane part, with nhgrp_priv as a header, followed by
    *   an arbirtrary number of 'struct weightened_nhop' object.
    *
    * Given nexthop groups are (mostly) immutable, allocate all data
    * in one go.
    *
    */
   __noinline static size_t
   get_nhgrp_alloc_size(uint32_t nhg_size, uint32_t num_nhops)
   {
           size_t sz;
   
           sz = sizeof(struct nhgrp_object);
           sz += nhg_size * sizeof(struct nhop_object *);
           sz += sizeof(struct nhgrp_priv);
           sz += num_nhops * sizeof(struct weightened_nhop);
           return (sz);
   }
   
   /*
    * Compile actual list of nexthops to be used by datapath from
    *  the nexthop group @dst.
    *
    * For example, compiling control plane list of 2 nexthops
    *  [(200, A), (100, B)] would result in the datapath array
    *  [A, A, B]
    */
   static void
   compile_nhgrp(struct nhgrp_priv *dst_priv, const struct weightened_nhop *x,
       uint32_t num_slots)
   {
           struct nhgrp_object *dst;
           int i, slot_idx, remaining_slots;
           uint64_t remaining_sum, nh_weight, nh_slots;
   
           slot_idx  = 0;
           dst = dst_priv->nhg;
           /* Calculate sum of all weights */
           remaining_sum = 0;
           for (i = 0; i < dst_priv->nhg_nh_count; i++)
                   remaining_sum += x[i].weight;
           remaining_slots = num_slots;
           FIB_NH_LOG(LOG_DEBUG3, x[0].nh, "sum: %lu, slots: %d",
               remaining_sum, remaining_slots);
           for (i = 0; i < dst_priv->nhg_nh_count; i++) {
                   /* Calculate number of slots for the current nexthop */
                   if (remaining_sum > 0) {
                           nh_weight = (uint64_t)x[i].weight;
                           nh_slots = (nh_weight * remaining_slots / remaining_sum);
                   } else
                           nh_slots = 0;
   
                   remaining_sum -= x[i].weight;
                   remaining_slots -= nh_slots;
   
                   FIB_NH_LOG(LOG_DEBUG3, x[0].nh,
                       " rem_sum: %lu, rem_slots: %d nh_slots: %d, slot_idx: %d",
                       remaining_sum, remaining_slots, (int)nh_slots, slot_idx);
   
                   KASSERT((slot_idx + nh_slots <= num_slots),
                       ("index overflow during nhg compilation"));
                   while (nh_slots-- > 0)
                           dst->nhops[slot_idx++] = x[i].nh;
           }
   }
   
   /*
    * Allocates new nexthop group for the list of weightened nexthops.
    * Assume sorted list.
    * Does NOT reference any nexthops in the group.
    * Returns group with refcount=1 or NULL.
    */
   static struct nhgrp_priv *
   alloc_nhgrp(struct weightened_nhop *wn, int num_nhops)
   {
           uint32_t nhgrp_size;
           struct nhgrp_object *nhg;
           struct nhgrp_priv *nhg_priv;
   
           nhgrp_size = calc_min_mpath_slots(wn, num_nhops);
           if (nhgrp_size == 0) {
                   /* Zero weights, abort */
                   return (NULL);
           }
   
           size_t sz = get_nhgrp_alloc_size(nhgrp_size, num_nhops);
           nhg = malloc(sz, M_NHOP, M_NOWAIT | M_ZERO);
           if (nhg == NULL) {
                   FIB_NH_LOG(LOG_INFO, wn[0].nh,
                       "unable to allocate group with num_nhops %d (compiled %u)",
                       num_nhops, nhgrp_size);
                   return (NULL);
           }
   
           /* Has to be the first to make NHGRP_PRIV() work */
           nhg->nhg_size = nhgrp_size;
           nhg->nhg_flags = MPF_MULTIPATH;
   
           nhg_priv = NHGRP_PRIV(nhg);
           nhg_priv->nhg_nh_count = num_nhops;
           refcount_init(&nhg_priv->nhg_refcount, 1);
   
           /* Please see nhgrp_free() comments on the initial value */
           refcount_init(&nhg_priv->nhg_linked, 2);
   
           nhg_priv->nhg = nhg;
           memcpy(&nhg_priv->nhg_nh_weights[0], wn,
             num_nhops * sizeof(struct weightened_nhop));
   
           FIB_NH_LOG(LOG_DEBUG, wn[0].nh, "num_nhops: %d, compiled_nhop: %u",
               num_nhops, nhgrp_size);
   
           compile_nhgrp(nhg_priv, wn, nhg->nhg_size);
   
           return (nhg_priv);
   }
   
   void
   nhgrp_ref_object(struct nhgrp_object *nhg)
   {
           struct nhgrp_priv *nhg_priv;
           u_int old __diagused;
   
           nhg_priv = NHGRP_PRIV(nhg);
           old = refcount_acquire(&nhg_priv->nhg_refcount);
           KASSERT(old > 0, ("%s: nhgrp object %p has 0 refs", __func__, nhg));
   }
   
   void
   nhgrp_free(struct nhgrp_object *nhg)
   {
           struct nhgrp_priv *nhg_priv;
           struct nh_control *ctl;
           struct epoch_tracker et;
   
           nhg_priv = NHGRP_PRIV(nhg);
   
           if (!refcount_release(&nhg_priv->nhg_refcount))
                   return;
   
           /*
            * group objects don't have an explicit lock attached to it.
            * As groups are reclaimed based on reference count, it is possible
            * that some groups will persist after vnet destruction callback
            * called. Given that, handle scenario with nhgrp_free_group() being
            * called either after or simultaneously with nhgrp_ctl_unlink_all()
            * by using another reference counter: nhg_linked.
            *
            * There are only 2 places, where nhg_linked can be decreased:
            *  rib destroy (nhgrp_ctl_unlink_all) and this function.
            * nhg_link can never be increased.
            *
            * Hence, use initial value of 2 to make use of
            *  refcount_release_if_not_last().
            *
            * There can be two scenarious when calling this function:
            *
            * 1) nhg_linked value is 2. This means that either
            *  nhgrp_ctl_unlink_all() has not been called OR it is running,
            *  but we are guaranteed that nh_control won't be freed in
            *  this epoch. Hence, nexthop can be safely unlinked.
            *
            * 2) nh_linked value is 1. In that case, nhgrp_ctl_unlink_all()
            *  has been called and nhgrp unlink can be skipped.
            */
   
           NET_EPOCH_ENTER(et);
           if (refcount_release_if_not_last(&nhg_priv->nhg_linked)) {
                   ctl = nhg_priv->nh_control;
                   if (unlink_nhgrp(ctl, nhg_priv) == NULL) {
                           /* Do not try to reclaim */
                           RT_LOG(LOG_INFO, "Failed to unlink nexhop group %p",
                               nhg_priv);
                           NET_EPOCH_EXIT(et);
                           return;
                   }
           }
           NET_EPOCH_EXIT(et);
   
           KASSERT((nhg_priv->nhg_idx == 0), ("gr_idx != 0"));
           NET_EPOCH_CALL(destroy_nhgrp_epoch, &nhg_priv->nhg_epoch_ctx);
   }
   
   /*
    * Destroys all local resources belonging to @nhg_priv.
    */
   __noinline static void
   destroy_nhgrp_int(struct nhgrp_priv *nhg_priv)
   {
   
           free(nhg_priv->nhg, M_NHOP);
   }
   
   __noinline static void
   destroy_nhgrp(struct nhgrp_priv *nhg_priv)
   {
   
           KASSERT((nhg_priv->nhg_refcount == 0), ("nhg_refcount != 0"));
           KASSERT((nhg_priv->nhg_idx == 0), ("gr_idx != 0"));
   
           IF_DEBUG_LEVEL(LOG_DEBUG2) {
                   char nhgbuf[NHOP_PRINT_BUFSIZE] __unused;
                   FIB_NH_LOG(LOG_DEBUG2, nhg_priv->nhg_nh_weights[0].nh,
                       "destroying %s", nhgrp_print_buf(nhg_priv->nhg,
                       nhgbuf, sizeof(nhgbuf)));
           }
   
           free_nhgrp_nhops(nhg_priv);
           destroy_nhgrp_int(nhg_priv);
   }
   
   /*
    * Epoch callback indicating group is safe to destroy
    */
   static void
   destroy_nhgrp_epoch(epoch_context_t ctx)
   {
           struct nhgrp_priv *nhg_priv;
   
           nhg_priv = __containerof(ctx, struct nhgrp_priv, nhg_epoch_ctx);
   
           destroy_nhgrp(nhg_priv);
   }
   
   static bool
   ref_nhgrp_nhops(struct nhgrp_priv *nhg_priv)
   {
   
           for (int i = 0; i < nhg_priv->nhg_nh_count; i++) {
                   if (nhop_try_ref_object(nhg_priv->nhg_nh_weights[i].nh) != 0)
                           continue;
   
                   /*
                    * Failed to ref the nexthop, b/c it's deleted.
                    * Need to rollback references back.
                    */
                   for (int j = 0; j < i; j++)
                           nhop_free(nhg_priv->nhg_nh_weights[j].nh);
                   return (false);
           }
   
           return (true);
   }
   
   static void
   free_nhgrp_nhops(struct nhgrp_priv *nhg_priv)
   {
   
           for (int i = 0; i < nhg_priv->nhg_nh_count; i++)
                   nhop_free(nhg_priv->nhg_nh_weights[i].nh);
   }
   
   /*
    * Allocate nexthop group of size @num_nhops with nexthops specified by
    * @wn. Nexthops have to be unique and match the fibnum/family of the group.
    * Returns unlinked nhgrp object on success or NULL and non-zero perror.
    */
   struct nhgrp_object *
   nhgrp_alloc(uint32_t fibnum, int family, struct weightened_nhop *wn, int num_nhops,
       int *perror)
   {
           struct rib_head *rh = rt_tables_get_rnh(fibnum, family);
           struct nhgrp_priv *nhg_priv;
           struct nh_control *ctl;
   
           if (rh == NULL) {
                   *perror = E2BIG;
                   return (NULL);
           }
   
           ctl = rh->nh_control;
   
           if (num_nhops > RIB_MAX_MPATH_WIDTH) {
                   *perror = E2BIG;
                   return (NULL);
           }
   
           if (ctl->gr_head.hash_size == 0) {
                   /* First multipath request. Bootstrap mpath datastructures. */
                   if (nhgrp_ctl_alloc_default(ctl, M_NOWAIT) == 0) {
                           *perror = ENOMEM;
                           return (NULL);
                   }
           }
   
           /* Sort nexthops & check there are no duplicates */
           sort_weightened_nhops(wn, num_nhops);
           uint32_t last_id = 0;
           for (int i = 0; i < num_nhops; i++) {
                   if (wn[i].nh->nh_priv->nh_control != ctl) {
                           *perror = EINVAL;
                           return (NULL);
                   }
                   if (wn[i].nh->nh_priv->nh_idx == last_id) {
                           *perror = EEXIST;
                           return (NULL);
                   }
                   last_id = wn[i].nh->nh_priv->nh_idx;
           }
   
           if ((nhg_priv = alloc_nhgrp(wn, num_nhops)) == NULL) {
                   *perror = ENOMEM;
                   return (NULL);
           }
           nhg_priv->nh_control = ctl;
   
           *perror = 0;
           return (nhg_priv->nhg);
   }
   
   /*
    * Finds an existing group matching @nhg or links @nhg to the tree.
    * Returns the referenced group or NULL and non-zero @perror.
    */
   struct nhgrp_object *
   nhgrp_get_nhgrp(struct nhgrp_object *nhg, int *perror)
   {
           struct nhgrp_priv *nhg_priv, *key = NHGRP_PRIV(nhg);
           struct nh_control *ctl = key->nh_control;
   
           nhg_priv = find_nhgrp(ctl, key);
           if (nhg_priv != NULL) {
                   /*
                    * Free originally-created group. As it hasn't been linked
                    *  and the dependent nexhops haven't been referenced, just free
                    *  the group.
                    */
                   destroy_nhgrp_int(key);
                   *perror = 0;
                   return (nhg_priv->nhg);
           } else {
                   /* No existing group, try to link the new one */
                   if (!ref_nhgrp_nhops(key)) {
                           /*
                            * Some of the nexthops have been scheduled for deletion.
                            * As the group hasn't been linked / no nexhops have been
                            *  referenced, call the final destructor immediately.
                            */
                           destroy_nhgrp_int(key);
                           *perror = EAGAIN;
                           return (NULL);
                   }
                   if (link_nhgrp(ctl, key) == 0) {
                           /* Unable to allocate index? */
                           *perror = EAGAIN;
                           free_nhgrp_nhops(key);
                           destroy_nhgrp_int(key);
                           return (NULL);
                   }
                   *perror = 0;
                   return (nhg);
           }
   
           /* NOTREACHED */
   }
   
   /*
    * Creates or looks up an existing nexthop group based on @wn and @num_nhops.
    *
    * Returns referenced nhop group or NULL, passing error code in @perror.
    */
   struct nhgrp_priv *
   get_nhgrp(struct nh_control *ctl, struct weightened_nhop *wn, int num_nhops,
       uint32_t uidx, int *perror)
   {
           struct nhgrp_object *nhg;
   
           nhg = nhgrp_alloc(ctl->ctl_rh->rib_fibnum, ctl->ctl_rh->rib_family,
               wn, num_nhops, perror);
           if (nhg == NULL)
                   return (NULL);
           nhgrp_set_uidx(nhg, uidx);
           nhg = nhgrp_get_nhgrp(nhg, perror);
           if (nhg != NULL)
                   return (NHGRP_PRIV(nhg));
           return (NULL);
   }
   
   
   /*
    * Appends one or more nexthops denoted by @wm to the nexthop group @gr_orig.
    *
    * Returns referenced nexthop group or NULL. In the latter case, @perror is
    *  filled with an error code.
    * Note that function does NOT care if the next nexthops already exists
    * in the @gr_orig. As a result, they will be added, resulting in the
    * same nexthop being present multiple times in the new group.
    */
   static struct nhgrp_priv *
   append_nhops(struct nh_control *ctl, const struct nhgrp_object *gr_orig,
       struct weightened_nhop *wn, int num_nhops, int *perror)
   {
           char storage[64];
           struct weightened_nhop *pnhops;
           struct nhgrp_priv *nhg_priv;
           const struct nhgrp_priv *src_priv;
           size_t sz;
           int curr_nhops;
   
           src_priv = NHGRP_PRIV_CONST(gr_orig);
           curr_nhops = src_priv->nhg_nh_count;
   
           *perror = 0;
   
           sz = (src_priv->nhg_nh_count + num_nhops) * (sizeof(struct weightened_nhop));
           /* optimize for <= 4 paths, each path=16 bytes */
           if (sz <= sizeof(storage))
                   pnhops = (struct weightened_nhop *)&storage[0];
           else {
                   pnhops = malloc(sz, M_TEMP, M_NOWAIT);
                   if (pnhops == NULL) {
                           *perror = ENOMEM;
                           return (NULL);
                   }
           }
   
           /* Copy nhops from original group first */
           memcpy(pnhops, src_priv->nhg_nh_weights,
             curr_nhops * sizeof(struct weightened_nhop));
           memcpy(&pnhops[curr_nhops], wn, num_nhops * sizeof(struct weightened_nhop));
           curr_nhops += num_nhops;
   
           nhg_priv = get_nhgrp(ctl, pnhops, curr_nhops, 0, perror);
   
           if (pnhops != (struct weightened_nhop *)&storage[0])
                   free(pnhops, M_TEMP);
   
           if (nhg_priv == NULL)
                   return (NULL);
   
           return (nhg_priv);
   }
   
   
   /*
    * Creates/finds nexthop group based on @wn and @num_nhops.
    * Returns 0 on success with referenced group in @rnd, or
    * errno.
    *
    * If the error is EAGAIN, then the operation can be retried.
    */
   int
   nhgrp_get_group(struct rib_head *rh, struct weightened_nhop *wn, int num_nhops,
       uint32_t uidx, struct nhgrp_object **pnhg)
   {
           struct nh_control *ctl = rh->nh_control;
           struct nhgrp_priv *nhg_priv;
           int error;
   
           nhg_priv = get_nhgrp(ctl, wn, num_nhops, uidx, &error);
           if (nhg_priv != NULL)
                   *pnhg = nhg_priv->nhg;
   
           return (error);
   }
   
   /*
    * Creates new nexthop group based on @src group without the nexthops
    * chosen by @flt_func.
    * Returns 0 on success, storring the reference nhop group/object in @rnd.
    */
   int
   nhgrp_get_filtered_group(struct rib_head *rh, const struct rtentry *rt,
       const struct nhgrp_object *src, rib_filter_f_t flt_func, void *flt_data,
       struct route_nhop_data *rnd)
   {
           char storage[64];
           struct nh_control *ctl = rh->nh_control;
           struct weightened_nhop *pnhops;
           const struct nhgrp_priv *mp_priv, *src_priv;
           size_t sz;
           int error, i, num_nhops;
   
           src_priv = NHGRP_PRIV_CONST(src);
   
           sz = src_priv->nhg_nh_count * (sizeof(struct weightened_nhop));
           /* optimize for <= 4 paths, each path=16 bytes */
           if (sz <= sizeof(storage))
                   pnhops = (struct weightened_nhop *)&storage[0];
           else {
                   if ((pnhops = malloc(sz, M_TEMP, M_NOWAIT)) == NULL)
                           return (ENOMEM);
           }
   
           /* Filter nexthops */
           error = 0;
           num_nhops = 0;
           for (i = 0; i < src_priv->nhg_nh_count; i++) {
                   if (flt_func(rt, src_priv->nhg_nh_weights[i].nh, flt_data))
                           continue;
                   memcpy(&pnhops[num_nhops++], &src_priv->nhg_nh_weights[i],
                     sizeof(struct weightened_nhop));
           }
   
           if (num_nhops == 0) {
                   rnd->rnd_nhgrp = NULL;
                   rnd->rnd_weight = 0;
           } else if (num_nhops == 1) {
                   rnd->rnd_nhop = pnhops[0].nh;
                   rnd->rnd_weight = pnhops[0].weight;
                   if (nhop_try_ref_object(rnd->rnd_nhop) == 0)
                           error = EAGAIN;
           } else {
                   mp_priv = get_nhgrp(ctl, pnhops, num_nhops, 0, &error);
                   if (mp_priv != NULL)
                           rnd->rnd_nhgrp = mp_priv->nhg;
                   rnd->rnd_weight = 0;
           }
   
           if (pnhops != (struct weightened_nhop *)&storage[0])
                   free(pnhops, M_TEMP);
   
           return (error);
   }
   
   /*
    * Creates new multipath group based on existing group/nhop in @rnd_orig and
    *  to-be-added nhop @wn_add.
    * Returns 0 on success and stores result in @rnd_new.
    */
   int
   nhgrp_get_addition_group(struct rib_head *rh, struct route_nhop_data *rnd_orig,
       struct route_nhop_data *rnd_add, struct route_nhop_data *rnd_new)
   {
           struct nh_control *ctl = rh->nh_control;
           struct nhgrp_priv *nhg_priv;
           struct weightened_nhop wn[2] = {};
           int error;
   
           if (rnd_orig->rnd_nhop == NULL) {
                   /* No paths to add to, just reference current nhop */
                   *rnd_new = *rnd_add;
                   if (nhop_try_ref_object(rnd_new->rnd_nhop) == 0)
                           return (EAGAIN);
                   return (0);
           }
   
           wn[0].nh = rnd_add->rnd_nhop;
           wn[0].weight = rnd_add->rnd_weight;
   
           if (!NH_IS_NHGRP(rnd_orig->rnd_nhop)) {
                   /* Simple merge of 2 non-multipath nexthops */
                   wn[1].nh = rnd_orig->rnd_nhop;
                   wn[1].weight = rnd_orig->rnd_weight;
                   nhg_priv = get_nhgrp(ctl, wn, 2, 0, &error);
           } else {
                   /* Get new nhop group with @rt->rt_nhop as an additional nhop */
                   nhg_priv = append_nhops(ctl, rnd_orig->rnd_nhgrp, &wn[0], 1,
                       &error);
           }
   
           if (nhg_priv == NULL)
                   return (error);
           rnd_new->rnd_nhgrp = nhg_priv->nhg;
           rnd_new->rnd_weight = 0;
   
           return (0);
   }
   
   /*
    * Returns pointer to array of nexthops with weights for
    * given @nhg. Stores number of items in the array into @pnum_nhops.
    */
   const struct weightened_nhop *
   nhgrp_get_nhops(const struct nhgrp_object *nhg, uint32_t *pnum_nhops)
   {
           const struct nhgrp_priv *nhg_priv;
   
           KASSERT(((nhg->nhg_flags & MPF_MULTIPATH) != 0), ("nhop is not mpath"));
   
           nhg_priv = NHGRP_PRIV_CONST(nhg);
           *pnum_nhops = nhg_priv->nhg_nh_count;
   
           return (nhg_priv->nhg_nh_weights);
   }
   
   void
   nhgrp_set_uidx(struct nhgrp_object *nhg, uint32_t uidx)
   {
           struct nhgrp_priv *nhg_priv;
   
           KASSERT(((nhg->nhg_flags & MPF_MULTIPATH) != 0), ("nhop is not mpath"));
   
           nhg_priv = NHGRP_PRIV(nhg);
   
           nhg_priv->nhg_uidx = uidx;
   }
   
   uint32_t
   nhgrp_get_uidx(const struct nhgrp_object *nhg)
   {
           const struct nhgrp_priv *nhg_priv;
   
           KASSERT(((nhg->nhg_flags & MPF_MULTIPATH) != 0), ("nhop is not mpath"));
   
           nhg_priv = NHGRP_PRIV_CONST(nhg);
           return (nhg_priv->nhg_uidx);
   }
   
   /*
    * Prints nexhop group @nhg data in the provided @buf.
    * Example: nhg#33/sz=3:[#1:100,#2:100,#3:100]
    * Example: nhg#33/sz=5:[#1:100,#2:100,..]
    */
   char *
   nhgrp_print_buf(const struct nhgrp_object *nhg, char *buf, size_t bufsize)
   {
           const struct nhgrp_priv *nhg_priv = NHGRP_PRIV_CONST(nhg);
   
           int off = snprintf(buf, bufsize, "nhg#%u/sz=%u:[", nhg_priv->nhg_idx,
               nhg_priv->nhg_nh_count);
   
           for (int i = 0; i < nhg_priv->nhg_nh_count; i++) {
                   const struct weightened_nhop *wn = &nhg_priv->nhg_nh_weights[i];
                   int len = snprintf(&buf[off], bufsize - off, "#%u:%u,",
                       wn->nh->nh_priv->nh_idx, wn->weight);
                   if (len + off + 3 >= bufsize) {
                           int len = snprintf(&buf[off], bufsize - off, "...");
                           off += len;
                           break;
                   }
                   off += len;
           }
           if (off > 0)
                   off--; // remove last ","
           if (off + 1 < bufsize)
                   snprintf(&buf[off], bufsize - off, "]");
           return buf;
   }
   
   __noinline static int
   dump_nhgrp_entry(struct rib_head *rh, const struct nhgrp_priv *nhg_priv,
       char *buffer, size_t buffer_size, struct sysctl_req *w)
   {
           struct rt_msghdr *rtm;
           struct nhgrp_external *nhge;
           struct nhgrp_container *nhgc;
           const struct nhgrp_object *nhg;
           struct nhgrp_nhop_external *ext;
           int error;
           size_t sz;
   
           nhg = nhg_priv->nhg;
   
           sz = sizeof(struct rt_msghdr) + sizeof(struct nhgrp_external);
           /* controlplane nexthops */
           sz += sizeof(struct nhgrp_container);
           sz += sizeof(struct nhgrp_nhop_external) * nhg_priv->nhg_nh_count;
           /* dataplane nexthops */
           sz += sizeof(struct nhgrp_container);
           sz += sizeof(struct nhgrp_nhop_external) * nhg->nhg_size;
   
           KASSERT(sz <= buffer_size, ("increase nhgrp buffer size"));
   
           bzero(buffer, sz);
   
           rtm = (struct rt_msghdr *)buffer;
           rtm->rtm_msglen = sz;
           rtm->rtm_version = RTM_VERSION;
           rtm->rtm_type = RTM_GET;
   
           nhge = (struct nhgrp_external *)(rtm + 1);
   
           nhge->nhg_idx = nhg_priv->nhg_idx;
           nhge->nhg_refcount = nhg_priv->nhg_refcount;
   
           /* fill in control plane nexthops firs */
           nhgc = (struct nhgrp_container *)(nhge + 1);
           nhgc->nhgc_type = NHG_C_TYPE_CNHOPS;
           nhgc->nhgc_subtype = 0;
           nhgc->nhgc_len = sizeof(struct nhgrp_container);
           nhgc->nhgc_len += sizeof(struct nhgrp_nhop_external) * nhg_priv->nhg_nh_count;
           nhgc->nhgc_count = nhg_priv->nhg_nh_count;
   
           ext = (struct nhgrp_nhop_external *)(nhgc + 1);
           for (int i = 0; i < nhg_priv->nhg_nh_count; i++) {
                   ext[i].nh_idx = nhg_priv->nhg_nh_weights[i].nh->nh_priv->nh_idx;
                   ext[i].nh_weight = nhg_priv->nhg_nh_weights[i].weight;
           }
   
           /* fill in dataplane nexthops */
           nhgc = (struct nhgrp_container *)(&ext[nhg_priv->nhg_nh_count]);
           nhgc->nhgc_type = NHG_C_TYPE_DNHOPS;
           nhgc->nhgc_subtype = 0;
           nhgc->nhgc_len = sizeof(struct nhgrp_container);
           nhgc->nhgc_len += sizeof(struct nhgrp_nhop_external) * nhg->nhg_size;
           nhgc->nhgc_count = nhg->nhg_size;
   
           ext = (struct nhgrp_nhop_external *)(nhgc + 1);
           for (int i = 0; i < nhg->nhg_size; i++) {
                   ext[i].nh_idx = nhg->nhops[i]->nh_priv->nh_idx;
                   ext[i].nh_weight = 0;
           }
   
           error = SYSCTL_OUT(w, buffer, sz);
   
           return (error);
   }
   
   uint32_t
   nhgrp_get_idx(const struct nhgrp_object *nhg)
   {
           const struct nhgrp_priv *nhg_priv;
   
           nhg_priv = NHGRP_PRIV_CONST(nhg);
           return (nhg_priv->nhg_idx);
   }
   
   uint8_t
   nhgrp_get_origin(const struct nhgrp_object *nhg)
   {
           return (NHGRP_PRIV_CONST(nhg)->nhg_origin);
   }
   
   void
   nhgrp_set_origin(struct nhgrp_object *nhg, uint8_t origin)
   {
           NHGRP_PRIV(nhg)->nhg_origin = origin;
   }
   
   uint32_t
   nhgrp_get_count(struct rib_head *rh)
   {
           struct nh_control *ctl;
           uint32_t count;
   
           ctl = rh->nh_control;
   
           NHOPS_RLOCK(ctl);
           count = ctl->gr_head.items_count;
           NHOPS_RUNLOCK(ctl);
   
           return (count);
   }
   
   int
   nhgrp_dump_sysctl(struct rib_head *rh, struct sysctl_req *w)
   {
           struct nh_control *ctl = rh->nh_control;
           struct epoch_tracker et;
           struct nhgrp_priv *nhg_priv;
           char *buffer;
           size_t sz;
           int error = 0;
   
           if (ctl->gr_head.items_count == 0)
                   return (0);
   
           /* Calculate the maximum nhop group size in bytes */
           sz = sizeof(struct rt_msghdr) + sizeof(struct nhgrp_external);
           sz += 2 * sizeof(struct nhgrp_container);
           sz += 2 * sizeof(struct nhgrp_nhop_external) * RIB_MAX_MPATH_WIDTH;
           buffer = malloc(sz, M_TEMP, M_NOWAIT);
           if (buffer == NULL)
                   return (ENOMEM);
   
           NET_EPOCH_ENTER(et);
           NHOPS_RLOCK(ctl);
           CHT_SLIST_FOREACH(&ctl->gr_head, mpath, nhg_priv) {
                   error = dump_nhgrp_entry(rh, nhg_priv, buffer, sz, w);
                   if (error != 0)
                           break;
           } CHT_SLIST_FOREACH_END;
           NHOPS_RUNLOCK(ctl);
           NET_EPOCH_EXIT(et);
   
           free(buffer, M_TEMP);
   
           return (error);
   }

Cache object: e38c4d103b7556385b8fe16338f39ef9