bird/proto/aggregator/aggregator.c

/*
 *	BIRD Internet Routing Daemon -- Route aggregation
 *
 *	(c) 2023--2023 Igor Putovny <igor.putovny@nic.cz>
 *	(c) 2023       CZ.NIC, z.s.p.o.
 *
 *	Can be freely distributed and used under the terms of the GNU GPL.
 */

/**
 * DOC: Route aggregation
 *
 * This is an implementation of route aggregation functionality.
 * It enables user to specify a set of route attributes in the configuarion file
 * and then, for a given destination (net), aggregate routes with the same
 * values of these attributes into a single multi-path route.
 *
 * Structure &channel contains pointer to aggregation list which is represented
 * by &aggr_list_linearized. In rt_notify_aggregated(), attributes from this
 * list are evaluated for every route of a given net and results are stored
 * in &rte_val_list which contains pointer to this route and array of &f_val.
 * Array of pointers to &rte_val_list entries is sorted using
 * sort_rte_val_list(). For comparison of &f_val structures, val_compare()
 * is used. Comparator function is written so that sorting is stable. If all
 * attributes have the same values, routes are compared by their global IDs.
 *
 * After sorting, &rte_val_list entries containing equivalent routes will be
 * adjacent to each other. Function process_rte_list() iterates through these
 * entries to identify sequences of equivalent routes. New route will be
 * created for each such sequence, even if only from a single route.
 * Only attributes from the aggreagation list will be set for the new route.
 * New &rta is created and prepare_rta() is used to copy static and dynamic
 * attributes to new &rta from &rta of the original route. New route is created
 * by create_merged_rte() from new &rta and exported to the routing table.
 */

#undef LOCAL_DEBUG

#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif

#include "nest/bird.h"
#include "nest/iface.h"
#include "filter/filter.h"
#include "proto/aggregator/aggregator.h"

#include <stdlib.h>
/*
#include "nest/route.h"
#include "nest/iface.h"
#include "lib/resource.h"
#include "lib/event.h"
#include "lib/timer.h"
#include "lib/string.h"
#include "conf/conf.h"
#include "filter/filter.h"
#include "filter/data.h"
#include "lib/hash.h"
#include "lib/string.h"
#include "lib/alloca.h"
#include "lib/flowspec.h"
*/

/* Context of &f_val comparison. */
struct cmp_ctx {
  const struct aggregator_proto *p;
  const struct network *net;
  const int val_count;
  u32 failed:1;
};

extern linpool *rte_update_pool;

/*
 * Set static attribute in @rta from static attribute in @old according to @sa.
 */
static void
rta_set_static_attr(struct rta *rta, const struct rta *old, struct f_static_attr sa)
{
  switch (sa.sa_code)
  {
    case SA_NET:
      break;

    case SA_FROM:
      rta->from = old->from;
      break;

    case SA_GW:
      rta->dest = RTD_UNICAST;
      rta->nh.gw = old->nh.gw;
      rta->nh.iface = old->nh.iface;
      rta->nh.next = NULL;
      rta->hostentry = NULL;
      rta->nh.labels = 0;
      break;

    case SA_SCOPE:
      rta->scope = old->scope;
      break;

    case SA_DEST:
      rta->dest = old->dest;
      rta->nh.gw = IPA_NONE;
      rta->nh.iface = NULL;
      rta->nh.next = NULL;
      rta->hostentry = NULL;
      rta->nh.labels = 0;
      break;

    case SA_IFNAME:
      rta->dest = RTD_UNICAST;
      rta->nh.gw = IPA_NONE;
      rta->nh.iface = old->nh.iface;
      rta->nh.next = NULL;
      rta->hostentry = NULL;
      rta->nh.labels = 0;
      break;

    case SA_GW_MPLS:
      rta->nh.labels = old->nh.labels;
      memcpy(&rta->nh.label, &old->nh.label, sizeof(u32) * old->nh.labels);
      break;

    case SA_WEIGHT:
      rta->nh.weight = old->nh.weight;
      break;

    case SA_PREF:
      rta->pref = old->pref;
      break;

    default:
      bug("Invalid static attribute access (%u/%u)", sa.f_type, sa.sa_code);
  }
}

/*
 * Compare list of &f_val entries.
 * @count: number of &f_val entries
 */
static int
same_val_list(const struct f_val *v1, const struct f_val *v2, uint len)
{
  for (uint i = 0; i < len; i++)
    if (!val_same(&v1[i], &v2[i]))
      return 0;

  return 1;
}

/*
 * Create and export new merged route.
 * @old: first route in a sequence of equivalent routes that are to be merged
 * @rte_val: first element in a sequence of equivalent rte_val_list entries
 * @length: number of equivalent routes that are to be merged (at least 1)
 * @ail: aggregation list
 */
static void
aggregator_bucket_update(struct aggregator_proto *p, struct aggregator_bucket *bucket, struct network *net)
{
  /* Empty bucket */
  if (!bucket->rte)
  {
    rte_update2(p->dst, net->n.addr, NULL, bucket->last_src);
    bucket->last_src = NULL;
    return;
  }

  /* Allocate RTA and EA list */
  struct rta *rta = allocz(rta_size(bucket->rte->attrs));
  rta->dest = RTD_UNREACHABLE;
  rta->source = RTS_AGGREGATED;
  rta->scope = SCOPE_UNIVERSE;

  struct ea_list *eal = allocz(sizeof(struct ea_list) + sizeof(struct eattr) * p->aggr_on_da_count);
  eal->next = NULL;
  eal->count = 0;
  rta->eattrs = eal;

  /* Seed the attributes from aggregator rule */
  for (uint i = 0; i < p->aggr_on_count; i++)
  {
    if (p->aggr_on[i].type == AGGR_ITEM_DYNAMIC_ATTR)
    {
      u32 ea_code = p->aggr_on[i].da.ea_code;
      const struct eattr *e = ea_find(bucket->rte->attrs->eattrs, ea_code);

      if (e)
        eal->attrs[eal->count++] = *e;
    }
    else if (p->aggr_on[i].type == AGGR_ITEM_STATIC_ATTR)
      rta_set_static_attr(rta, bucket->rte->attrs, p->aggr_on[i].sa);
  }

  struct rte *new = rte_get_temp(rta, bucket->rte->src);
  new->net = net;

  log("=============== CREATE MERGED ROUTE ===============");
  log("New route created: id = %d, protocol: %s", new->src->global_id, new->src->proto->name);
  log("===================================================");


  /* merge filter needs one argument called "routes" */
  struct f_val val = {
    .type = T_ROUTES_BLOCK,
    .val.rte = bucket->rte,
  };

  /* Actually run the filter */
  enum filter_return fret = f_eval_rte(p->merge_by, &new, rte_update_pool, 1, &val, 0);

  /* Src must be stored now, rte_update2() may return new */
  struct rte_src *new_src = new ? new->src : NULL;

  /* Finally import the route */
  switch (fret)
  {
    /* Pass the route to the protocol */
    case F_ACCEPT:
      rte_update2(p->dst, net->n.addr, new, bucket->last_src ?: new->src);
      break;

    /* Something bad happened */
    default:
      ASSERT_DIE(fret == F_ERROR);
      /* fall through */

    /* We actually don't want this route */
    case F_REJECT:
      if (bucket->last_src)
	rte_update2(p->dst, net->n.addr, NULL, bucket->last_src);
      break;
  }

  /* Switch source lock for bucket->last_src */
  if (bucket->last_src != new_src)
  {
    if (new_src)
      rt_lock_source(new_src);
    if (bucket->last_src)
      rt_unlock_source(bucket->last_src);

    bucket->last_src = new_src;
  }
}

/*
 * Reload all the buckets on reconfiguration if merge filter has changed.
 * TODO: make this splitted
 */
static void
aggregator_reload_buckets(void *data)
{
  struct aggregator_proto *p = data;

  HASH_WALK(p->buckets, next_hash, b)
    if (b->rte)
      aggregator_bucket_update(p, b, b->rte->net);
  HASH_WALK_END;
}


/*
 * Evaluate static attribute of @rt1 according to @sa
 * and store result in @pos.
 */
static void
eval_static_attr(const struct rte *rt1, struct f_static_attr sa, struct f_val *pos)
{
  const struct rta *rta = rt1->attrs;

#define RESULT(_type, value, result)    \
  do {                                  \
    pos->type = _type;                  \
    pos->val.value = result;            \
  } while (0)

  switch (sa.sa_code)
  {
    case SA_NET:	RESULT(sa.f_type, net, rt1->net->n.addr); break;
    case SA_FROM:       RESULT(sa.f_type, ip, rta->from); break;
    case SA_GW:	        RESULT(sa.f_type, ip, rta->nh.gw); break;
    case SA_PROTO:	    RESULT(sa.f_type, s, rt1->src->proto->name); break;
    case SA_SOURCE:	    RESULT(sa.f_type, i, rta->source); break;
    case SA_SCOPE:	    RESULT(sa.f_type, i, rta->scope); break;
    case SA_DEST:	    RESULT(sa.f_type, i, rta->dest); break;
    case SA_IFNAME:	    RESULT(sa.f_type, s, rta->nh.iface ? rta->nh.iface->name : ""); break;
    case SA_IFINDEX:	RESULT(sa.f_type, i, rta->nh.iface ? rta->nh.iface->index : 0); break;
    case SA_WEIGHT:	    RESULT(sa.f_type, i, rta->nh.weight + 1); break;
    case SA_PREF:	    RESULT(sa.f_type, i, rta->pref); break;
    case SA_GW_MPLS:    RESULT(sa.f_type, i, rta->nh.labels ? rta->nh.label[0] : MPLS_NULL); break;
    default:
      bug("Invalid static attribute access (%u/%u)", sa.f_type, sa.sa_code);
  }

#undef RESULT
}

/*
 * Evaluate dynamic attribute of @rt1 according to @da
 * and store result in @pos.
 */
static void
eval_dynamic_attr(const struct rte *rt1, struct f_dynamic_attr da, struct f_val *pos)
{
  const struct rta *rta = rt1->attrs;
  const struct eattr *e = ea_find(rta->eattrs, da.ea_code);

#define RESULT(_type, value, result)    \
  do {                                  \
    pos->type = _type;                  \
    pos->val.value = result;            \
  } while (0)

#define RESULT_VOID         \
  do {                      \
    pos->type = T_VOID;     \
  } while (0)

  if (!e)
  {
    /* A special case: undefined as_path looks like empty as_path */
    if (da.type == EAF_TYPE_AS_PATH)
    {
      RESULT(T_PATH, ad, &null_adata);
      return;
    }

    /* The same special case for int_set */
    if (da.type == EAF_TYPE_INT_SET)
    {
      RESULT(T_CLIST, ad, &null_adata);
      return;
    }

    /* The same special case for ec_set */
    if (da.type == EAF_TYPE_EC_SET)
    {
      RESULT(T_ECLIST, ad, &null_adata);
      return;
    }

    /* The same special case for lc_set */
    if (da.type == EAF_TYPE_LC_SET)
    {
      RESULT(T_LCLIST, ad, &null_adata);
      return;
    }

    /* Undefined value */
    RESULT_VOID;
    return;
  }

  switch (e->type & EAF_TYPE_MASK)
  {
    case EAF_TYPE_INT:
      RESULT(da.f_type, i, e->u.data);
      break;
    case EAF_TYPE_ROUTER_ID:
      RESULT(T_QUAD, i, e->u.data);
      break;
    case EAF_TYPE_OPAQUE:
      RESULT(T_ENUM_EMPTY, i, 0);
      break;
    case EAF_TYPE_IP_ADDRESS:
      RESULT(T_IP, ip, *((ip_addr *) e->u.ptr->data));
      break;
    case EAF_TYPE_AS_PATH:
      RESULT(T_PATH, ad, e->u.ptr);
      break;
    case EAF_TYPE_BITFIELD:
      RESULT(T_BOOL, i, !!(e->u.data & (1u << da.bit)));
      break;
    case EAF_TYPE_INT_SET:
      RESULT(T_CLIST, ad, e->u.ptr);
      break;
    case EAF_TYPE_EC_SET:
      RESULT(T_ECLIST, ad, e->u.ptr);
      break;
    case EAF_TYPE_LC_SET:
      RESULT(T_LCLIST, ad, e->u.ptr);
      break;
    default:
      bug("Unknown dynamic attribute type");
  }

#undef RESULT
#undef RESULT_VOID
}

static inline u32 aggr_route_hash(const rte *e)
{
  struct {
    net *net;
    struct rte_src *src;
  } obj = {
    .net = e->net,
    .src = e->src,
  };

  return mem_hash(&obj, sizeof obj);
}

#define AGGR_RTE_KEY(n)			(&(n)->rte)
#define AGGR_RTE_NEXT(n)		((n)->next_hash)
#define AGGR_RTE_EQ(a,b)		(((a)->src == (b)->src) && ((a)->net == (b)->net))
#define AGGR_RTE_FN(_n)			aggr_route_hash(_n)
#define AGGR_RTE_ORDER			4 /* Initial */

#define AGGR_RTE_REHASH			aggr_rte_rehash
#define AGGR_RTE_PARAMS			/8, *2, 2, 2, 4, 24

HASH_DEFINE_REHASH_FN(AGGR_RTE, struct aggregator_route);


#define AGGR_BUCK_KEY(n)		(n)
#define AGGR_BUCK_NEXT(n)		((n)->next_hash)
#define AGGR_BUCK_EQ(a,b)		(((a)->hash == (b)->hash) && (same_val_list((a)->aggr_data, (b)->aggr_data, p->aggr_on_count)))
#define AGGR_BUCK_FN(n)			((n)->hash)
#define AGGR_BUCK_ORDER			4 /* Initial */

#define AGGR_BUCK_REHASH		aggr_buck_rehash
#define AGGR_BUCK_PARAMS		/8, *2, 2, 2, 4, 24

HASH_DEFINE_REHASH_FN(AGGR_BUCK, struct aggregator_bucket);


#define AGGR_DATA_MEMSIZE	(sizeof(struct f_val) * p->aggr_on_count)

static void
aggregator_rt_notify(struct proto *P, struct channel *src_ch, net *net, rte *new, rte *old)
{
  struct aggregator_proto *p = SKIP_BACK(struct aggregator_proto, p, P);
  ASSERT_DIE(src_ch == p->src);
  struct aggregator_bucket *new_bucket = NULL, *old_bucket = NULL;
  struct aggregator_route *old_route = NULL;

  /* Find the objects for the old route */
  if (old)
    old_route = HASH_FIND(p->routes, AGGR_RTE, old);

  if (old_route)
    old_bucket = old_route->bucket;

  /* Find the bucket for the new route */
  if (new)
  {
    /* Routes are identical, do nothing */
    if (old_route && rte_same(&old_route->rte, new))
      return;

    /* Evaluate route attributes. */
    struct aggregator_bucket *tmp_bucket = sl_allocz(p->bucket_slab);

    for (uint val_idx = 0; val_idx < p->aggr_on_count; val_idx++)
    {
      int type = p->aggr_on[val_idx].type;

      switch (type)
      {
        case AGGR_ITEM_TERM: {
          const struct f_line *line = p->aggr_on[val_idx].line;
          struct rte *rt1 = new;
          enum filter_return fret = f_eval_rte(line, &new, rte_update_pool, 0, NULL, &tmp_bucket->aggr_data[val_idx]);

          if (rt1 != new)
          {
            rte_free(rt1);
            log(L_WARN "Aggregator rule modifies the route, reverting");
          }

          if (fret > F_RETURN)
            log(L_WARN "%s.%s: Wrong number of items left on stack after evaluation of aggregation list", rt1->src->proto->name, rt1->sender);

          break;
        }

        case AGGR_ITEM_STATIC_ATTR: {
          struct f_val *pos = &tmp_bucket->aggr_data[val_idx];
          eval_static_attr(new, p->aggr_on[val_idx].sa, pos);
          break;
        }

        case AGGR_ITEM_DYNAMIC_ATTR: {
          struct f_val *pos = &tmp_bucket->aggr_data[val_idx];
          eval_dynamic_attr(new, p->aggr_on[val_idx].da, pos);
          break;
        }

        default:
          break;
      }
    }

    /* Compute the hash */
    tmp_bucket->hash = mem_hash(tmp_bucket->aggr_data, AGGR_DATA_MEMSIZE);

    /* Find the existing bucket */
    if (new_bucket = HASH_FIND(p->buckets, AGGR_BUCK, tmp_bucket))
      sl_free(tmp_bucket);
    else
    {
      new_bucket = tmp_bucket;
      HASH_INSERT2(p->buckets, AGGR_BUCK, p->p.pool, new_bucket);
    }

    /* Store the route attributes */
    if (rta_is_cached(new->attrs))
      rta_clone(new->attrs);
    else
      new->attrs = rta_lookup(new->attrs);

    /* Insert the new route into the bucket */
    struct aggregator_route *arte = sl_alloc(p->route_slab);
    *arte = (struct aggregator_route) {
      .bucket = new_bucket,
      .rte = *new,
    };
    arte->rte.next = new_bucket->rte,
    new_bucket->rte = &arte->rte;
    new_bucket->count++;
    HASH_INSERT2(p->routes, AGGR_RTE, p->p.pool, arte);
  }

  /* Remove the old route from its bucket */
  if (old_bucket)
  {
    for (struct rte **k = &old_bucket->rte; *k; k = &(*k)->next)
      if (*k == &old_route->rte)
      {
	*k = (*k)->next;
	break;
      }

    old_bucket->count--;
    HASH_REMOVE2(p->routes, AGGR_RTE, p->p.pool, old_route);
    rta_free(old_route->rte.attrs);
    sl_free(old_route);
  }

  /* Announce changes */
  if (old_bucket)
    aggregator_bucket_update(p, old_bucket, net);

  if (new_bucket && (new_bucket != old_bucket))
    aggregator_bucket_update(p, new_bucket, net);

  /* Cleanup the old bucket if empty */
  if (old_bucket && (!old_bucket->rte || !old_bucket->count))
  {
    ASSERT_DIE(!old_bucket->rte && !old_bucket->count);
    HASH_REMOVE2(p->buckets, AGGR_BUCK, p->p.pool, old_bucket);
    sl_free(old_bucket);
  }
}

static int
aggregator_preexport(struct channel *C, struct rte *new)
{
  struct aggregator_proto *p = SKIP_BACK(struct aggregator_proto, p, C->proto);
  /* Reject our own routes */
  if (new->sender == p->dst)
    return -1;

  /* Disallow aggregating already aggregated routes */
  if (new->attrs->source == RTS_AGGREGATED)
  {
    log(L_ERR "Multiple aggregations of the same route not supported in BIRD 2.");
    return -1;
  }

  return 0;
}

static void
aggregator_postconfig(struct proto_config *CF)
{
  struct aggregator_config *cf = SKIP_BACK(struct aggregator_config, c, CF);

  if (!cf->dst->table)
    cf_error("Source table not specified");

  if (!cf->src->table)
    cf_error("Destination table not specified");

  if (cf->dst->table->addr_type != cf->src->table->addr_type)
    cf_error("Both tables must be of the same type");

  cf->dst->in_filter = cf->src->in_filter;

  cf->src->in_filter = FILTER_REJECT;
  cf->dst->out_filter = FILTER_REJECT;

  cf->dst->debug = cf->src->debug;
}

static struct proto *
aggregator_init(struct proto_config *CF)
{
  struct proto *P = proto_new(CF);
  struct aggregator_proto *p = SKIP_BACK(struct aggregator_proto, p, P);
  struct aggregator_config *cf = SKIP_BACK(struct aggregator_config, c, CF);

  proto_configure_channel(P, &p->src, cf->src);
  proto_configure_channel(P, &p->dst, cf->dst);

  p->aggr_on_count = cf->aggr_on_count;
  p->aggr_on_da_count = cf->aggr_on_da_count;
  p->aggr_on = cf->aggr_on;
  p->merge_by = cf->merge_by;

  P->rt_notify = aggregator_rt_notify;
  P->preexport = aggregator_preexport;

  return P;
}

static int
aggregator_start(struct proto *P)
{
  struct aggregator_proto *p = SKIP_BACK(struct aggregator_proto, p, P);

  p->bucket_slab = sl_new(P->pool, sizeof(struct aggregator_bucket) + AGGR_DATA_MEMSIZE);
  HASH_INIT(p->buckets, P->pool, AGGR_BUCK_ORDER);

  p->route_slab = sl_new(P->pool, sizeof(struct aggregator_route));
  HASH_INIT(p->routes, P->pool, AGGR_RTE_ORDER);

  p->reload_buckets = (event) {
    .hook = aggregator_reload_buckets,
    .data = p,
  };

  return PS_UP;
}

static int
aggregator_shutdown(struct proto *P)
{
  struct aggregator_proto *p = SKIP_BACK(struct aggregator_proto, p, P);

  HASH_WALK_DELSAFE(p->buckets, next_hash, b)
  {
    while (b->rte)
    {
      struct aggregator_route *arte = SKIP_BACK(struct aggregator_route, rte, b->rte);
      b->rte = arte->rte.next;
      b->count--;
      HASH_REMOVE(p->routes, AGGR_RTE, arte);
      rta_free(arte->rte.attrs);
      sl_free(arte);
    }

    ASSERT_DIE(b->count == 0);
    HASH_REMOVE(p->buckets, AGGR_BUCK, b);
    sl_free(b);
  }
  HASH_WALK_END;

  return PS_DOWN;
}

static int
aggregator_reconfigure(struct proto *P, struct proto_config *CF)
{
  struct aggregator_proto *p = SKIP_BACK(struct aggregator_proto, p, P);
  struct aggregator_config *cf = SKIP_BACK(struct aggregator_config, c, CF);

  TRACE(D_EVENTS, "Reconfiguring");

  /* Compare numeric values (shortcut) */
  if (cf->aggr_on_count != p->aggr_on_count)
    return 0;

  if (cf->aggr_on_da_count != p->aggr_on_da_count)
    return 0;

  /* Compare aggregator rule */
  for (uint i = 0; i < p->aggr_on_count; i++)
    switch (cf->aggr_on[i].type)
    {
      case AGGR_ITEM_TERM:
	if (!f_same(cf->aggr_on[i].line, p->aggr_on[i].line))
	  return 0;
	break;
      case AGGR_ITEM_STATIC_ATTR:
	if (memcmp(&cf->aggr_on[i].sa, &p->aggr_on[i].sa, sizeof(struct f_static_attr)) != 0)
	  return 0;
	break;
      case AGGR_ITEM_DYNAMIC_ATTR:
	if (memcmp(&cf->aggr_on[i].da, &p->aggr_on[i].da, sizeof(struct f_dynamic_attr)) != 0)
	  return 0;
	break;
      default:
	bug("Broken aggregator rule");
    }

  /* Compare merge filter */
  if (!f_same(cf->merge_by, p->merge_by))
    ev_schedule(&p->reload_buckets);

  p->aggr_on = cf->aggr_on;
  p->merge_by = cf->merge_by;

  return 1;
}

struct protocol proto_aggregator = {
  .name =		"Aggregator",
  .template =		"aggregator%d",
  .class =		PROTOCOL_AGGREGATOR,
  .preference =		1,
  .channel_mask =	NB_ANY,
  .proto_size =		sizeof(struct aggregator_proto),
  .config_size =	sizeof(struct aggregator_config),
  .postconfig =		aggregator_postconfig,
  .init =		aggregator_init,
  .start =		aggregator_start,
  .shutdown =		aggregator_shutdown,
  .reconfigure =	aggregator_reconfigure,
};

void
aggregator_build(void)
{
  proto_build(&proto_aggregator);
}