diff --git a/pimd/pim_rpf.c b/pimd/pim_rpf.c
new file mode 100644
index 0000000..7fdeecf
--- /dev/null
+++ b/pimd/pim_rpf.c
@@ -0,0 +1,254 @@
+/*
+  PIM for Quagga
+  Copyright (C) 2008  Everton da Silva Marques
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  General Public License for more details.
+  
+  You should have received a copy of the GNU General Public License
+  along with this program; see the file COPYING; if not, write to the
+  Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
+  MA 02110-1301 USA
+  
+  $QuaggaId: $Format:%an, %ai, %h$ $
+*/
+
+#include <zebra.h>
+
+#include "log.h"
+#include "prefix.h"
+#include "memory.h"
+
+#include "pimd.h"
+#include "pim_rpf.h"
+#include "pim_pim.h"
+#include "pim_str.h"
+#include "pim_iface.h"
+#include "pim_zlookup.h"
+#include "pim_ifchannel.h"
+
+static struct in_addr pim_rpf_find_rpf_addr(struct pim_upstream *up);
+
+int pim_nexthop_lookup(struct pim_nexthop *nexthop,
+		       struct in_addr addr)
+{
+  struct pim_zlookup_nexthop nexthop_tab[PIM_NEXTHOP_IFINDEX_TAB_SIZE];
+  int num_ifindex;
+  struct interface *ifp;
+  int first_ifindex;
+
+  num_ifindex = zclient_lookup_nexthop(qpim_zclient_lookup, nexthop_tab,
+				       PIM_NEXTHOP_IFINDEX_TAB_SIZE,
+				       addr, PIM_NEXTHOP_LOOKUP_MAX);
+  if (num_ifindex < 1) {
+    char addr_str[100];
+    pim_inet4_dump("<addr?>", addr, addr_str, sizeof(addr_str));
+    zlog_warn("%s %s: could not find nexthop ifindex for address %s",
+	      __FILE__, __PRETTY_FUNCTION__,
+	      addr_str);
+    return -1;
+  }
+
+  first_ifindex = nexthop_tab[0].ifindex;
+
+  if (num_ifindex > 1) {
+    char addr_str[100];
+    pim_inet4_dump("<addr?>", addr, addr_str, sizeof(addr_str));
+    zlog_debug("%s %s: FIXME ignoring multiple nexthop ifindex'es num_ifindex=%d for address %s (using only ifindex=%d)",
+	      __FILE__, __PRETTY_FUNCTION__,
+	      num_ifindex, addr_str, first_ifindex);
+    /* debug warning only, do not return */
+  }
+
+  ifp = if_lookup_by_index(first_ifindex);
+  if (!ifp) {
+    char addr_str[100];
+    pim_inet4_dump("<addr?>", addr, addr_str, sizeof(addr_str));
+    zlog_warn("%s %s: could not find interface for ifindex %d (address %s)",
+	      __FILE__, __PRETTY_FUNCTION__,
+	      first_ifindex, addr_str);
+    return -2;
+  }
+
+  if (!ifp->info) {
+    char addr_str[100];
+    pim_inet4_dump("<addr?>", addr, addr_str, sizeof(addr_str));
+    zlog_warn("%s: multicast not enabled on input interface %s (ifindex=%d, RPF for source %s)",
+	      __PRETTY_FUNCTION__,
+	      ifp->name, first_ifindex, addr_str);
+    /* debug warning only, do not return */
+  }
+
+  if (PIM_DEBUG_PIM_TRACE) {
+    char nexthop_str[100];
+    char addr_str[100];
+    pim_inet4_dump("<nexthop?>", nexthop_tab[0].nexthop_addr, nexthop_str, sizeof(nexthop_str));
+    pim_inet4_dump("<addr?>", addr, addr_str, sizeof(addr_str));
+    zlog_debug("%s %s: found nexthop %s for address %s: interface %s ifindex=%d metric=%d pref=%d",
+	       __FILE__, __PRETTY_FUNCTION__,
+	       nexthop_str, addr_str,
+	       ifp->name, first_ifindex,
+	       nexthop_tab[0].route_metric,
+	       nexthop_tab[0].protocol_distance);
+  }
+
+  /* update nextop data */
+  nexthop->interface              = ifp;
+  nexthop->mrib_nexthop_addr      = nexthop_tab[0].nexthop_addr;
+  nexthop->mrib_metric_preference = nexthop_tab[0].protocol_distance;
+  nexthop->mrib_route_metric      = nexthop_tab[0].route_metric;
+
+  return 0;
+}
+
+static int nexthop_mismatch(const struct pim_nexthop *nh1,
+			    const struct pim_nexthop *nh2)
+{
+  return (nh1->interface != nh2->interface) 
+    ||
+    (nh1->mrib_nexthop_addr.s_addr != nh2->mrib_nexthop_addr.s_addr)
+    ||
+    (nh1->mrib_metric_preference != nh2->mrib_metric_preference)
+    ||
+    (nh1->mrib_route_metric != nh2->mrib_route_metric);
+}
+
+enum pim_rpf_result pim_rpf_update(struct pim_upstream *up,
+				   struct in_addr *old_rpf_addr)
+{
+  struct in_addr      save_rpf_addr;
+  struct pim_nexthop  save_nexthop;
+  struct pim_rpf     *rpf = &up->rpf;
+
+  save_nexthop  = rpf->source_nexthop; /* detect change in pim_nexthop */
+  save_rpf_addr = rpf->rpf_addr;       /* detect change in RPF'(S,G) */
+
+  if (pim_nexthop_lookup(&rpf->source_nexthop,
+			 up->source_addr)) {
+    return PIM_RPF_FAILURE;
+  }
+
+  rpf->rpf_addr = pim_rpf_find_rpf_addr(up);
+  if (PIM_INADDR_IS_ANY(rpf->rpf_addr)) {
+    /* RPF'(S,G) not found */
+    char src_str[100];
+    char grp_str[100];
+    pim_inet4_dump("<src?>", up->source_addr, src_str, sizeof(src_str));
+    pim_inet4_dump("<grp?>", up->group_addr, grp_str, sizeof(grp_str));
+    zlog_warn("%s %s: RPF'(%s,%s) not found: won't send join upstream",
+              __FILE__, __PRETTY_FUNCTION__,
+              src_str, grp_str);
+    /* warning only */
+  }
+
+  /* detect change in pim_nexthop */
+  if (nexthop_mismatch(&rpf->source_nexthop, &save_nexthop)) {
+    char src_str[100];
+    char grp_str[100];
+    char nhaddr_str[100];
+    pim_inet4_dump("<src?>", up->source_addr, src_str, sizeof(src_str));
+    pim_inet4_dump("<grp?>", up->group_addr, grp_str, sizeof(grp_str));
+    pim_inet4_dump("<addr?>", rpf->source_nexthop.mrib_nexthop_addr, nhaddr_str, sizeof(nhaddr_str));
+    zlog_warn("%s %s: (S,G)=(%s,%s) source nexthop now is: interface=%s address=%s pref=%d metric=%d",
+              __FILE__, __PRETTY_FUNCTION__,
+              src_str, grp_str,
+	      rpf->source_nexthop.interface ? rpf->source_nexthop.interface->name : "<ifname?>",
+	      nhaddr_str,
+	      rpf->source_nexthop.mrib_metric_preference,
+	      rpf->source_nexthop.mrib_route_metric);
+    /* warning only */
+
+    pim_upstream_update_join_desired(up);
+    pim_upstream_update_could_assert(up);
+    pim_upstream_update_my_assert_metric(up);
+  }
+
+  /* detect change in RPF_interface(S) */
+  if (save_nexthop.interface != rpf->source_nexthop.interface) {
+    char src_str[100];
+    char grp_str[100];
+    pim_inet4_dump("<src?>", up->source_addr, src_str, sizeof(src_str));
+    pim_inet4_dump("<grp?>", up->group_addr, grp_str, sizeof(grp_str));
+    zlog_warn("%s %s: (S,G)=(%s,%s) RPF_interface(S) changed from %s to %s",
+              __FILE__, __PRETTY_FUNCTION__,
+              src_str, grp_str,
+	      save_nexthop.interface ? save_nexthop.interface->name : "<oldif?>",
+	      rpf->source_nexthop.interface ? rpf->source_nexthop.interface->name : "<newif?>");
+    /* warning only */
+
+    pim_upstream_rpf_interface_changed(up, save_nexthop.interface);
+  }
+
+  /* detect change in RPF'(S,G) */
+  if (save_rpf_addr.s_addr != rpf->rpf_addr.s_addr) {
+
+    /* return old rpf to caller ? */
+    if (old_rpf_addr)
+      *old_rpf_addr = save_rpf_addr;
+
+    return PIM_RPF_CHANGED;
+  }
+
+  return PIM_RPF_OK;
+}
+
+/*
+  RFC 4601: 4.1.6.  State Summarization Macros
+
+     neighbor RPF'(S,G) {
+         if ( I_Am_Assert_Loser(S, G, RPF_interface(S) )) {
+              return AssertWinner(S, G, RPF_interface(S) )
+         } else {
+              return NBR( RPF_interface(S), MRIB.next_hop( S ) )
+         }
+     }
+
+  RPF'(*,G) and RPF'(S,G) indicate the neighbor from which data
+  packets should be coming and to which joins should be sent on the RP
+  tree and SPT, respectively.
+*/
+static struct in_addr pim_rpf_find_rpf_addr(struct pim_upstream *up)
+{
+  struct pim_ifchannel *rpf_ch;
+  struct pim_neighbor *neigh;
+  struct in_addr rpf_addr;
+
+  if (!up->rpf.source_nexthop.interface) {
+    char src_str[100];
+    char grp_str[100];
+    pim_inet4_dump("<src?>", up->source_addr, src_str, sizeof(src_str));
+    pim_inet4_dump("<grp?>", up->group_addr, grp_str, sizeof(grp_str));
+    zlog_warn("%s: missing RPF interface for upstream (S,G)=(%s,%s)",
+	      __PRETTY_FUNCTION__,
+	      src_str, grp_str);
+
+    rpf_addr.s_addr = PIM_NET_INADDR_ANY;
+    return rpf_addr;
+  }
+
+  rpf_ch = pim_ifchannel_find(up->rpf.source_nexthop.interface,
+			      up->source_addr, up->group_addr);
+  if (rpf_ch) {
+    if (rpf_ch->ifassert_state == PIM_IFASSERT_I_AM_LOSER) {
+      return rpf_ch->ifassert_winner;
+    }
+  }
+
+  /* return NBR( RPF_interface(S), MRIB.next_hop( S ) ) */
+
+  neigh = pim_if_find_neighbor(up->rpf.source_nexthop.interface,
+			       up->rpf.source_nexthop.mrib_nexthop_addr);
+  if (neigh)
+    rpf_addr = neigh->source_addr;
+  else
+    rpf_addr.s_addr = PIM_NET_INADDR_ANY;
+
+  return rpf_addr;
+}