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bgpd: Fix import check removal

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Fix: 06e4e90132

Modified BGP to pay more attention the prefix returned from
zebra to ensure that a LPM wasn't accidently causing BGP
import checks to think it had a match when it did not.
This unfortunately removed the check to handle the route
removal.

This sequence of config and events would leave BGP in a bad state:
ip route 100.100.100.0/24 Null0
router bgp 32932
  bgp network import-check
  address-family ipv4 uni
    network 100.100.100.0/24

Then if you removed the static route the import check would
still think the route existed:

donatas-pc(config)# ip route 100.100.100.0/24 Null0

donatas-pc(config)# do sh ip bgp import-check-table
Current BGP import check cache:
 100.100.100.0 valid [IGP metric 0], #paths 1
  blackhole
  Last update: Sat Apr 23 22:51:34 2022

donatas-pc(config)# do sh ip nht
100.100.100.0
 resolved via static
 is directly connected, Null0
 Client list: bgp(fd 17)

donatas-pc(config)# do sh ip bgp neighbors 192.168.10.123 advertised-routes | include 100.100.100.0
*> 100.100.100.0/24 0.0.0.0                  0         32768 i

donatas-pc(config)# no ip route 100.100.100.0/24 Null0

donatas-pc(config)# do sh ip nht
100.100.100.0
 resolved via kernel
 via 192.168.10.1, enp3s0
 Client list: bgp(fd 17)

donatas-pc(config)# do sh ip bgp import-check-table
Current BGP import check cache:
 100.100.100.0 valid [IGP metric 0], #paths 1
  blackhole
  Last update: Sat Apr 23 22:51:34 2022

donatas-pc(config)# do sh ip bgp neighbors 192.168.10.123 advertised-routes | include 100.100.100.0
*> 100.100.100.0/24 0.0.0.0                  0         32768 i
donatas-pc(config)#

Fix this by moving the code to handle the prefix check to the
evaluation function and mark the bnc as not matching and actually
evaluate the bnc.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>
This commit is contained in:
Donald Sharp 2022-04-24 16:52:46 -04:00
parent c27892b24d
commit 9f002fa5dd
1 changed files with 20 additions and 14 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

34
bgpd/bgp_nht.c
View file

@ -390,7 +390,8 @@ void bgp_delete_connected_nexthop(afi_t afi, struct peer *peer)
}
static void bgp_process_nexthop_update(struct bgp_nexthop_cache *bnc,
struct zapi_route *nhr)
struct zapi_route *nhr,
bool import_check)
{
struct nexthop *nexthop;
struct nexthop *oldnh;
@ -421,7 +422,21 @@ static void bgp_process_nexthop_update(struct bgp_nexthop_cache *bnc,
if (nhr->nexthop_num != bnc->nexthop_num)
bnc->change_flags |= BGP_NEXTHOP_CHANGED;
if (nhr->nexthop_num) {
if (import_check && (nhr->type == ZEBRA_ROUTE_BGP ||
!prefix_same(&bnc->prefix, &nhr->prefix))) {
SET_FLAG(bnc->change_flags, BGP_NEXTHOP_CHANGED);
UNSET_FLAG(bnc->flags, BGP_NEXTHOP_VALID);
UNSET_FLAG(bnc->flags, BGP_NEXTHOP_LABELED_VALID);
UNSET_FLAG(bnc->flags, BGP_NEXTHOP_EVPN_INCOMPLETE);
bnc_nexthop_free(bnc);
bnc->nexthop = NULL;
if (BGP_DEBUG(nht, NHT))
zlog_debug(
"%s: Import Check does not resolve to the same prefix for %pFX received %pFX or matching route is BGP",
__func__, &bnc->prefix, &nhr->prefix);
} else if (nhr->nexthop_num) {
struct peer *peer = bnc->nht_info;
/* notify bgp fsm if nbr ip goes from invalid->valid */
@ -695,7 +710,7 @@ void bgp_parse_nexthop_update(int command, vrf_id_t vrf_id)
"parse nexthop update(%pFX(%u)(%s)): bnc info not found for nexthop cache",
&nhr.prefix, nhr.srte_color, bgp->name_pretty);
} else
bgp_process_nexthop_update(bnc_nhc, &nhr);
bgp_process_nexthop_update(bnc_nhc, &nhr, false);
tree = &bgp->import_check_table[afi];
@ -706,17 +721,8 @@ void bgp_parse_nexthop_update(int command, vrf_id_t vrf_id)
"parse nexthop update(%pFX(%u)(%s)): bnc info not found for import check",
&nhr.prefix, nhr.srte_color, bgp->name_pretty);
return;
} else {
if (nhr.type == ZEBRA_ROUTE_BGP
|| !prefix_same(&bnc_import->prefix, &nhr.prefix)) {
if (BGP_DEBUG(nht, NHT))
zlog_debug(
"%s: Import Check does not resolve to the same prefix for %pFX received %pFX",
__func__, &bnc_import->prefix, &nhr.prefix);
return;
}
bgp_process_nexthop_update(bnc_import, &nhr);
}
bgp_process_nexthop_update(bnc_import, &nhr, true);
/*
* HACK: if any BGP route is dependant on an SR-policy that doesn't
@ -739,7 +745,7 @@ void bgp_parse_nexthop_update(int command, vrf_id_t vrf_id)
|| CHECK_FLAG(bnc_iter->flags, BGP_NEXTHOP_VALID))
continue;
bgp_process_nexthop_update(bnc_iter, &nhr);
bgp_process_nexthop_update(bnc_iter, &nhr, false);
}
}
}