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Set 'rr_client' and 'next_hop_self' attributes on BGP neighbor data #2575

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Merged
ipspace merged 1 commit into from
Aug 6, 2025
Merged

Set 'rr_client' and 'next_hop_self' attributes on BGP neighbor data #2575

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59 changes: 28 additions & 31 deletions netsim/modules/bgp.py
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Original file line number Diff line number Diff line change
Expand Up @@ -178,38 +178,32 @@ def get_remote_ibgp_endpoint(n: Box) -> Box:
* Other nodes need IBGP sessions with all RRs in the same AS
"""
def build_ibgp_sessions(node: Box, sessions: Box, topology: Box) -> None:
rrlist = find_bgp_rr(node.bgp.get("as"),topology)
has_ibgp = False # Assume we have no IBGP sessions (yet)

# If we don't have route reflectors, or if the current node is a route
# reflector, we need BGP sessions to all other nodes in the same AS
if not(rrlist) or node.bgp.get("rr",None):
for name,n in topology.nodes.items():
if "bgp" in n:
if n.bgp.get("as") == node.bgp.get("as") and n.name != node.name:
n_intf = get_remote_ibgp_endpoint(n)
neighbor_data = bgp_neighbor(n,n_intf,'ibgp',sessions,get_neighbor_rr(n))
if not neighbor_data is None:
if 'loopback' in node:
neighbor_data._source_intf = node.loopback
node.bgp.neighbors.append(neighbor_data)
has_ibgp = True

#
# The node is not a route reflector, and we have a non-empty RR list
# We need BGP sessions with the route reflectors
node_as = node.bgp['as'] # Set up variables that will come handy, starting with node AS
is_rr = node.bgp.get("rr",None) # Is this node an RR?
bgp_nhs = node.bgp.get("next_hop_self",None) # Do we have to set next hop on IBGP sessions?
rrlist = [] if is_rr else find_bgp_rr(node_as,topology)

if is_rr or not rrlist: # If the current node is RR or we have a full mesh
ibgp_ngb_list = [ # ... we need IBGP sessions to all nodes in the AS
ngb for ngb in topology.nodes.values() # ... but while building the node list
if ngb.name != node.name and # ... skip current node
ngb.get('bgp.as',None) == node_as] # ... and everyone not in the current AS (or not running BGP)
else:
for n in rrlist:
if n.name != node.name:
n_intf = get_remote_ibgp_endpoint(n)
neighbor_data = bgp_neighbor(n,n_intf,'ibgp',sessions,get_neighbor_rr(n))
if not neighbor_data is None:
if 'loopback' in node:
neighbor_data._source_intf = node.loopback
node.bgp.neighbors.append(neighbor_data)
has_ibgp = True

if not has_ibgp:
ibgp_ngb_list = rrlist

for n in ibgp_ngb_list:
n_intf = get_remote_ibgp_endpoint(n)
neighbor_data = bgp_neighbor(n,n_intf,'ibgp',sessions,get_neighbor_rr(n))
if not neighbor_data is None:
if 'loopback' in node:
neighbor_data._source_intf = node.loopback
if bgp_nhs:
neighbor_data.next_hop_self = True
if is_rr and not 'rr' in neighbor_data:
neighbor_data.rr_client = True
node.bgp.neighbors.append(neighbor_data)

if not ibgp_ngb_list:
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@jbemmel jbemmel Aug 8, 2025 •
edited
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This change leads to a warning about missing IGP even though the topology specifies bgp.sessions.ipv4: [ ebgp ] to exclude any IBGP sessions

The difference seems to be that the has_ibgp flag wouldn't get set in that case, but the new ibgp_ngb_list contains nodes even though the bgp.sessions parameter says those sessions shouldn't get built

return

# Do we have to warn the user that IBGP sessions work better with IGP?
Expand Down Expand Up @@ -387,6 +381,9 @@ def build_ebgp_sessions(node: Box, sessions: Box, topology: Box) -> None:
ebgp_data = bgp_neighbor(neighbor,ngb_ifdata,session_type,sessions,extra_data)
if not ebgp_data is None:
ebgp_data['as'] = neighbor_local_as
if session_type == 'localas_ibgp':
ebgp_data.rr_client = True
ebgp_data.next_hop_self = 'all'
if intf_vrf : # VRF neighbor
if node.vrfs[l.vrf].bgp is False: # Is BGP disabled for this VRF?
continue # ... yeah, move on
Expand Down
2 changes: 2 additions & 0 deletions tests/topology/expected/6pe.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -358,6 +358,7 @@ nodes:
as: 65000
ipv4: 10.0.0.2
name: pe2
next_hop_self: true
type: ibgp
- activate:
ipv4: true
Expand Down Expand Up @@ -473,6 +474,7 @@ nodes:
as: 65000
ipv4: 10.0.0.1
name: pe1
next_hop_self: true
type: ibgp
- activate:
ipv4: true
Expand Down
12 changes: 12 additions & 0 deletions tests/topology/expected/addressing-ipv6-only.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,7 @@ nodes:
as: 65000
ipv6: 2001:db8:0:15::1
name: r2
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -151,6 +152,7 @@ nodes:
as: 65000
ipv6: 2001:db8:0:2a::1
name: r3
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -166,6 +168,7 @@ nodes:
as: 65000
ipv6: 2001:db8:0:1::1
name: r4
next_hop_self: true
type: ibgp
next_hop_self: true
router_id: 10.0.0.7
Expand Down Expand Up @@ -291,6 +294,7 @@ nodes:
as: 65000
ipv6: 2001:db8:0:7::1
name: r1
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -306,6 +310,7 @@ nodes:
as: 65000
ipv6: 2001:db8:0:2a::1
name: r3
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -321,6 +326,7 @@ nodes:
as: 65000
ipv6: 2001:db8:0:1::1
name: r4
next_hop_self: true
type: ibgp
next_hop_self: true
router_id: 10.0.0.21
Expand Down Expand Up @@ -443,6 +449,7 @@ nodes:
as: 65000
ipv6: 2001:db8:0:7::1
name: r1
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -458,6 +465,7 @@ nodes:
as: 65000
ipv6: 2001:db8:0:15::1
name: r2
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -473,6 +481,7 @@ nodes:
as: 65000
ipv6: 2001:db8:0:1::1
name: r4
next_hop_self: true
type: ibgp
next_hop_self: true
router_id: 10.0.0.42
Expand Down Expand Up @@ -573,6 +582,7 @@ nodes:
as: 65000
ipv6: 2001:db8:0:7::1
name: r1
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -588,6 +598,7 @@ nodes:
as: 65000
ipv6: 2001:db8:0:15::1
name: r2
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -603,6 +614,7 @@ nodes:
as: 65000
ipv6: 2001:db8:0:2a::1
name: r3
next_hop_self: true
type: ibgp
next_hop_self: true
router_id: 10.0.0.1
Expand Down
12 changes: 12 additions & 0 deletions tests/topology/expected/addressing-ipv6-prefix.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -112,6 +112,7 @@ nodes:
as: 65000
ipv6: 2001:db8::15
name: r2
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -127,6 +128,7 @@ nodes:
as: 65000
ipv6: 2001:db8::2a
name: r3
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -142,6 +144,7 @@ nodes:
as: 65000
ipv6: 2001:db8::1
name: r4
next_hop_self: true
type: ibgp
next_hop_self: true
router_id: 10.0.0.7
Expand Down Expand Up @@ -236,6 +239,7 @@ nodes:
as: 65000
ipv6: 2001:db8::7
name: r1
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -251,6 +255,7 @@ nodes:
as: 65000
ipv6: 2001:db8::2a
name: r3
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -266,6 +271,7 @@ nodes:
as: 65000
ipv6: 2001:db8::1
name: r4
next_hop_self: true
type: ibgp
next_hop_self: true
router_id: 10.0.0.21
Expand Down Expand Up @@ -373,6 +379,7 @@ nodes:
as: 65000
ipv6: 2001:db8::7
name: r1
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -388,6 +395,7 @@ nodes:
as: 65000
ipv6: 2001:db8::15
name: r2
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -403,6 +411,7 @@ nodes:
as: 65000
ipv6: 2001:db8::1
name: r4
next_hop_self: true
type: ibgp
next_hop_self: true
router_id: 10.0.0.42
Expand Down Expand Up @@ -495,6 +504,7 @@ nodes:
as: 65000
ipv6: 2001:db8::7
name: r1
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -508,6 +518,7 @@ nodes:
as: 65000
ipv6: 2001:db8::15
name: r2
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -521,6 +532,7 @@ nodes:
as: 65000
ipv6: 2001:db8::2a
name: r3
next_hop_self: true
type: ibgp
next_hop_self: true
router_id: 10.0.0.1
Expand Down
2 changes: 2 additions & 0 deletions tests/topology/expected/bgp-anycast.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,7 @@ nodes:
as: 65000
ipv4: 10.0.0.2
name: l2
next_hop_self: true
type: ibgp
next_hop_self: true
router_id: 10.0.0.1
Expand Down Expand Up @@ -147,6 +148,7 @@ nodes:
as: 65000
ipv4: 10.0.0.1
name: l1
next_hop_self: true
type: ibgp
next_hop_self: true
router_id: 10.0.0.2
Expand Down
15 changes: 15 additions & 0 deletions tests/topology/expected/bgp-autogroup.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -171,6 +171,7 @@ nodes:
as: 65101
ipv4: 10.0.0.6
name: a2
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -186,6 +187,7 @@ nodes:
as: 65101
ipv4: 10.0.0.7
name: a3
next_hop_self: true
type: ibgp
- activate:
ipv4: true
Expand Down Expand Up @@ -259,6 +261,7 @@ nodes:
as: 65101
ipv4: 10.0.0.5
name: a1
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -274,6 +277,7 @@ nodes:
as: 65101
ipv4: 10.0.0.7
name: a3
next_hop_self: true
type: ibgp
- activate:
ipv4: true
Expand Down Expand Up @@ -347,6 +351,7 @@ nodes:
as: 65101
ipv4: 10.0.0.5
name: a1
next_hop_self: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -362,6 +367,7 @@ nodes:
as: 65101
ipv4: 10.0.0.6
name: a2
next_hop_self: true
type: ibgp
- activate:
ipv4: true
Expand Down Expand Up @@ -436,6 +442,7 @@ nodes:
as: 65000
ipv4: 10.0.0.4
name: s1
next_hop_self: true
rr: true
type: ibgp
next_hop_self: true
Expand Down Expand Up @@ -514,6 +521,7 @@ nodes:
as: 65000
ipv4: 10.0.0.4
name: s1
next_hop_self: true
rr: true
type: ibgp
- activate:
Expand Down Expand Up @@ -628,6 +636,7 @@ nodes:
as: 65000
ipv4: 10.0.0.4
name: s1
next_hop_self: true
rr: true
type: ibgp
- activate:
Expand Down Expand Up @@ -724,6 +733,8 @@ nodes:
as: 65000
ipv4: 10.0.0.1
name: l1
next_hop_self: true
rr_client: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -740,6 +751,8 @@ nodes:
as: 65000
ipv4: 10.0.0.2
name: l2
next_hop_self: true
rr_client: true
type: ibgp
- _source_intf:
ifindex: 0
Expand All @@ -756,6 +769,8 @@ nodes:
as: 65000
ipv4: 10.0.0.3
name: l3
next_hop_self: true
rr_client: true
type: ibgp
next_hop_self: true
router_id: 10.0.0.4
Expand Down
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