FRR: Add SRv6 bgp support

netsim/ansible/templates/srv6/frr.bgp.j2

@@ -1,15 +1,28 @@
+{% if 'bgp' in srv6.igp|default([]) %}
+interface ${SRv6_DEV}
+  ipv6 address {{ srv6.locator }}
+{% endif %}
+
 router bgp {{ bgp.as }}
+ ! bgp default software-version-capability latest-encoding
  segment-routing srv6
   locator {{ inventory_hostname }}
  exit
 
+ {% if 'bgp' in srv6.igp|default([]) %}
+ address-family ipv6 unicast
+  network {{ srv6.locator }}
+ exit-address-family
+ {% endif %}
+
 {#
   The core bgp module only provisions neighbors for which the transport matches the address family, i.e. IPv4 over v4
   and IPv6 over v6. This template modifies IPv6 neighbors, adding VPNv4/6 AF over IPv6 transport and setting various
   next hop handling flags
 #}
 {% macro bgp_neighbor(n,peer,af) %}
   neighbor {{ peer }} activate
+  neighbor {{ peer }} encapsulation-srv6
   neighbor {{ peer }} send-community both
 {%   if n.next_hop_unchanged is defined %}
   neighbor {{ peer }} attribute-unchanged next-hop
@@ -19,7 +32,7 @@ router bgp {{ bgp.as }}
 {%   endif %}
 {% endmacro -%}
 
-{% if srv6.vpn is defined %}
+{% if srv6.vpn is defined or srv6.bgp is defined %}
 {%   for n in bgp.neighbors|default([]) if n.ipv6 is defined %}
 {%     set peer = n.ipv6 %}
  neighbor {{ peer }} remote-as {{ n.as }}
@@ -29,10 +42,18 @@ router bgp {{ bgp.as }}
 {%     endif %}
 
 {%-    for af in ['ipv4','ipv6'] %}
-{%       if n.type in srv6.vpn.get(af,[]) %}
+{%       if srv6.bgp is defined and n.type in srv6.bgp.get(af,[]) %}
+ address-family {{ af }} unicast
+!
+  sid export auto
+{{         bgp_neighbor(n,peer,af) -}}
+!
+{%       endif %}
+{%       if srv6.vpn is defined and n.type in srv6.vpn.get(af,[]) %}
  address-family {{ af }} vpn
 !
 {{         bgp_neighbor(n,peer,af) -}}
+!
 {%       endif %}
 {%     endfor %}
 {%   endfor %}

netsim/ansible/templates/srv6/frr.j2

@@ -3,12 +3,23 @@
 set -e
 
 export SRv6_DEV="sr0"
+export SRv6_VRF_DEV="vrf-srv6"
 
 if [ ! -e /sys/devices/virtual/net/${SRv6_DEV} ]; then
 ip link add ${SRv6_DEV} type dummy
 ip link set ${SRv6_DEV} up
 fi
 
+#
+# Create SRv6 default VRF, needed to install SRv6 nexthops
+#
+{% if 'bgp' in srv6.igp|default([]) %}
+if [ ! -e /sys/devices/virtual/net/${SRv6_VRF_DEV} ]; then
+ip link add ${SRv6_VRF_DEV} type vrf table 254
+ip link set ${SRv6_VRF_DEV} up
+fi
+{% endif %}
+
 # See https://onvox.net/2024/12/16/srv6-frr/
 sysctl -w net.ipv6.seg6_flowlabel=1
 sysctl -w net.ipv6.conf.all.seg6_enabled=1
@@ -44,7 +55,7 @@ router isis {{ isis.instance }}
 exit
 {% endif %}
 
-{% if srv6.vpn is defined and bgp.as is defined %}
+{% if (srv6.vpn is defined or srv6.bgp is defined) and bgp.as is defined %}
 {%   include "frr.bgp.j2" %}
 {% endif %}
 

netsim/devices/frr.yml

@@ -184,7 +184,7 @@ features:
     af: [ ipv4, ipv6 ]
     protocol: [ isis, ospfv2 ]
   srv6:
-    bgp: false
+    bgp: true
     isis: true
     vpn: true
   stp:

netsim/modules/srv6.py

@@ -29,21 +29,16 @@ def get_pool_name() -> str:
 """
 def configure_bgp_for_srv6(node: Box, topology: Box) -> None:
   srv6_bgp = node.get('srv6.bgp',{})
-  srv6_vpn = node.get('srv6.vpn',{})
+  srv6_igp = node.get('srv6.igp',[])
   for nb in list(node.get('bgp.neighbors',[])):
     if 'ipv6' not in nb:                               # Skip IPv4-only neighbors
       continue
 
     for af in DEFAULT_BGP_AF.keys():
-      if nb.type in srv6_bgp.get(af,[]) or nb.type in srv6_vpn.get(af,[]):
-# If anything, deactivating BGP AFs would break SR-OS and not achieve anything on FRR
-#        nb.activate[af] = False                        # Disable regular BGP activation
-        pass
-      else:
-        continue                                       # Skip if neither AF is activated
+      nb.activate[af] = nb.type in srv6_bgp.get(af,[]) or (af=='ipv6' and nb.type=='ebgp' and 'bgp' in srv6_igp)
 
 # The following code is untested and thus commented out
-#      if nb.type=='ebgp':                              # Set next hop unchanged for EBGP peers, to get end-2-end SID routing
+#      if nb.type=='ebgp':                             # Set next hop unchanged for EBGP peers, to get end-2-end SID routing
 #        nb.next_hop_unchanged = True
       if af=='ipv4' and 'ipv4' not in nb:
         nb.extended_nexthop = True                     # Enable extended next hops when IPv4 AF is used without IPv4 transport

netsim/modules/srv6.yml

@@ -21,7 +21,7 @@ attributes:
       _alt_types: [ bool, BoxList ]
       ipv4: { type: list, true_value: [ ibgp ] }
       ipv6: { type: list, true_value: [ ibgp ] }
-    igp: { type: list, valid_values: [ isis, ospf ] }
+    igp: { type: list, valid_values: [ isis, ospf, bgp ] }
     vpn: # BGP VPN v4/v6
       _alt_types: [ bool, BoxList ]
       ipv4: { type: list, true_value: [ ibgp ] }

tests/integration/srv6/03-srv6-bgp-ipv4.yml

@@ -0,0 +1,133 @@
+---
+message: |
+  The tested device (DUT) is a PE-router running BGP and SRv6 across an IPv6-only network to interconnect
+  two IPv4-only networks. The validation test checks end-to-end IPv4 connectivity across a SRv6 core.
+  See https://www.ietf.org/archive/id/draft-mishra-idr-v4-islands-v6-core-4pe-06.html
+
+defaults.sources.extra: [ ../wait_times.yml ]
+
+plugin: [ bgp.session ]       # For bgp.allowas_in, the PE AS needs to be able to transit via the P AS
+
+addressing:
+  core:
+    ipv4: False               # ipv6-only
+    ipv6: 2001:1::/48         # SRv6 requires ipv6 addresses on interfaces
+
+  loopback:
+    ipv4: False               # No need for ipv4 loopbacks, this avoids creating ipv4 ibgp sessions too
+    ipv6: 2001:db8::/48
+
+  lb_ce:
+    ipv4: 192.168.0.0/24
+    prefix: 32
+
+srv6.allocate_loopback: False  # Don't allocate loopback addresses from the locator range
+srv6.igp: [ bgp ]
+srv6.bgp:
+  ipv4: True                  # Enable IPv4 in the overlay (for IBGP)
+  ipv6: False
+srv6.vpn: False
+
+bgp.as: 65000                 # PE iBGP AS for IPv4 overlay
+defaults.bgp.warnings.missing_igp: False
+
+groups:
+  _auto_create: True
+  hosts:
+    members: [ h1, h2 ]
+    device: linux
+    provider: clab
+  pe:
+    members: [ dut, pe2 ]
+    module: [ bgp, srv6 ]
+    bgp.import: [ connected ]
+    bgp.advertise_loopback: True  # BGP-only underlay needs loopback reachability in BGP
+  core:
+    members: [ p ]
+    module: [ bgp ]               # No srv6 module, just BGP
+  ce:
+    members: [ ce1, ce2 ]
+    module: [ bgp ]
+    loopback.pool: lb_ce
+  x_switches:
+    members: [ p, pe2, ce1, ce2 ]
+    device: frr
+    provider: clab
+
+nodes:
+  dut:
+  pe2:
+  p:
+    bgp.as: 65010             # Different AS to use eBGP for SID/locator exchange
+  ce1:
+    bgp.as: 65101
+  ce2:
+    bgp.as: 65102
+
+links:
+- group: core
+  pool: core
+  members:
+  - dut:
+      bgp.allowas_in: True          # Allow transit via P AS
+    p:
+  - p:
+    pe2:
+      bgp.allowas_in: True          # Allow transit via P AS
+- group: edge
+  members: [ h1-dut, h2-pe2 ]
+- group: customer
+  members: [ ce1-dut, ce2-pe2 ]
+
+validate:
+  ebgp_ulay_dut:
+    description: Check eBGP underlay session P-DUT over IPv6
+    wait: ebgp_session
+    wait_msg: Waiting for eBGP underlay sessions to start
+    nodes: [ p ]
+    plugin: bgp_neighbor(node.bgp.neighbors,'dut',af='ipv6')
+    stop_on_error: true
+  ebgp_ulay_pe2:
+    description: Check eBGP underlay session P-PE2 over IPv6
+    wait: ebgp_session
+    wait_msg: Waiting for eBGP underlay sessions to start
+    nodes: [ p ]
+    plugin: bgp_neighbor(node.bgp.neighbors,'pe2',af='ipv6')
+    stop_on_error: true
+  ebgp_dut:
+    description: Check EBGP session DUT-CE1
+    wait: ebgp_session
+    wait_msg: Waiting for EBGP session DUT-CE1
+    nodes: [ ce1 ]
+    plugin: bgp_neighbor(node.bgp.neighbors,'dut',af='ipv4')
+  ebgp_pe2:
+    description: Check EBGP session PE2-CE2
+    wait: ebgp_session
+    wait_msg: Waiting for EBGP session PE2-CE2
+    nodes: [ ce2 ]
+    plugin: bgp_neighbor(node.bgp.neighbors,'pe2',af='ipv4')
+  ibgp:
+    description: Check IBGP session with activation of IPv4 over IPv6
+    wait: 10
+    wait_msg: Waiting for IBGP sessions to start
+    nodes: [ pe2 ]
+    plugin: bgp_neighbor(node.bgp.neighbors,'dut',af='ipv6',activate='ipv4')
+    stop_on_error: true
+  ping_hh:
+    description: Ping-based host-to-host reachability test
+    wait_msg: We might have to wait a bit longer
+    wait: 10
+    nodes: [ h1 ]
+    plugin: ping('h2')
+  ping_h_ce:
+    description: Ping-based host-to-CE reachability test
+    wait_msg: We might have to wait a bit longer
+    wait: 10
+    nodes: [ h1, h2 ]
+    plugin: ping('ce1')
+  ping_ce_ce:
+    description: Ping-based CE-to-CE reachability test
+    wait_msg: We might have to wait a bit longer
+    wait: 10
+    nodes: [ ce1 ]
+    plugin: ping(nodes.ce2.loopback.ipv4,src=nodes.ce1.loopback.ipv4)