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SRv6 BGP SID reachability #14810

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merged 4 commits into from
Feb 27, 2024
Merged

SRv6 BGP SID reachability #14810

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f49fc76
doc: bgp ipv4 l3vpn sid reachability
dmytroshytyi-6WIND Nov 15, 2023
26c747e
bgpd: extend make_prefix to form srv6-based prefix
dmytroshytyi-6WIND Nov 15, 2023
b3ac502
bgpd: srv6 sid reachability verification
dmytroshytyi-6WIND Nov 15, 2023
5101463
tests: an srv6 sid reachability use-case
dmytroshytyi-6WIND Nov 6, 2023
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52 changes: 34 additions & 18 deletions bgpd/bgp_nht.c
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Original file line number Diff line number Diff line change
Expand Up @@ -116,24 +116,36 @@ static int bgp_isvalid_nexthop_for_mplsovergre(struct bgp_nexthop_cache *bnc,
static int bgp_isvalid_nexthop_for_mpls(struct bgp_nexthop_cache *bnc,
struct bgp_path_info *path)
{
return (bnc && (bnc->nexthop_num > 0 &&
(CHECK_FLAG(path->flags, BGP_PATH_ACCEPT_OWN) ||
CHECK_FLAG(bnc->flags, BGP_NEXTHOP_LABELED_VALID) ||
bgp_isvalid_nexthop_for_ebgp(bnc, path) ||
bgp_isvalid_nexthop_for_mplsovergre(bnc, path))));
}

static bool bgp_isvalid_nexthop_for_l3vpn(struct bgp_nexthop_cache *bnc,
struct bgp_path_info *path)
{
if (bgp_zebra_num_connects() == 0)
return 1;

if (path->attr->srv6_l3vpn || path->attr->srv6_vpn) {
/* In the case of SRv6-VPN, we need to track the reachability to the
* SID (in other words, IPv6 address). We check that the SID is
* available in the BGP update; then if it is available, we check
* for the nexthop reachability.
*/
if (bnc && (bnc->nexthop_num > 0 && bgp_isvalid_nexthop(bnc)))
return 1;
return 0;
}
/*
* - In the case of MPLS-VPN, the label is learned from LDP or other
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* In the case of MPLS-VPN, the label is learned from LDP or other
* protocols, and nexthop tracking is enabled for the label.
* The value is recorded as BGP_NEXTHOP_LABELED_VALID.
* - In the case of SRv6-VPN, we need to track the reachability to the
* SID (in other words, IPv6 address). As in MPLS, we need to record
* the value as BGP_NEXTHOP_SID_VALID. However, this function is
* currently not implemented, and this function assumes that all
* Transit routes for SRv6-VPN are valid.
* - Otherwise check for mpls-gre acceptance
*/
return (bgp_zebra_num_connects() == 0 ||
(bnc && (bnc->nexthop_num > 0 &&
(CHECK_FLAG(path->flags, BGP_PATH_ACCEPT_OWN) ||
CHECK_FLAG(bnc->flags, BGP_NEXTHOP_LABELED_VALID) ||
bnc->bgp->srv6_enabled ||
bgp_isvalid_nexthop_for_ebgp(bnc, path) ||
bgp_isvalid_nexthop_for_mplsovergre(bnc, path)))));
return bgp_isvalid_nexthop_for_mpls(bnc, path);
}

static void bgp_unlink_nexthop_check(struct bgp_nexthop_cache *bnc)
Expand Down Expand Up @@ -496,7 +508,7 @@ int bgp_find_or_add_nexthop(struct bgp *bgp_route, struct bgp *bgp_nexthop,
else if (safi == SAFI_UNICAST && pi &&
pi->sub_type == BGP_ROUTE_IMPORTED && pi->extra &&
pi->extra->num_labels && !bnc->is_evpn_gwip_nexthop)
return bgp_isvalid_nexthop_for_mpls(bnc, pi);
return bgp_isvalid_nexthop_for_l3vpn(bnc, pi);
else if (safi == SAFI_MPLS_VPN && pi &&
pi->sub_type != BGP_ROUTE_IMPORTED)
/* avoid not redistributing mpls vpn routes */
Expand Down Expand Up @@ -1045,8 +1057,11 @@ static int make_prefix(int afi, struct bgp_path_info *pi, struct prefix *p)
break;
case AFI_IP6:
p->family = AF_INET6;

if (is_bgp_static) {
if (pi->attr && pi->attr->srv6_l3vpn) {
IPV6_ADDR_COPY(&(p->u.prefix6),
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no need to check for pi != NULL. it is alread done above.

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Thanks fixed.

&(pi->attr->srv6_l3vpn->sid));
p->prefixlen = IPV6_MAX_BITLEN;
} else if (is_bgp_static) {
p->u.prefix6 = p_orig->u.prefix6;
p->prefixlen = p_orig->prefixlen;
} else {
Expand Down Expand Up @@ -1294,8 +1309,9 @@ void evaluate_paths(struct bgp_nexthop_cache *bnc)
&& (path->attr->evpn_overlay.type
!= OVERLAY_INDEX_GATEWAY_IP)) {
bnc_is_valid_nexthop =
bgp_isvalid_nexthop_for_mpls(bnc, path) ? true
: false;
bgp_isvalid_nexthop_for_l3vpn(bnc, path)
? true
: false;
} else if (safi == SAFI_MPLS_VPN &&
path->sub_type != BGP_ROUTE_IMPORTED) {
/* avoid not redistributing mpls vpn routes */
Expand Down
25 changes: 25 additions & 0 deletions doc/user/bgp.rst
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Expand Up @@ -3172,6 +3172,31 @@ L3VPN SRv6
Specify the SRv6 locator to be used for SRv6 L3VPN. The Locator name must
be set in zebra, but user can set it in any order.

L3VPN SRv6 SID reachability
---------------------------

In the context of IPv4 L3VPN over SRv6 specific usecase, 2001:db8:12::2
is the peer IPv6 address of r2, and 2001:db8:2:2:: is the SRv6 SID
advertised by router r2 for prefix P. On r1, the SID reachability is
checked in order to install the prefix P. The below output indicates
that the 2001:db8:2:2:: prefix is valid.


.. code-block:: frr

r1# show bgp nexthop detail
Current BGP nexthop cache:
2001:db8:2:2:: valid [IGP metric 0], #paths 4
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gate 2001:db8:12::2, if eth0
Last update: Tue Nov 14 10:36:28 2023
Paths:
1/1 192.168.2.0/24 VRF vrf10 flags 0x4018
1/3 192.168.2.0/24 RD 65002:10 VRF default flags 0x418
2001:db8:12::2 valid [IGP metric 0], #paths 0, peer 2001:db8:12::2
if eth0
Last update: Tue Nov 14 10:36:26 2023
Paths:

General configuration
^^^^^^^^^^^^^^^^^^^^^

Expand Down
Empty file added tests/topotests/bgp_srv6_sid_reachability/c11/bgpd.conf
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Empty file.
4 changes: 4 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/c11/staticd.conf
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@@ -0,0 +1,4 @@
!
ip route 0.0.0.0/0 192.168.1.254
ipv6 route ::/0 2001:1::ffff
!
6 changes: 6 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/c11/zebra.conf
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@@ -0,0 +1,6 @@
hostname c11
!
interface eth0
ip address 192.168.1.1/24
ipv6 address 2001:1::1/64
!
Empty file added tests/topotests/bgp_srv6_sid_reachability/c12/bgpd.conf
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4 changes: 4 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/c12/staticd.conf
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@@ -0,0 +1,4 @@
!
ip route 0.0.0.0/0 192.168.1.254
ipv6 route ::/0 2001:1::ffff
!
6 changes: 6 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/c12/zebra.conf
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@@ -0,0 +1,6 @@
hostname c12
!
interface eth0
ip address 192.168.1.1/24
ipv6 address 2001:1::1/64
!
Empty file added tests/topotests/bgp_srv6_sid_reachability/c21/bgpd.conf
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4 changes: 4 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/c21/staticd.conf
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@@ -0,0 +1,4 @@
!
ip route 0.0.0.0/0 192.168.2.254
ipv6 route ::/0 2001:2::ffff
!
6 changes: 6 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/c21/zebra.conf
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@@ -0,0 +1,6 @@
hostname c21
!
interface eth0
ip address 192.168.2.1/24
ipv6 address 2001:2::1/64
!
Empty file added tests/topotests/bgp_srv6_sid_reachability/c22/bgpd.conf
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5 changes: 5 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/c22/staticd.conf
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@@ -0,0 +1,5 @@

!
ip route 0.0.0.0/0 192.168.2.254
ipv6 route ::/0 2001:2::ffff
!
9 changes: 9 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/c22/zebra.conf
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@@ -0,0 +1,9 @@
hostname c22
!
interface eth0
ip address 192.168.2.1/24
ipv6 address 2001:2::1/64
!
ip route 0.0.0.0/0 192.168.2.254
ipv6 route ::/0 2001:2::ffff
!
Empty file added tests/topotests/bgp_srv6_sid_reachability/c31/bgpd.conf
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4 changes: 4 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/c31/staticd.conf
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!
ip route 0.0.0.0/0 192.168.3.254
ipv6 route ::/0 2001:3::ffff
!
6 changes: 6 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/c31/zebra.conf
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hostname c31
!
interface eth0
ip address 192.168.3.1/24
ipv6 address 2001:3::1/64
!
Empty file added tests/topotests/bgp_srv6_sid_reachability/c32/bgpd.conf
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4 changes: 4 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/c32/staticd.conf
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!
ip route 0.0.0.0/0 192.168.3.254
ipv6 route ::/0 2001:3::ffff
!
6 changes: 6 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/c32/zebra.conf
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hostname c32
!
interface eth0
ip address 192.168.3.1/24
ipv6 address 2001:3::1/64
!
61 changes: 61 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/r1/bgpd.conf
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frr defaults traditional
!
hostname r1
password zebra
!
log commands
!
router bgp 65001
bgp router-id 192.0.2.1
no bgp ebgp-requires-policy
no bgp default ipv4-unicast
neighbor 2001:db8:12::2 remote-as 65002
neighbor 2001:db8:12::2 timers 3 10
neighbor 2001:db8:12::2 timers connect 1
neighbor 2001:db8:12::2 capability extended-nexthop
neighbor 2001:db8:13::3 remote-as 65001
neighbor 2001:db8:13::3 timers 3 10
neighbor 2001:db8:13::3 timers connect 1
neighbor 2001:db8:13::3 capability extended-nexthop
!
segment-routing srv6
locator default
!
address-family ipv4 vpn
neighbor 2001:db8:12::2 activate
neighbor 2001:db8:13::3 activate
exit-address-family
!
!
router bgp 65001 vrf vrf10
bgp router-id 192.0.2.1
!
address-family ipv4 unicast
redistribute connected
sid vpn export 1
rd vpn export 65001:10
rt vpn both 0:10
import vpn
export vpn
exit-address-family
!
!
router bgp 65001 vrf vrf20
bgp router-id 192.0.2.1
!
address-family ipv4 unicast
redistribute connected
sid vpn export 2
rd vpn export 65001:20
rt vpn both 0:20
import vpn
export vpn
exit-address-family
!
!
interface eth0
mpls bgp forwarding
!
interface eth1
mpls bgp forwarding
!
4 changes: 4 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/r1/staticd.conf
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!
ipv6 route 2001:db8:2:2::/64 2001:db8:12::2
ipv6 route 2001:db8:3:3::/64 2001:db8:13::3
!
32 changes: 32 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/r1/zebra.conf
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log file zebra.log
!
hostname r1
!
interface lo
ipv6 address 2001:db8:1:1::1/128
!
interface eth0
ipv6 address 2001:db8:12::1/64
!
interface eth1
ipv6 address 2001:db8:13::1/64
!
interface eth2 vrf vrf10
ip address 192.168.1.254/24
!
interface eth3 vrf vrf20
ip address 192.168.1.254/24
!
segment-routing
srv6
locators
locator default
prefix 2001:db8:1:1::/64
!
!
!
ip forwarding
ipv6 forwarding
!
line vty
!
50 changes: 50 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/r2/bgpd.conf
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frr defaults traditional
!
hostname r2
password zebra
!
log commands
!
router bgp 65002
bgp router-id 192.0.2.2
no bgp ebgp-requires-policy
no bgp default ipv4-unicast
neighbor 2001:db8:12::1 remote-as 65001
neighbor 2001:db8:12::1 timers 3 10
neighbor 2001:db8:12::1 timers connect 1
neighbor 2001:db8:12::1 capability extended-nexthop
!
segment-routing srv6
locator default
!
address-family ipv4 vpn
neighbor 2001:db8:12::1 activate
exit-address-family
!
!
router bgp 65002 vrf vrf10
bgp router-id 192.0.2.2
!
address-family ipv4 unicast
redistribute connected
sid vpn export 1
rd vpn export 65002:10
rt vpn both 0:10
import vpn
export vpn
exit-address-family
!
!
router bgp 65002 vrf vrf20
bgp router-id 192.0.2.2
!
address-family ipv4 unicast
redistribute connected
sid vpn export 2
rd vpn export 65002:20
rt vpn both 0:20
import vpn
export vpn
exit-address-family
!
!
4 changes: 4 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/r2/staticd.conf
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!
ipv6 route 2001:db8:1:1::/64 2001:db8:12::1
ipv6 route 2001:db8:3:3::/64 2001:db8:12::1
!
29 changes: 29 additions & 0 deletions tests/topotests/bgp_srv6_sid_reachability/r2/zebra.conf
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log file zebra.log
!
hostname r2
!
interface lo
ipv6 address 2001:db8:2:2::1/128
!
interface eth0
ipv6 address 2001:db8:12::2/64
!
interface eth1 vrf vrf10
ip address 192.168.2.254/24
!
interface eth2 vrf vrf20
ip address 192.168.2.254/24
!
segment-routing
srv6
locators
locator default
prefix 2001:db8:2:2::/64
!
!
!
ip forwarding
ipv6 forwarding
!
line vty
!
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