bgpd: Allow overriding MPLS VPN next-hops via route-maps

Just do not reset next-hop for MPLS VPN routes.

Example of 172.16.255.1/32 (using extended next-hop capability):

```
pe2# sh bgp ipv4 vpn
BGP table version is 4, local router ID is 10.10.10.20, vrf id 0
Default local pref 100, local AS 65001
Status codes:  s suppressed, d damped, h history, * valid, > best, = multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

    Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 192.168.1.2:2
 *>i10.0.0.0/24      2001:db8:1::1            0    100      0 65000 ?
    UN=2001:db8:1::1 EC{192.168.1.2:2} label=1111 type=bgp, subtype=0
 *>i172.16.255.1/32  2001:db8::1              0    100      0 65000 ?
    UN=2001:db8::1 EC{192.168.1.2:2} label=1111 type=bgp, subtype=0
 *>i192.168.1.0/24   2001:db8:1::1            0    100      0 65000 ?
    UN=2001:db8:1::1 EC{192.168.1.2:2} label=1111 type=bgp, subtype=0
 *>i192.168.2.0/24   2001:db8:1::1                 100      0 65000 ?
    UN=2001:db8:1::1 EC{192.168.1.2:2} label=1111 type=bgp, subtype=0
Route Distinguisher: 192.168.2.2:2
 *> 10.0.0.0/24      192.168.2.1@4<           0     50      0 65000 ?
    UN=192.168.2.1 EC{192.168.2.2:2} label=2222 type=bgp, subtype=5
 *> 172.16.255.1/32  192.168.2.1@4<                 50      0 65000 ?
    UN=192.168.2.1 EC{192.168.2.2:2} label=2222 type=bgp, subtype=5
 *> 192.168.1.0/24   192.168.2.1@4<                 50      0 65000 ?
    UN=192.168.2.1 EC{192.168.2.2:2} label=2222 type=bgp, subtype=5
 *> 192.168.2.0/24   192.168.2.1@4<           0     50      0 65000 ?
    UN=192.168.2.1 EC{192.168.2.2:2} label=2222 type=bgp, subtype=5

Displayed  8 routes and 8 total paths
```

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>

4 files changed, 40 insertions, 16 deletions

diff --git a/bgpd/bgp_attr.h b/bgpd/bgp_attr.h
index bc82d0c6ed..d5f26f240d 100644
--- a/bgpd/bgp_attr.h
+++ b/bgpd/bgp_attr.h
@@ -344,6 +344,8 @@ struct attr {
 #define BATTR_RMAP_IPV6_PREFER_GLOBAL_CHANGED (1 << 6)
 #define BATTR_RMAP_LINK_BW_SET (1 << 7)
 #define BATTR_RMAP_L3VPN_ACCEPT_GRE (1 << 8)
+#define BATTR_RMAP_VPNV4_NHOP_CHANGED (1 << 9)
+#define BATTR_RMAP_VPNV6_GLOBAL_NHOP_CHANGED (1 << 10)
 
 /* Router Reflector related structure. */
 struct cluster_list {
@@ -476,15 +478,18 @@ extern enum bgp_attr_parse_ret bgp_attr_nexthop_valid(struct peer *peer,
 static inline int bgp_rmap_nhop_changed(uint32_t out_rmap_flags,
 					uint32_t in_rmap_flags)
 {
-	return ((CHECK_FLAG(out_rmap_flags, BATTR_RMAP_NEXTHOP_PEER_ADDRESS)
-		 || CHECK_FLAG(out_rmap_flags, BATTR_RMAP_NEXTHOP_UNCHANGED)
-		 || CHECK_FLAG(out_rmap_flags, BATTR_RMAP_IPV4_NHOP_CHANGED)
-		 || CHECK_FLAG(out_rmap_flags,
-			       BATTR_RMAP_IPV6_GLOBAL_NHOP_CHANGED)
-		 || CHECK_FLAG(out_rmap_flags,
-			       BATTR_RMAP_IPV6_PREFER_GLOBAL_CHANGED)
-		 || CHECK_FLAG(out_rmap_flags, BATTR_RMAP_IPV6_LL_NHOP_CHANGED)
-		 || CHECK_FLAG(in_rmap_flags, BATTR_RMAP_NEXTHOP_UNCHANGED))
+	return ((CHECK_FLAG(out_rmap_flags, BATTR_RMAP_NEXTHOP_PEER_ADDRESS) ||
+		 CHECK_FLAG(out_rmap_flags, BATTR_RMAP_NEXTHOP_UNCHANGED) ||
+		 CHECK_FLAG(out_rmap_flags, BATTR_RMAP_IPV4_NHOP_CHANGED) ||
+		 CHECK_FLAG(out_rmap_flags, BATTR_RMAP_VPNV4_NHOP_CHANGED) ||
+		 CHECK_FLAG(out_rmap_flags,
+			    BATTR_RMAP_VPNV6_GLOBAL_NHOP_CHANGED) ||
+		 CHECK_FLAG(out_rmap_flags,
+			    BATTR_RMAP_IPV6_GLOBAL_NHOP_CHANGED) ||
+		 CHECK_FLAG(out_rmap_flags,
+			    BATTR_RMAP_IPV6_PREFER_GLOBAL_CHANGED) ||
+		 CHECK_FLAG(out_rmap_flags, BATTR_RMAP_IPV6_LL_NHOP_CHANGED) ||
+		 CHECK_FLAG(in_rmap_flags, BATTR_RMAP_NEXTHOP_UNCHANGED))
 			? 1
 			: 0);
 }
diff --git a/bgpd/bgp_routemap.c b/bgpd/bgp_routemap.c
index b736e6c38a..9422469bca 100644
--- a/bgpd/bgp_routemap.c
+++ b/bgpd/bgp_routemap.c
@@ -3725,6 +3725,8 @@ route_set_vpnv4_nexthop(void *rule, const struct prefix *prefix, void *object)
 	path->attr->mp_nexthop_global_in = *address;
 	path->attr->mp_nexthop_len = BGP_ATTR_NHLEN_IPV4;
 
+	SET_FLAG(path->attr->rmap_change_flags, BATTR_RMAP_VPNV4_NHOP_CHANGED);
+
 	return RMAP_OKAY;
 }
 
@@ -3762,6 +3764,9 @@ route_set_vpnv6_nexthop(void *rule, const struct prefix *prefix, void *object)
 	       sizeof(struct in6_addr));
 	path->attr->mp_nexthop_len = BGP_ATTR_NHLEN_VPNV6_GLOBAL;
 
+	SET_FLAG(path->attr->rmap_change_flags,
+		 BATTR_RMAP_VPNV6_GLOBAL_NHOP_CHANGED);
+
 	return RMAP_OKAY;
 }
 
diff --git a/bgpd/bgp_updgrp.h b/bgpd/bgp_updgrp.h
index 56289d399d..ecd92a996e 100644
--- a/bgpd/bgp_updgrp.h
+++ b/bgpd/bgp_updgrp.h
@@ -88,6 +88,8 @@ typedef struct {
 #define BPKT_ATTRVEC_FLAGS_RMAP_IPV4_NH_CHANGED   (1 << 4)
 #define BPKT_ATTRVEC_FLAGS_RMAP_IPV6_GNH_CHANGED  (1 << 5)
 #define BPKT_ATTRVEC_FLAGS_RMAP_IPV6_LNH_CHANGED  (1 << 6)
+#define BPKT_ATTRVEC_FLAGS_RMAP_VPNV4_NH_CHANGED  (1 << 7)
+#define BPKT_ATTRVEC_FLAGS_RMAP_VPNV6_GNH_CHANGED (1 << 8)
 
 typedef struct bpacket_attr_vec_arr {
 	bpacket_attr_vec entries[BGP_ATTR_VEC_MAX];
diff --git a/bgpd/bgp_updgrp_packet.c b/bgpd/bgp_updgrp_packet.c
index 9de97cf060..b52d67ed3c 100644
--- a/bgpd/bgp_updgrp_packet.c
+++ b/bgpd/bgp_updgrp_packet.c
@@ -379,10 +379,11 @@ struct stream *bpacket_reformat_for_peer(struct bpacket *pkt,
 
 		route_map_sets_nh =
 			(CHECK_FLAG(vec->flags,
-				    BPKT_ATTRVEC_FLAGS_RMAP_IPV4_NH_CHANGED)
-			 || CHECK_FLAG(
-				 vec->flags,
-				 BPKT_ATTRVEC_FLAGS_RMAP_NH_PEER_ADDRESS));
+				    BPKT_ATTRVEC_FLAGS_RMAP_IPV4_NH_CHANGED) ||
+			 CHECK_FLAG(vec->flags,
+				    BPKT_ATTRVEC_FLAGS_RMAP_VPNV4_NH_CHANGED) ||
+			 CHECK_FLAG(vec->flags,
+				    BPKT_ATTRVEC_FLAGS_RMAP_NH_PEER_ADDRESS));
 
 		switch (nhlen) {
 		case BGP_ATTR_NHLEN_IPV4:
@@ -468,10 +469,12 @@ struct stream *bpacket_reformat_for_peer(struct bpacket *pkt,
 
 		route_map_sets_nh =
 			(CHECK_FLAG(vec->flags,
-				    BPKT_ATTRVEC_FLAGS_RMAP_IPV6_GNH_CHANGED)
-			 || CHECK_FLAG(
+				    BPKT_ATTRVEC_FLAGS_RMAP_IPV6_GNH_CHANGED) ||
+			 CHECK_FLAG(
 				 vec->flags,
-				 BPKT_ATTRVEC_FLAGS_RMAP_NH_PEER_ADDRESS));
+				 BPKT_ATTRVEC_FLAGS_RMAP_VPNV6_GNH_CHANGED) ||
+			 CHECK_FLAG(vec->flags,
+				    BPKT_ATTRVEC_FLAGS_RMAP_NH_PEER_ADDRESS));
 
 		/*
 		 * The logic here is rather similar to that for IPv4, the
@@ -1276,6 +1279,15 @@ bpacket_vec_arr_inherit_attr_flags(struct bpacket_attr_vec_arr *vecarr,
 		SET_FLAG(vecarr->entries[BGP_ATTR_VEC_NH].flags,
 			 BPKT_ATTRVEC_FLAGS_RMAP_IPV6_GNH_CHANGED);
 
+	if (CHECK_FLAG(attr->rmap_change_flags, BATTR_RMAP_VPNV4_NHOP_CHANGED))
+		SET_FLAG(vecarr->entries[BGP_ATTR_VEC_NH].flags,
+			 BPKT_ATTRVEC_FLAGS_RMAP_VPNV4_NH_CHANGED);
+
+	if (CHECK_FLAG(attr->rmap_change_flags,
+		       BATTR_RMAP_VPNV6_GLOBAL_NHOP_CHANGED))
+		SET_FLAG(vecarr->entries[BGP_ATTR_VEC_NH].flags,
+			 BPKT_ATTRVEC_FLAGS_RMAP_VPNV6_GNH_CHANGED);
+
 	if (CHECK_FLAG(attr->rmap_change_flags,
 		       BATTR_RMAP_IPV6_LL_NHOP_CHANGED))
 		SET_FLAG(vecarr->entries[BGP_ATTR_VEC_NH].flags,