bgpd: Add set as-path replace <any|ASN> cmd for route-maps

```
route-map tstas permit 10
 set as-path replace 1
exit
```

Before:

```
donatas-laptop(config-router-af)# do show ip bgp 10.10.10.10/32
BGP routing table entry for 10.10.10.10/32, version 13
Paths: (1 available, best #1, table default)
  Advertised to non peer-group peers:
  192.168.10.65
  65000 1 2 3 123
    192.168.10.65 from 192.168.10.65 (10.10.10.11)
      Origin IGP, metric 0, valid, external, best (First path received)
      Last update: Mon Apr 25 10:39:50 2022
```

After:

```
donatas-laptop(config-router-af)# do show ip bgp 10.10.10.10/32
BGP routing table entry for 10.10.10.10/32, version 15
Paths: (1 available, best #1, table default)
  Advertised to non peer-group peers:
  192.168.10.65
  65000 65010 2 3 123
    192.168.10.65 from 192.168.10.65 (10.10.10.11)
      Origin IGP, metric 0, valid, external, best (First path received)
      Last update: Mon Apr 25 10:40:16 2022
```

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

bgpd/bgp_aspath.c

@@ -1258,6 +1258,28 @@ struct aspath *aspath_replace_specific_asn(struct aspath *aspath,
 	return new;
 }
 
+/* Replace all ASNs with our own ASN */
+struct aspath *aspath_replace_all_asn(struct aspath *aspath, as_t our_asn)
+{
+	struct aspath *new;
+	struct assegment *seg;
+
+	new = aspath_dup(aspath);
+	seg = new->segments;
+
+	while (seg) {
+		int i;
+
+		for (i = 0; i < seg->length; i++)
+			seg->as[i] = our_asn;
+
+		seg = seg->next;
+	}
+
+	aspath_str_update(new, false);
+	return new;
+}
+
 /* Replace all private ASNs with our own ASN */
 struct aspath *aspath_replace_private_asns(struct aspath *aspath, as_t asn,
 					   as_t peer_asn)

bgpd/bgp_aspath.h

@@ -112,6 +112,8 @@ extern bool aspath_single_asn_check(struct aspath *, as_t asn);
 extern struct aspath *aspath_replace_specific_asn(struct aspath *aspath,
 						  as_t target_asn,
 						  as_t our_asn);
+extern struct aspath *aspath_replace_all_asn(struct aspath *aspath,
+					     as_t our_asn);
 extern struct aspath *aspath_replace_private_asns(struct aspath *aspath,
 						  as_t asn, as_t peer_asn);
 extern struct aspath *aspath_remove_private_asns(struct aspath *aspath,

bgpd/bgp_routemap.c

@@ -2174,6 +2174,57 @@ static const struct route_map_rule_cmd route_set_aspath_exclude_cmd = {
 	route_aspath_free,
 };
 
+/* `set as-path replace AS-PATH` */
+static void *route_aspath_replace_compile(const char *arg)
+{
+	return XSTRDUP(MTYPE_ROUTE_MAP_COMPILED, arg);
+}
+
+static void route_aspath_replace_free(void *rule)
+{
+	XFREE(MTYPE_ROUTE_MAP_COMPILED, rule);
+}
+
+static enum route_map_cmd_result_t
+route_set_aspath_replace(void *rule, const struct prefix *dummy, void *object)
+{
+	struct aspath *aspath_new;
+	const char *replace = rule;
+	struct bgp_path_info *path = object;
+	as_t own_asn = path->peer->change_local_as ? path->peer->change_local_as
+						   : path->peer->local_as;
+
+	if (path->peer->sort != BGP_PEER_EBGP) {
+		zlog_warn(
+			"`set as-path replace` is supported only for EBGP peers");
+		return RMAP_NOOP;
+	}
+
+	if (path->attr->aspath->refcnt)
+		aspath_new = aspath_dup(path->attr->aspath);
+	else
+		aspath_new = path->attr->aspath;
+
+	if (strmatch(replace, "any")) {
+		path->attr->aspath =
+			aspath_replace_all_asn(aspath_new, own_asn);
+	} else {
+		as_t replace_asn = strtoul(replace, NULL, 10);
+
+		path->attr->aspath = aspath_replace_specific_asn(
+			aspath_new, replace_asn, own_asn);
+	}
+
+	return RMAP_OKAY;
+}
+
+static const struct route_map_rule_cmd route_set_aspath_replace_cmd = {
+	"as-path replace",
+	route_set_aspath_replace,
+	route_aspath_replace_compile,
+	route_aspath_replace_free,
+};
+
 /* `set community COMMUNITY' */
 struct rmap_com_set {
 	struct community *com;
@@ -5389,6 +5440,43 @@ DEFUN_YANG (set_aspath_prepend_lastas,
 	return nb_cli_apply_changes(vty, NULL);
 }
 
+DEFPY_YANG (set_aspath_replace_asn,
+	    set_aspath_replace_asn_cmd,
+	    "set as-path replace <any|(1-4294967295)>$replace",
+	    SET_STR
+	    "Transform BGP AS_PATH attribute\n"
+	    "Replace AS number to local AS number\n"
+	    "Replace any AS number to local AS number\n"
+	    "Replace a specific AS number to local AS number\n")
+{
+	const char *xpath =
+		"./set-action[action='frr-bgp-route-map:as-path-replace']";
+	char xpath_value[XPATH_MAXLEN];
+
+	nb_cli_enqueue_change(vty, xpath, NB_OP_CREATE, NULL);
+	snprintf(xpath_value, sizeof(xpath_value),
+		 "%s/rmap-set-action/frr-bgp-route-map:replace-as-path", xpath);
+	nb_cli_enqueue_change(vty, xpath_value, NB_OP_MODIFY, replace);
+	return nb_cli_apply_changes(vty, NULL);
+}
+
+DEFPY_YANG (no_set_aspath_replace_asn,
+	    no_set_aspath_replace_asn_cmd,
+	    "no set as-path replace [<any|(1-4294967295)>]",
+	    NO_STR
+	    SET_STR
+	    "Transform BGP AS_PATH attribute\n"
+	    "Replace AS number to local AS number\n"
+	    "Replace any AS number to local AS number\n"
+	    "Replace a specific AS number to local AS number\n")
+{
+	const char *xpath =
+		"./set-action[action='frr-bgp-route-map:as-path-replace']";
+
+	nb_cli_enqueue_change(vty, xpath, NB_OP_DESTROY, NULL);
+	return nb_cli_apply_changes(vty, NULL);
+}
+
 DEFUN_YANG (no_set_aspath_prepend,
 	    no_set_aspath_prepend_cmd,
 	    "no set as-path prepend [(1-4294967295)]",
@@ -6727,6 +6815,7 @@ void bgp_route_map_init(void)
 	route_map_install_set(&route_set_distance_cmd);
 	route_map_install_set(&route_set_aspath_prepend_cmd);
 	route_map_install_set(&route_set_aspath_exclude_cmd);
+	route_map_install_set(&route_set_aspath_replace_cmd);
 	route_map_install_set(&route_set_origin_cmd);
 	route_map_install_set(&route_set_atomic_aggregate_cmd);
 	route_map_install_set(&route_set_aggregator_as_cmd);
@@ -6800,10 +6889,12 @@ void bgp_route_map_init(void)
 	install_element(RMAP_NODE, &set_aspath_prepend_asn_cmd);
 	install_element(RMAP_NODE, &set_aspath_prepend_lastas_cmd);
 	install_element(RMAP_NODE, &set_aspath_exclude_cmd);
+	install_element(RMAP_NODE, &set_aspath_replace_asn_cmd);
 	install_element(RMAP_NODE, &no_set_aspath_prepend_cmd);
 	install_element(RMAP_NODE, &no_set_aspath_prepend_lastas_cmd);
 	install_element(RMAP_NODE, &no_set_aspath_exclude_cmd);
 	install_element(RMAP_NODE, &no_set_aspath_exclude_all_cmd);
+	install_element(RMAP_NODE, &no_set_aspath_replace_asn_cmd);
 	install_element(RMAP_NODE, &set_origin_cmd);
 	install_element(RMAP_NODE, &no_set_origin_cmd);
 	install_element(RMAP_NODE, &set_atomic_aggregate_cmd);

bgpd/bgp_routemap_nb.c

@@ -296,6 +296,13 @@ const struct frr_yang_module_info frr_bgp_route_map_info = {
 				.destroy = lib_route_map_entry_set_action_rmap_set_action_exclude_as_path_destroy,
 			}
 		},
+		{
+			.xpath = "/frr-route-map:lib/route-map/entry/set-action/rmap-set-action/frr-bgp-route-map:replace-as-path",
+			.cbs = {
+				.modify = lib_route_map_entry_set_action_rmap_set_action_replace_as_path_modify,
+				.destroy = lib_route_map_entry_set_action_rmap_set_action_replace_as_path_destroy,
+			}
+		},
 		{
 			.xpath = "/frr-route-map:lib/route-map/entry/set-action/rmap-set-action/frr-bgp-route-map:community-none",
 			.cbs = {

bgpd/bgp_routemap_nb.h

@@ -108,6 +108,10 @@ int lib_route_map_entry_set_action_rmap_set_action_last_as_modify(struct nb_cb_m
 int lib_route_map_entry_set_action_rmap_set_action_last_as_destroy(struct nb_cb_destroy_args *args);
 int lib_route_map_entry_set_action_rmap_set_action_exclude_as_path_modify(struct nb_cb_modify_args *args);
 int lib_route_map_entry_set_action_rmap_set_action_exclude_as_path_destroy(struct nb_cb_destroy_args *args);
+int lib_route_map_entry_set_action_rmap_set_action_replace_as_path_modify(
+	struct nb_cb_modify_args *args);
+int lib_route_map_entry_set_action_rmap_set_action_replace_as_path_destroy(
+	struct nb_cb_destroy_args *args);
 int lib_route_map_entry_set_action_rmap_set_action_community_none_modify(struct nb_cb_modify_args *args);
 int lib_route_map_entry_set_action_rmap_set_action_community_none_destroy(struct nb_cb_destroy_args *args);
 int lib_route_map_entry_set_action_rmap_set_action_community_string_modify(struct nb_cb_modify_args *args);

bgpd/bgp_routemap_nb_config.c

@@ -2207,6 +2207,58 @@ lib_route_map_entry_set_action_rmap_set_action_exclude_as_path_destroy(
 	return NB_OK;
 }
 
+/*
+ * XPath:
+ * /frr-route-map:lib/route-map/entry/set-action/rmap-set-action/frr-bgp-route-map:replace-as-path
+ */
+int lib_route_map_entry_set_action_rmap_set_action_replace_as_path_modify(
+	struct nb_cb_modify_args *args)
+{
+	struct routemap_hook_context *rhc;
+	const char *type;
+	int rv;
+
+	switch (args->event) {
+	case NB_EV_VALIDATE:
+	case NB_EV_PREPARE:
+	case NB_EV_ABORT:
+		break;
+	case NB_EV_APPLY:
+		/* Add configuration. */
+		rhc = nb_running_get_entry(args->dnode, NULL, true);
+		type = yang_dnode_get_string(args->dnode, NULL);
+
+		/* Set destroy information. */
+		rhc->rhc_shook = generic_set_delete;
+		rhc->rhc_rule = "as-path replace";
+		rhc->rhc_event = RMAP_EVENT_SET_DELETED;
+
+		rv = generic_set_add(rhc->rhc_rmi, "as-path replace", type,
+				     args->errmsg, args->errmsg_len);
+		if (rv != CMD_SUCCESS) {
+			rhc->rhc_shook = NULL;
+			return NB_ERR_INCONSISTENCY;
+		}
+	}
+
+	return NB_OK;
+}
+
+int lib_route_map_entry_set_action_rmap_set_action_replace_as_path_destroy(
+	struct nb_cb_destroy_args *args)
+{
+	switch (args->event) {
+	case NB_EV_VALIDATE:
+	case NB_EV_PREPARE:
+	case NB_EV_ABORT:
+		break;
+	case NB_EV_APPLY:
+		return lib_route_map_entry_set_destroy(args);
+	}
+
+	return NB_OK;
+}
+
 /*
  * XPath:
  * /frr-route-map:lib/route-map/entry/set-action/rmap-set-action/frr-bgp-route-map:community-none

doc/user/bgp.rst

@@ -1983,6 +1983,11 @@ Using AS Path in Route Map
    Prepend the existing last AS number (the leftmost ASN) to the AS_PATH.
    The no form of this command removes this set operation from the route-map.
 
+.. clicmd:: set as-path replace <any|ASN>
+
+   Replace a specific AS number to local AS number. ``any`` replaces each
+   AS number in the AS-PATH with the local AS number.
+
 .. _bgp-communities-attribute:
 
 Communities Attribute

lib/routemap.h

@@ -370,6 +370,7 @@ DECLARE_QOBJ_TYPE(route_map);
 	(strmatch(A, "frr-bgp-route-map:as-path-prepend"))
 #define IS_SET_AS_EXCLUDE(A)                                                   \
 	(strmatch(A, "frr-bgp-route-map:as-path-exclude"))
+#define IS_SET_AS_REPLACE(A) (strmatch(A, "frr-bgp-route-map:as-path-replace"))
 #define IS_SET_IPV6_NH_GLOBAL(A)                                               \
 	(strmatch(A, "frr-bgp-route-map:ipv6-nexthop-global"))
 #define IS_SET_IPV6_VPN_NH(A)                                                  \

lib/routemap_cli.c

@@ -1197,6 +1197,11 @@ void route_map_action_show(struct vty *vty, const struct lyd_node *dnode,
 			yang_dnode_get_string(
 				dnode,
 				"./rmap-set-action/frr-bgp-route-map:exclude-as-path"));
+	} else if (IS_SET_AS_REPLACE(action)) {
+		vty_out(vty, " set as-path replace %s\n",
+			yang_dnode_get_string(
+				dnode,
+				"./rmap-set-action/frr-bgp-route-map:replace-as-path"));
 	} else if (IS_SET_AS_PREPEND(action)) {
 		if (yang_dnode_exists(
 			    dnode,

tests/topotests/bgp_set_aspath_replace/r1/bgpd.conf

@@ -0,0 +1,17 @@
+!
+router bgp 65001
+ no bgp ebgp-requires-policy
+ neighbor 192.168.1.2 remote-as external
+ neighbor 192.168.1.2 timers 3 10
+ address-family ipv4 unicast
+  neighbor 192.168.1.2 route-map r2 in
+ exit-address-family
+!
+ip prefix-list p1 seq 5 permit 172.16.255.31/32
+!
+route-map r2 permit 10
+ match ip address prefix-list p1
+ set as-path replace 65003
+route-map r2 permit 20
+ set as-path replace any
+!

tests/topotests/bgp_set_aspath_replace/r1/zebra.conf

@@ -0,0 +1,6 @@
+!
+interface r1-eth0
+ ip address 192.168.1.1/24
+!
+ip forwarding
+!

tests/topotests/bgp_set_aspath_replace/r2/bgpd.conf

@@ -0,0 +1,8 @@
+!
+router bgp 65002
+ no bgp ebgp-requires-policy
+ neighbor 192.168.1.1 remote-as external
+ neighbor 192.168.1.1 timers 3 10
+ neighbor 192.168.2.1 remote-as external
+ neighbor 192.168.2.1 timers 3 10
+!

tests/topotests/bgp_set_aspath_replace/r2/zebra.conf

@@ -0,0 +1,9 @@
+!
+interface r2-eth0
+ ip address 192.168.1.2/24
+!
+interface r2-eth1
+ ip address 192.168.2.2/24
+!
+ip forwarding
+!

tests/topotests/bgp_set_aspath_replace/r3/bgpd.conf

@@ -0,0 +1,9 @@
+!
+router bgp 65003
+ no bgp ebgp-requires-policy
+ neighbor 192.168.2.2 remote-as external
+ neighbor 192.168.2.2 timers 3 10
+ address-family ipv4 unicast
+  redistribute connected
+ exit-address-family
+!

tests/topotests/bgp_set_aspath_replace/r3/zebra.conf

@@ -0,0 +1,10 @@
+!
+int lo
+ ip address 172.16.255.31/32
+ ip address 172.16.255.32/32
+!
+interface r3-eth0
+ ip address 192.168.2.1/24
+!
+ip forwarding
+!