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>

6 files changed, 178 insertions, 0 deletions

diff --git a/bgpd/bgp_aspath.c b/bgpd/bgp_aspath.c
index fd644ebf0a..880e15fadb 100644
--- a/bgpd/bgp_aspath.c
+++ b/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)
diff --git a/bgpd/bgp_aspath.h b/bgpd/bgp_aspath.h
index 4b16818167..912db7b254 100644
--- a/bgpd/bgp_aspath.h
+++ b/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,
diff --git a/bgpd/bgp_routemap.c b/bgpd/bgp_routemap.c
index 6c303a9e5f..20ee2e4d49 100644
--- a/bgpd/bgp_routemap.c
+++ b/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);
diff --git a/bgpd/bgp_routemap_nb.c b/bgpd/bgp_routemap_nb.c
index caf1553ec1..585596e1aa 100644
--- a/bgpd/bgp_routemap_nb.c
+++ b/bgpd/bgp_routemap_nb.c
@@ -297,6 +297,13 @@ const struct frr_yang_module_info frr_bgp_route_map_info = {
 			}
 		},
 		{
+			.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 = {
 				.modify = lib_route_map_entry_set_action_rmap_set_action_community_none_modify,
diff --git a/bgpd/bgp_routemap_nb.h b/bgpd/bgp_routemap_nb.h
index e0b3a6926f..a01adf7d5d 100644
--- a/bgpd/bgp_routemap_nb.h
+++ b/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);
diff --git a/bgpd/bgp_routemap_nb_config.c b/bgpd/bgp_routemap_nb_config.c
index 773538ee41..b87877b1e0 100644
--- a/bgpd/bgp_routemap_nb_config.c
+++ b/bgpd/bgp_routemap_nb_config.c
@@ -2209,6 +2209,58 @@ 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
+ */
+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
  */
 int lib_route_map_entry_set_action_rmap_set_action_community_none_modify(