bgpd: Create BGP alias names for community/large-community

Show alias name instead of numerical value in `show bgp <prefix>. E.g.:

```
root@exit1-debian-9:~/frr# vtysh -c 'sh run' | grep 'bgp community alias'
bgp community alias 65001:123 community-1
bgp community alias 65001:123:1 lcommunity-1
root@exit1-debian-9:~/frr#
```

```
exit1-debian-9# sh ip bgp 172.16.16.1/32
BGP routing table entry for 172.16.16.1/32, version 21
Paths: (2 available, best #2, table default)
  Advertised to non peer-group peers:
  65030
    192.168.0.2 from home-spine1.donatas.net(192.168.0.2) (172.16.16.1)
      Origin incomplete, metric 0, valid, external, best (Neighbor IP)
      Community: 65001:12 65001:13 community-1 65001:65534
      Large Community: lcommunity-1 65001:123:2
      Last update: Fri Apr 16 12:51:27 2021
exit1-debian-9#
```

Signed-off-by: Donatas Abraitis <donatas.abraitis@gmail.com>

14 files changed, 304 insertions, 9 deletions

diff --git a/bgpd/bgp_community.c b/bgpd/bgp_community.c
index 43138b82f..b034ec9f7 100644
--- a/bgpd/bgp_community.c
+++ b/bgpd/bgp_community.c
@@ -28,6 +28,7 @@
 
 #include "bgpd/bgp_memory.h"
 #include "bgpd/bgp_community.h"
+#include "bgpd/bgp_community_alias.h"
 
 /* Hash of community attribute. */
 static struct hash *comhash;
@@ -292,7 +293,7 @@ static void set_community_string(struct community *com, bool make_json)
 			len += strlen(" no-peer");
 			break;
 		default:
-			len += strlen(" 65536:65535");
+			len = BUFSIZ;
 			break;
 		}
 	}
@@ -450,7 +451,7 @@ static void set_community_string(struct community *com, bool make_json)
 			val = comval & 0xFFFF;
 			char buf[32];
 			snprintf(buf, sizeof(buf), "%u:%d", as, val);
-			strlcat(str, buf, len);
+			strlcat(str, bgp_community2alias(buf), len);
 			if (make_json) {
 				json_string = json_object_new_string(buf);
 				json_object_array_add(json_community_list,
diff --git a/bgpd/bgp_community_alias.c b/bgpd/bgp_community_alias.c
new file mode 100644
index 000000000..6e510a0a0
--- /dev/null
+++ b/bgpd/bgp_community_alias.c
@@ -0,0 +1,154 @@
+/* BGP community, large-community aliasing.
+ *
+ * Copyright (C) 2021 Donatas Abraitis <donatas.abraitis@gmail.com>
+ *
+ * This file is part of FRRouting (FRR).
+ *
+ * FRR is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 2, or (at your option) any later version.
+ *
+ * FRR is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; see the file COPYING; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "memory.h"
+#include "lib/jhash.h"
+
+#include "bgpd/bgpd.h"
+#include "bgpd/bgp_community_alias.h"
+
+static struct hash *bgp_ca_alias_hash;
+static struct hash *bgp_ca_community_hash;
+
+static unsigned int bgp_ca_community_hash_key(const void *p)
+{
+	const struct community_alias *ca = p;
+
+	return jhash(ca->community, sizeof(ca->community), 0);
+}
+
+static bool bgp_ca_community_hash_cmp(const void *p1, const void *p2)
+{
+	const struct community_alias *ca1 = p1;
+	const struct community_alias *ca2 = p2;
+
+	return (strncmp(ca1->community, ca2->community,
+			sizeof(struct community_alias))
+		== 0);
+}
+
+static unsigned int bgp_ca_alias_hash_key(const void *p)
+{
+	const struct community_alias *ca = p;
+
+	return jhash(ca->alias, sizeof(ca->alias), 0);
+}
+
+static bool bgp_ca_alias_hash_cmp(const void *p1, const void *p2)
+{
+	const struct community_alias *ca1 = p1;
+	const struct community_alias *ca2 = p2;
+
+	return (strncmp(ca1->alias, ca2->alias, sizeof(struct community_alias))
+		== 0);
+}
+
+static void *bgp_community_alias_alloc(void *p)
+{
+	const struct community_alias *ca = p;
+	struct communtiy_alias *new;
+
+	new = XCALLOC(MTYPE_COMMUNITY_ALIAS, sizeof(struct community_alias));
+	memcpy(new, ca, sizeof(struct community_alias));
+
+	return new;
+}
+
+void bgp_community_alias_init(void)
+{
+	bgp_ca_community_hash = hash_create(bgp_ca_community_hash_key,
+					       bgp_ca_community_hash_cmp,
+					       "BGP community alias (community)");
+	bgp_ca_alias_hash =
+		hash_create(bgp_ca_alias_hash_key, bgp_ca_alias_hash_cmp,
+			    "BGP community alias (alias)");
+}
+
+void bgp_community_alias_finish(void)
+{
+	hash_free(bgp_ca_community_hash);
+	hash_free(bgp_ca_alias_hash);
+}
+
+static void bgp_community_alias_show_iterator(struct hash_bucket *hb,
+					      struct vty *vty)
+{
+	struct community_alias *ca = hb->data;
+
+	vty_out(vty, "bgp community alias %s %s\n", ca->community, ca->alias);
+}
+
+int bgp_community_alias_write(struct vty *vty)
+{
+	hash_iterate(bgp_ca_community_hash,
+		     (void (*)(struct hash_bucket *,
+			       void *))bgp_community_alias_show_iterator,
+		     vty);
+	return 1;
+}
+
+void bgp_ca_community_insert(struct community_alias *ca)
+{
+	hash_get(bgp_ca_community_hash, ca, bgp_community_alias_alloc);
+}
+
+void bgp_ca_alias_insert(struct community_alias *ca)
+{
+	hash_get(bgp_ca_alias_hash, ca, bgp_community_alias_alloc);
+}
+
+void bgp_ca_community_delete(struct community_alias *ca)
+{
+	struct community_alias *data = hash_release(bgp_ca_community_hash, ca);
+
+	XFREE(MTYPE_COMMUNITY_ALIAS, data);
+}
+
+void bgp_ca_alias_delete(struct community_alias *ca)
+{
+	struct community_alias *data = hash_release(bgp_ca_alias_hash, ca);
+
+	XFREE(MTYPE_COMMUNITY_ALIAS, data);
+}
+
+struct community_alias *bgp_ca_community_lookup(struct community_alias *ca)
+{
+	return hash_lookup(bgp_ca_community_hash, ca);
+}
+
+struct community_alias *bgp_ca_alias_lookup(struct community_alias *ca)
+{
+	return hash_lookup(bgp_ca_alias_hash, ca);
+}
+
+const char *bgp_community2alias(char *community)
+{
+	struct community_alias ca;
+	struct community_alias *find;
+
+	memset(&ca, 0, sizeof(ca));
+	strlcpy(ca.community, community, sizeof(ca.community));
+
+	find = bgp_ca_community_lookup(&ca);
+	if (find)
+		return find->alias;
+
+	return community;
+}
diff --git a/bgpd/bgp_community_alias.h b/bgpd/bgp_community_alias.h
new file mode 100644
index 000000000..c84119a0d
--- /dev/null
+++ b/bgpd/bgp_community_alias.h
@@ -0,0 +1,46 @@
+/* BGP community, large-community aliasing.
+ *
+ * Copyright (C) 2021 Donatas Abraitis <donatas.abraitis@gmail.com>
+ *
+ * This file is part of FRRouting (FRR).
+ *
+ * FRR is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 2, or (at your option) any later version.
+ *
+ * FRR is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; see the file COPYING; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "bgpd/bgp_lcommunity.h"
+
+#ifndef FRR_BGP_COMMUNITY_ALIAS_H
+#define FRR_BGP_COMMUNITY_ALIAS_H
+
+struct community_alias {
+	/* Human readable community string */
+	char community[LCOMMUNITY_SIZE * 3];
+
+	/* Human readable community alias */
+	char alias[BUFSIZ];
+};
+
+extern void bgp_community_alias_init(void);
+extern void bgp_community_alias_finish(void);
+extern struct community_alias *bgp_ca_alias_lookup(struct community_alias *ca);
+extern struct community_alias *
+bgp_ca_community_lookup(struct community_alias *ca);
+extern void bgp_ca_community_insert(struct community_alias *ca);
+extern void bgp_ca_alias_insert(struct community_alias *ca);
+extern void bgp_ca_community_delete(struct community_alias *ca);
+extern void bgp_ca_alias_delete(struct community_alias *ca);
+extern int bgp_community_alias_write(struct vty *vty);
+extern const char *bgp_community2alias(char *community);
+
+#endif /* FRR_BGP_COMMUNITY_ALIAS_H */
diff --git a/bgpd/bgp_lcommunity.c b/bgpd/bgp_lcommunity.c
index 88a85c979..ff34937ef 100644
--- a/bgpd/bgp_lcommunity.c
+++ b/bgpd/bgp_lcommunity.c
@@ -30,6 +30,7 @@
 
 #include "bgpd/bgpd.h"
 #include "bgpd/bgp_lcommunity.h"
+#include "bgpd/bgp_community_alias.h"
 #include "bgpd/bgp_aspath.h"
 
 /* Hash of community attribute. */
@@ -213,7 +214,7 @@ static void set_lcommunity_string(struct lcommunity *lcom, bool make_json)
 	}
 
 	/* 1 space + lcom->size lcom strings + null terminator */
-	size_t str_buf_sz = (LCOMMUNITY_STRLEN * lcom->size) + 2;
+	size_t str_buf_sz = BUFSIZ;
 	str_buf = XCALLOC(MTYPE_LCOMMUNITY_STR, str_buf_sz);
 
 	for (i = 0; i < lcom->size; i++) {
@@ -231,7 +232,7 @@ static void set_lcommunity_string(struct lcommunity *lcom, bool make_json)
 		snprintf(lcsb, sizeof(lcsb), "%u:%u:%u", global, local1,
 			 local2);
 
-		len = strlcat(str_buf, lcsb, str_buf_sz);
+		len = strlcat(str_buf, bgp_community2alias(lcsb), str_buf_sz);
 		assert((unsigned int)len < str_buf_sz);
 
 		if (make_json) {
diff --git a/bgpd/bgp_main.c b/bgpd/bgp_main.c
index ea74a82ce..995917b6b 100644
--- a/bgpd/bgp_main.c
+++ b/bgpd/bgp_main.c
@@ -66,6 +66,7 @@
 #include "bgpd/bgp_evpn_mh.h"
 #include "bgpd/bgp_nht.h"
 #include "bgpd/bgp_routemap_nb.h"
+#include "bgpd/bgp_community_alias.h"
 
 #ifdef ENABLE_BGP_VNC
 #include "bgpd/rfapi/rfapi_backend.h"
@@ -220,6 +221,9 @@ static __attribute__((__noreturn__)) void bgp_exit(int status)
 	/* reverse bgp_dump_init */
 	bgp_dump_finish();
 
+	/* BGP community aliases */
+	bgp_community_alias_finish();
+
 	/* reverse bgp_route_init */
 	bgp_route_finish();
 
diff --git a/bgpd/bgp_memory.c b/bgpd/bgp_memory.c
index 36bdc05eb..fc508496c 100644
--- a/bgpd/bgp_memory.c
+++ b/bgpd/bgp_memory.c
@@ -65,6 +65,8 @@ DEFINE_MTYPE(BGPD, AS_LIST, "BGP AS list");
 DEFINE_MTYPE(BGPD, AS_FILTER, "BGP AS filter");
 DEFINE_MTYPE(BGPD, AS_FILTER_STR, "BGP AS filter str");
 
+DEFINE_MTYPE(BGPD, COMMUNITY_ALIAS, "community");
+
 DEFINE_MTYPE(BGPD, COMMUNITY, "community");
 DEFINE_MTYPE(BGPD, COMMUNITY_VAL, "community val");
 DEFINE_MTYPE(BGPD, COMMUNITY_STR, "community str");
diff --git a/bgpd/bgp_memory.h b/bgpd/bgp_memory.h
index 29923424e..408024803 100644
--- a/bgpd/bgp_memory.h
+++ b/bgpd/bgp_memory.h
@@ -61,6 +61,8 @@ DECLARE_MTYPE(AS_LIST);
 DECLARE_MTYPE(AS_FILTER);
 DECLARE_MTYPE(AS_FILTER_STR);
 
+DECLARE_MTYPE(COMMUNITY_ALIAS);
+
 DECLARE_MTYPE(COMMUNITY);
 DECLARE_MTYPE(COMMUNITY_VAL);
 DECLARE_MTYPE(COMMUNITY_STR);
diff --git a/bgpd/bgp_route.c b/bgpd/bgp_route.c
index 49b94e6d7..77a0b5fea 100644
--- a/bgpd/bgp_route.c
+++ b/bgpd/bgp_route.c
@@ -51,6 +51,7 @@
 #include "bgpd/bgp_aspath.h"
 #include "bgpd/bgp_regex.h"
 #include "bgpd/bgp_community.h"
+#include "bgpd/bgp_community_alias.h"
 #include "bgpd/bgp_ecommunity.h"
 #include "bgpd/bgp_lcommunity.h"
 #include "bgpd/bgp_clist.h"
diff --git a/bgpd/bgp_vty.c b/bgpd/bgp_vty.c
index 0347f49cb..7cd36ef53 100644
--- a/bgpd/bgp_vty.c
+++ b/bgpd/bgp_vty.c
@@ -46,6 +46,7 @@
 #include "bgpd/bgp_attr.h"
 #include "bgpd/bgp_aspath.h"
 #include "bgpd/bgp_community.h"
+#include "bgpd/bgp_community_alias.h"
 #include "bgpd/bgp_ecommunity.h"
 #include "bgpd/bgp_lcommunity.h"
 #include "bgpd/bgp_damp.h"
@@ -1497,6 +1498,62 @@ void cli_show_router_bgp_router_id(struct vty *vty, struct lyd_node *dnode,
 	vty_out(vty, " bgp router-id %s\n", yang_dnode_get_string(dnode, NULL));
 }
 
+DEFPY(bgp_community_alias, bgp_community_alias_cmd,
+      "[no$no] bgp community alias WORD$community WORD$alias",
+      NO_STR BGP_STR
+      "Add community specific parameters\n"
+      "Create an alias for a community\n"
+      "Community (AA:BB or AA:BB:CC)\n"
+      "Alias name\n")
+{
+	struct community_alias ca1;
+	struct community_alias ca2;
+	struct community_alias *lookup_community;
+	struct community_alias *lookup_alias;
+
+	if (!community_str2com(community) && !lcommunity_str2com(community)) {
+		vty_out(vty, "Invalid community format\n");
+		return CMD_WARNING;
+	}
+
+	memset(&ca1, 0, sizeof(ca1));
+	memset(&ca2, 0, sizeof(ca2));
+	strlcpy(ca1.community, community, sizeof(ca1.community));
+	strlcpy(ca1.alias, alias, sizeof(ca1.alias));
+
+	lookup_community = bgp_ca_community_lookup(&ca1);
+	lookup_alias = bgp_ca_alias_lookup(&ca1);
+
+	if (no) {
+		bgp_ca_alias_delete(&ca1);
+		bgp_ca_community_delete(&ca1);
+	} else {
+		if (lookup_alias) {
+			/* Lookup if community hash table has an item
+			 * with the same alias name.
+			 */
+			strlcpy(ca2.community, lookup_alias->community,
+				sizeof(ca2.community));
+			if (bgp_ca_community_lookup(&ca2)) {
+				vty_out(vty,
+					"community (%s) already has this alias (%s)\n",
+					lookup_alias->community,
+					lookup_alias->alias);
+				return CMD_WARNING;
+			}
+			bgp_ca_alias_delete(&ca1);
+		}
+
+		if (lookup_community)
+			bgp_ca_community_delete(&ca1);
+
+		bgp_ca_alias_insert(&ca1);
+		bgp_ca_community_insert(&ca1);
+	}
+
+	return CMD_SUCCESS;
+}
+
 DEFPY (bgp_global_suppress_fib_pending,
        bgp_global_suppress_fib_pending_cmd,
        "[no] bgp suppress-fib-pending",
@@ -19261,6 +19318,8 @@ void bgp_vty_init(void)
 	/* Community-list. */
 	community_list_vty();
 
+	community_alias_vty();
+
 	/* vpn-policy commands */
 	install_element(BGP_IPV4_NODE, &af_rd_vpn_export_cmd);
 	install_element(BGP_IPV6_NODE, &af_rd_vpn_export_cmd);
@@ -20467,3 +20526,18 @@ static void community_list_vty(void)
 	install_element(VIEW_NODE, &show_bgp_lcommunity_list_cmd);
 	install_element(VIEW_NODE, &show_bgp_lcommunity_list_arg_cmd);
 }
+
+static struct cmd_node community_alias_node = {
+	.name = "community alias",
+	.node = COMMUNITY_ALIAS_NODE,
+	.prompt = "",
+	.config_write = bgp_community_alias_write,
+};
+
+void community_alias_vty(void)
+{
+	install_node(&community_alias_node);
+
+	/* Community-list.  */
+	install_element(CONFIG_NODE, &bgp_community_alias_cmd);
+}
diff --git a/bgpd/bgp_vty.h b/bgpd/bgp_vty.h
index 251bdc3fe..051b2e958 100644
--- a/bgpd/bgp_vty.h
+++ b/bgpd/bgp_vty.h
@@ -154,6 +154,7 @@ struct bgp;
 	} while (0)
 
 extern void bgp_vty_init(void);
+extern void community_alias_vty(void);
 extern const char *get_afi_safi_str(afi_t afi, safi_t safi, bool for_json);
 extern int bgp_get_vty(struct bgp **bgp, as_t *as, const char *name,
 		       enum bgp_instance_type inst_type);
diff --git a/bgpd/bgpd.c b/bgpd/bgpd.c
index 2c9aad5d2..73c1cbbbd 100644
--- a/bgpd/bgpd.c
+++ b/bgpd/bgpd.c
@@ -55,6 +55,7 @@
 #include "bgpd/bgp_debug.h"
 #include "bgpd/bgp_errors.h"
 #include "bgpd/bgp_community.h"
+#include "bgpd/bgp_community_alias.h"
 #include "bgpd/bgp_conditional_adv.h"
 #include "bgpd/bgp_attr.h"
 #include "bgpd/bgp_regex.h"
@@ -7697,6 +7698,7 @@ void bgp_init(unsigned short instance)
 	/* BGP inits. */
 	bgp_attr_init();
 	bgp_debug_init();
+	bgp_community_alias_init();
 	bgp_dump_init();
 	bgp_route_init();
 	bgp_route_map_init();
diff --git a/bgpd/subdir.am b/bgpd/subdir.am
index 2c73f1459..b54c41cab 100644
--- a/bgpd/subdir.am
+++ b/bgpd/subdir.am
@@ -57,6 +57,7 @@ bgpd_libbgp_a_SOURCES = \
 	bgpd/bgp_bfd.c \
 	bgpd/bgp_clist.c \
 	bgpd/bgp_community.c \
+	bgpd/bgp_community_alias.c \
 	bgpd/bgp_conditional_adv.c \
 	bgpd/bgp_damp.c \
 	bgpd/bgp_debug.c \
@@ -137,6 +138,7 @@ noinst_HEADERS += \
 	bgpd/bgp_bfd.h \
 	bgpd/bgp_clist.h \
 	bgpd/bgp_community.h \
+	bgpd/bgp_community_alias.h \
 	bgpd/bgp_conditional_adv.h \
 	bgpd/bgp_damp.h \
 	bgpd/bgp_debug.h \
diff --git a/lib/command.h b/lib/command.h
index 7e135dbcf..51da4c52e 100644
--- a/lib/command.h
+++ b/lib/command.h
@@ -137,6 +137,7 @@ enum node_type {
 	PREFIX_IPV6_NODE,	/* Prefix list node. */
 	AS_LIST_NODE,		 /* AS list node. */
 	COMMUNITY_LIST_NODE,     /* Community list node. */
+	COMMUNITY_ALIAS_NODE, /* Community alias node. */
 	RMAP_NODE,		 /* Route map node. */
 	PBRMAP_NODE,		 /* PBR map node. */
 	SMUX_NODE,		 /* SNMP configuration node. */
diff --git a/vtysh/vtysh_config.c b/vtysh/vtysh_config.c
index 3414c764c..f92b0e920 100644
--- a/vtysh/vtysh_config.c
+++ b/vtysh/vtysh_config.c
@@ -380,6 +380,9 @@ void vtysh_config_parse_line(void *arg, const char *line)
 				    strlen("bgp large-community-list"))
 				    == 0)
 			config = config_get(COMMUNITY_LIST_NODE, line);
+		else if (strncmp(line, "bgp community alias",
+				 strlen("bgp community alias")) == 0)
+			config = config_get(COMMUNITY_ALIAS_NODE, line);
 		else if (strncmp(line, "ip route", strlen("ip route")) == 0)
 			config = config_get(IP_NODE, line);
 		else if (strncmp(line, "ipv6 route", strlen("ipv6 route")) == 0)
@@ -452,11 +455,12 @@ void vtysh_config_parse_line(void *arg, const char *line)
 #define NO_DELIMITER(I)                                                        \
 	((I) == ACCESS_NODE || (I) == PREFIX_NODE || (I) == IP_NODE            \
 	 || (I) == AS_LIST_NODE || (I) == COMMUNITY_LIST_NODE                  \
-	 || (I) == ACCESS_IPV6_NODE || (I) == ACCESS_MAC_NODE                  \
-	 || (I) == PREFIX_IPV6_NODE || (I) == FORWARDING_NODE                  \
-	 || (I) == DEBUG_NODE || (I) == AAA_NODE || (I) == VRF_DEBUG_NODE      \
-	 || (I) == NORTHBOUND_DEBUG_NODE || (I) == RMAP_DEBUG_NODE             \
-	 || (I) == RESOLVER_DEBUG_NODE || (I) == MPLS_NODE)
+	 || (I) == COMMUNITY_ALIAS_NODE || (I) == ACCESS_IPV6_NODE             \
+	 || (I) == ACCESS_MAC_NODE || (I) == PREFIX_IPV6_NODE                  \
+	 || (I) == FORWARDING_NODE || (I) == DEBUG_NODE || (I) == AAA_NODE     \
+	 || (I) == VRF_DEBUG_NODE || (I) == NORTHBOUND_DEBUG_NODE              \
+	 || (I) == RMAP_DEBUG_NODE || (I) == RESOLVER_DEBUG_NODE               \
+	 || (I) == MPLS_NODE)
 
 /* Display configuration to file pointer. */
 void vtysh_config_dump(void)