added well known communities and merge method

backend/bgp_communities.go

@@ -0,0 +1,75 @@
+package main
+
+/*
+Implement BGP Communities Lookup Base
+
+We initialize the dictionary with well known communities and
+store the representation as a string with : as delimiter.
+
+From: https://www.iana.org/assignments/bgp-well-known-communities/bgp-well-known-communities.xhtml
+
+    0x00000000-0x0000FFFF   Reserved    [RFC1997]
+    0x00010000-0xFFFEFFFF   Reserved for Private Use    [RFC1997]
+
+    0xFFFF0000  GRACEFUL_SHUTDOWN   [RFC8326]
+    0xFFFF0001  ACCEPT_OWN          [RFC7611]
+    0xFFFF0002  ROUTE_FILTER_TRANSLATED_v4  [draft-l3vpn-legacy-rtc]
+    0xFFFF0003  ROUTE_FILTER_v4     [draft-l3vpn-legacy-rtc]
+    0xFFFF0004  ROUTE_FILTER_TRANSLATED_v6  [draft-l3vpn-legacy-rtc]
+    0xFFFF0005  ROUTE_FILTER_v6     [draft-l3vpn-legacy-rtc]
+    0xFFFF0006  LLGR_STALE          [draft-uttaro-idr-bgp-persistence]
+    0xFFFF0007  NO_LLGR             [draft-uttaro-idr-bgp-persistence]
+    0xFFFF0008  accept-own-nexthop  [draft-agrewal-idr-accept-own-nexthop]
+
+    0xFFFF0009-0xFFFF0299   Unassigned
+
+    0xFFFF029A  BLACKHOLE           [RFC7999]
+
+    0xFFFF029B-0xFFFFFF00   Unassigned
+
+    0xFFFFFF01  NO_EXPORT           [RFC1997]
+    0xFFFFFF02  NO_ADVERTISE        [RFC1997]
+    0xFFFFFF03  NO_EXPORT_SUBCONFED [RFC1997]
+    0xFFFFFF04  NOPEER              [RFC3765]
+    0xFFFFFF05-0xFFFFFFFF   Unassigned
+*/
+
+type BgpCommunities map[string]string
+
+func MakeWellKnownBgpCommunities() BgpCommunities {
+	c := BgpCommunities{
+		"65535:0": "graceful shutdown",
+		"65535:1": "accept own",
+		"65535:2": "route filter translated v4",
+		"65535:3": "route filter v4",
+		"65535:4": "route filter translated v6",
+		"65535:5": "route filter v6",
+		"65535:6": "llgr stale",
+		"65535:7": "no llgr",
+		"65535:8": "accept-own-nexthop",
+
+		"65535:666": "blackhole",
+
+		"65535:1048321": "no export",
+		"65535:1048322": "no advertise",
+		"65535:1048323": "no export subconfed",
+		"65535:1048324": "nopeer",
+	}
+
+	return c
+}
+
+func (self BgpCommunities) Merge(communities BgpCommunities) BgpCommunities {
+	merged := BgpCommunities{}
+
+	// Make copy, don't mutate
+	for k, v := range self {
+		merged[k] = v
+	}
+
+	for k, v := range communities {
+		merged[k] = v
+	}
+
+	return merged
+}

backend/bgp_communities_test.go

@@ -0,0 +1,23 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestMergeCommunities(t *testing.T) {
+
+	c := MakeWellKnownBgpCommunities()
+
+	merged := c.Merge(BgpCommunities{
+		"2342:0":   "foo",
+		"2342:123": "bar",
+	})
+
+	if merged["65535:666"] != "blackhole" {
+		t.Error("old values should be present")
+	}
+
+	if merged["2342:123"] != "bar" {
+		t.Error("new values should be present")
+	}
+}