From 898b4123fbcad646de1aad2beab16de4819d027f Mon Sep 17 00:00:00 2001
From: Nate Sales <nate@natesales.net>
Date: Sun, 4 Jul 2021 18:37:21 -0700
Subject: [PATCH] add remove-communities attribute

---
 config.go           | 22 ++++++++++++++++++++++
 templates/peer.tmpl |  7 +++++++
 2 files changed, 29 insertions(+)

diff --git a/config.go b/config.go
index c15c8c47..55cdb2a5 100644
--- a/config.go
+++ b/config.go
@@ -63,6 +63,7 @@ type peer struct {
 	ImportCommunities   *[]string `yaml:"import-communities" description:"List of communities to add to all imported routes" default:"-"`
 	ExportCommunities   *[]string `yaml:"export-communities" description:"List of communities to add to all exported routes" default:"-"`
 	AnnounceCommunities *[]string `yaml:"announce-communities" description:"Announce all routes matching these communities to the peer" default:"-"`
+	RemoveCommunities   *[]string `yaml:"remove-communities" description:"List of communities to remove before from routes announced by this peer" default:"-"`
 
 	// Filtering
 	ASSet                   *string `yaml:"as-set" description:"Peer's as-set for filtering" default:"-"`
@@ -115,6 +116,8 @@ type peer struct {
 	ExportLargeCommunities      *[]string `yaml:"-" description:"-" default:"-"`
 	AnnounceStandardCommunities *[]string `yaml:"-" description:"-" default:"-"`
 	AnnounceLargeCommunities    *[]string `yaml:"-" description:"-" default:"-"`
+	RemoveStandardCommunities   *[]string `yaml:"-" description:"-" default:"-"`
+	RemoveLargeCommunities      *[]string `yaml:"-" description:"-" default:"-"`
 }
 
 type vrrpInstance struct {
@@ -429,6 +432,25 @@ func loadConfig(configBlob []byte) (*config, error) {
 				}
 			}
 		}
+		if peerData.RemoveCommunities != nil {
+			for _, community := range *peerData.RemoveCommunities {
+				communityType := categorizeCommunity(community)
+
+				if communityType == "standard" {
+					if peerData.RemoveStandardCommunities == nil {
+						peerData.RemoveStandardCommunities = &[]string{}
+					}
+					*peerData.RemoveStandardCommunities = append(*peerData.RemoveStandardCommunities, community)
+				} else if communityType == "large" {
+					if peerData.RemoveLargeCommunities == nil {
+						peerData.RemoveLargeCommunities = &[]string{}
+					}
+					*peerData.RemoveLargeCommunities = append(*peerData.RemoveLargeCommunities, strings.ReplaceAll(community, ":", ","))
+				} else {
+					return nil, errors.New("Invalid remove community: " + community)
+				}
+			}
+		}
 
 		// Check for no originated prefixes but announce-originated enabled
 		if len(c.Prefixes) < 1 && *peerData.AnnounceOriginated {
diff --git a/templates/peer.tmpl b/templates/peer.tmpl
index bad7d332..9e4b36fa 100644
--- a/templates/peer.tmpl
+++ b/templates/peer.tmpl
@@ -55,6 +55,13 @@ protocol bgp {{ UniqueProtocolName $peer.ProtocolName $af }} {
             {{ if BoolDeref $peer.EnforcePeerNexthop }}enforce_peer_nexthop({{ $neighbor }});{{ end }}
             {{ if BoolDeref $peer.FilterTransitASNs }}reject_transit_paths();{{ end }}
 
+            {{ range $i, $pattern := StringSliceIter $peer.RemoveStandardCommunities }}
+            bgp_community.delete([({{ $pattern }})]);
+            {{ end }}
+            {{ range $i, $pattern := StringSliceIter $peer.RemoveLargeCommunities }}
+            bgp_large_community.delete([({{ $pattern }})]);
+            {{ end }}
+
             {{ if BoolDeref $peer.AllowBlackholeCommunity }}process_blackholes();{{ end }}
 
             bgp_local_pref = {{ $peer.LocalPref }};