*: support replace-peer-as (aka as-override)

we use the term replace-peer-as instead of as-override
since openconfig is using it.

cli

```
$ gobgp n add <neighbor-addr> as <asn> replace-peer-as
```

config

```
neighbor:
  config:
    peer-as: <asn>
    neighbor-address: <neighbor-addr>
  as-path-options:
    config:
      replace-peer-as: true
```

Signed-off-by: Wataru Ishida <ishida.wataru@lab.ntt.co.jp>

1 files changed, 5 insertions, 0 deletions

diff --git a/server/peer.go b/server/peer.go
index bd977b85..5e04ccf6 100644
--- a/server/peer.go
+++ b/server/peer.go
@@ -267,6 +267,11 @@ func (peer *Peer) filterpath(path, old *table.Path) *table.Path {
 		}
 	}
 
+	// replace-peer-as handling
+	if path != nil && !path.IsWithdraw && peer.fsm.pConf.AsPathOptions.State.ReplacePeerAs {
+		path = path.ReplaceAS(peer.fsm.pConf.Config.LocalAs, peer.fsm.pConf.Config.PeerAs)
+	}
+
 	if path = filterpath(peer, path, old); path == nil {
 		return nil
 	}