docs: add a document about how to use gobgp as a bgp library

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

2 files changed, 86 insertions, 0 deletions

diff --git a/README.md b/README.md
index 486802c6..97886d49 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,7 @@ No dependency hell (library, package, etc) thanks to Go.
  * [Flowspec](https://github.com/osrg/gobgp/blob/master/docs/sources/flowspec.md)
  * [RPKI](https://github.com/osrg/gobgp/blob/master/docs/sources/rpki.md)
  * [Managing GoBGP with your favorite language](https://github.com/osrg/gobgp/blob/master/docs/sources/grpc-client.md)
+ * [Using GoBGP as a Go Native BGP library](https://github.com/osrg/gobgp/blob/master/docs/sources/lib.md)
  
 ## Community, discussion and support
 
diff --git a/docs/sources/lib.md b/docs/sources/lib.md
new file mode 100644
index 00000000..a8e55894
--- /dev/null
+++ b/docs/sources/lib.md
@@ -0,0 +1,85 @@
+# GoBGP as a Go Native BGP library
+
+This page explains how to use GoBGP as a Go Native BGP library.
+
+## Contents
+- [Basic Example](#basic)
+
+## <a name="basic"> Basic Example
+
+```go
+package main
+
+import (
+	log "github.com/Sirupsen/logrus"
+	api "github.com/osrg/gobgp/api"
+	"github.com/osrg/gobgp/gobgp/cmd"
+	"github.com/osrg/gobgp/packet"
+	gobgp "github.com/osrg/gobgp/server"
+)
+
+func main() {
+	log.SetLevel(log.DebugLevel)
+	s := gobgp.NewBgpServer()
+	go s.Serve()
+
+	// start grpc api server. this is not mandatory
+	// but you will be able to use `gobgp` cmd with this.
+	g := gobgp.NewGrpcServer(gobgp.GRPC_PORT, s.GrpcReqCh)
+	go g.Serve()
+
+	// global configuration
+	req := gobgp.NewGrpcRequest(gobgp.REQ_MOD_GLOBAL_CONFIG, "", bgp.RouteFamily(0), &api.ModGlobalConfigArguments{
+		Operation: api.Operation_ADD,
+		Global: &api.Global{
+			As:       65003,
+			RouterId: "192.168.0.4",
+			Port:     -1, // gobgp won't listen on tcp:179
+		},
+	})
+	s.GrpcReqCh <- req
+	res := <-req.ResponseCh
+	if err := res.Err(); err != nil {
+		log.Fatal(err)
+	}
+
+	// neighbor configuration
+	req = gobgp.NewGrpcRequest(gobgp.REQ_MOD_NEIGHBOR, "", bgp.RouteFamily(0), &api.ModNeighborArguments{
+		Operation: api.Operation_ADD,
+		Peer: &api.Peer{
+			Conf: &api.PeerConf{
+				NeighborAddress: "192.168.0.3",
+				PeerAs:          65000,
+			},
+			Transport: &api.Transport{
+				LocalAddress: "192.168.0.4",
+			},
+		},
+	})
+	s.GrpcReqCh <- req
+	res = <-req.ResponseCh
+	if err := res.Err(); err != nil {
+		log.Fatal(err)
+	}
+
+	// add routes
+	path, _ := cmd.ParsePath(bgp.RF_IPv4_UC, []string{"10.0.0.0/24", "nexthop", "10.10.10.10"})
+	req = gobgp.NewGrpcRequest(gobgp.REQ_MOD_PATH, "", bgp.RouteFamily(0), &api.ModPathArguments{
+		Resource: api.Resource_GLOBAL,
+		Paths:    []*api.Path{path},
+	})
+	s.GrpcReqCh <- req
+	res = <-req.ResponseCh
+	if err := res.Err(); err != nil {
+		log.Fatal(err)
+	}
+
+	// monitor new routes
+	req = gobgp.NewGrpcRequest(gobgp.REQ_MONITOR_GLOBAL_BEST_CHANGED, "", bgp.RF_IPv4_UC, nil)
+	s.GrpcReqCh <- req
+	for res := range req.ResponseCh {
+		p, _ := cmd.ApiStruct2Path(res.Data.(*api.Destination).Paths[0])
+		cmd.ShowRoute(p, false, false, false, true, false)
+	}
+}
+```