Natively modify host route table

api/gobgp.proto

@@ -100,6 +100,8 @@ service GobgpApi {
 
   rpc EnableZebra(EnableZebraRequest) returns(google.protobuf.Empty);
 
+  rpc EnableModifyHostFIB(EnableModifyHostFIBRequest) returns(google.protobuf.Empty);
+
   rpc EnableMrt(EnableMrtRequest) returns(google.protobuf.Empty);
   rpc DisableMrt(DisableMrtRequest) returns(google.protobuf.Empty);
 
@@ -403,6 +405,9 @@ message EnableZebraRequest {
   string software_name = 7;
 }
 
+message EnableModifyHostFIBRequest {
+}
+
 message EnableMrtRequest {
   enum DumpType { UPDATES = 0; TABLE = 1; }
   DumpType type = 1;

docs/sources/modify-host-fib.md

@@ -0,0 +1,112 @@
+# modify-host-fib
+
+**WARNING: Experimental!**
+
+`modify-host-fib` provides experimental functionality to inject learned routes into the
+routing table of the host running GoBGP. i.e. it provides a subset of something like
+Zebra's functionality without requiring the external dependency of Zebra.
+
+This could be extended in the future to support bidirectional functionality but
+currently only learning routes is supported.
+
+This currently only works on Windows, with IPv4. The initial implementation goal was
+only to get BGP working on Windows desktop OSs (Windows Server has native BGP support -
+if you're here for Windows Server support you should probably use that).
+
+**This is not supported by the core GoBGP team at all. Use at your own risk.**
+
+## Users
+
+Add this to your config:
+
+```toml
+[experimental]
+    [experimental.modify-host-fib]
+        [experimental.modify-host-fib.config]
+            enabled = true
+```
+
+## Developers
+
+### Code flow
+
+The implementation and flow mirrors the Zebra integration. The Zebra integration:
+
+- `/tools/pyang_plugins/gobgp.yang` defines the user-facing configuration options for
+  Zebra in YANG format
+- pyyang converts this into Go structures in `internal/config/bgp_configs.go`
+- If Zebra is enabled, `InitialConfig()` in `pkg/config/config.go` calls `EnableZebra()`
+- `EnableZebra()` in `pkg/server/server.go` calls `NewZebraClient()` to create a new
+  Zebra client and add it to the `BgpServer` singleton
+- `NewZebraClient()` in `pkg/server/zclient.go` sets up the connection to Zebra and
+  kicks off `loop()` as a goroutine
+- `loop()` in `pkg/server/zclient.go` watches for events from `BgpServer` and the Zebra
+  daemon and triggers a matching effect on the opposite side
+
+Additionally a gprc request defined in `api/gobgp.proto` - rendered into `gobgp.pb.go`
+and `gobgp_grpc.pb.go` by `tools/grpc/genproto.sh` - can be used to call
+`EnableZebra()`.
+
+This implementation:
+
+- `/tools/pyang_plugins/gobgp.yang` defines the user-facing configuration options for
+  this feature in YANG format
+- pyyang converts this into Go structures in `internal/config/bgp_configs.go`
+- If this feature is enabled, `InitialConfig()` in `pkg/config/config.go` calls
+  `EnableModifyHostFIB()`
+- `EnableModifyHostFIB()` in `pkg/server/server.go` calls `NewModifyHostFIBClient()` to
+  create a new client and add it to the `BgpServer` singleton
+- `NewModifyHostFIBClient()` in `pkg/server/modify_host_fib.go` kicks off `loop()` as a
+  goroutine
+- `loop()` in `pkg/server/modify_host_fib.go` watches for events from `BgpServer` and
+  updates the host's routing table to match
+- Some external activity (e.g. CTRL+C) triggers `stopServer()` in `main.go`
+- `stopServer()` calls `Stop()` on `bgpServer` in `server.go`
+- `Stop()` calls `stop()` in `modify_host_fib.go`
+- `stop()` stops `loop()`, waits for it to finish, then removes all BGP routes from the
+  host's routing table to clean up
+
+Additionally a gprc request defined in `api/gobgp.proto` - rendered into `gobgp.pb.go`
+and `gobgp_grpc.pb.go` by `tools/grpc/genproto.sh` - can be used to call
+`EnableModifyHostFIB()`.
+
+### Adding a new platform
+
+To support multiple platforms this uses the `<filename>_<platform>.go` pattern used
+elsewhere: each platform's specific implementation is in a separate file and Go `build:`
+ parameters are used to only include the correct files for each platform.
+
+- Add a new `pkg/server/modify_host_fib_<platform>.go` file, e.g.
+   `pkg/server/modify_host_fib_linux.go`
+- Set it to only build for that platform:
+
+```go
+//go:build <platform>
+// +build <platform>
+```
+
+e.g.
+
+```go
+//go:build linux
+// +build linux
+```
+
+- Exclude the default stub file `pkg/server/modify_host_fib_stub.go` from your platform
+
+```go
+//go:build <existing> && !<platform>
+// +build <existing> && !<platform>
+```
+
+e.g.
+
+```go
+//go:build !windows && !linux
+// +build !windows && !linux
+```
+
+- Copy the contents of `pkg/server/modify_host_fib_windows.go` and implement the
+   functions for your platform. The only required functions are
+   `newModifyHostFIBClient()` and `stop()` as these are called by other code in the
+   `server` package. The rest are implementation details.

go.mod

@@ -18,6 +18,7 @@ require (
 	github.com/vishvananda/netlink v1.2.1-beta.2
 	golang.org/x/net v0.4.0
 	golang.org/x/text v0.5.0
+	golang.zx2c4.com/wireguard/windows v0.5.3
 	google.golang.org/grpc v1.51.0
 	google.golang.org/protobuf v1.28.1
 )

go.sum

@@ -416,6 +416,8 @@ golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8T
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.zx2c4.com/wireguard/windows v0.5.3 h1:On6j2Rpn3OEMXqBq00QEDC7bWSZrPIHKIus8eIuExIE=
+golang.zx2c4.com/wireguard/windows v0.5.3/go.mod h1:9TEe8TJmtwyQebdFwAkEWOPr3prrtqm+REGFifP60hI=
 google.golang.org/api v0.4.0/go.mod h1:8k5glujaEP+g9n7WNsDg8QP6cUVNI86fCNMcbazEtwE=
 google.golang.org/api v0.7.0/go.mod h1:WtwebWUNSVBH/HAw79HIFXZNqEvBhG+Ra+ax0hx3E3M=
 google.golang.org/api v0.8.0/go.mod h1:o4eAsZoiT+ibD93RtjEohWalFOjRDx6CVaqeizhEnKg=

internal/pkg/config/serve.go

@@ -15,6 +15,7 @@ type BgpConfigSet struct {
 	Vrfs              []Vrf              `mapstructure:"vrfs"`
 	MrtDump           []Mrt              `mapstructure:"mrt-dump"`
 	Zebra             Zebra              `mapstructure:"zebra"`
+	Experimental      Experimental       `mapstructure:"experimental"`
 	Collector         Collector          `mapstructure:"collector"`
 	DefinedSets       DefinedSets        `mapstructure:"defined-sets"`
 	PolicyDefinitions []PolicyDefinition `mapstructure:"policy-definitions"`

pkg/config/config.go

@@ -250,6 +250,13 @@ func InitialConfig(ctx context.Context, bgpServer *server.BgpServer, newConfig *
 		}
 	}
 
+	if newConfig.Experimental.ModifyHostFib.Config.Enabled {
+		if err := bgpServer.EnableModifyHostFIB(ctx, &api.EnableModifyHostFIBRequest{}); err != nil {
+			bgpServer.Log().Fatal("failed to enable ModifyHostFIB functionality",
+				log.Fields{"Topic": "config", "Error": err})
+		}
+	}
+
 	if len(newConfig.Collector.Config.Url) > 0 {
 		bgpServer.Log().Fatal("collector feature is not supported",
 			log.Fields{"Topic": "config"})

pkg/server/modify_host_fib.go

@@ -0,0 +1,32 @@
+// Copyright (C) 2015 Nippon Telegraph and Telephone Corporation.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+// implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// bits of modify-host-fib functionality that should be included for all platforms.
+
+package server
+
+import (
+	"context"
+	"sync"
+)
+
+type modifyHostFIBClient struct {
+	// global parent struct
+	server *BgpServer
+	// called to stop the loop() goroutine when we shut down
+	stopLoop context.CancelFunc
+	// blocks until loop() is fully shut down after calling stopLoop
+	loopFinished *sync.WaitGroup
+}