commit 2ca078305c10f18660e11c832dc4922fe3054f91 Author: Mahadevan Date: Sat Aug 5 13:06:25 2017 +0530 Initial commit diff --git a/LICENSE b/LICENSE new file mode 100644 index 0000000..8f71f43 --- /dev/null +++ b/LICENSE @@ -0,0 +1,202 @@ + Apache License + Version 2.0, January 2004 + http://www.apache.org/licenses/ + + TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION + + 1. Definitions. + + "License" shall mean the terms and conditions for use, reproduction, + and distribution as defined by Sections 1 through 9 of this document. + + "Licensor" shall mean the copyright owner or entity authorized by + the copyright owner that is granting the License. + + "Legal Entity" shall mean the union of the acting entity and all + other entities that control, are controlled by, or are under common + control with that entity. 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Do not use it for anything serious._ + +vlan-nats creates a virtual LAN using [NATS](https://nats.io/). Backed by a NATS +server (or cluster), vlan-nats can create and run a network interface that is +connected to a virtual L2 switch. + +vlan-nats is written in entirely in Go. Currently, it works only on Linux. +Multicast is not supported. + +First, get and build vlan-nats: + +``` +$ go get github.com/rapidloop/vlan-nats +``` + +Then, on each machine, do: + +``` +sudo vlan-nats -n nats://{MY-NATS-SERVER}:4222 & +sudo ip addr add 10.1.0.{CHANGEME} broadcast 10.1.255.255 dev vnats0 +sudo ip link set vnats0 up +sudo ip route add 10.1.0.0/16 dev vnats0 +``` + +You should replace `{CHANGEME}` with a unique number. The `{MY-NATS-SERVER}` is +the IP or host of a reachable NATS server (all machines must connect to the same +NATS cluster). + +Congratulations! You now have all your machines reachable on the virtual subnet +10.1.0.0/16. You should be able to ping each other: + +``` +$ ip a show vnats0 +7: vnats0: mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 1000 + link/ether 7e:8f:d4:17:2b:0c brd ff:ff:ff:ff:ff:ff + inet 10.1.0.1/32 brd 10.1.255.255 scope global vnats0 + valid_lft forever preferred_lft forever + inet6 fe80::7c8f:d4ff:fe17:2b0c/64 scope link tentative dadfailed + valid_lft forever preferred_lft forever +$ ping 10.1.0.2 +PING 10.1.0.2 (10.1.0.2) 56(84) bytes of data. +64 bytes from 10.1.0.2: icmp_seq=1 ttl=64 time=1.70 ms +64 bytes from 10.1.0.2: icmp_seq=2 ttl=64 time=1.60 ms +^C +--- 10.1.0.2 ping statistics --- +2 packets transmitted, 2 received, 0% packet loss, time 1003ms +rtt min/avg/max/mdev = 1.603/1.654/1.706/0.065 ms +$ +``` + +Cool! + +To cleanup, just `sudo pkill vlan-nats`. The interface is not persisted. + +### How It Works + +vlan-nats creates a TAP interface. All broadcast frames from the interface are +published to the NATS topic `vlan.{ID}` and unicast frames are published to +`vlan.{ID}.{DST_ETHADDR}`. The process subscribes to `vlan.{ID}` and +`vlan.{ID}.{OWN_ETHADDR}` and writes out any received frames into the TAP +interface. + +Windows and OS X do not natively support TAP devices, but (free) 3rd party +drivers are available. + +### Things To Try Out + +* Windows and OS X can be supported with 3rd party TAP drivers. +* Run a DHCP server instead of assigning static IPs. +* Use a TLS-enabled, authenticated, public NATS server -- like a VPN! + + diff --git a/main.go b/main.go new file mode 100644 index 0000000..74c02a7 --- /dev/null +++ b/main.go @@ -0,0 +1,105 @@ +package main + +import ( + "flag" + "fmt" + "log" + "net" + "time" + + nats "github.com/nats-io/go-nats" + "github.com/songgao/water" + "github.com/songgao/water/waterutil" +) + +var ( + natsURL = flag.String("n", nats.DefaultURL, "the NATS URL to connect to") + vlanID = flag.Uint("v", 0, "a VLAN ID (default 0)") +) + +func main() { + // parse command-line args + flag.Parse() + + // connect to nats + nc, err := nats.Connect(*natsURL, nats.Timeout(5*time.Second)) + if err != nil { + log.Fatal(err) + } + defer nc.Close() + + // create a TAP interface + config := water.Config{ + DeviceType: water.TAP, + } + config.Name = fmt.Sprintf("vnats%d", *vlanID) + ifce, err := water.New(config) + if err != nil { + log.Fatal(err) + } + + // get ethernet address of the interface we just created + var ownEth net.HardwareAddr + nifces, err := net.Interfaces() + if err != nil { + log.Fatal(err) + } + for _, nifce := range nifces { + if nifce.Name == config.Name { + ownEth = nifce.HardwareAddr + break + } + } + if len(ownEth) == 0 { + log.Fatal("failed to get own ethernet address") + } + + // sub to our frame address + subTopic := fmt.Sprintf("vlan.%d.%x", *vlanID, ownEth) + sub, err := nc.Subscribe(subTopic, func(m *nats.Msg) { + if _, err := ifce.Write(m.Data); err != nil { + log.Print(err) + } + }) + if err != nil { + log.Fatal(err) + } + defer sub.Unsubscribe() + + // sub to broadcasts + broadcastTopic := fmt.Sprintf("vlan.%d", *vlanID) + bsub, err := nc.Subscribe(broadcastTopic, func(m *nats.Msg) { + if _, err := ifce.Write(m.Data); err != nil { + log.Print(err) + } + }) + if err != nil { + log.Fatal(err) + } + defer bsub.Unsubscribe() + + // read each frame and publish it to appropriate topic + var frame [1500]byte + for { + // read frame from interface + n, err := ifce.Read(frame[:]) + if err != nil { + log.Fatal(err) + } + frame2 := frame[:n] + + // the topic to publish to + dst := waterutil.MACDestination(frame2) + var pubTopic string + if waterutil.IsBroadcast(dst) { + pubTopic = broadcastTopic + } else { + pubTopic = fmt.Sprintf("vlan.%d.%x", *vlanID, dst) + } + + // publish + if err := nc.Publish(pubTopic, frame2); err != nil { + log.Fatal(err) + } + } +}