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package main
import (
"bufio"
"context"
"flag"
"fmt"
"io"
"log"
"net/http"
"strings"
// We need to import libp2p's libraries that we use in this project.
"github.com/libp2p/go-libp2p"
"github.com/libp2p/go-libp2p-core/host"
"github.com/libp2p/go-libp2p-core/network"
"github.com/libp2p/go-libp2p-core/peer"
"github.com/libp2p/go-libp2p-core/peerstore"
ma "github.com/multiformats/go-multiaddr"
manet "github.com/multiformats/go-multiaddr-net"
)
// Protocol defines the libp2p protocol that we will use for the libp2p proxy
// service that we are going to provide. This will tag the streams used for
// this service. Streams are multiplexed and their protocol tag helps
// libp2p handle them to the right handler functions.
const Protocol = "/proxy-example/0.0.1"
// makeRandomHost creates a libp2p host with a randomly generated identity.
// This step is described in depth in other tutorials.
func makeRandomHost(port int) host.Host {
host, err := libp2p.New(context.Background(), libp2p.ListenAddrStrings(fmt.Sprintf("/ip4/127.0.0.1/tcp/%d", port)))
if err != nil {
log.Fatalln(err)
}
return host
}
// ProxyService provides HTTP proxying on top of libp2p by launching an
// HTTP server which tunnels the requests to a destination peer running
// ProxyService too.
type ProxyService struct {
host host.Host
dest peer.ID
proxyAddr ma.Multiaddr
}
// NewProxyService attaches a proxy service to the given libp2p Host.
// The proxyAddr parameter specifies the address on which the
// HTTP proxy server listens. The dest parameter specifies the peer
// ID of the remote peer in charge of performing the HTTP requests.
//
// ProxyAddr/dest may be nil/"" it is not necessary that this host
// provides a listening HTTP server (and instead its only function is to
// perform the proxied http requests it receives from a different peer.
//
// The addresses for the dest peer should be part of the host's peerstore.
func NewProxyService(h host.Host, proxyAddr ma.Multiaddr, dest peer.ID) *ProxyService {
// We let our host know that it needs to handle streams tagged with the
// protocol id that we have defined, and then handle them to
// our own streamHandling function.
h.SetStreamHandler(Protocol, streamHandler)
fmt.Println("Proxy server is ready")
fmt.Println("libp2p-peer addresses:")
for _, a := range h.Addrs() {
fmt.Printf("%s/ipfs/%s\n", a, peer.IDB58Encode(h.ID()))
}
return &ProxyService{
host: h,
dest: dest,
proxyAddr: proxyAddr,
}
}
// streamHandler is our function to handle any libp2p-net streams that belong
// to our protocol. The streams should contain an HTTP request which we need
// to parse, make on behalf of the original node, and then write the response
// on the stream, before closing it.
func streamHandler(stream network.Stream) {
// Remember to close the stream when we are done.
defer stream.Close()
// Create a new buffered reader, as ReadRequest needs one.
// The buffered reader reads from our stream, on which we
// have sent the HTTP request (see ServeHTTP())
buf := bufio.NewReader(stream)
// Read the HTTP request from the buffer
req, err := http.ReadRequest(buf)
if err != nil {
stream.Reset()
log.Println(err)
return
}
defer req.Body.Close()
// We need to reset these fields in the request
// URL as they are not maintained.
req.URL.Scheme = "http"
hp := strings.Split(req.Host, ":")
if len(hp) > 1 && hp[1] == "443" {
req.URL.Scheme = "https"
} else {
req.URL.Scheme = "http"
}
req.URL.Host = req.Host
outreq := new(http.Request)
*outreq = *req
// We now make the request
fmt.Printf("Making request to %s\n", req.URL)
resp, err := http.DefaultTransport.RoundTrip(outreq)
if err != nil {
stream.Reset()
log.Println(err)
return
}
// resp.Write writes whatever response we obtained for our
// request back to the stream.
resp.Write(stream)
}
// Serve listens on the ProxyService's proxy address. This effectively
// allows to set the listening address as http proxy.
func (p *ProxyService) Serve() {
_, serveArgs, _ := manet.DialArgs(p.proxyAddr)
fmt.Println("proxy listening on ", serveArgs)
if p.dest != "" {
http.ListenAndServe(serveArgs, p)
}
}
// ServeHTTP implements the http.Handler interface. WARNING: This is the
// simplest approach to a proxy. Therefore we do not do any of the things
// that should be done when implementing a reverse proxy (like handling
// headers correctly). For how to do it properly, see:
// https://golang.org/src/net/http/httputil/reverseproxy.go?s=3845:3920#L121
//
// ServeHTTP opens a stream to the dest peer for every HTTP request.
// Streams are multiplexed over single connections so, unlike connections
// themselves, they are cheap to create and dispose of.
func (p *ProxyService) ServeHTTP(w http.ResponseWriter, r *http.Request) {
fmt.Printf("proxying request for %s to peer %s\n", r.URL, p.dest.Pretty())
// We need to send the request to the remote libp2p peer, so
// we open a stream to it
stream, err := p.host.NewStream(context.Background(), p.dest, Protocol)
// If an error happens, we write an error for response.
if err != nil {
log.Println(err)
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
defer stream.Close()
// r.Write() writes the HTTP request to the stream.
err = r.Write(stream)
if err != nil {
stream.Reset()
log.Println(err)
http.Error(w, err.Error(), http.StatusServiceUnavailable)
return
}
// Now we read the response that was sent from the dest
// peer
buf := bufio.NewReader(stream)
resp, err := http.ReadResponse(buf, r)
if err != nil {
stream.Reset()
log.Println(err)
http.Error(w, err.Error(), http.StatusServiceUnavailable)
return
}
// Copy any headers
for k, v := range resp.Header {
for _, s := range v {
w.Header().Add(k, s)
}
}
// Write response status and headers
w.WriteHeader(resp.StatusCode)
// Finally copy the body
io.Copy(w, resp.Body)
resp.Body.Close()
}
// addAddrToPeerstore parses a peer multiaddress and adds
// it to the given host's peerstore, so it knows how to
// contact it. It returns the peer ID of the remote peer.
func addAddrToPeerstore(h host.Host, addr string) peer.ID {
// The following code extracts target's the peer ID from the
// given multiaddress
ipfsaddr, err := ma.NewMultiaddr(addr)
if err != nil {
log.Fatalln(err)
}
pid, err := ipfsaddr.ValueForProtocol(ma.P_IPFS)
if err != nil {
log.Fatalln(err)
}
peerid, err := peer.IDB58Decode(pid)
if err != nil {
log.Fatalln(err)
}
// Decapsulate the /ipfs/<peerID> part from the target
// /ip4/<a.b.c.d>/ipfs/<peer> becomes /ip4/<a.b.c.d>
targetPeerAddr, _ := ma.NewMultiaddr(
fmt.Sprintf("/ipfs/%s", peer.IDB58Encode(peerid)))
targetAddr := ipfsaddr.Decapsulate(targetPeerAddr)
// We have a peer ID and a targetAddr so we add
// it to the peerstore so LibP2P knows how to contact it
h.Peerstore().AddAddr(peerid, targetAddr, peerstore.PermanentAddrTTL)
return peerid
}
const help = `
This example creates a simple HTTP Proxy using two libp2p peers. The first peer
provides an HTTP server locally which tunnels the HTTP requests with libp2p
to a remote peer. The remote peer performs the requests and
send the sends the response back.
Usage: Start remote peer first with: ./proxy
Then start the local peer with: ./proxy -d <remote-peer-multiaddress>
Then you can do something like: curl -x "localhost:9900" "http://ipfs.io".
This proxies sends the request through the local peer, which proxies it to
the remote peer, which makes it and sends the response back.
`
func main() {
flag.Usage = func() {
fmt.Println(help)
flag.PrintDefaults()
}
// Parse some flags
destPeer := flag.String("d", "", "destination peer address")
port := flag.Int("p", 9900, "proxy port")
p2pport := flag.Int("l", 12000, "libp2p listen port")
flag.Parse()
// If we have a destination peer we will start a local server
if *destPeer != "" {
// We use p2pport+1 in order to not collide if the user
// is running the remote peer locally on that port
host := makeRandomHost(*p2pport + 1)
// Make sure our host knows how to reach destPeer
destPeerID := addAddrToPeerstore(host, *destPeer)
proxyAddr, err := ma.NewMultiaddr(fmt.Sprintf("/ip4/127.0.0.1/tcp/%d", *port))
if err != nil {
log.Fatalln(err)
}
// Create the proxy service and start the http server
proxy := NewProxyService(host, proxyAddr, destPeerID)
proxy.Serve() // serve hangs forever
} else {
host := makeRandomHost(*p2pport)
// In this case we only need to make sure our host
// knows how to handle incoming proxied requests from
// another peer.
_ = NewProxyService(host, nil, "")
<-make(chan struct{}) // hang forever
}
}
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