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package main
import (
"io"
"log"
"net"
"sync"
"github.com/ishidawataru/sctp"
)
// SCTPProxy is a proxy for SCTP connections. It implements the Proxy interface to
// handle SCTP traffic forwarding between the frontend and backend addresses.
type SCTPProxy struct {
listener *sctp.SCTPListener
frontendAddr *sctp.SCTPAddr
backendAddr *sctp.SCTPAddr
}
// NewSCTPProxy creates a new SCTPProxy.
func NewSCTPProxy(frontendAddr, backendAddr *sctp.SCTPAddr) (*SCTPProxy, error) {
// detect version of hostIP to bind only to correct version
ipVersion := ipv4
if frontendAddr.IPAddrs[0].IP.To4() == nil {
ipVersion = ipv6
}
listener, err := sctp.ListenSCTP("sctp"+string(ipVersion), frontendAddr)
if err != nil {
return nil, err
}
// If the port in frontendAddr was 0 then ListenSCTP will have a picked
// a port to listen on, hence the call to Addr to get that actual port:
return &SCTPProxy{
listener: listener,
frontendAddr: listener.Addr().(*sctp.SCTPAddr),
backendAddr: backendAddr,
}, nil
}
func (proxy *SCTPProxy) clientLoop(client *sctp.SCTPConn, quit chan bool) {
backend, err := sctp.DialSCTP("sctp", nil, proxy.backendAddr)
if err != nil {
log.Printf("Can't forward traffic to backend sctp/%v: %s\n", proxy.backendAddr, err)
client.Close()
return
}
clientC := sctp.NewSCTPSndRcvInfoWrappedConn(client)
backendC := sctp.NewSCTPSndRcvInfoWrappedConn(backend)
var wg sync.WaitGroup
var broker = func(to, from net.Conn) {
io.Copy(to, from)
from.Close()
to.Close()
wg.Done()
}
wg.Add(2)
go broker(clientC, backendC)
go broker(backendC, clientC)
finish := make(chan struct{})
go func() {
wg.Wait()
close(finish)
}()
select {
case <-quit:
case <-finish:
}
clientC.Close()
backendC.Close()
<-finish
}
// Run starts forwarding the traffic using SCTP.
func (proxy *SCTPProxy) Run() {
quit := make(chan bool)
defer close(quit)
for {
client, err := proxy.listener.Accept()
if err != nil {
log.Printf("Stopping proxy on sctp/%v for sctp/%v (%s)", proxy.frontendAddr, proxy.backendAddr, err)
return
}
go proxy.clientLoop(client.(*sctp.SCTPConn), quit)
}
}
// Close stops forwarding the traffic.
func (proxy *SCTPProxy) Close() { proxy.listener.Close() }
// FrontendAddr returns the SCTP address on which the proxy is listening.
func (proxy *SCTPProxy) FrontendAddr() net.Addr { return proxy.frontendAddr }
// BackendAddr returns the SCTP proxied address.
func (proxy *SCTPProxy) BackendAddr() net.Addr { return proxy.backendAddr }
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