SO_REUSEPORT

Just add "reuseport=true" to an address:

evio.Serve(events, "tcp://0.0.0.0:1234?reuseport=true")

README.md

@@ -34,6 +34,7 @@ The reason I wrote this framework is so I can build certain network services tha
 - Fallback for non-epoll/kqueue operating systems by simulating events with the [net](https://golang.org/pkg/net/) package
 - Ability to [wake up](#wake-up) connections from long running background operations
 - [Dial](#dial-out) an outbound connection and process/proxy on the event loop
+- [SO_REUSEPORT](#so_reuseport) socket option
 
 ## Getting Started
 
@@ -205,7 +206,7 @@ events = evio.Translate(events, nil,
 	},
 )
 
-log.Fatal(Serve(events, "tcp://0.0.0.0:443"))
+log.Fatal(evio.Serve(events, "tcp://0.0.0.0:443"))
 ```
 
 Here we wrapped the event with a TLS translator. The `evio.NopConn` function is used to converts the `ReadWriter` a `net.Conn` so the `tls.Server()` call will work.
@@ -235,6 +236,16 @@ The `Serve` function can bind to UDP addresses.
 - The `Wake` and `Dial` operations are not available to UDP connections.
 - All incoming and outgoing packets are not buffered and sent individually.
 
+## SO_REUSEPORT
+
+Servers can utilize the [SO_REUSEPORT](https://lwn.net/Articles/542629/) option which allows multiple sockets on the same host to bind to the same port.
+
+Just provide `reuseport=true` to an address:
+
+```go
+evio.Serve(events, "tcp://0.0.0.0:1234?reuseport=true"))
+```
+
 ## More examples
 
 Please check out the [examples](examples) subdirectory for a simplified [redis](examples/redis-server/main.go) clone, an [echo](examples/echo-server/main.go) server, and a very basic [http](examples/http-server/main.go) server with TLS support.

evio.go

@@ -10,6 +10,8 @@ import (
 	"os"
 	"strings"
 	"time"
+
+	"github.com/kavu/go_reuseport"
 )
 
 // Action is an action that occurs after the completion of an event.
@@ -140,7 +142,7 @@ func Serve(events Events, addr ...string) error {
 	for _, addr := range addr {
 		var ln listener
 		var stdlibt bool
-		ln.network, ln.addr, stdlibt = parseAddr(addr)
+		ln.network, ln.addr, ln.opts, stdlibt = parseAddr(addr)
 		if stdlibt {
 			stdlib = true
 		}
@@ -149,9 +151,17 @@ func Serve(events Events, addr ...string) error {
 		}
 		var err error
 		if ln.network == "udp" {
-			ln.pconn, err = net.ListenPacket(ln.network, ln.addr)
+			if ln.opts.reusePort() {
+				ln.pconn, err = reuseport.ListenPacket(ln.network, ln.addr)
+			} else {
+				ln.pconn, err = net.ListenPacket(ln.network, ln.addr)
+			}
 		} else {
-			ln.ln, err = net.Listen(ln.network, ln.addr)
+			if ln.opts.reusePort() {
+				ln.ln, err = reuseport.Listen(ln.network, ln.addr)
+			} else {
+				ln.ln, err = net.Listen(ln.network, ln.addr)
+			}
 		}
 		if err != nil {
 			return err
@@ -204,15 +214,27 @@ type listener struct {
 	ln      net.Listener
 	lnaddr  net.Addr
 	pconn   net.PacketConn
+	opts    addrOpts
 	f       *os.File
 	fd      int
 	network string
 	addr    string
 }
 
-func parseAddr(addr string) (network, address string, stdlib bool) {
+type addrOpts map[string]string
+
+func (opts addrOpts) reusePort() bool {
+	switch opts["reuseport"] {
+	case "yes", "true", "1":
+		return true
+	}
+	return false
+}
+
+func parseAddr(addr string) (network, address string, opts addrOpts, stdlib bool) {
 	network = "tcp"
 	address = addr
+	opts = make(map[string]string)
 	if strings.Contains(address, "://") {
 		network = strings.Split(address, "://")[0]
 		address = strings.Split(address, "://")[1]
@@ -221,5 +243,15 @@ func parseAddr(addr string) (network, address string, stdlib bool) {
 		stdlib = true
 		network = network[:len(network)-4]
 	}
+	q := strings.Index(address, "?")
+	if q != -1 {
+		for _, part := range strings.Split(address[q+1:], "&") {
+			kv := strings.Split(part, "=")
+			if len(kv) == 2 {
+				opts[kv[0]] = kv[1]
+			}
+		}
+		address = address[:q]
+	}
 	return
 }

evio_loop.go

@@ -322,7 +322,7 @@ func serve(events Events, lns []*listener) error {
 	}()
 	var rsa syscall.Sockaddr
 	var sa6 syscall.SockaddrInet6
-
+	var detached []int
 	var packet [0xFFFF]byte
 	var evs = internal.MakeEvents(64)
 	nextTicker := time.Now()
@@ -394,6 +394,7 @@ func serve(events Events, lns []*listener) error {
 				continue
 			}
 		}
+		detached = detached[:0]
 		lock()
 		for i := 0; i < pn; i++ {
 			var in []byte
@@ -416,7 +417,16 @@ func serve(events Events, lns []*listener) error {
 			ln = nil
 			c = fdconn[fd]
 			if c == nil {
-				syscall.Close(fd)
+				var found bool
+				for _, dfd := range detached {
+					if dfd == fd {
+						found = true
+						break
+					}
+				}
+				if !found {
+					syscall.Close(fd)
+				}
 				goto next
 			}
 			if c.opening {
@@ -665,6 +675,13 @@ func serve(events Events, lns []*listener) error {
 			delete(idconn, c.id)
 			if c.action == Detach {
 				if events.Detached != nil {
+					if err = internal.DelRead(p, c.fd, &c.readon, &c.writeon); err != nil {
+						goto fail
+					}
+					if err = internal.DelWrite(p, c.fd, &c.readon, &c.writeon); err != nil {
+						goto fail
+					}
+					detached = append(detached, c.fd)
 					c.detached = true
 					if len(c.outbuf)-c.outpos > 0 {
 						c.outbuf = append(c.outbuf[:0], c.outbuf[c.outpos:]...)
@@ -708,7 +725,7 @@ func serve(events Events, lns []*listener) error {
 // resolve resolves an evio address and retuns a sockaddr for socket
 // connection to external servers.
 func resolve(addr string) (sa syscall.Sockaddr, err error) {
-	network, address, _ := parseAddr(addr)
+	network, address, _, _ := parseAddr(addr)
 	var taddr net.Addr
 	switch network {
 	default:

evio_net.go

@@ -275,7 +275,7 @@ func servenet(events Events, lns []*listener) error {
 			}
 			id := int(atomic.AddInt64(&idc, 1))
 			go func() {
-				network, address, _ := parseAddr(addr)
+				network, address, _, _ := parseAddr(addr)
 				var conn net.Conn
 				var err error
 				if timeout > 0 {

evio_other.go

@@ -20,7 +20,7 @@ func (ln *listener) close() {
 	}
 }
 
-func (ln *listener) system() error {
+func (ln *listener) system(opts map[string]string) error {
 	return nil
 }
 

examples/echo-server/main.go

@@ -8,20 +8,28 @@ import (
 	"flag"
 	"fmt"
 	"log"
+	"strings"
 
 	"github.com/tidwall/evio"
 )
 
 func main() {
 	var port int
 	var udp bool
+	var trace bool
+	var reuseport bool
 	flag.IntVar(&port, "port", 5000, "server port")
 	flag.BoolVar(&udp, "udp", false, "listen on udp")
+	flag.BoolVar(&reuseport, "reuseport", false, "reuseport (SO_REUSEPORT)")
+	flag.BoolVar(&trace, "trace", false, "print packets to console")
 	flag.Parse()
 
 	var events evio.Events
 	events.Serving = func(srv evio.Server) (action evio.Action) {
 		log.Printf("echo server started on port %d", port)
+		if reuseport {
+			log.Printf("reuseport")
+		}
 		return
 	}
 	events.Opened = func(id int, info evio.Info) (out []byte, opts evio.Options, action evio.Action) {
@@ -33,12 +41,15 @@ func main() {
 		return
 	}
 	events.Data = func(id int, in []byte) (out []byte, action evio.Action) {
+		if trace {
+			log.Printf("%s", strings.TrimSpace(string(in)))
+		}
 		out = in
 		return
 	}
 	scheme := "tcp"
 	if udp {
 		scheme = "udp"
 	}
-	log.Fatal(evio.Serve(events, fmt.Sprintf("%s://:%d", scheme, port)))
+	log.Fatal(evio.Serve(events, fmt.Sprintf("%s://:%d?reuseport=%t", scheme, port, reuseport)))
 }

vendor/.stub

@@ -0,0 +1 @@
+stub