add link to q3rcon client

rename upsert to insert since we only call it if there isn't a session.

.dockerignore

@@ -0,0 +1,6 @@
+*
+!cmd/
+!pkg/
+
+!go.mod
+!go.sum

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.21
+FROM golang:1.21 AS build_image
 
 WORKDIR /usr/src/app
 
@@ -6,9 +6,16 @@ WORKDIR /usr/src/app
 COPY go.mod go.sum ./
 RUN go mod download && go mod verify
 
-# build binary and place into /usr/local/bin/
 COPY . .
-RUN go build -v -o /usr/local/bin/q3rcon-proxy ./cmd/q3rcon-proxy/
+
+# build binary, place into ./bin/
+RUN CGO_ENABLED=0 GOOS=linux go build -o ./bin/q3rcon-proxy ./cmd/q3rcon-proxy/
+
+FROM scratch AS final_image
+
+WORKDIR /bin/
+
+COPY --from=build_image /usr/src/app/bin/q3rcon-proxy .
 
 # Command to run when starting the container
-ENTRYPOINT [ "q3rcon-proxy" ]
+ENTRYPOINT [ "./q3rcon-proxy" ]

README.md

@@ -8,12 +8,12 @@ Unfortunately the Q3Rcon engine ties the rcon port to the game servers public po
 
 ### Use
 
-Run one or multiple rcon proxies by setting an environment variable `Q3RCON_PROXY`
+Run one or multiple rcon proxies by setting an environment variable `Q3RCON_TARGET_PORTS`
 
 for example:
 
 ```bash
-export Q3RCON_PROXY="20000:28960;20001:28961;20002:28962"
+export Q3RCON_TARGET_PORTS="20000:28960;20001:28961;20002:28962"
 ```
 
 This would configure q3rcon-proxy to run 3 proxy servers listening on ports `20000`, `20001` and `20002` that redirect rcon requests to game servers on ports `28960`, `28961` and `28962` respectively.
@@ -32,3 +32,9 @@ Set the log level with environment variable `Q3RCON_LOGLEVEL`:
 
 [lilproxy_url]: https://github.com/dgparker/lilproxy
 [user_link]: https://github.com/dgparker
+
+### Further Notes
+
+For a compatible rcon client also written in Go consider checking out the [Q3 Rcon][q3rcon] package.
+
+[q3rcon]: https://github.com/onyx-and-iris/q3rcon

cmd/q3rcon-proxy/main.go

@@ -5,6 +5,7 @@ import (
 	"os"
 	"slices"
 	"strings"
+	"time"
 
 	log "github.com/sirupsen/logrus"
 
@@ -30,20 +31,28 @@ func main() {
 		host = "0.0.0.0"
 	}
 
+	sessionTimeout, err := getEnvInt("Q3RCON_SESSION_TIMEOUT")
+	if err != nil {
+		log.Fatalf("unable to parse Q3RCON_SESSION_TIMEOUT: %s", err.Error())
+	}
+
 	for _, proxy := range strings.Split(proxies, ";") {
-		go start(host, proxy)
+		go start(host, proxy, sessionTimeout)
 	}
 
 	<-make(chan int)
 }
 
-func start(host, proxy string) {
+func start(host, proxy string, sessionTimeout int) {
 	port, target := func() (string, string) {
 		x := strings.Split(proxy, ":")
 		return x[0], x[1]
 	}()
 
-	c, err := udpproxy.New(fmt.Sprintf("%s:%s", host, port), fmt.Sprintf("127.0.0.1:%s", target))
+	c, err := udpproxy.New(
+		fmt.Sprintf("%s:%s", host, port),
+		fmt.Sprintf("127.0.0.1:%s", target),
+		udpproxy.WithSessionTimeout(time.Duration(sessionTimeout)*time.Minute))
 	if err != nil {
 		log.Fatal(err)
 	}

pkg/udpproxy/sessioncache.go

@@ -0,0 +1,41 @@
+package udpproxy
+
+import "sync"
+
+// sessionCache tracks connection sessions
+type sessionCache struct {
+	mu   sync.RWMutex
+	data map[string]*session
+}
+
+// newSessionCache creates a usable sessionCache.
+func newSessionCache() sessionCache {
+	return sessionCache{
+		data: make(map[string]*session),
+	}
+}
+
+// read returns the associated session for an addr
+func (sc *sessionCache) read(addr string) (*session, bool) {
+	sc.mu.RLock()
+	defer sc.mu.RUnlock()
+
+	v, ok := sc.data[addr]
+	return v, ok
+}
+
+// insert adds a session for a given addr.
+func (sc *sessionCache) insert(addr string, session *session) {
+	sc.mu.Lock()
+	defer sc.mu.Unlock()
+
+	sc.data[addr] = session
+}
+
+// delete removes the session for the given addr.
+func (sc *sessionCache) delete(addr string) {
+	sc.mu.Lock()
+	defer sc.mu.Unlock()
+
+	delete(sc.data, addr)
+}

pkg/udpproxy/udpproxy.go

@@ -2,23 +2,37 @@ package udpproxy
 
 import (
 	"net"
-	"sync"
 	"time"
 
 	log "github.com/sirupsen/logrus"
 )
 
+// Option is a functional option type that allows us to configure the Client.
+type Option func(*Client)
+
+// WithSessionTimeout is a functional option to set the session timeout
+func WithSessionTimeout(timeout time.Duration) Option {
+	return func(c *Client) {
+		if timeout < time.Minute {
+			log.Warnf("cannot set stale session timeout to less than 1 minute.. defaulting to 5 minutes")
+			return
+		}
+
+		c.sessionTimeout = timeout
+	}
+}
+
 type Client struct {
 	laddr *net.UDPAddr
 	raddr *net.UDPAddr
 
 	proxyConn *net.UDPConn
 
-	mutex    sync.RWMutex
-	sessions map[string]*session
+	sessionCache   sessionCache
+	sessionTimeout time.Duration
 }
 
-func New(port, target string) (*Client, error) {
+func New(port, target string, options ...Option) (*Client, error) {
 	laddr, err := net.ResolveUDPAddr("udp", port)
 	if err != nil {
 		return nil, err
@@ -29,12 +43,18 @@ func New(port, target string) (*Client, error) {
 		return nil, err
 	}
 
-	return &Client{
-		laddr:    laddr,
-		raddr:    raddr,
-		mutex:    sync.RWMutex{},
-		sessions: map[string]*session{},
-	}, nil
+	c := &Client{
+		laddr:          laddr,
+		raddr:          raddr,
+		sessionCache:   newSessionCache(),
+		sessionTimeout: 5 * time.Minute,
+	}
+
+	for _, o := range options {
+		o(c)
+	}
+
+	return c, nil
 }
 
 func (c *Client) ListenAndServe() error {
@@ -53,7 +73,7 @@ func (c *Client) ListenAndServe() error {
 			log.Error(err)
 		}
 
-		session, ok := c.sessions[caddr.String()]
+		session, ok := c.sessionCache.read(caddr.String())
 		if !ok {
 			session, err = newSession(caddr, c.raddr, c.proxyConn)
 			if err != nil {
@@ -61,7 +81,7 @@ func (c *Client) ListenAndServe() error {
 				continue
 			}
 
-			c.sessions[caddr.String()] = session
+			c.sessionCache.insert(caddr.String(), session)
 		}
 
 		go session.proxyTo(buf[:n])
@@ -71,15 +91,12 @@ func (c *Client) ListenAndServe() error {
 func (c *Client) pruneSessions() {
 	ticker := time.NewTicker(1 * time.Minute)
 
-	// the locks here could be abusive and i dont even know if this is a real
-	// problem but we definitely need to clean up stale sessions
 	for range ticker.C {
-		for _, session := range c.sessions {
-			c.mutex.RLock()
-			if time.Since(session.updateTime) > time.Minute*5 {
-				delete(c.sessions, session.caddr.String())
+		for _, session := range c.sessionCache.data {
+			if time.Since(session.updateTime) > c.sessionTimeout {
+				c.sessionCache.delete(session.caddr.String())
+				log.Tracef("session for %s deleted", session.caddr)
 			}
-			c.mutex.RUnlock()
 		}
 	}
 }