NAT, Docker, wildcard dialplan, μ-law perf, RTP playback pipeline

Makefile

@@ -30,4 +30,24 @@ race:
 lint:
 	golangci-lint run
 
-.PHONY: build install clean test integrationtest bench race lint
+DOCKER_COMPOSE := docker compose -f docker/compose.yml
+
+docker-build:
+	$(DOCKER_COMPOSE) build
+
+docker-up:
+	$(DOCKER_COMPOSE) up
+
+docker-up-d:
+	$(DOCKER_COMPOSE) up -d
+
+docker-stop:
+	$(DOCKER_COMPOSE) stop
+
+docker-down:
+	$(DOCKER_COMPOSE) down
+
+docker-logs:
+	$(DOCKER_COMPOSE) logs -f
+
+.PHONY: build install clean test integrationtest bench race lint docker-build docker-up docker-up-d docker-stop docker-down docker-logs

cmd/trecsd/main.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"flag"
 	"log/slog"
+	"net"
 	"os"
 	"os/signal"
 	"syscall"
@@ -28,10 +29,10 @@ var (
 	flagLogFormat     string
 	flagNoPRACK       bool
 	flagTrunks        string
+	flagExternalIP    string
+	flagNATAddress    string
 )
 
-var serverIP = "127.0.0.1"
-
 func init() {
 	flag.StringVar(&flagAddr, "addr", ":5060", "SIP listen address")
 	flag.IntVar(&flagRTPMin, "rtp-min", 0, "RTP port range start (0 = OS-assigned)")
@@ -43,6 +44,8 @@ func init() {
 	flag.StringVar(&flagLogFormat, "log-format", "text", "Log format (text, json, or compact)")
 	flag.BoolVar(&flagNoPRACK, "no-prack", false, "Disable PRACK (RFC 3262) support for reliable provisional responses")
 	flag.StringVar(&flagTrunks, "trunks", "", "Path to trunk configuration JSON file")
+	flag.StringVar(&flagExternalIP, "external-ip", "", "External IP for SDP c= lines and Contact headers")
+	flag.StringVar(&flagNATAddress, "nat-address", "", "NAT address to replace loopback in client SDP (e.g., host.docker.internal)")
 	flag.Parse()
 }
 
@@ -78,6 +81,16 @@ func main() {
 	}
 	slog.SetDefault(slog.New(slogHandler))
 
+	serverIP := flagExternalIP
+	if serverIP == "" {
+		host, _, err := net.SplitHostPort(flagAddr)
+		if err != nil || host == "" || host == "0.0.0.0" || host == "::" {
+			serverIP = "127.0.0.1"
+		} else {
+			serverIP = host
+		}
+	}
+
 	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
 	defer stop()
 
@@ -147,6 +160,7 @@ func main() {
 		RTPPortMax:     flagRTPMax,
 		PRACKEnabled:   !flagNoPRACK,
 		TrunkMgr:       trunkMgr,
+		NATAddress:     flagNATAddress,
 	})
 
 	if flagAuthMaxFailed < 1 || flagAuthMaxFailed > 10 {

docker/Dockerfile

@@ -0,0 +1,12 @@
+FROM golang:1.26-alpine AS builder
+WORKDIR /src
+COPY go.mod go.sum ./
+RUN go mod download
+COPY . .
+RUN CGO_ENABLED=0 go build -o /trecsd ./cmd/trecsd/
+
+FROM alpine:3.20
+RUN apk add --no-cache ca-certificates
+COPY --from=builder /trecsd /usr/local/bin/trecsd
+
+ENTRYPOINT ["trecsd"]

docker/compose.yml

@@ -0,0 +1,45 @@
+services:
+  front:
+    build:
+      context: ..
+      dockerfile: docker/Dockerfile
+    command:
+      - -addr=:5060
+      - -external-ip=127.0.0.1
+      - -nat-address=host.docker.internal
+      - -rtp-min=40000
+      - -rtp-max=40010
+      - -dialplan=/conf/dialplan.json
+      - -trunks=/conf/trunks.json
+      - -log-level=debug
+    ports:
+      - "5060:5060/udp"
+      - "5060:5060/tcp"
+      - "40000-40010:40000-40010/udp"
+    volumes:
+      - ./configs/front/dialplan.json:/conf/dialplan.json:ro
+      - ./configs/front/trunks.json:/conf/trunks.json:ro
+      - ../audio-files:/srv/audio:ro
+    depends_on:
+      - back
+    networks:
+      - trec-net
+
+  back:
+    build:
+      context: ..
+      dockerfile: docker/Dockerfile
+    command:
+      - -addr=:5060
+      - -external-ip=back
+      - -dialplan=/conf/dialplan.json
+      - -log-level=debug
+    volumes:
+      - ./configs/back/dialplan.json:/conf/dialplan.json:ro
+      - ../audio-files:/srv/audio:ro
+    networks:
+      - trec-net
+
+networks:
+  trec-net:
+    driver: bridge

docker/configs/back/dialplan.json

@@ -0,0 +1,5 @@
+{
+  "extensions": {
+    "*": { "action": "play", "file": "/srv/audio/the_mentor_8k_lpcm16.wav" }
+  }
+}

docker/configs/front/dialplan.json

@@ -0,0 +1,6 @@
+{
+  "extensions": {
+    "local": { "action": "play", "file": "/srv/audio/EDIS-SCD-02_8k_lpcm16.wav" },
+    "mentor": { "action": "play", "file": "/srv/audio/the_mentor_8k_lpcm16.wav" }
+  }
+}

docker/configs/front/trunks.json

@@ -0,0 +1,20 @@
+{
+  "trunks": [
+    {
+      "name": "back",
+      "type": "static",
+      "host": "back",
+      "port": 5060,
+      "transport": "udp",
+      "local_ip": "front",
+      "max_channels": 50
+    }
+  ],
+  "outbound_routes": [
+    {
+      "name": "catch-all",
+      "pattern": "^\\d+$",
+      "trunk": "back"
+    }
+  ]
+}

docs/examples/trunks.json

@@ -21,6 +21,7 @@
       "port": 5061,
       "transport": "tcp",
       "trusted_ips": ["10.0.1.0/24"],
+      "local_ip": "10.0.1.10",
       "max_channels": 20,
       "caller_id": "pbx-main",
       "strip_headers": ["X-Extension"]

integrationtest/dialplan/dialplan_test.go

@@ -51,6 +51,28 @@ func TestIntegration_DialplanEcho(t *testing.T) {
 
 		runEchoTest(t, ts, "tcp", false)
 	})
+
+	t.Run("UDP_EarlyOffer_NATAddress", func(t *testing.T) {
+		if _, err := net.LookupHost("host.docker.internal"); err != nil {
+			t.Skip("host.docker.internal not resolvable (not in Docker)")
+		}
+		ts := integrationtest.StartTestServerWithDialplan(t, "127.0.0.1", dp,
+			integrationtest.WithNATAddress("host.docker.internal"))
+		defer ts.Stop()
+
+		runEchoTest(t, ts, "udp", true)
+	})
+
+	t.Run("TCP_EarlyOffer_NATAddress", func(t *testing.T) {
+		if _, err := net.LookupHost("host.docker.internal"); err != nil {
+			t.Skip("host.docker.internal not resolvable (not in Docker)")
+		}
+		ts := integrationtest.StartTestServerWithDialplan(t, "127.0.0.1", dp,
+			integrationtest.WithNATAddress("host.docker.internal"))
+		defer ts.Stop()
+
+		runEchoTest(t, ts, "tcp", true)
+	})
 }
 
 func TestIntegration_DialplanPlayback(t *testing.T) {

integrationtest/testserver.go

@@ -53,6 +53,13 @@ func WithTrunkManager(tm *trunk.TrunkManager) ServerOption {
 	}
 }
 
+// WithNATAddress sets the NAT address for replacing loopback client SDP addresses.
+func WithNATAddress(natAddr string) ServerOption {
+	return func(cfg *b2bua.Config) {
+		cfg.NATAddress = natAddr
+	}
+}
+
 // StartTestServer creates and starts a trecs server with a registrar, dialplan,
 // and B2BUA handler for integration testing. Logging is routed to t.Log(). The server
 // binds to host:0 (random OS-assigned port). The caller must call Stop() when done.