add a wait-for-it script to check if a QUIC server is up

sim/Dockerfile

@@ -26,6 +26,17 @@ RUN ./waf build  && \
   cd out/lib && du -sh . && strip -v * && du -sh . && cd ../.. && \
   cd out/scratch && rm -r subdir helper scratch-simulator*
 
+RUN cd / && \
+  wget https://dl.google.com/go/go1.15.linux-amd64.tar.gz && \
+  tar xfz go1.15.linux-amd64.tar.gz && \
+  rm go1.15.linux-amd64.tar.gz
+
+RUN ls -al /go
+
+ENV PATH="/go/bin:${PATH}"
+COPY wait-for-it-quic /wait-for-it-quic
+RUN cd /wait-for-it-quic && go build .
+
 FROM ubuntu:20.04
 
 RUN apt-get update && \
@@ -36,6 +47,7 @@ WORKDIR /ns3
 COPY --from=builder /ns3/out/src/fd-net-device/*optimized /ns3/out/src/fd-net-device/*debug /ns3/src/fd-net-device/
 COPY --from=builder /ns3/out/scratch/*/* /ns3/scratch/
 COPY --from=builder /ns3/out/lib/ /ns3/lib
+COPY --from=builder /wait-for-it-quic/wait-for-it-quic /usr/bin
 
 # see https://gitlab.com/nsnam/ns-3-dev/issues/97
 ENV PATH="/ns3/src/fd-net-device/:${PATH}"

sim/run.sh

@@ -1,5 +1,7 @@
 #!/bin/bash
 
+set -e
+
 # We are using eth0 and eth1 as EmuFdNetDevices in ns3.
 # ns3 usually uses MAC address spoofing to separate ns3 from other traffic,
 # see https://www.nsnam.org/docs/models/html/fd-net-device.html#emufdnetdevicehelper.
@@ -18,6 +20,10 @@ ifconfig eth1 promisc
 iptables -A FORWARD -i eth0 -o eth1 -j DROP
 iptables -A FORWARD -i eth1 -o eth0 -j DROP
 
+if [[ -n "$WAITFORSERVER" ]]; then
+  wait-for-it-quic -t 10s $WAITFORSERVER
+fi
+
 echo "Using scenario:" $SCENARIO
 
 eval ./scratch/"$SCENARIO &"

sim/wait-for-it-quic/go.mod

@@ -0,0 +1,3 @@
+module github.com/marten-seemann/quic-network-simulator/sim/wait-for-it-quic
+
+go 1.15

sim/wait-for-it-quic/wait-for-it.go

@@ -0,0 +1,70 @@
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"log"
+	"net"
+	"time"
+	"os"
+)
+
+// compose a packet that will elicit a Version Negotiation packet
+var packet = append([]byte{0xc0, 0x57, 0x41, 0x49, 0x54, 0, 0}, make([]byte, 1200)...)
+
+func main() {
+	startTime := time.Now()
+	var timeout time.Duration
+	flag.DurationVar(&timeout, "t", 0, "timeout (e.g. 10s)")
+	flag.Parse()
+	host := flag.Arg(0)
+	if flag.NArg() < 1 {
+		flag.Usage()
+		return
+	}
+	if timeout == 0 {
+		fmt.Printf("waiting for %s without a timeout\n", host)
+	} else {
+		fmt.Printf("waiting %s for %s\n", timeout, host)
+	}
+	addr, err := net.ResolveUDPAddr("udp", host)
+	if err != nil {
+		log.Fatal(err)
+	}
+	for range time.NewTicker(time.Second/2).C {
+		dur := time.Since(startTime)
+		if timeout > 0 && dur > timeout {
+			fmt.Printf("Failed to connect after %s\n", dur)
+			os.Exit(1)
+		}
+		if err := waitForIt(addr); err == nil {
+			break
+		}
+		time.Sleep(time.Second)
+	}
+	fmt.Printf("%s is available after %s\n", host, time.Since(startTime))
+}
+
+func waitForIt(addr *net.UDPAddr) error {
+	conn, err := net.DialUDP("udp", nil, addr)
+	if err != nil {
+		return err
+	}
+	if _, err := conn.Write(packet); err != nil {
+		return err
+	}
+	b := make([]byte, 1500)
+	n, err := conn.Read(b)
+	if err != nil {
+		return err
+	}
+	b = b[:n]
+	if len(b) < 5 {
+		log.Fatal("invalid packet")
+	}
+	if !bytes.Equal(b[1:5], []byte{0, 0, 0, 0}) {
+		log.Fatal("expected Version Negotiation packet")
+	}
+	return nil
+}