f-15: script: add script for running dhcp in netns

Signed-off-by: GnomeZworc <nicolas.boufidjeline@g3e.fr>

.forgejo/workflows/prerelease.yml

@@ -38,6 +38,7 @@ jobs:
           - metacli
           - agent
           - vpc
+          - dhcp
     uses: ./.forgejo/workflows/build.yml
     with:
       tag: ${{ needs.set-release-target.outputs.release_cible }}
@@ -51,4 +52,4 @@ jobs:
     uses: ./.forgejo/workflows/release.yml
     with:
       tag: ${{ needs.set-release-target.outputs.release_cible }}
-    secrets: inherit
+    secrets: inherit

cmd/dhcp/main.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"net"
+	"os"
+
+	"git.g3e.fr/syonad/two/internal/dhcp"
+	"git.g3e.fr/syonad/two/pkg/systemd"
+)
+
+func main() {
+	subnet := flag.String("subnet", "", "Subnet CIDR (e.g. 10.10.10.0/24)")
+	name := flag.String("name", "", "Config name (e.g. vpc1_br-00002)")
+	gateway := flag.String("gateway", "", "Gateway IP (e.g. 10.10.10.1)")
+	confDir := flag.String("confdir", "/etc/dnsmasq.d", "dnsmasq config directory")
+	flag.Parse()
+
+	if *subnet == "" || *name == "" || *gateway == "" {
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	_, network, err := net.ParseCIDR(*subnet)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "invalid subnet: %v\n", err)
+		os.Exit(1)
+	}
+
+	gw := net.ParseIP(*gateway)
+	if gw == nil {
+		fmt.Fprintf(os.Stderr, "invalid gateway IP: %q\n", *gateway)
+		os.Exit(1)
+	}
+
+	conf := dhcp.Config{
+		Network: network,
+		Gateway: gw,
+		Name:    *name,
+		ConfDir: *confDir,
+	}
+
+	confPath, err := dhcp.GenerateConfig(conf)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error generating config: %v\n", err)
+		os.Exit(1)
+	}
+	fmt.Printf("dnsmasq config written to %s\n", confPath)
+
+	svc, err := systemd.New()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error connecting to systemd: %v\n", err)
+		os.Exit(1)
+	}
+	defer svc.Close()
+
+	unit := "dnsmasq@" + *name + ".service"
+	if err := svc.Start(unit); err != nil {
+		fmt.Fprintf(os.Stderr, "error starting %s: %v\n", unit, err)
+		os.Exit(1)
+	}
+	fmt.Printf("started %s\n", unit)
+}

internal/dhcp/generate.go

@@ -0,0 +1,47 @@
+package dhcp
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+func GenerateConfig(c Config) (string, error) {
+	mask := fmt.Sprintf("%d.%d.%d.%d", c.Network.Mask[0], c.Network.Mask[1], c.Network.Mask[2], c.Network.Mask[3])
+
+	var sb strings.Builder
+	fmt.Fprintf(&sb, "no-resolv\n")
+	fmt.Fprintf(&sb, "dhcp-range=%s,static,%s,12h\n", c.Network.IP.String(), mask)
+	fmt.Fprintf(&sb, "dhcp-option=3,%s\n", c.Gateway.String())
+	fmt.Fprintf(&sb, "dhcp-option=6,1.1.1.1,8.8.8.8\n\n")
+
+	i := 0
+	for ip := cloneIP(c.Network.IP); c.Network.Contains(ip); incrementIP(ip) {
+		fmt.Fprintf(&sb, "dhcp-host=00:22:33:%02X:%02X:%02X,%s\n",
+			(i>>16)&0xFF, (i>>8)&0xFF, i&0xFF, ip)
+		i++
+	}
+
+	outPath := filepath.Join(c.ConfDir, c.Name+".conf")
+	if err := os.MkdirAll(c.ConfDir, 0755); err != nil {
+		return "", err
+	}
+	return outPath, os.WriteFile(outPath, []byte(sb.String()), 0644)
+}
+
+func incrementIP(ip net.IP) {
+	for j := len(ip) - 1; j >= 0; j-- {
+		ip[j]++
+		if ip[j] != 0 {
+			break
+		}
+	}
+}
+
+func cloneIP(ip net.IP) net.IP {
+	clone := make(net.IP, len(ip))
+	copy(clone, ip)
+	return clone
+}

internal/dhcp/struct.go

@@ -0,0 +1,12 @@
+package dhcp
+
+import (
+	"net"
+)
+
+type Config struct {
+	Network *net.IPNet
+	Gateway net.IP
+	Name    string
+	ConfDir string
+}

scripts/run-dnsmasq-in-netns.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+set -e
+
+# Expects one argument: netns_bridge (e.g. vpc-00003_br-00002 or vpc1_br0)
+arg="$1"
+NETNS="${arg%%_*}"
+BRIDGE="${arg#*_}"
+
+echo "start dnsmasq ${NETNS} ${BRIDGE}"
+
+exec ip netns exec "${NETNS}" \
+  dnsmasq \
+    --no-daemon \
+    --interface="${BRIDGE}" \
+    --bind-interfaces \
+    --pid-file="/run/dnsmasq-$arg.pid" \
+    --conf-file="/etc/dnsmasq.d/$arg.conf" \
+    --no-hosts \
+    --no-resolv \
+    --log-facility="/var/log/dnsmasq-$arg.log" \
+    --no-daemon -p0

systemd/dnsmasq@.service

@@ -0,0 +1,11 @@
+[Unit]
+Description=dnsmasq in netns %i
+After=network.target
+
+[Service]
+Type=simple
+ExecStart=/usr/local/bin/run-dnsmasq-in-netns.sh %i
+ExecStopPost=/bin/rm -f /run/dnsmasq-%i.pid
+
+[Install]
+WantedBy=multi-user.target