f-15: code: add generate dhcp file

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

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
+}