mikeandClaude Sonnet 5
c135f205fa
Splits the LAN into four /24 zones: 10.0.0.0/24 static (no DHCP, DNS only), 10.0.1.0/24 fixed DHCP reservations by MAC, 10.0.2.0/24 dynamic DHCP pool, 10.0.3.0/24 spare/unused. ipadm now derives the required subnet from whether a host has a MAC, auto-assigns free IPs, and auto-migrates a host's IP when its MAC is added/removed. Migrated the existing archerc80 reservation from 10.0.0.2 to 10.0.1.2. Also fixes a latent bug found while doing this: dnsmasq's SIGHUP (`systemctl reload`) only re-reads /etc/hosts, not the conf-dir files ipadm writes to, so config changes were silently not applied on reload. ipadm now restarts dnsmasq instead. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
91 lines
2.7 KiB
Go
91 lines
2.7 KiB
Go
package main
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import (
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"fmt"
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"os"
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"os/exec"
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"sort"
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"strings"
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)
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// renderDnsmasqConfig builds the content of the generated dnsmasq include
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// file from the current host list. Every host gets a host-record (forward +
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// reverse DNS). Hosts with a MAC additionally get a dhcp-host static lease.
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func renderDnsmasqConfig(hosts []Host) string {
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sorted := make([]Host, len(hosts))
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copy(sorted, hosts)
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sort.Slice(sorted, func(i, j int) bool {
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return strings.ToLower(sorted[i].Name) < strings.ToLower(sorted[j].Name)
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})
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var b strings.Builder
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b.WriteString("# Generated by ipadm -u — DO NOT EDIT MANUALLY.\n")
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b.WriteString("# Edit hosts with `ipadm` and re-run `ipadm -u` to regenerate this file.\n\n")
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for _, h := range sorted {
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if h.Comment != "" {
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fmt.Fprintf(&b, "# %s: %s\n", h.Name, h.Comment)
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}
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fmt.Fprintf(&b, "host-record=%s,%s\n", h.Name, h.IP)
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if h.MAC != "" {
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fmt.Fprintf(&b, "dhcp-host=%s,%s,%s,infinite\n", h.MAC, h.IP, h.Name)
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}
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b.WriteString("\n")
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}
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return b.String()
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}
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// applyDnsmasqConfig writes the generated config to path, validates the full
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// dnsmasq configuration, and on success restarts the dnsmasq service. On
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// validation failure the previous file content is restored and the service
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// is left untouched.
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func applyDnsmasqConfig(path string, content string) error {
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var backup []byte
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hadFile := false
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if b, err := os.ReadFile(path); err == nil {
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backup = b
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hadFile = true
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} else if !os.IsNotExist(err) {
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return fmt.Errorf("cannot read existing %s: %w", path, err)
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}
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if err := os.WriteFile(path, []byte(content), 0644); err != nil {
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return fmt.Errorf("cannot write %s: %w", path, err)
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}
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if err := runDnsmasqTest(); err != nil {
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// roll back so a bad generated file never lingers
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if hadFile {
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os.WriteFile(path, backup, 0644)
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} else {
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os.Remove(path)
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}
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return fmt.Errorf("dnsmasq config invalid, change rolled back: %w", err)
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}
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if err := restartDnsmasq(); err != nil {
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return fmt.Errorf("%s written, but restart failed: %w", path, err)
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}
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return nil
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}
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func runDnsmasqTest() error {
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out, err := exec.Command("dnsmasq", "--test").CombinedOutput()
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if err != nil {
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return fmt.Errorf("%s", strings.TrimSpace(string(out)))
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}
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return nil
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}
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// restartDnsmasq does a full restart rather than `systemctl reload`
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// (SIGHUP): dnsmasq's SIGHUP handler only re-reads /etc/hosts and a few
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// specific hosts-file options, not the conf-dir files this generated
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// hosts.conf lives in, so a reload would silently keep serving the old
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// host-record/dhcp-host entries.
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func restartDnsmasq() error {
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out, err := exec.Command("systemctl", "restart", "dnsmasq").CombinedOutput()
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if err != nil {
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return fmt.Errorf("%s", strings.TrimSpace(string(out)))
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}
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return nil
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}
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