banger/internal/daemon/dns_routing.go
Thales Maciel b7f6d1fe1b
Route .vm DNS through systemd-resolved
Banger was already serving VM records on 127.0.0.1:42069, but hosts using systemd-resolved were not routing .vm queries there. That made direct lookups against the local server work while normal host resolution and commands like opencode attach <vm>.vm:4096 failed.\n\nSync resolvectl dns/domain/default-route settings onto the banger bridge when the daemon opens and whenever VM DNS records are published, and revert that bridge-scoped configuration on daemon shutdown. This uses sudo resolvectl because unprivileged resolved reconfiguration on this host requires interactive authentication.\n\nValidation: GOCACHE=/tmp/banger-gocache go test ./..., make build, daemon restart, resolvectl dns/domain br-fc, resolvectl query vrum.vm, and curl http://vrum.vm:4096.
2026-03-22 15:07:22 -03:00

63 lines
1.7 KiB
Go

package daemon
import (
"context"
"strings"
"banger/internal/system"
"banger/internal/vmdns"
)
const vmResolverRouteDomain = "~vm"
var (
lookupExecutableFunc = system.LookupExecutable
vmDNSAddrFunc = func(server *vmdns.Server) string { return server.Addr() }
)
func (d *Daemon) syncVMDNSResolverRouting(ctx context.Context) error {
if d == nil || d.vmDNS == nil {
return nil
}
if strings.TrimSpace(d.config.BridgeName) == "" {
return nil
}
if _, err := lookupExecutableFunc("resolvectl"); err != nil {
return nil
}
if _, err := d.runner.Run(ctx, "ip", "link", "show", d.config.BridgeName); err != nil {
return nil
}
serverAddr := strings.TrimSpace(vmDNSAddrFunc(d.vmDNS))
if serverAddr == "" {
return nil
}
if _, err := d.runner.RunSudo(ctx, "resolvectl", "dns", d.config.BridgeName, serverAddr); err != nil {
return err
}
if _, err := d.runner.RunSudo(ctx, "resolvectl", "domain", d.config.BridgeName, vmResolverRouteDomain); err != nil {
return err
}
_, err := d.runner.RunSudo(ctx, "resolvectl", "default-route", d.config.BridgeName, "no")
return err
}
func (d *Daemon) clearVMDNSResolverRouting(ctx context.Context) error {
if d == nil || strings.TrimSpace(d.config.BridgeName) == "" {
return nil
}
if _, err := lookupExecutableFunc("resolvectl"); err != nil {
return nil
}
if _, err := d.runner.Run(ctx, "ip", "link", "show", d.config.BridgeName); err != nil {
return nil
}
_, err := d.runner.RunSudo(ctx, "resolvectl", "revert", d.config.BridgeName)
return err
}
func (d *Daemon) ensureVMDNSResolverRouting(ctx context.Context) {
if err := d.syncVMDNSResolverRouting(ctx); err != nil && d.logger != nil {
d.logger.Warn("vm dns resolver route sync failed", "bridge", d.config.BridgeName, "error", err.Error())
}
}