net/dns: add documentation to openresolv's config fetch.
@@ -49,11 +49,15 @@ func (m openresolvManager) SupportsSplitDNS() bool {
}
func (m openresolvManager) GetBaseConfig() (OSConfig, error) {
+ // List the names of all config snippets openresolv is aware
+ // of. Snippets get listed in priority order (most to least),
+ // which we'll exploit later.
bs, err := exec.Command("resolvconf", "-i").CombinedOutput()
if err != nil {
return OSConfig{}, err
}
+ // Remove the "tailscale" snippet from the list.
args := []string{"-l"}
for _, f := range strings.Split(strings.TrimSpace(string(bs)), " ") {
if f == "tailscale" {
@@ -62,6 +66,17 @@ func (m openresolvManager) GetBaseConfig() (OSConfig, error) {
args = append(args, f)
}
+ // List all resolvconf snippets except our own, and parse that as
+ // a resolv.conf. This effectively generates a blended config of
+ // "everyone except tailscale", which is what would be in use if
+ // tailscale hadn't set exclusive mode.
+ //
+ // Note that this is not _entirely_ true. To be perfectly correct,
+ // we should be looking for other interfaces marked exclusive that
+ // predated tailscale, and stick to only those. However, in
+ // practice, openresolv uses are generally quite limited, and boil
+ // down to 1-2 DHCP leases, for which the correct outcome is a
+ // blended config like the one we produce here.
var buf bytes.Buffer
cmd := exec.Command("resolvconf", args...)
cmd.Stdout = &buf
