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Random suffix only on collision.

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0.16.0 introduced random suffixes to all machine given names
(DNS hostnames) regardless of collisions within a namespace.
This commit brings Headscale more inline with Tailscale by only
adding a suffix if the hostname will collide within the namespace.

The suffix generation differs from Tailscale.
See https://tailscale.com/kb/1098/machine-names/
This commit is contained in:
= 2022-08-31 12:41:01 +01:00 • committed by Kristoffer Dalby
parent 98f5b7f638
commit 2aebd2927d
No known key found for this signature in database
5 changed files with 154 additions and 49 deletions
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64
machine.go
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@ -348,6 +348,22 @@ func (h *Headscale) GetMachine(namespace string, name string) (*Machine, error)
return nil, ErrMachineNotFound
}
// GetMachineByGivenName finds a Machine by given name and namespace and returns the Machine struct.
func (h *Headscale) GetMachineByGivenName(namespace string, givenName string) (*Machine, error) {
machines, err := h.ListMachinesInNamespace(namespace)
if err != nil {
return nil, err
}
for _, m := range machines {
if m.GivenName == givenName {
return &m, nil
}
}
return nil, ErrMachineNotFound
}
// GetMachineByID finds a Machine by ID and returns the Machine struct.
func (h *Headscale) GetMachineByID(id uint64) (*Machine, error) {
m := Machine{}
@ -1018,11 +1034,7 @@ func (machine *Machine) RoutesToProto() *v1.Routes {
}
}
func (h *Headscale) GenerateGivenName(suppliedName string) (string, error) {
// If a hostname is or will be longer than 63 chars after adding the hash,
// it needs to be trimmed.
trimmedHostnameLength := labelHostnameLength - MachineGivenNameHashLength - MachineGivenNameTrimSize
func (h *Headscale) generateGivenName(suppliedName string, randomSuffix bool) (string, error) {
normalizedHostname, err := NormalizeToFQDNRules(
suppliedName,
h.cfg.OIDC.StripEmaildomain,
@ -1031,18 +1043,40 @@ func (h *Headscale) GenerateGivenName(suppliedName string) (string, error) {
return "", err
}
postfix, err := GenerateRandomStringDNSSafe(MachineGivenNameHashLength)
if err != nil {
return "", err
}
if randomSuffix {
// Trim if a hostname will be longer than 63 chars after adding the hash.
trimmedHostnameLength := labelHostnameLength - MachineGivenNameHashLength - MachineGivenNameTrimSize
if len(normalizedHostname) > trimmedHostnameLength {
normalizedHostname = normalizedHostname[:trimmedHostnameLength]
}
// Verify that that the new unique name is shorter than the maximum allowed
// DNS segment.
if len(normalizedHostname) <= trimmedHostnameLength {
normalizedHostname = fmt.Sprintf("%s-%s", normalizedHostname, postfix)
} else {
normalizedHostname = fmt.Sprintf("%s-%s", normalizedHostname[:trimmedHostnameLength], postfix)
suffix, err := GenerateRandomStringDNSSafe(MachineGivenNameHashLength)
if err != nil {
return "", err
}
normalizedHostname += "-" + suffix
}
return normalizedHostname, nil
}
func (h *Headscale) GenerateGivenName(namespace string, machineKey string, suppliedName string) (string, error) {
givenName, err := h.generateGivenName(suppliedName, false)
if err != nil {
return "", err
}
// Tailscale rules (may differ) https://tailscale.com/kb/1098/machine-names/
machine, _ := h.GetMachineByGivenName(namespace, givenName)
if machine != nil && machine.MachineKey != machineKey && machine.GivenName == givenName {
postfixedName, err := h.generateGivenName(suppliedName, true)
if err != nil {
return "", err
}
givenName = postfixedName
}
return givenName, nil
}