AdguardTeam/AdGuardHome · error

couldn't parse MAC address: %w

Error message

couldn't parse MAC address: %w

What it means

Converting a static-lease API payload (leaseStatic) to a Lease failed because HWAddr is not a parseable MAC address per net.ParseMAC. Raised in the HTTP layer when adding/updating a static lease.

Source

Thrown at internal/dhcpd/http_unix.go:103

func leasesToStatic(leases []*dhcpsvc.Lease) (static []*leaseStatic) {
	static = make([]*leaseStatic, len(leases))

	for i, l := range leases {
		static[i] = &leaseStatic{
			HWAddr:   l.HWAddr.String(),
			IP:       l.IP,
			Hostname: l.Hostname,
		}
	}

	return static
}

// toLease converts leaseStatic to Lease or returns error.
func (l *leaseStatic) toLease() (lease *dhcpsvc.Lease, err error) {
	addr, err := net.ParseMAC(l.HWAddr)
	if err != nil {
		return nil, fmt.Errorf("couldn't parse MAC address: %w", err)
	}

	return &dhcpsvc.Lease{
		HWAddr:   addr,
		IP:       l.IP,
		Hostname: l.Hostname,
		IsStatic: true,
	}, nil
}

// leaseDynamic is the JSON form of dynamic DHCP lease.
type leaseDynamic struct {
	HWAddr   string     `json:"mac"`
	IP       netip.Addr `json:"ip"`
	Hostname string     `json:"hostname"`
	Expiry   string     `json:"expires"`
}

View on GitHub (pinned to b41aefbe51)

Solutions

1. Supply the MAC in a standard format like aa:bb:cc:dd:ee:ff
2. Double-check the field you are filling (HWAddr vs IP)
3. Trim whitespace/newlines from pasted values

Example fix

// before
{"hwaddr": "192.168.1.50"}
// after
{"hwaddr": "aa:bb:cc:dd:ee:ff"}

if _, err := net.ParseMAC(req.HWAddr); err != nil { http.Error(w, "invalid MAC", 400); return }

func isValidMAC(s string) bool { _, err := net.ParseMAC(s); return err == nil }

if _, err := net.ParseMAC(input); err != nil { /* 400 Bad Request, echo field name */ }

When it happens

Trigger: POSTing to the DHCP static-lease API (or UI form) with HWAddr empty, containing separators in the wrong places, invalid hex, or an IP address mistakenly supplied as the MAC.

Common situations: Typos in the UI form; pasting an IP into the MAC field; using unusual separator styles; sending already-normalized bytes instead of a string.

Related errors

• decoding json: %w
• parsing: %w
• parsing hardware address: %w
• subnet %s does not contain the ip %q
• %v is not an IPv4 %s

AI-assisted analysis of AdguardTeam/AdGuardHome@b41aefbe51 (2026-08-27). Data as JSON: /api/errors/2eb4a4abd9653ae7. Report an issue: GitHub.