[dhcpv6] Solicit messages derive default IAID from MAC address

IAID must be set by the client. This patch generates the IAID from the
MAC address of the interface. To do so, a new WithIAID modifier is
added, the interface of NewSolicitWithCID now requires a hwaddr
parameter, and NewAdvertiseFromSolicit copies the IA_NA option from the
solicit if present.

Signed-off-by: Andrea Barberio <insomniac@slackware.it>

1 files changed, 15 insertions, 0 deletions

diff --git a/dhcpv6/modifiers.go b/dhcpv6/modifiers.go
index eaa370d..200a602 100644
--- a/dhcpv6/modifiers.go
+++ b/dhcpv6/modifiers.go
@@ -77,6 +77,21 @@ func WithIANA(addrs ...OptIAAddress) Modifier {
 	}
 }
 
+// WithIAID updates an OptIANA option with the provided IAID
+func WithIAID(iaid [4]byte) Modifier {
+	return func(d DHCPv6) {
+		opt := d.GetOneOption(OptionIANA)
+		if opt == nil {
+			opt = &OptIANA{
+				Options: Options{},
+			}
+		}
+		iaNa := opt.(*OptIANA)
+		copy(iaNa.IaId[:], iaid[:])
+		d.UpdateOption(iaNa)
+	}
+}
+
 // WithDNS adds or updates an OptDNSRecursiveNameServer
 func WithDNS(dnses ...net.IP) Modifier {
 	return func(d DHCPv6) {