dhcp6: fix VendorOpts getter

RFC 8415 Section 21.17 states it may appear more than once:

   Multiple instances of the Vendor-specific Information option may
   appear in a DHCP message.  Each instance of the option is interpreted
   according to the option codes defined by the vendor identified by the
   Enterprise Number in that option.  Servers and clients MUST NOT send
   more than one instance of the Vendor-specific Information option with
   the same Enterprise Number.

Signed-off-by: Chris Koch <chrisko@google.com>

1 files changed, 31 insertions, 7 deletions

diff --git a/dhcpv6/dhcpv6message.go b/dhcpv6/dhcpv6message.go
index 76404f2..0927038 100644
--- a/dhcpv6/dhcpv6message.go
+++ b/dhcpv6/dhcpv6message.go
@@ -179,16 +179,40 @@ func (mo MessageOptions) UserClasses() [][]byte {
 	return nil
 }
 
-// VendorOpts returns the enterprise number and a list of vendor options.
-func (mo MessageOptions) VendorOpts() (uint32, Options) {
-	opt := mo.Options.GetOne(OptionVendorOpts)
+// VendorOpts returns the all vendor-specific options.
+//
+// RFC 8415 Section 21.17:
+//
+//   Multiple instances of the Vendor-specific Information option may appear in
+//   a DHCP message.
+func (mo MessageOptions) VendorOpts() []*OptVendorOpts {
+	opt := mo.Options.Get(OptionVendorOpts)
 	if opt == nil {
-		return 0, nil
+		return nil
+	}
+	var vo []*OptVendorOpts
+	for _, o := range opt {
+		if t, ok := o.(*OptVendorOpts); ok {
+			vo = append(vo, t)
+		}
 	}
-	if t, ok := opt.(*OptVendorOpts); ok {
-		return t.EnterpriseNumber, t.VendorOpts
+	return vo
+}
+
+// VendorOpt returns the vendor options matching the given enterprise number.
+//
+// RFC 8415 Section 21.17:
+//
+//   Servers and clients MUST NOT send more than one instance of the
+//   Vendor-specific Information option with the same Enterprise Number.
+func (mo MessageOptions) VendorOpt(enterpriseNumber uint32) Options {
+	vo := mo.VendorOpts()
+	for _, v := range vo {
+		if v.EnterpriseNumber == enterpriseNumber {
+			return v.VendorOpts
+		}
 	}
-	return 0, nil
+	return nil
 }
 
 // ElapsedTime returns the Elapsed Time option as defined by RFC 3315 Section 22.9.