dhcpv4: enable deletion of options and add modifier for it

Signed-off-by: Dennis Marttinen <twelho@welho.tech>

4 files changed, 30 insertions, 0 deletions

diff --git a/dhcpv4/dhcpv4.go b/dhcpv4/dhcpv4.go
index b894fbb..900bb22 100644
--- a/dhcpv4/dhcpv4.go
+++ b/dhcpv4/dhcpv4.go
@@ -382,6 +382,13 @@ func (d *DHCPv4) GetOneOption(code OptionCode) []byte {
 	return d.Options.Get(code)
 }
 
+// DeleteOption deletes an existing option with the given option code.
+func (d *DHCPv4) DeleteOption(code OptionCode) {
+	if d.Options != nil {
+		d.Options.Del(code)
+	}
+}
+
 // UpdateOption replaces an existing option with the same option code with the
 // given one, adding it if not already present.
 func (d *DHCPv4) UpdateOption(opt Option) {
diff --git a/dhcpv4/modifiers.go b/dhcpv4/modifiers.go
index 0ab35bc..68da298 100644
--- a/dhcpv4/modifiers.go
+++ b/dhcpv4/modifiers.go
@@ -99,6 +99,13 @@ func WithOption(opt Option) Modifier {
 	}
 }
 
+// WithoutOption removes the DHCPv4 option with the given code
+func WithoutOption(code OptionCode) Modifier {
+	return func(d *DHCPv4) {
+		d.DeleteOption(code)
+	}
+}
+
 // WithUserClass adds a user class option to the packet.
 // The rfc parameter allows you to specify if the userclass should be
 // rfc compliant or not. More details in issue #113
diff --git a/dhcpv4/modifiers_test.go b/dhcpv4/modifiers_test.go
index 274b409..57d8ff0 100644
--- a/dhcpv4/modifiers_test.go
+++ b/dhcpv4/modifiers_test.go
@@ -44,6 +44,17 @@ func TestWithOptionModifier(t *testing.T) {
 	require.Equal(t, "slackware.it", dnOpt)
 }
 
+func TestWithoutOptionModifier(t *testing.T) {
+	d, err := New(
+		WithOption(OptDomainName("slackware.it")),
+		WithoutOption(OptionDomainName),
+	)
+	require.NoError(t, err)
+
+	require.False(t, d.Options.Has(OptionDomainName))
+	require.Equal(t, "", d.DomainName())
+}
+
 func TestUserClassModifier(t *testing.T) {
 	d, err := New(WithUserClass("linuxboot", false))
 	require.NoError(t, err)
diff --git a/dhcpv4/options.go b/dhcpv4/options.go
index fdc79ae..9d404b4 100644
--- a/dhcpv4/options.go
+++ b/dhcpv4/options.go
@@ -81,6 +81,11 @@ func (o Options) Has(opcode OptionCode) bool {
 	return ok
 }
 
+// Del deletes the option matching the option code.
+func (o Options) Del(opcode OptionCode) {
+	delete(o, opcode.Code())
+}
+
 // Update updates the existing options with the passed option, adding it
 // at the end if not present already
 func (o Options) Update(option Option) {