From 3354013a47fe53f073c520c3c486ab9b7ff53601 Mon Sep 17 00:00:00 2001
From: Francis Dupont <fdupont@isc.org>
Date: Tue, 13 Oct 2020 10:15:00 +0200
Subject: [PATCH] Checkpoint: code done, need tests

---
 client/dhclient.c | 94 ++++++++++++++++++++++++++++++++++++-----------
 includes/dhcpd.h  |  3 +-
 2 files changed, 74 insertions(+), 23 deletions(-)

diff --git a/client/dhclient.c b/client/dhclient.c
index b989d1b7..1a7ac85e 100644
--- a/client/dhclient.c
+++ b/client/dhclient.c
@@ -1242,49 +1242,79 @@ void state_init (cpp)
 	send_discover (client);
 }
 
-/* v6only_timeout is called when the V6ONLY_WAIT timer expired. */
+/* check_v6only is called by dhcpoffer and dhcpack. It checks if a
+ * requested v6-only-preferred option is present and returned the
+ * V6ONLY_WAIT delay to suspend DHCPv4. */
 
-void finish_v6only(cpp)
-	void *cpp;
-{
-	struct client_state *client = cpp;
-	client->state = S_INIT;
-	state_init(cpp);
-}
-
-/*
- * state_v6only is called when a requested v6-only-preferred option was
- * returned by the server. */
-
-void start_v6only(packet, client)
+uint32_t check_v6only(packet, client)
 	struct packet *packet;
 	struct client_state *client;
 {
+	int i;
+	struct option **req;
+	isc_boolean_t found = ISC_FALSE;
 	struct option_cache *oc;
 	struct data_string data;
 	uint32_t v6only_wait = 0;
-	struct timeval tv;
 
+	/* Check if the v6-only-preferred was requested. */
+	req = client->config->requested_options;
+
+	if (req == NULL)
+		return 0;
+
+	for (i = 0 ; req[i] != NULL ; i++) {
+		if ((req[i]->universe == &dhcp_universe) &&
+		    (req[i]->code == DHO_V6_ONLY_PREFERRED)) {
+			found = ISC_TRUE;
+			break;
+		}
+	}
+
+	if (found == ISC_FALSE)
+		return 0;
+	
 	/* Get the V6ONLY_WAIT timer. */
 	oc = lookup_option(&dhcp_universe, packet->options,
 			   DHO_V6_ONLY_PREFERRED);
-	if (!oc) {
-		/* Should not happen... */
-		return;
-	}
+	if (!oc)
+		return 0;
 
 	memset(&data, 0, sizeof(data));
 
 	if (evaluate_option_cache(&data, packet, (struct lease *)0, client,
 				  packet->options, (struct option_state *)0,
 				  &global_scope, oc, MDL)) {
-		if (data.len > 3)
+		if (data.len > 3) {
 			v6only_wait = getULong(data.data);
+			if (v6only_wait < MIN_V6ONLY_WAIT)
+				v6only_wait = MIN_V6ONLY_WAIT;
+		}
 		data_string_forget(&data, MDL);
 	}
 
-	if (v6only_wait < MIN_V6ONLY_WAIT)
-		v6only_wait = MIN_V6ONLY_WAIT;
+	return (v6only_wait);
+}
+
+/* finish_v6only is called when the V6ONLY_WAIT timer expired. */
+
+void finish_v6only(cpp)
+	void *cpp;
+{
+	struct client_state *client = cpp;
+	client->state = S_INIT;
+	state_init(cpp);
+}
+
+/*
+ * start_v6only is called when a requested v6-only-preferred option was
+ * returned by the server. */
+
+void start_v6only(client, v6only_wait)
+	struct client_state *client;
+	uint32_t v6only_wait;
+{
+	struct timeval tv;
 
 	/* Enter V6ONLY state. */
 
@@ -1404,6 +1434,7 @@ void dhcpack (packet)
 {
 	struct interface_info *ip = packet -> interface;
 	struct client_state *client;
+	uint32_t v6only_wait;
 	struct client_lease *lease;
 	struct option_cache *oc;
 	struct data_string ds;
@@ -1439,6 +1470,15 @@ void dhcpack (packet)
 		  inet_ntoa(packet->raw->yiaddr),
 		  piaddr (packet->client_addr));
 
+	/* Check v6only first. */
+	v6only_wait = check_v6only(packet, client);
+	if (v6only_wait > 0) {
+		log_info("v6 only preferred for %lu.",
+			 (long unsigned)v6only_wait);
+		start_v6only(client, v6only_wait);
+		return;
+	}
+
 	lease = packet_to_lease (packet, client);
 	if (!lease) {
 		log_info ("packet_to_lease failed.");
@@ -2077,6 +2117,7 @@ void dhcpoffer (packet)
 {
 	struct interface_info *ip = packet -> interface;
 	struct client_state *client;
+	uint32_t v6only_wait;
 	struct client_lease *lease, *lp;
 	struct option **req;
 	int i;
@@ -2112,6 +2153,15 @@ void dhcpoffer (packet)
 		 inet_ntoa(packet->raw->yiaddr),
 		 piaddr(packet->client_addr));
 
+	/* Check v6only first. */
+	v6only_wait = check_v6only(packet, client);
+	if (v6only_wait > 0) {
+		log_info("%s: v6 only preferred for %lu.", obuf,
+			 (long unsigned)v6only_wait);
+		start_v6only(client, v6only_wait);
+		return;
+	}
+
 	/* If this lease doesn't supply the minimum required DHCPv4 parameters,
 	 * ignore it.
 	 */
diff --git a/includes/dhcpd.h b/includes/dhcpd.h
index caeeaeda..f9217ea8 100644
--- a/includes/dhcpd.h
+++ b/includes/dhcpd.h
@@ -3008,7 +3008,8 @@ void state_bound (void *);
 void state_stop (void *);
 void state_panic (void *);
 
-void start_v6only (struct packet *, struct client_state *);
+uint32_t check_v6only (struct packet *, struct client_state *);
+void start_v6only (struct client_state *, uint32_t);
 void finish_v6only (void *);
 
 void bind_lease (struct client_state *);
-- 
2.39.2