From: Roy Marples <roy@marples.name>
Date: Mon, 10 Sep 2018 11:02:55 +0000 (+0100)
Subject: dhcp6: always move to the DISCOVER phase if the offered lease is invalid
X-Git-Tag: v7.1.0~27
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=838c5eba20279f98f4d9b0daaae158497143ecf5;p=thirdparty%2Fdhcpcd.git

dhcp6: always move to the DISCOVER phase if the offered lease is invalid
---

diff --git a/src/dhcp6.c b/src/dhcp6.c
index de51ee56..2a6dcb25 100644
--- a/src/dhcp6.c
+++ b/src/dhcp6.c
@@ -3299,15 +3299,26 @@ dhcp6_recvif(struct interface *ifp, struct dhcp6_message *r, size_t len)
 			if (dhcp6_validatelease(ifp, r, len,
 			    ctx->sfrom, NULL) == -1)
 			{
-#ifndef SMALL
-				/* PD doesn't use CONFIRM, so REBIND could
-				 * throw up an invalid prefix if we
-				 * changed link */
-				if (state->state == DH6S_REBIND &&
-				    dhcp6_hasprefixdelegation(ifp))
+				/*
+				 * If we can't use the lease, fallback to
+				 * DISCOVER and try and get a new one.
+				 *
+				 * This is needed become some servers
+				 * renumber the prefix or address
+				 * and deny the current one before it expires
+				 * rather than sending it back with a zero
+				 * lifetime along with the new prefix or
+				 * address to use.
+				 * This behavior is wrong, but moving to the
+				 * DISCOVER phase works around it.
+				 *
+				 * The currently held lease is still valid
+				 * until a new one is found.
+				 */
+				if (state->state != DH6S_DISCOVER) {
 					dhcp6_startdiscover(ifp);
-#endif
-				return;
+					return;
+				}
 			}
 			if (state->state == DH6S_DISCOVER)
 				state->state = DH6S_REQUEST;