From: Roy Marples <roy@marples.name>
Date: Fri, 17 May 2024 22:12:26 +0000 (+0000)
Subject: DHCP6: Wait for IRT to elapse before requesting advertisments
X-Git-Tag: v10.0.7~2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8dc7f72c63f1a4ba50e5b3c42c85f42f34f41fbf;p=thirdparty%2Fdhcpcd.git

DHCP6: Wait for IRT to elapse before requesting advertisments

RFC 8415 15 and 18.2.1 list this as a MUST.

Fixes #317.
---

diff --git a/src/dhcp6.c b/src/dhcp6.c
index e187a376..7cc51f99 100644
--- a/src/dhcp6.c
+++ b/src/dhcp6.c
@@ -181,6 +181,7 @@ static void dhcp6_bind(struct interface *, const char *, const char *);
 static void dhcp6_failinform(void *);
 static void dhcp6_recvaddr(void *, unsigned short);
 static void dhcp6_startdecline(struct interface *);
+static void dhcp6_startrequest(struct interface *);
 
 #ifdef SMALL
 #define dhcp6_hasprefixdelegation(a)	(0)
@@ -1427,11 +1428,38 @@ dhcp6_sendinform(void *arg)
 	dhcp6_sendmessage(arg, dhcp6_sendinform);
 }
 
+static void
+dhcp6_senddiscover2(void *arg)
+{
+
+	dhcp6_sendmessage(arg, dhcp6_senddiscover2);
+}
+
+static void
+dhcp6_senddiscover1(void *arg)
+{
+	/*
+	 * So the initial RT has elapsed.
+	 * If we have any ADVERTs we can now REQUEST them.
+	 * RFC 8415 15 and 18.2.1
+	 */
+	struct interface *ifp = arg;
+	struct dhcp6_state *state = D6_STATE(ifp);
+
+	if (state->recv == NULL || state->recv->type != DHCP6_ADVERTISE)
+		dhcp6_sendmessage(arg, dhcp6_senddiscover2);
+	else
+		dhcp6_startrequest(ifp);
+}
+
 static void
 dhcp6_senddiscover(void *arg)
 {
+	struct interface *ifp = arg;
+	struct dhcp6_state *state = D6_STATE(ifp);
 
-	dhcp6_sendmessage(arg, dhcp6_senddiscover);
+	dhcp6_sendmessage(arg,
+	    state->IMD != 0 ? dhcp6_senddiscover : dhcp6_senddiscover1);
 }
 
 static void
@@ -1890,7 +1918,6 @@ dhcp6_startrebind(void *arg)
 #endif
 }
 
-
 static void
 dhcp6_startrequest(struct interface *ifp)
 {
@@ -3461,6 +3488,16 @@ dhcp6_recvif(struct interface *ifp, const char *sfrom,
 			valid_op = false;
 			break;
 		}
+		if (state->recv_len && state->recv->type == DHCP6_ADVERTISE) {
+			/* We already have an advertismemnt.
+			 * RFC 8415 says we have to wait for the IRT to elapse.
+			 * To keep the same behaviour we won't do anything with
+			 * this. In the future we should make a lists of
+			 * ADVERTS and pick the "best" one. */
+			logdebugx("%s: discarding ADVERTISMENT from %s",
+			    ifp->name, sfrom);
+			return;
+		}
 		/* RFC7083 */
 		o = dhcp6_findmoption(r, len, D6_OPTION_SOL_MAX_RT, &ol);
 		if (o && ol == sizeof(uint32_t)) {
@@ -3586,7 +3623,7 @@ dhcp6_recvif(struct interface *ifp, const char *sfrom,
 		else
 			loginfox("%s: ADV %s from %s",
 			    ifp->name, ia->saddr, sfrom);
-		dhcp6_startrequest(ifp);
+		// We will request when the IRT elapses
 		return;
 	}