dhcpcd-discuss

On 14/01/2019 11:23, Roy Marples wrote:
> dhcpcd treats the link down/up event as a reboot, thus seeds the random 
> number from the hardware address.
> This can be changed, will work on it.

Attached is a patch to address this.
I've tested it on Arch Linux and NetBSD.
Will test on others before comitting.

If you can test it to ensure dhcpcd now passes the conformance test, I'd 
appreciate it.

Roy

diff --git a/src/ipv4ll.c b/src/ipv4ll.c
index 103bce0a..92af9ba0 100644
--- a/src/ipv4ll.c
+++ b/src/ipv4ll.c
@@ -318,7 +318,8 @@ ipv4ll_conflicted(struct arp_state *astate, const struct arp_msg *amsg)
 	if (++state->conflicts == MAX_CONFLICTS)
 		logerr("%s: failed to acquire an IPv4LL address",
 		    ifp->name);
-	astate->addr.s_addr = ipv4ll_pickaddr(astate);
+	state->pickedaddr.s_addr = ipv4ll_pickaddr(astate);
+	astate->addr = state->pickedaddr;
 	eloop_timeout_add_sec(ifp->ctx->eloop,
 		state->conflicts >= MAX_CONFLICTS ?
 		RATE_LIMIT_INTERVAL : PROBE_WAIT,
@@ -331,7 +332,7 @@ ipv4ll_arpfree(struct arp_state *astate)
 	struct ipv4ll_state *state;
 
 	state = IPV4LL_STATE(astate->iface);
-	if (state->arp == astate)
+	if (state != NULL && state->arp == astate)
 		state->arp = NULL;
 }
 
@@ -353,14 +354,11 @@ ipv4ll_start(void *arg)
 		}
 	}
 
-	if (state->arp != NULL)
-		return;
-
 	/* RFC 3927 Section 2.1 states that the random number generator
 	 * SHOULD be seeded with a value derived from persistent information
 	 * such as the IEEE 802 MAC address so that it usually picks
 	 * the same address without persistent storage. */
-	if (state->conflicts == 0) {
+	if (!state->seeded) {
 		unsigned int seed;
 		char *orig;
 
@@ -380,8 +378,11 @@ ipv4ll_start(void *arg)
 
 		/* Set back the original state until we need the seeded one. */
 		setstate(ifp->ctx->randomstate);
+		state->seeded = true;
 	}
 
+	if (state->arp != NULL)
+		return;
 	if ((astate = arp_new(ifp, NULL)) == NULL)
 		return;
 
@@ -391,8 +392,15 @@ ipv4ll_start(void *arg)
 	astate->conflicted_cb = ipv4ll_conflicted;
 	astate->free_cb = ipv4ll_arpfree;
 
+	/* Find the previosuly used address. */
+	if (state->pickedaddr.s_addr != INADDR_ANY)
+		ia = ipv4_iffindaddr(ifp, &state->pickedaddr, NULL);
+	else
+		ia = NULL;
+
 	/* Find an existing IPv4LL address and ensure we can work with it. */
-	ia = ipv4_iffindlladdr(ifp);
+	if (ia == NULL)
+		ia = ipv4_iffindlladdr(ifp);
 
 #ifdef IN_IFF_TENTATIVE
 	if (ia != NULL && ia->addr_flags & IN_IFF_DUPLICATED) {
@@ -402,7 +410,7 @@ ipv4ll_start(void *arg)
 #endif
 
 	if (ia != NULL) {
-		astate->addr = ia->addr;
+		state->pickedaddr = astate->addr = ia->addr;
 #ifdef IN_IFF_TENTATIVE
 		if (ia->addr_flags & (IN_IFF_TENTATIVE | IN_IFF_DETACHED)) {
 			loginfox("%s: waiting for DAD to complete on %s",
@@ -416,7 +424,9 @@ ipv4ll_start(void *arg)
 	}
 
 	loginfox("%s: probing for an IPv4LL address", ifp->name);
-	astate->addr.s_addr = ipv4ll_pickaddr(astate);
+	if (state->pickedaddr.s_addr == INADDR_ANY)
+		state->pickedaddr.s_addr = ipv4ll_pickaddr(astate);
+	astate->addr = state->pickedaddr;
 #ifdef IN_IFF_TENTATIVE
 	ipv4ll_probed(astate);
 #else
@@ -424,56 +434,72 @@ ipv4ll_start(void *arg)
 #endif
 }
 
+static void
+ipv4ll_freearp(struct interface *ifp)
+{
+	struct ipv4ll_state *state;
+
+	state = IPV4LL_STATE(ifp);
+	if (state == NULL || state->arp == NULL)
+		return;
+
+	eloop_timeout_delete(ifp->ctx->eloop, NULL, state->arp);
+	arp_free(state->arp);
+	state->arp = NULL;
+}
+
 void
-ipv4ll_freedrop(struct interface *ifp, int drop)
+ipv4ll_drop(struct interface *ifp)
 {
 	struct ipv4ll_state *state;
-	int dropped;
+	bool dropped = false;
+	struct ipv4_state *istate;
 
 	assert(ifp != NULL);
-	state = IPV4LL_STATE(ifp);
-	dropped = 0;
 
-	/* Free ARP state first because ipv4_deladdr might also ... */
-	if (state && state->arp) {
-		eloop_timeout_delete(ifp->ctx->eloop, NULL, state->arp);
-		arp_free(state->arp);
-		state->arp = NULL;
-	}
+	ipv4ll_freearp(ifp);
 
-	if (drop && (ifp->options->options & DHCPCD_NODROP) != DHCPCD_NODROP) {
-		struct ipv4_state *istate;
+#ifndef IN_IFF_TENATIVE
+	if ((ifp->options->options & DHCPCD_NODROP) == DHCPCD_NODROP)
+#endif
+		return;
 
-		if (state && state->addr != NULL) {
-			ipv4_deladdr(state->addr, 1);
-			state->addr = NULL;
-			dropped = 1;
-		}
+	state = IPV4LL_STATE(ifp);
+	if (state && state->addr != NULL) {
+		ipv4_deladdr(state->addr, 1);
+		state->addr = NULL;
+		dropped = true;
+	}
 
-		/* Free any other link local addresses that might exist. */
-		if ((istate = IPV4_STATE(ifp)) != NULL) {
-			struct ipv4_addr *ia, *ian;
+	/* Free any other link local addresses that might exist. */
+	if ((istate = IPV4_STATE(ifp)) != NULL) {
+		struct ipv4_addr *ia, *ian;
 
-			TAILQ_FOREACH_SAFE(ia, &istate->addrs, next, ian) {
-				if (IN_LINKLOCAL(ntohl(ia->addr.s_addr))) {
-					ipv4_deladdr(ia, 0);
-					dropped = 1;
-				}
+		TAILQ_FOREACH_SAFE(ia, &istate->addrs, next, ian) {
+			if (IN_LINKLOCAL(ntohl(ia->addr.s_addr))) {
+				ipv4_deladdr(ia, 0);
+				dropped = true;
 			}
 		}
 	}
 
-	if (state) {
-		free(state);
-		ifp->if_data[IF_DATA_IPV4LL] = NULL;
-
-		if (dropped) {
-			rt_build(ifp->ctx, AF_INET);
-			script_runreason(ifp, "IPV4LL");
-		}
+	if (dropped) {
+		rt_build(ifp->ctx, AF_INET);
+		script_runreason(ifp, "IPV4LL");
 	}
 }
 
+void
+ipv4ll_free(struct interface *ifp)
+{
+
+	assert(ifp != NULL);
+
+	ipv4ll_freearp(ifp);
+	free(IPV4LL_STATE(ifp));
+	ifp->if_data[IF_DATA_IPV4LL] = NULL;
+}
+
 /* This may cause issues in BSD systems, where running as a single dhcpcd
  * daemon would solve this issue easily. */
 #ifdef HAVE_ROUTE_METRIC
diff --git a/src/ipv4ll.h b/src/ipv4ll.h
index 6ead6ea5..acff2d9b 100644
--- a/src/ipv4ll.h
+++ b/src/ipv4ll.h
@@ -40,11 +40,13 @@
 #include "arp.h"
 
 struct ipv4ll_state {
+	struct in_addr pickedaddr;
 	struct ipv4_addr *addr;
 	struct arp_state *arp;
 	unsigned int conflicts;
 	struct timespec defend;
 	char randomstate[128];
+	bool seeded;
 	uint8_t down;
 };
 
@@ -66,9 +68,8 @@ void ipv4ll_handle_failure(void *);
 int ipv4ll_recvrt(int, const struct rt *);
 #endif
 
-#define	ipv4ll_free(ifp)		ipv4ll_freedrop((ifp), 0);
-#define	ipv4ll_drop(ifp)		ipv4ll_freedrop((ifp), 1);
-void ipv4ll_freedrop(struct interface *, int);
+void ipv4ll_drop(struct interface *);
+void ipv4ll_free(struct interface *);
 #else
 #define	IPV4LL_STATE_RUNNING(ifp)	(0)
 #define	ipv4ll_subnetroute(route, ifp)	(0)