IPv4LL: Restart ARP probling on address conflict

When IPv4LL address conflict is detected, it is failed to restart IPv4LL
since IPv4LL is running. The commit fixes the problem by restarting ARP
probing instead of restarting IPv4LL.

src/ipv4ll.c

@@ -50,6 +50,12 @@
 #include "sa.h"
 #include "script.h"
 
+#ifndef KERNEL_RFC5227
+static void ipv4ll_start_arp(void *arg);
+#else
+static void ipv4ll_start_arp(void *arg) { (void)arg; };
+#endif
+
 static const struct in_addr inaddr_llmask = {
 	.s_addr = HTONL(LINKLOCAL_MASK)
 };
@@ -275,7 +281,7 @@ ipv4ll_found(struct interface *ifp)
 	eloop_timeout_add_sec(ifp->ctx->eloop,
 	    state->conflicts >= MAX_CONFLICTS ?
 	    RATE_LIMIT_INTERVAL : PROBE_WAIT,
-	    ipv4ll_start, ifp);
+	    ipv4ll_start_arp, ifp);
 }
 
 static void
@@ -290,7 +296,7 @@ ipv4ll_defend_failed(struct interface *ifp)
 	rt_build(ifp->ctx, AF_INET);
 	script_runreason(ifp, "IPV4LL");
 	ipv4ll_pickaddr(ifp);
-	ipv4ll_start(ifp);
+	ipv4ll_start_arp(ifp);
 }
 
 #ifndef KERNEL_RFC5227
@@ -323,9 +329,6 @@ ipv4ll_start(void *arg)
 	struct ipv4ll_state *state;
 	struct ipv4_addr *ia;
 	bool repick;
-#ifndef KERNEL_RFC5227
-	struct arp_state *astate;
-#endif
 
 	if ((state = IPV4LL_STATE(ifp)) == NULL) {
 		ifp->if_data[IF_DATA_IPV4LL] = calloc(1, sizeof(*state));
@@ -410,6 +413,20 @@ ipv4ll_start(void *arg)
 #ifdef KERNEL_RFC5227
 	ipv4ll_not_found(ifp);
 #else
+	ipv4ll_start_arp(ifp);
+#endif
+}
+
+#ifndef KERNEL_RFC5227
+static void
+ipv4ll_start_arp(void *arg)
+{
+	struct interface *ifp = arg;
+	struct ipv4ll_state *state;
+	struct arp_state *astate;
+
+	state = IPV4LL_STATE(ifp);
+
 	ipv4ll_freearp(ifp);
 	state->arp = astate = arp_new(ifp, &state->pickedaddr);
 	if (state->arp == NULL)
@@ -421,8 +438,8 @@ ipv4ll_start(void *arg)
 	astate->defend_failed_cb = ipv4ll_defend_failed_arp;
 	astate->free_cb = ipv4ll_free_arp;
 	arp_probe(astate);
-#endif
 }
+#endif
 
 void
 ipv4ll_drop(struct interface *ifp)