Check local interfaces for a duplicate IPv4LL address before ARP.

diff --git a/ipv4ll.c b/ipv4ll.c
index 1d59bc9dbee1590fc3869fb15d5923a27fff72a9..a10f886e9a817c4a6991503f443a6c6493da3a9e 100644 (file)
--- a/ipv4ll.c
+++ b/ipv4ll.c
@@ -71,15 +71,29 @@ ipv4ll_make_lease(uint32_t addr)
 }
 
 static struct dhcp_message *
-ipv4ll_find_lease(uint32_t old_addr)
+ipv4ll_find_lease(struct dhcpcd_ctx *ctx)
 {
        uint32_t addr;
+       struct interface *ifp;
+       const struct dhcp_state *state;
 
        for (;;) {
-               addr = htonl(LINKLOCAL_ADDR |
+               addr = ntohl(LINKLOCAL_ADDR |
                    (uint32_t)(abs((int)arc4random_uniform(0xFD00)) + 0x0100));
-               if (addr != old_addr &&
-                   IN_LINKLOCAL(ntohl(addr)))
+
+               /* Sanity */
+               if (!IN_LINKLOCAL(htonl(addr)))
+                       continue;
+
+               /* Ensure we don't have the address on another interface */
+               TAILQ_FOREACH(ifp, ctx->ifaces, next) {
+                       state = D_CSTATE(ifp);
+                       if (state && state->addr.s_addr == addr)
+                               break;
+               }
+
+               /* Yay, this should be a unique and workable IPv4LL address */
+               if (ifp == NULL)
                        break;
        }
        return ipv4ll_make_lease(addr);
@@ -126,7 +140,7 @@ ipv4ll_start(void *arg)
                addr = 0;
        }
        if (addr == 0)
-               state->offer = ipv4ll_find_lease(addr);
+               state->offer = ipv4ll_find_lease(ifp->ctx);
        else
                state->offer = ipv4ll_make_lease(addr);
        if (state->offer == NULL)