Fix the check for multicast or broadcast addresses in evutil_check_interfaces

First of all, it is totally okay to have an address end with .255,
depending on what your netmask is, so we shouldn't reject a local
address if it ends with .255.

Second, our check for ending with .255 was broken.  So was our check
for class-d addresses.

Found by Dave Hart.

diff --git a/evutil.c b/evutil.c
index 0f376e09add0117e48951f05b437e44eaea63f8d..9d9863a23c5f374cf97f87295c5e1d3b2f7c955b 100644 (file)
--- a/evutil.c
+++ b/evutil.c
@@ -511,6 +511,15 @@ evutil_socket_finished_connecting(evutil_socket_t fd)
    set by evutil_check_interfaces. */
 static int have_checked_interfaces, had_ipv4_address, had_ipv6_address;
 
+/* Macro: True iff the IPv4 address 'addr', in host order, is in 127.0.0.0/8
+ */
+#define EVUTIL_V4ADDR_IS_LOCALHOST(addr) (((addr)>>24) == 127)
+
+/* Macro: True iff the IPv4 address 'addr', in host order, is a class D
+ * (multiclass) address.
+ */
+#define EVUTIL_V4ADDR_IS_CLASSD(addr) ((((addr)>>24) & 0xf0) == 0xe0)
+
 /* Test whether we have an ipv4 interface and an ipv6 interface.  Return 0 if
  * the test seemed successful. */
 static int
@@ -554,8 +563,9 @@ evutil_check_interfaces(int force_recheck)
            getsockname(fd, (struct sockaddr*)&sin_out, &sin_out_len) == 0) {
                /* We might have an IPv4 interface. */
                ev_uint32_t addr = ntohl(sin_out.sin_addr.s_addr);
-               if (addr == 0 || (addr&0xff000000) == 127 ||
-                   (addr & 0xff) == 255 || (addr & 0xf0) == 14) {
+               if (addr == 0 ||
+                   EVUTIL_V4ADDR_IS_LOCALHOST(addr) ||
+                   EVUTIL_V4ADDR_IS_CLASSD(addr)) {
                        evutil_inet_ntop(AF_INET, &sin_out.sin_addr,
                            buf, sizeof(buf));
                        /* This is a reserved, ipv4compat, ipv4map, loopback,