fixing -Wstrict-aliasing (part 1)

tpws/helpers.c

@@ -155,7 +155,7 @@ bool saconvmapped(struct sockaddr_storage *a)
 {
 	if ((a->ss_family == AF_INET6) && saismapped((struct sockaddr_in6*)a))
 	{
-		uint32_t ip4 = *(uint32_t*)(((struct sockaddr_in6*)a)->sin6_addr.s6_addr+12);
+		uint32_t ip4 = IN6_EXTRACT_MAP4(((struct sockaddr_in6*)a)->sin6_addr.s6_addr);
 		uint16_t port = ((struct sockaddr_in6*)a)->sin6_port;
 		a->ss_family = AF_INET;
 		((struct sockaddr_in*)a)->sin_addr.s_addr = ip4;

tpws/helpers.h

@@ -59,3 +59,12 @@ bool pf_parse(const char *s, port_filter *pf);
 #ifndef IN_LOOPBACK
 #define IN_LOOPBACK(a)          ((((uint32_t) (a)) & 0xff000000) == 0x7f000000)
 #endif
+
+#ifdef __GNUC__
+#define IN6_EXTRACT_MAP4(a) \
+  (__extension__                                                              \
+   ({ const struct in6_addr *__a = (const struct in6_addr *) (a);             \
+      (((const uint32_t *) (__a))[3]); }))
+#else
+#define IN6_EXTRACT_MAP4(a)	(((const uint32_t *) (a))[3])
+#endif