Repeat https://github.com/grpc/grpc/issues/3049 for OSX

include/grpc/support/port_platform.h

@@ -174,8 +174,6 @@
 #endif /* _LP64 */
 #elif defined(__APPLE__)
 #include <TargetConditionals.h>
-/* Provides IPV6_RECVPKTINFO */
-#define __APPLE_USE_RFC_3542
 #ifndef _BSD_SOURCE
 #define _BSD_SOURCE
 #endif

src/core/iomgr/udp_server.c

@@ -235,7 +235,7 @@ static int prepare_socket(int fd, const struct sockaddr *addr, int addr_len) {
   rc = setsockopt(fd, IPPROTO_IP, IP_PKTINFO, &get_local_ip,
                   sizeof(get_local_ip));
   if (rc == 0 && addr->sa_family == AF_INET6) {
-#if !TARGET_OS_IPHONE
+#if !defined(__APPLE__)
     rc = setsockopt(fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, &get_local_ip,
                     sizeof(get_local_ip));
 #endif