macOS: Fix crash on OS X 10.8 caused by missing connectx function

The connectx() function call appeared in Darwin 15.0.0.
That covers OS X 10.11, iOS 9 and tvOS 9.

Because connectx is not declared with weak_import attribute it's not
possible to build libcurl on OS X 10.11 and later and target systems
which don't have _connectx symbol declared in libsystem_kernel.dylib
(i.e. OS X 10.8 and earlier).

Solution is to use connectx only on platforms that officially support it
i.e. by defining CFLAGS="-mmacosx-version-min=10.11" in configure step.

Note: It is possible to conditionally use connectx() in libcurl
targeting range of systems based on availability determined during
runtime using dlsym().

Fixes curl#1330
Closes curl#1336

CMake/CurlTests.c

@@ -549,3 +549,21 @@ main() {
   return 0;
 }
 #endif
+#ifdef HAVE_VALID_CONNECTX
+#  include <Availability.h>
+#  include <sys/socket.h>
+#  if defined(__MAC_OS_X_VERSION_MIN_REQUIRED)
+#    if (__MAC_OS_X_VERSION_MIN_REQUIRED < 101100)
+#      error Function requires deployment target OS X 10.11 or later
+#    endif
+#  elif defined(__IPHONE_OS_VERSION_MIN_REQUIRED)
+#    if (__IPHONE_OS_VERSION_MIN_REQUIRED < 90000)
+#      error Function requires deployment target iOS 9.0 or later
+#    endif
+#  endif
+
+main() {
+  connectx(0, 0, 0, 0, 0, 0, 0, 0);
+  return 0;
+}
+#endif

CMakeLists.txt

@@ -880,6 +880,15 @@ check_symbol_exists(fcntl          "${CURL_INCLUDES}" HAVE_FCNTL)
 check_symbol_exists(ioctl          "${CURL_INCLUDES}" HAVE_IOCTL)
 check_symbol_exists(setsockopt     "${CURL_INCLUDES}" HAVE_SETSOCKOPT)
 
+# The connectx() function call appeared in Darwin 15.0.0
+# but it's not declared using availability attribute.
+# Additionally _connectx symbol is part of OS X 10.9/10.10
+# system lib but does not have specified functionality.
+check_symbol_exists(connectx       "${CURL_INCLUDES}" HAVE_CONNECTX)
+if(HAVE_CONNECTX)
+  curl_internal_test_run(HAVE_VALID_CONNECTX)
+endif(HAVE_CONNECTX)
+
 # symbol exists in win32, but function does not.
 if(WIN32)
   if(ENABLE_INET_PTON)

acinclude.m4

@@ -2970,3 +2970,43 @@ AC_DEFUN([CURL_SUPPORTS_BUILTIN_AVAILABLE], [
     AC_MSG_RESULT([no])
   ])
 ])
+
+
+dnl CURL_CHECK_FUNC_CONNECTX
+dnl
+dnl Check if connectx() function is present.
+dnl The connectx() function call appeared in Darwin 15.0.0
+dnl but it's not declared using availability attribute.
+dnl Additionally _connectx symbol is part of OS X 10.9/10.10
+dnl system lib but does not have specified functionality.
+dnl
+
+AC_DEFUN([CURL_CHECK_FUNC_CONNECTX], [
+  AC_REQUIRE([CURL_MAC_CFLAGS])dnl
+  AC_CHECK_FUNCS([connectx])
+  AC_MSG_CHECKING([if connectx is available in deployment target])
+  AC_COMPILE_IFELSE(
+    [AC_LANG_PROGRAM([[
+#if defined(HAVE_CONNECTX)
+#  include <Availability.h>
+#  if defined(__MAC_OS_X_VERSION_MIN_REQUIRED)
+#    if (__MAC_OS_X_VERSION_MIN_REQUIRED < 101100)
+#      error Function requires deployment target OS X 10.11 or later
+#    endif
+#  elif defined(__IPHONE_OS_VERSION_MIN_REQUIRED)
+#    if (__IPHONE_OS_VERSION_MIN_REQUIRED < 90000)
+#      error Function requires deployment target iOS 9.0 or later
+#    endif
+#  endif
+#else
+#  error Function not present in the headers
+#endif
+    ]])],
+    [
+      AC_DEFINE(HAVE_VALID_CONNECTX, 1,
+        [Set to 1 if connectx() function have specified functionality.])
+      AC_MSG_RESULT([yes])
+    ],
+    [AC_MSG_RESULT([no])]
+  )
+])

configure.ac

@@ -3328,6 +3328,7 @@ CURL_CHECK_FUNC_BASENAME
 CURL_CHECK_FUNC_CLOSESOCKET
 CURL_CHECK_FUNC_CLOSESOCKET_CAMEL
 CURL_CHECK_FUNC_CONNECT
+CURL_CHECK_FUNC_CONNECTX
 CURL_CHECK_FUNC_FCNTL
 CURL_CHECK_FUNC_FDOPEN
 CURL_CHECK_FUNC_FREEADDRINFO

lib/connect.c

@@ -1058,26 +1058,17 @@ static CURLcode singleipconnect(struct connectdata *conn,
   /* Connect TCP sockets, bind UDP */
   if(!isconnected && (conn->socktype == SOCK_STREAM)) {
     if(conn->bits.tcp_fastopen) {
-#if defined(CONNECT_DATA_IDEMPOTENT) /* OS X */
-#ifdef HAVE_BUILTIN_AVAILABLE
-      if(__builtin_available(macOS 10.11, iOS 9.0, tvOS 9.0, watchOS 2.0, *)) {
-#endif /* HAVE_BUILTIN_AVAILABLE */
-        sa_endpoints_t endpoints;
-        endpoints.sae_srcif = 0;
-        endpoints.sae_srcaddr = NULL;
-        endpoints.sae_srcaddrlen = 0;
-        endpoints.sae_dstaddr = &addr.sa_addr;
-        endpoints.sae_dstaddrlen = addr.addrlen;
-
-        rc = connectx(sockfd, &endpoints, SAE_ASSOCID_ANY,
-                      CONNECT_RESUME_ON_READ_WRITE | CONNECT_DATA_IDEMPOTENT,
-                      NULL, 0, NULL, NULL);
-#ifdef HAVE_BUILTIN_AVAILABLE
-      }
-      else {
-        rc = connect(sockfd, &addr.sa_addr, addr.addrlen);
-      }
-#endif /* HAVE_BUILTIN_AVAILABLE */
+#if defined(HAVE_VALID_CONNECTX) /* Darwin */
+      sa_endpoints_t endpoints;
+      endpoints.sae_srcif = 0;
+      endpoints.sae_srcaddr = NULL;
+      endpoints.sae_srcaddrlen = 0;
+      endpoints.sae_dstaddr = &addr.sa_addr;
+      endpoints.sae_dstaddrlen = addr.addrlen;
+
+      rc = connectx(sockfd, &endpoints, SAE_ASSOCID_ANY,
+                    CONNECT_RESUME_ON_READ_WRITE | CONNECT_DATA_IDEMPOTENT,
+                    NULL, 0, NULL, NULL);
 #elif defined(MSG_FASTOPEN) /* Linux */
       if(conn->given->flags & PROTOPT_SSL)
         rc = connect(sockfd, &addr.sa_addr, addr.addrlen);

lib/curl_config.h.cmake

@@ -127,6 +127,9 @@
 /* Define to 1 if bool is an available type. */
 #cmakedefine HAVE_BOOL_T 1
 
+/* Define to 1 if you have the connectx function. */
+#cmakedefine HAVE_CONNECTX 1
+
 /* Define to 1 if you have the clock_gettime function and monotonic timer. */
 #cmakedefine HAVE_CLOCK_GETTIME_MONOTONIC 1
 
@@ -716,6 +719,9 @@
 /* Define to 1 if you have the <utime.h> header file. */
 #cmakedefine HAVE_UTIME_H 1
 
+/* Define to 1 if you have valid connectx function. */
+#cmakedefine HAVE_VALID_CONNECTX 1
+
 /* Define to 1 if compiler supports C99 variadic macro style. */
 #cmakedefine HAVE_VARIADIC_MACROS_C99 1
 

lib/url.c

@@ -2900,7 +2900,7 @@ CURLcode Curl_setopt(struct Curl_easy *data, CURLoption option,
     data->set.tcp_keepintvl = va_arg(param, long);
     break;
   case CURLOPT_TCP_FASTOPEN:
-#if defined(CONNECT_DATA_IDEMPOTENT) || defined(MSG_FASTOPEN)
+#if defined(HAVE_VALID_CONNECTX) || defined(MSG_FASTOPEN)
     data->set.tcp_fastopen = (0 != va_arg(param, long))?TRUE:FALSE;
 #else
     result = CURLE_NOT_BUILT_IN;