William Ahern:

  Make UDP sockets non-blocking. I've confirmed that at least on Linux 2.4 a
  read event can come back from poll() on a valid SOCK_DGRAM socket but
  recv(2) will still block. This patch doesn't ignore EAGAIN in
  read_udp_packets(), though maybe it should. (This patch was edited by Daniel
  Stenberg and a new configure test was added (imported from curl's configure)
  to properly detect what non-blocking socket approach to use.)

4 files changed, 202 insertions, 23 deletions

diff --git a/ares/CHANGES b/ares/CHANGES
index cb1fdac24..678319dad 100644
--- a/ares/CHANGES
+++ b/ares/CHANGES
@@ -4,6 +4,13 @@
 
 - William Ahern:
 
+  Make UDP sockets non-blocking. I've confirmed that at least on Linux 2.4 a
+  read event can come back from poll() on a valid SOCK_DGRAM socket but
+  recv(2) will still block. This patch doesn't ignore EAGAIN in
+  read_udp_packets(), though maybe it should. (This patch was edited by Daniel
+  Stenberg and a new configure test was added (imported from curl's configure)
+  to properly detect what non-blocking socket approach to use.)
+
   I'm not quite sure how this was happening, but I've been seeing PTR queries
   which seem to return empty responses. At least, they were empty when calling
   ares_expand_name() on the record. Here's a patch which guarantees to
diff --git a/ares/acinclude.m4 b/ares/acinclude.m4
index 1b197f0a0..2f6256ae4 100644
--- a/ares/acinclude.m4
+++ b/ares/acinclude.m4
@@ -1,3 +1,126 @@
+dnl Check for how to set a socket to non-blocking state. There seems to exist

+dnl four known different ways, with the one used almost everywhere being POSIX

+dnl and XPG3, while the other different ways for different systems (old BSD,

+dnl Windows and Amiga).

+dnl

+dnl There are two known platforms (AIX 3.x and SunOS 4.1.x) where the

+dnl O_NONBLOCK define is found but does not work. This condition is attempted

+dnl to get caught in this script by using an excessive number of #ifdefs...

+dnl

+AC_DEFUN([CURL_CHECK_NONBLOCKING_SOCKET],

+[

+  AC_MSG_CHECKING([non-blocking sockets style])

+

+  AC_TRY_COMPILE([

+/* headers for O_NONBLOCK test */

+#include <sys/types.h>

+#include <unistd.h>

+#include <fcntl.h>

+],[

+/* try to compile O_NONBLOCK */

+

+#if defined(sun) || defined(__sun__) || defined(__SUNPRO_C) || defined(__SUNPRO_CC)

+# if defined(__SVR4) || defined(__srv4__)

+#  define PLATFORM_SOLARIS

+# else

+#  define PLATFORM_SUNOS4

+# endif

+#endif

+#if (defined(_AIX) || defined(__xlC__)) && !defined(_AIX4)

+# define PLATFORM_AIX_V3

+#endif

+

+#if defined(PLATFORM_SUNOS4) || defined(PLATFORM_AIX_V3) || defined(__BEOS__)

+#error "O_NONBLOCK does not work on this platform"

+#endif

+  int socket;

+  int flags = fcntl(socket, F_SETFL, flags | O_NONBLOCK);

+],[

+dnl the O_NONBLOCK test was fine

+nonblock="O_NONBLOCK"

+AC_DEFINE(HAVE_O_NONBLOCK, 1, [use O_NONBLOCK for non-blocking sockets])

+],[

+dnl the code was bad, try a different program now, test 2

+

+  AC_TRY_COMPILE([

+/* headers for FIONBIO test */

+#include <unistd.h>

+#include <stropts.h>

+],[

+/* FIONBIO source test (old-style unix) */

+ int socket;

+ int flags = ioctl(socket, FIONBIO, &flags);

+],[

+dnl FIONBIO test was good

+nonblock="FIONBIO"

+AC_DEFINE(HAVE_FIONBIO, 1, [use FIONBIO for non-blocking sockets])

+],[

+dnl FIONBIO test was also bad

+dnl the code was bad, try a different program now, test 3

+

+  AC_TRY_COMPILE([

+/* headers for ioctlsocket test (cygwin?) */

+#include <windows.h>

+],[

+/* ioctlsocket source code */

+ int socket;

+ unsigned long flags = ioctlsocket(socket, FIONBIO, &flags);

+],[

+dnl ioctlsocket test was good

+nonblock="ioctlsocket"

+AC_DEFINE(HAVE_IOCTLSOCKET, 1, [use ioctlsocket() for non-blocking sockets])

+],[

+dnl ioctlsocket didnt compile!, go to test 4

+

+  AC_TRY_LINK([

+/* headers for IoctlSocket test (Amiga?) */

+#include <sys/ioctl.h>

+],[

+/* IoctlSocket source code */

+ int socket;

+ int flags = IoctlSocket(socket, FIONBIO, (long)1);

+],[

+dnl ioctlsocket test was good

+nonblock="IoctlSocket"

+AC_DEFINE(HAVE_IOCTLSOCKET_CASE, 1, [use Ioctlsocket() for non-blocking sockets])

+],[

+dnl Ioctlsocket didnt compile, do test 5!

+  AC_TRY_COMPILE([

+/* headers for SO_NONBLOCK test (BeOS) */

+#include <socket.h>

+],[

+/* SO_NONBLOCK source code */

+ long b = 1;

+ int socket;

+ int flags = setsockopt(socket, SOL_SOCKET, SO_NONBLOCK, &b, sizeof(b));

+],[

+dnl the SO_NONBLOCK test was good

+nonblock="SO_NONBLOCK"

+AC_DEFINE(HAVE_SO_NONBLOCK, 1, [use SO_NONBLOCK for non-blocking sockets])

+],[

+dnl test 5 didnt compile!

+nonblock="nada"

+AC_DEFINE(HAVE_DISABLED_NONBLOCKING, 1, [disabled non-blocking sockets])

+])

+dnl end of fifth test

+

+])

+dnl end of forth test

+

+])

+dnl end of third test

+

+])

+dnl end of second test

+

+])

+dnl end of non-blocking try-compile test

+  AC_MSG_RESULT($nonblock)

+

+  if test "$nonblock" = "nada"; then

+    AC_MSG_WARN([non-block sockets disabled])

+  fi

+])

 

 dnl We create a function for detecting which compiler we use and then set as

 dnl pendantic compiler options as possible for that particular compiler. The

diff --git a/ares/ares_process.c b/ares/ares_process.c
index 15d372642..a1e16af28 100644
--- a/ares/ares_process.c
+++ b/ares/ares_process.c
@@ -466,13 +466,76 @@ void ares__send_query(ares_channel channel, struct query *query, time_t now)
     }
 }
 
-static int open_tcp_socket(ares_channel channel, struct server_state *server)
+/*
+ * nonblock() set the given socket to either blocking or non-blocking mode
+ * based on the 'nonblock' boolean argument. This function is highly portable.
+ */
+static int nonblock(ares_socket_t sockfd,    /* operate on this */
+                    int nonblock   /* TRUE or FALSE */)
 {
-#if defined(WIN32)
-  u_long flags;
-#else
+#undef SETBLOCK
+#define SETBLOCK 0
+#ifdef HAVE_O_NONBLOCK
+  /* most recent unix versions */
+  int flags;
+
+  flags = fcntl(sockfd, F_GETFL, 0);
+  if (TRUE == nonblock)
+    return fcntl(sockfd, F_SETFL, flags | O_NONBLOCK);
+  else
+    return fcntl(sockfd, F_SETFL, flags & (~O_NONBLOCK));
+#undef SETBLOCK
+#define SETBLOCK 1
+#endif
+
+#if defined(HAVE_FIONBIO) && (SETBLOCK == 0)
+  /* older unix versions */
   int flags;
+
+  flags = nonblock;
+  return ioctl(sockfd, FIONBIO, &flags);
+#undef SETBLOCK
+#define SETBLOCK 2
+#endif
+
+#if defined(HAVE_IOCTLSOCKET) && (SETBLOCK == 0)
+  /* Windows? */
+  unsigned long flags;
+  flags = nonblock;
+
+  return ioctlsocket(sockfd, FIONBIO, &flags);
+#undef SETBLOCK
+#define SETBLOCK 3
+#endif
+
+#if defined(HAVE_IOCTLSOCKET_CASE) && (SETBLOCK == 0)
+  /* presumably for Amiga */
+  return IoctlSocket(sockfd, FIONBIO, (long)nonblock);
+#undef SETBLOCK
+#define SETBLOCK 4
+#endif
+
+#if defined(HAVE_SO_NONBLOCK) && (SETBLOCK == 0)
+  /* BeOS */
+  long b = nonblock ? 1 : 0;
+  return setsockopt(sockfd, SOL_SOCKET, SO_NONBLOCK, &b, sizeof(b));
+#undef SETBLOCK
+#define SETBLOCK 5
+#endif
+
+#ifdef HAVE_DISABLED_NONBLOCKING
+  return 0; /* returns success */
+#undef SETBLOCK
+#define SETBLOCK 6
+#endif
+
+#if (SETBLOCK == 0)
+#error "no non-blocking method was found/used/set"
 #endif
+}
+
+static int open_tcp_socket(ares_channel channel, struct server_state *server)
+{
   ares_socket_t s;
   struct sockaddr_in sockin;
 
@@ -482,25 +545,7 @@ static int open_tcp_socket(ares_channel channel, struct server_state *server)
     return -1;
 
   /* Set the socket non-blocking. */
-
-#if defined(WIN32) || defined(WATT32)
-  flags = 1;
-  ioctlsocket(s, FIONBIO, &flags);
-#else
-  flags = fcntl(s, F_GETFL, 0);
-
-  if (flags == -1)
-    {
-      closesocket(s);
-      return -1;
-    }
-  flags |= O_NONBLOCK;
-  if (fcntl(s, F_SETFL, flags) == -1)
-    {
-      closesocket(s);
-      return -1;
-    }
-#endif
+  nonblock(s, TRUE);
 
   /* Connect to the server. */
   memset(&sockin, 0, sizeof(sockin));
@@ -531,6 +576,9 @@ static int open_udp_socket(ares_channel channel, struct server_state *server)
   if (s == ARES_SOCKET_BAD)
     return -1;
 
+  /* Set the socket non-blocking. */
+  nonblock(s, TRUE);
+
   /* Connect to the server. */
   memset(&sockin, 0, sizeof(sockin));
   sockin.sin_family = AF_INET;
diff --git a/ares/configure.ac b/ares/configure.ac
index 120119812..e3a9c968a 100644
--- a/ares/configure.ac
+++ b/ares/configure.ac
@@ -328,5 +328,6 @@ AC_CHECK_SIZEOF(struct in_addr, ,
 

 AC_CHECK_FUNCS([bitncmp if_indextoname])

 

+CURL_CHECK_NONBLOCKING_SOCKET

 

 AC_OUTPUT(Makefile)