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.)

1 files changed, 71 insertions, 23 deletions

diff --git a/ares_process.c b/ares_process.c
index 15d3726..a1e16af 100644
--- a/ares_process.c
+++ b/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;