Switch TCP socket sources to nonblocking mode.

This follows a suggestion from Christian Eddie Dost <ecd@brainaid.de>,
who had this to say:

  However, gpsd hangs when used with a tcp:// device, if you start the
  device without waiting for clients (-n option), there will never be a
  client connection accepted. If you start gpsd without -n option one
  client will be accepted and receive data, but when closing the client
  connection there will be no new connection possible.

  The problem is gpsd hangs inside consume_packets() or more exactly
  inside a blocking read() on the tcp socket a few functions further
  down. consume_packets() never returns to the main select() loop.

  The following patch configures sockets to non blocking, this fixes the
  problem and gpsd works fine for me with tcp:// devices. Using this
  patch should allow the special udp handling at the end of the function
  consume_packets() to be removed.

I applied the suggested patch and also removed the special UDP
handing.  All regressions test pass (including the UDP one), and gpsd
-N tcp://data.aishub.net:4006 reads AIS data as expected.

1 files changed, 4 insertions, 0 deletions

diff --git a/netlib.c b/netlib.c
index 9726f36f..bff75c7b 100644
--- a/netlib.c
+++ b/netlib.c
@@ -34,6 +34,7 @@
 #include <unistd.h>
 #endif /* S_SPLINT_S */
 #include <string.h>
+#include <fcntl.h>
 
 #include "gpsd.h"
 #include "sockaddr.h"
@@ -138,6 +139,9 @@ socket_t netlib_connectsock(int af, const char *host, const char *service,
 	setsockopt(s, IPPROTO_TCP, TCP_NODELAY, (char *)&one, sizeof one);
 #endif
 
+    /* set socket to noblocking */
+    fcntl(s, F_SETFL, fcntl(s, F_GETFL) | O_NONBLOCK);
+
     gpsd_report(LOG_SPIN, "netlib_connectsock() returns socket on fd %d\n",
 		s);
     return s;