Make UDP sockets not blocking

 This is needs if mountd is running multithreaded else multiple threads
 will be blocked on a UDP port with nothing to read and so won't
 be able to serve up-calls from the kernel.

 Thanks to "Murali Krishna V" <vm.krishna@gmail.com> for highlighting
 the problem.

diff --git a/support/nfs/svc_socket.c b/support/nfs/svc_socket.c
index d712cabbba387967d21275b546acafa3dc6be3f7..33076009ac0538de8569fd3489282bbeb2d672ed 100644 (file)
--- a/support/nfs/svc_socket.c
+++ b/support/nfs/svc_socket.c
@@ -113,11 +113,22 @@ svc_socket (u_long number, int type, int protocol, int reuse)
        }
     }
 
-  if (sock >= 0 && protocol == IPPROTO_TCP)
+  if (sock >= 0)
     {
-       /* Make the TCP rendezvous socket non-block to avoid
-        * problems with blocking in accept() after a spurious
-        * wakeup from the kernel */
+           /* This socket might be shared among multiple processes
+            * if mountd is run multi-threaded.  So it is safest to
+            * make it non-blocking, else all threads might wake
+            * one will get the data, and the others will block
+            * indefinitely.
+            * In all cases, transaction on this socket are atomic
+            * (accept for TCP, packet-read and packet-write for UDP)
+            * so O_NONBLOCK will not confuse unprepared code causing
+            * it to corrupt messages.
+            * It generally safest to have O_NONBLOCK when doing an accept
+            * as if we get a RST after the SYN and before accept runs,
+            * we can block despite being told there was an acceptable
+            * connection.
+            */
        int flags;
        if ((flags = fcntl(sock, F_GETFL)) < 0)
          {