rpc: Add the {repoll,retry} logic in virNetClientSetTLSSession

As advised by the GNU TLS, the caller should attempt again
if the gnutls_record_{recv,send} return EAGAIN or EINTR;
check the following link to view the details:
https://www.gnutls.org/manual/html_node/Data-transfer-and-termination.html

virNetClientSetTLSSession failed to handle EINTR/EGAIN,
though EGAIN seems like it ought to be unlikely given that
the caller waited for G_IO_IN.

Add the {repoll, retry} logic to handle EINTR/EGAIN that
may happen theoretically. This may reduce the likelihood
that the upper application receives the following error
message utmostly when it calls the virConnectOpenAuth API:
Unable to read TLS confirmation: Resource temporarily unavailable

Note that in order to fully avoid the mentioned problem, the
upper application should retry virConnectOpenAuth.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Hyman Huang <yong.huang@smartx.com>

diff --git a/src/rpc/virnetclient.c b/src/rpc/virnetclient.c
index 92933220e2b5602522d090c2c059e9f81af37e88..ee729d5e62e91d3fee479aaa2cc028dced910466 100644 (file)
--- a/src/rpc/virnetclient.c
+++ b/src/rpc/virnetclient.c
@@ -987,6 +987,7 @@ int virNetClientSetTLSSession(virNetClient *client,
      * etc.  If we make the grade, it will send us a '\1' byte.
      */
 
+ repoll:
     source = virEventGLibAddSocketWatch(virNetSocketGetFD(client->sock),
                                         G_IO_IN,
                                         client->eventCtx,
@@ -1003,7 +1004,14 @@ int virNetClientSetTLSSession(virNetClient *client,
     ignore_value(pthread_sigmask(SIG_SETMASK, &oldmask, NULL));
 #endif /* !WIN32 */
 
+ retry:
     len = virNetTLSSessionRead(client->tls, buf, 1);
+    if (len < 0 && errno == EINTR) {
+        goto retry;
+    }
+    if (len < 0 && errno == EAGAIN) {
+        goto repoll;
+    }
     if (len < 0 && errno != ENOMSG) {
         virReportSystemError(errno, "%s",
                              _("Unable to read TLS confirmation"));