From: Hyman Huang <yong.huang@smartx.com> If EAGAIN or EINTR are returned from the gnutls_record_recv, GNU TLS suggests calling the gnutls_record_recv once again to get the data. Refer to the following link to see details: https://www.gnutls.org/manual/html_node/Data-transfer-and-termination.html To follow this guidance, add the re-read logic in the virNetClientSetTLSSession function. This prevent the upper application, when calling the virConnectOpenAuth API, from receiving the follwoing error message: Unable to read TLS confirmation: Resource temporarily unavailable --- src/rpc/virnetclient.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/src/rpc/virnetclient.c b/src/rpc/virnetclient.c index XXXXXXX..XXXXXXX 100644 --- a/src/rpc/virnetclient.c +++ b/src/rpc/virnetclient.c @@ -XXX,XX +XXX,XX @@ int virNetClientSetTLSSession(virNetClient *client, ignore_value(pthread_sigmask(SIG_SETMASK, &oldmask, NULL)); #endif /* !WIN32 */ + reread: len = virNetTLSSessionRead(client->tls, buf, 1); + /* + * GNU TLS advises calling the function again to obtain the data if EAGAIN is returned. + * See reference: https://www.gnutls.org/manual/html_node/Data-transfer-and-termination.html + * */ + if (len < 0 && (errno == EAGAIN || errno == EINTR)) { + VIR_WARN("Try reading data from the TLS session again"); + goto reread; + } if (len < 0 && errno != ENOMSG) { virReportSystemError(errno, "%s", _("Unable to read TLS confirmation")); -- 2.27.0 From: Hyman Huang <yong.huang@smartx.com> v2: 1. Move the retry logic outside of virNetTLSSession{Read,Write} 2. Try re-polling when handing EAGAIN suggested by Daniel v1: 1. Encapsulate the retry logic inside virNetTLSSession{Read,Write} 2. Use VIR_DEBUG instead of VIR_WARN to log the retry operation rfc: https://patchew.org/Libvirt/d716a59dc2c61916917c6d2e07d62055745606d5.1744044211.git.yong.huang@smartx.com/ Please review, thanks. Yong Hyman Huang (1): rpc: Add the {repoll,retry} logic in virNetClientSetTLSSession src/rpc/virnetclient.c | 8 ++++++++ 1 file changed, 8 insertions(+) -- 2.27.0 From: Hyman Huang <yong.huang@smartx.com> 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. --- src/rpc/virnetclient.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/src/rpc/virnetclient.c b/src/rpc/virnetclient.c index XXXXXXX..XXXXXXX 100644 --- a/src/rpc/virnetclient.c +++ b/src/rpc/virnetclient.c @@ -XXX,XX +XXX,XX @@ 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, @@ -XXX,XX +XXX,XX @@ 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")); -- 2.27.0