From 1e05472dff94675ce60b16558f1524309aaaf80c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?=
 <marmarek@invisiblethingslab.com>
Date: Tue, 28 May 2024 02:55:52 +0200
Subject: [PATCH 1/3] daemon: attempt starting target vm only if not running
 yet

Do not call admin.vm.Start method on every (autostart) call. Do it only
if the target qrexec daemon is not running - or rather, when connecting
to it fails. This makes the happy path of a call a bit quicker (3-5ms in
some basic tests), but more importantly it avoids needlessly checking
with libvirt if the VM is running - which would block if some other
slow operation is running at the time (like, starting another VM).
---
 daemon/qrexec-daemon-common.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/daemon/qrexec-daemon-common.c b/daemon/qrexec-daemon-common.c
index fa4a89ce..209870af 100644
--- a/daemon/qrexec-daemon-common.c
+++ b/daemon/qrexec-daemon-common.c
@@ -135,7 +135,8 @@ bool qrexec_execute_vm(const char *target, bool autostart, int remote_domain_id,
             return false;
         }
     }
-    if (autostart) {
+    int s = disposable ? -2 : connect_unix_socket(target);
+    if (s == -2 && autostart) {
         buf = qubesd_call(target, "admin.vm.Start", "", &resp_len);
         if (buf == NULL) // error already printed by qubesd_call
             return false;
@@ -150,9 +151,9 @@ bool qrexec_execute_vm(const char *target, bool autostart, int remote_domain_id,
             return false;
         }
         free(buf);
+        s = connect_unix_socket(target);
     }
-    int s = connect_unix_socket(target);
-    if (s == -1)
+    if (s < 0)
         goto kill;
     int data_domain;
     int data_port;
@@ -199,6 +200,11 @@ int connect_unix_socket_by_id(unsigned int domid)
     return connect_unix_socket(id_str);
 }
 
+/* Returns:
+ * - FD on success,
+ * - -2 target qrexec daemon is not running,
+ * - -1 on other errors
+ */
 int connect_unix_socket(const char *domname)
 {
     int s, len, res;
@@ -217,12 +223,15 @@ int connect_unix_socket(const char *domname)
     if (res >= (int)sizeof(remote.sun_path)) {
         LOG(ERROR, "%s/qrexec.%s is too long for AF_UNIX socket path",
              socket_dir, domname);
+        close(s);
         return -1;
     }
     len = (size_t)res + 1 + offsetof(struct sockaddr_un, sun_path);
     if (connect(s, (struct sockaddr *) &remote, len) == -1) {
+        int saved_errno = errno;
         LOG(ERROR, "connect %s", remote.sun_path);
-        return -1;
+        close(s);
+        return (saved_errno == ENOENT || saved_errno == ECONNREFUSED) ? -2 : -1;
     }
     if (handle_daemon_handshake(s) < 0)
         return -1;

From 6760cfa978e864aae6df938b518f8ff6d05caa1c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?=
 <marmarek@invisiblethingslab.com>
Date: Tue, 28 May 2024 03:07:25 +0200
Subject: [PATCH 2/3] Make stderr line-buffered for logging

qrexec_logv uses several separate fprintf() calls for a single message.
Since stderr is unbuffered by default, this sometimes leads to
splitting one log message with another. Avoid the issue by turning
stderr into line-buffered mode.
Documentation for setlinebuf() (or more precisely - for underlying
setvbuf()) says it can be called only after opening the stream but
before any other operation. Since setup_logging() is called as the first
thing in main(), it should be okay.
---
 libqrexec/log.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libqrexec/log.c b/libqrexec/log.c
index f3f2283b..f569d3f9 100644
--- a/libqrexec/log.c
+++ b/libqrexec/log.c
@@ -88,5 +88,10 @@ void setup_logging(const char *program_name) {
             errx(125, "File descriptor %d is closed, cannot continue", i);
     }
 
+    /* qrexec_logv() uses several separate fprintf calls, print them at once */
+    errno = 0;
+    if (setvbuf(stderr, NULL, _IOLBF, 0))
+        warn("Failed to enable line buffering on stderr");
+
     qrexec_program_name = program_name;
 }

From c87b9e7e1e899cb0aa2c57504f0dfb1a23c74010 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?=
 <marmarek@invisiblethingslab.com>
Date: Tue, 28 May 2024 23:17:11 +0200
Subject: [PATCH 3/3] Remove redundant log line

On successful service call there is later a message from
handle_process_common anyway.
---
 libqrexec/exec.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/libqrexec/exec.c b/libqrexec/exec.c
index ab3f9f96..0dec6844 100644
--- a/libqrexec/exec.c
+++ b/libqrexec/exec.c
@@ -624,7 +624,6 @@ static int qubes_tcp_connect(const char *host, const char *port)
         close(sockfd);
     } else {
         rc = sockfd;
-        LOG(DEBUG, "Connection succeeded");
     }
 freeaddrs:
     freeaddrinfo(addrs);