From 23c8e64cbbd9fe642f47808b19aba6cd5177fdd2 Mon Sep 17 00:00:00 2001
Message-Id: <23c8e64cbbd9fe642f47808b19aba6cd5177fdd2@dist-git>
From: Michal Privoznik <mprivozn@redhat.com>
Date: Thu, 16 Feb 2023 11:46:55 +0100
Subject: [PATCH] qemu_passt: Let passt write the PID file

The way we start passt currently is: we use
virCommandSetPidFile() to use our virCommand machinery to acquire
the PID file and leak opened FD into passt. Then, we use
virPidFile*() APIs to read the PID file (which is needed when
placing it into CGroups or killing it). But this does not fly
really because passt daemonizes itself. Thus the process we
started dies soon and thus the PID file is closed and unlocked.

We could work around this by passing '--foreground' argument, but
that weakens passt as it can't create new PID namespace (because
it doesn't fork()).

The solution is to let passt write the PID file, but since it
does not lock the file and closes it as soon as it is written, we
have to switch to those virPidFile APIs which don't expect PID
file to be locked.

Resolves: https://bugzilla.redhat.com/2169244

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Laine Stump <laine@redhat.com>
(cherry picked from commit 029a892abdb2fe508f3fb77af00a14464b98b824)
Signed-off-by: Laine Stump <laine@redhat.com>
---
 src/qemu/qemu_passt.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/qemu/qemu_passt.c b/src/qemu/qemu_passt.c
index 2733f8e03f..1217a6a087 100644
--- a/src/qemu/qemu_passt.c
+++ b/src/qemu/qemu_passt.c
@@ -72,7 +72,7 @@ qemuPasstGetPid(virDomainObj *vm,
 {
     g_autofree char *pidfile = qemuPasstCreatePidFilename(vm, net);
 
-    return virPidFileReadPathIfLocked(pidfile, pid);
+    return virPidFileReadPath(pidfile, pid);
 }
 
 
@@ -106,11 +106,14 @@ static void
 qemuPasstKill(const char *pidfile)
 {
     virErrorPtr orig_err;
+    pid_t pid = 0;
 
     virErrorPreserveLast(&orig_err);
 
-    if (virPidFileForceCleanupPath(pidfile) < 0)
-        VIR_WARN("Unable to kill passt process");
+    ignore_value(virPidFileReadPath(pidfile, &pid));
+    if (pid != 0)
+        virProcessKillPainfully(pid, true);
+    unlink(pidfile);
 
     virErrorRestore(&orig_err);
 }
@@ -161,13 +164,13 @@ qemuPasstStart(virDomainObj *vm,
     cmd = virCommandNew(PASST);
 
     virCommandClearCaps(cmd);
-    virCommandSetPidFile(cmd, pidfile);
     virCommandSetErrorBuffer(cmd, &errbuf);
 
     virCommandAddArgList(cmd,
                          "--one-off",
                          "--socket", passtSocketName,
                          "--mac-addr", virMacAddrFormat(&net->mac, macaddr),
+                         "--pid", pidfile,
                          NULL);
 
     if (net->mtu) {
-- 
2.39.2