From 173b80e8f8103f26438d344e9b97335d4e5036b4 Mon Sep 17 00:00:00 2001
From: Michal Privoznik <[email protected]>
Date: Thu, 11 Jun 2020 16:43:22 +0200
Subject: [PATCH 2/6] leaseshelper: Wait to acquire PID file
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On a DHCP transaction, dnsmasq runs our leases helper which
updates corresponding JSON files. While one dnsmasq won't run the
leaseshelper in parallel, two dnsmasqs (from two distinct
networks) might. To avoid corrupting JSON file, the leaseshelper
acquires PID file first. Well, the way it's acquiring it is not
ideal - it calls virPidFileAcquirePath(wait = false); which
means, that either it acquires the PID file instantly or returns
an error and does not touch the JSON at all. This in turn means
that there might be a leases record missing. With wait = true,
this won't happen.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1840307

cherry pick from: 876211ef4a192df1603b45715044ec14567d7e9f

Signed-off-by: Michal Privoznik <[email protected]>
Reviewed-by: Daniel P. Berrangé <[email protected]>
---
 src/network/leaseshelper.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/network/leaseshelper.c b/src/network/leaseshelper.c
index a1780ca..86c847d 100644
--- a/src/network/leaseshelper.c
+++ b/src/network/leaseshelper.c
@@ -160,7 +160,7 @@ main(int argc, char **argv)
     pid_file = g_strdup(RUNSTATEDIR "/leaseshelper.pid");
 
     /* Try to claim the pidfile, exiting if we can't */
-    if ((pid_file_fd = virPidFileAcquirePath(pid_file, false, getpid())) < 0)
+    if ((pid_file_fd = virPidFileAcquirePath(pid_file, true, getpid())) < 0)
         goto cleanup;
 
     /* Since interfaces can be hot plugged, we need to make sure that the
-- 
1.8.3.1