child_cleanup: reap as many child processes as possible

Under load it's possible multiple child processes have been killed before
we start processing the SIGCHILD signal, leaving zombie processes behind
everytime we miss a process.
Reap as many processes as possible instead of assuming one handler
call = one process like we currently did.

Can be reproduced by running the following commands in parallel:
 - tcpdump -i lo -w /tmp/test -C 1 -z /usr/bin/true
 - iperf3 -s
 - iperf3 -c localhost

(cherry picked from commit b5f0be2196d897c76144a5b90b168836df54d6fa)

diff --git a/tcpdump.c b/tcpdump.c
index c98265f404b6184ff9607c43a149a1a2406bdb0f..b7d0a3636356d91e72d35b65c025d17e8cf85840 100644 (file)
--- a/tcpdump.c
+++ b/tcpdump.c
@@ -2780,7 +2780,7 @@ cleanup(int signo _U_)
 static void
 child_cleanup(int signo _U_)
 {
-  wait(NULL);
+  while (waitpid(-1, NULL, WNOHANG) >= 0);
 }
 #endif /* HAVE_FORK && HAVE_VFORK */