I'm trying to get relayd to send pings with a different source
address so I can combine them with "route-to" pf rules so I can
test a remote host via several network paths to see if it's alive.
As my attempts to modify "check icmp" to let me set the source
address have so far failed, I'm trying to use "check script"
to let me do this instead.
check_script.c:script_exec() causes relayd to fork, set an
interval timer to fire after a timeout, and exec a program to
check host liveliness. fwiw, I'm using a shell script like this:
myif=$(route -q -n get $1 | awk '/if addr/ {print $3}')
ping -c1 -w1 -I $myif somehost.example.com > /dev/null && exit 1
If the program exit()s with a non-zero return code, this
indicates success. If it exit()s with a zero return code,
this is taken to indicate failure. (Other way round than
I'd expect, but I can live with that).
If the script does not exit() (which is checked with WIFEXITED),
this is taken to indicate a problem with the checking script only;
the host status is marked as "unknown" and the host is not treated
as if it was down.
If the interval timer fires, the script is sent SIGKILL, so of
course does not get to exit(), so the host status is marked
unknown.
I can always increase relayd's timeout to give my script chance to
exit normally and indicate failure, but it seems counter-intuitive
a timeout should be taken as "unknown" in "check script" rather
than the "host down" it would cause with the other check methods.
So two questions.
- Is there any point in treating a check script that doesn't
exit() as 'unknown'? If it's ok to change this so that it indicates
'down' instead, the diff below helps.
- If we can't change this, can anyone suggest a (simple|safe)
way to indicate from the timer (sigalrm handler) that the check
script was killed due to a timeout rather than some other reason,
so we can differentiate between them?
Index: check_script.c
===================================================================
RCS file: /cvs/src/usr.sbin/relayd/check_script.c,v
retrieving revision 1.10
diff -u -p -r1.10 check_script.c
--- check_script.c 5 Jun 2009 23:39:51 -0000 1.10
+++ check_script.c 7 Feb 2011 21:20:49 -0000
@@ -156,7 +156,7 @@ script_exec(struct relayd *env, struct c
if (WIFEXITED(status))
ret = WEXITSTATUS(status);
else
- ret = -1;
+ ret = 0;
}
done:
