[Openvpn-devel] Workaround FreeBSD 12+ race condition on tun/tap open with IPv6.
Commit Message
On FreeBSD 12 (tested and verified on 12.1-RELEASE-p2), after "ifconfig
inet6" for a tun/tap interface, there sometimes is a race condition
where the "IFDISABLED" flag shows up after a short time frame, under
a second, and never clears itself. This disables use of the configured
IPv6 address on the interface, breaking IPv6 over tun/tap operation.
This only happens if ipv6_activate_all_interfaces="YES" is not
set in /etc/rc.conf - but there might be reasons why this is not so.
As a workaround until this can be fixed on the FreeBSD side (or a
better workaround is found), sleep(1) after ifconfig, then call
"ifconfig $dev inet6 -ifdisable".
Yes, this is massively ugly but makes the problem completely go
away for my test systems.
(The same effect can be achieved with an --up script that does this,
but it's even less pretty - see trac ticket)
FreeBSD: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=248172
v2: reword text, refer to FreeBSD bug with much more details
Trac: 1226
Signed-off-by: Gert Doering <gert@greenie.muc.de>
---
src/openvpn/tun.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
Comments
Am 23.07.20 um 14:19 schrieb Gert Doering:
> On FreeBSD 12 (tested and verified on 12.1-RELEASE-p2), after "ifconfig
> inet6" for a tun/tap interface, there sometimes is a race condition
> where the "IFDISABLED" flag shows up after a short time frame, under
> a second, and never clears itself. This disables use of the configured
> IPv6 address on the interface, breaking IPv6 over tun/tap operation.
>
> This only happens if ipv6_activate_all_interfaces="YES" is not
> set in /etc/rc.conf - but there might be reasons why this is not so.
>
> As a workaround until this can be fixed on the FreeBSD side (or a
> better workaround is found), sleep(1) after ifconfig, then call
> "ifconfig $dev inet6 -ifdisable".
>
> Yes, this is massively ugly but makes the problem completely go
> away for my test systems.
>
> (The same effect can be achieved with an --up script that does this,
> but it's even less pretty - see trac ticket)
>
> FreeBSD: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=248172
>
> v2: reword text, refer to FreeBSD bug with much more details
Acked-By: Arne Schwabe <arne@rfc2549.org>
This looks like a ugly workaround but if it is the best we can, so be it.
Arne
Your patch has been applied to the master and release/2.5 branch.
commit 5e19cc2c1bf22d44f10dc585ba69d48951dc7a86 (master)
commit 6dac3342d851995bdee75db4b52cfb3a3f9232e3 (release/2.5)
Author: Gert Doering
Date: Thu Jul 23 14:19:49 2020 +0200
Workaround FreeBSD 12+ race condition on tun/tap open with IPv6.
Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <20200723121949.78223-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg20553.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
--
kind regards,
Gert Doering
@@ -1038,6 +1038,29 @@ do_ifconfig_ipv6(struct tuntap *tt, const char *ifname, int tun_mtu,
openvpn_execve_check(&argv, es, S_FATAL,
"generic BSD ifconfig inet6 failed");
+#if defined(TARGET_FREEBSD) && __FreeBSD_version >= 1200000
+ /* On FreeBSD 12 and up, there is ipv6_activate_all_interfaces="YES"
+ * in rc.conf, which is not set by default. If it is *not* set,
+ * "all new interfaces that are not already up" are configured by
+ * devd + /etc/pccard_ether as "inet6 ifdisabled".
+ *
+ * The "is this interface already up?" test is a non-zero time window
+ * which we manage to hit with our ifconfig often enough to cause
+ * frequent fails in the openvpn test environment.
+ *
+ * Thus: assume that the system might interfere, wait for things to
+ * settle (it's a very short time window), and remove -ifdisable again.
+ *
+ * See: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=248172
+ */
+ sleep(1);
+ argv_printf(&argv, "%s %s inet6 -ifdisabled", IFCONFIG_PATH, ifname);
+ argv_msg(M_INFO, &argv);
+
+ openvpn_execve_check(&argv, es, S_FATAL,
+ "FreeBSD BSD 'ifconfig inet6 -ifdisabled' failed");
+#endif
+
#if defined(TARGET_OPENBSD) || defined(TARGET_NETBSD) \
|| defined(TARGET_DARWIN)
/* and, hooray, we explicitly need to add a route... */