On 6/8/20 2:39 PM, Daniel Henrique Barboza wrote:
On 6/5/20 2:56 PM, Laine Stump wrote:
Juan Quintela noticed that when he restarted libvirt he was getting
extra iptables rules added by libvirt even though he didn't have any
libvirt networks that used iptables rules. It turns out this also
happens if the firewalld service is restarted. The extra rules are
just the private chains, and they're sometimes being added
unnecessarily because they are added separately in a global
networkPreReloadFirewallRules() that does the init if there are any
active networks, regardless of whether or not any of those networks
will actually add rules to the host firewall.
The fix is to change the check for "any active networks" to instead
check for "any active networks that add firewall rules".
(NB: although the timing seems suspicious, this isn't a new regression
caused by the recently pushed f5418b427 (which forces recreation of
private chains when firewalld is restarted); it was an existing bug
since iptables rules were first put into private chains, even after
commit c6cbe18771 delayed creation of the private chains. The
implication is that any downstream based on v5.1.0 or later that cares
about these extraneous (but harmless) private chains would want to
backport this patch (along with the other two if they aren't already
there))
Signed-off-by: Laine Stump <laine@xxxxxxxxxx>
---
src/network/bridge_driver_linux.c | 49 ++++++++++++++++++++++++-------
1 file changed, 38 insertions(+), 11 deletions(-)
diff --git a/src/network/bridge_driver_linux.c
b/src/network/bridge_driver_linux.c
index b0bd207250..4145411b4b 100644
--- a/src/network/bridge_driver_linux.c
+++ b/src/network/bridge_driver_linux.c
@@ -91,28 +91,55 @@ static void networkSetupPrivateChains(void)
static int
-networkHasRunningNetworksHelper(virNetworkObjPtr obj,
+networkHasRunningNetworksWithFWHelper(virNetworkObjPtr obj,
void *opaque)
{
- bool *running = opaque;
+ bool *activeWithFW = opaque;
virObjectLock(obj);
- if (virNetworkObjIsActive(obj))
- *running = true;
+ if (virNetworkObjIsActive(obj)) {
+ virNetworkDefPtr def = virNetworkObjGetDef(obj);
+
+ switch ((virNetworkForwardType) def->forward.type) {
+ case VIR_NETWORK_FORWARD_NONE:
+ case VIR_NETWORK_FORWARD_NAT:
+ case VIR_NETWORK_FORWARD_ROUTE:
+ *activeWithFW = true;
+ break;
+
What's the rationale of "VIR_NETWORK_FORWARD_NONE" changing firewall
rules? Is
this a corner case that the NONE type covers? Functions such as
networkAddIPSpecificFirewallRules() are operating just with the NAT
and ROUTE
forward types.
For historical reasons, a libvirt network that has no <forward> element
is an "isolated" network, and libvirt adds rules to prevent any traffic
from guests connected to that network from being forwarded anywhere
else. These include 1) rules to allow incoming dhcp and dns requests
(and possibly tftp) from guests on the network to the host, 2) allow
traffic between guests on the isolated bridge (this rule would only be
necessary in the case that the br_netfilter kernel module is loaded and
there was some other lower priority rule that would otherwise block this
traffic), and 3) reject forwarding of all packets to/from guests
connected to this network and anywhere else outside the network
(including a endpoints connected to a different network on the same
host). Details are in
https://libvirt.org/firewall.html
(side note: there is no "firewall" string in formatdomain.html.in
docs. I think
it's a good idea to mention that certain <forward> types will change
firewall
settings of the host)
Sure. With maybe a pointer from there to firewall.html, which explains
this all in excruciating detail. Patches welcome :-) . When libvirt
virtual networks were first created, the lore is that part of the idea
was to avoid exposing the user to complicated things like iptables and
dnsmasq configuration, and we were also a bit more relaxed about what
was required in terms of documentation. Around 2011 or so danpb sent an
email to the list that ended up being referenced so much that it was
saved as firewall.html, but I guess nobody ever thought to put a link
from formatdomain.html to that document (maybe because it's not a part
of the official API, and so is subject to change; I don't think there
was ever any conscious decision that it *shouldn't* be linked from
there; it just wasn't. It *does* come up when you do a google search for
"libvirt firewall" though...).
