From 4d8a10886f4dffd08fcf6a93694e12f76a2afd66 Mon Sep 17 00:00:00 2001

Message-Id: <4d8a10886f4dffd08fcf6a93694e12f76a2afd66@dist-git>

From: Laine Stump <laine@redhat.com>

Date: Fri, 15 Jan 2021 22:51:51 -0500

Subject: [PATCH] util: call iptables directly rather than via firewalld

When libvirt added support for firewalld, we were unable to use

firewalld's higher level rules, because they weren't detailed enough

and could not be applied to the iptables FORWARD or OUTPUT chains

(only to the INPUT chain). Instead we changed our code so that rather

than running the iptables/ip6tables/ebtables binaries ourselves, we

would send these commands to firewalld as "passthrough commands", and

firewalld would run the appropriate program on our behalf.

This was done under the assumption that firewalld was somehow tracking

all these rules, and that this tracking was benefitting proper

operation of firewalld and the system in general.

Several years later this came up in a discussion on IRC, and we

learned from the firewalld developers that, in fact, adding iptables

and ebtables rules with firewalld's passthrough commands actually has

*no* advantage; firewalld doesn't keep track of these rules in any

way, and doesn't use them to tailor the construction of its own rules.

Meanwhile, users have been complaining for some time that whenever

firewalld is restarted on a system with libvirt virtual networks

and/or nwfilter rules active, the system logs would be flooded with

warning messages whining that [lots of different rules] could not be

deleted because they didn't exist. For example:

firewalld[3536040]: WARNING: COMMAND_FAILED:

  '/usr/sbin/iptables -w10 -w --table filter --delete LIBVIRT_OUT

  --out-interface virbr4 --protocol udp --destination-port 68

  --jump ACCEPT' failed: iptables: Bad rule

  (does a matching rule exist in that chain?).

See:

  https://bugzilla.redhat.com/1607929 (RHEL8)

  https://bugzilla.redhat.com/1790837 (RHEL8-AV)

for many more examples and a discussion)

Note that these messages are created by iptables, but are logged by

firewalld - when an iptables/ebtables command fails, firewalld grabs

whatever is in stderr of the program, and spits it out to the system

log as a warning. We've requested that firewalld not do this (and

instead leave it up to the calling application to do the appropriate

logging), but this request has been respectfully denied.

But combining the two problems above ( 1) firewalld doesn't do

anything useful when you use it as a proxy to add/remove iptables

rules, 2) firewalld often insists on logging lots of

annoying/misleading/useless "error" messages when you use it as a

proxy to remove iptables rules that don't already exist), leads to a

solution - simply stop using firewalld to add and remove iptables

rules. Instead, exec iptables/ip6tables/ebtables directly in the same

way we do when firewalld isn't active.

We still need to keep track of whether or not firewalld is active, as

there are some things that must be done, e.g. we need to add some

actual firewalld rules in the firewalld "libvirt" zone, and we need to

take notice when firewalld restarts, so that we can reload all our

rules.

This patch doesn't remove the infrastructure that allows having

different firewall backends that perform their functions in different

ways, as that will very possibly come in handy in the future when we

want to have an nftables direct backend, and possibly a "pure"

firewalld backend (now that firewalld supports more complex rules, and

can add those rules to the FORWARD and OUTPUT chains). Instead, it

just changes the action when the selected backend is "firewalld" so

that it adds rules directly rather than through firewalld, while

leaving as much of the existing code intact as possible.

In order for tests to still pass, virfirewalltest also had to be

modified to behave in a different way (i.e. by capturing the generated

commandline as it does for the DIRECT backend, rather than capturing

dbus messages using a mocked dbus API).

Signed-off-by: Laine Stump <laine@redhat.com>

Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>

(cherry picked from commit b19863640d10b47b7c4a7cbadb21f196d61d96a2)

Message-Id: <20210116035151.1066734-9-laine@redhat.com>

Reviewed-by: Jiri Denemark <jdenemar@redhat.com>

---

 src/util/virfirewall.c  | 13 +++++++++++--

 tests/virfirewalltest.c | 30 ++++++++++++++++++++----------

 2 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/src/util/virfirewall.c b/src/util/virfirewall.c

index 66d20d3f17..2ea821ec17 100644

--- a/src/util/virfirewall.c

+++ b/src/util/virfirewall.c

@@ -644,7 +644,7 @@ virFirewallApplyRuleDirect(virFirewallRulePtr rule,

 }

-static int

+static int G_GNUC_UNUSED

 virFirewallApplyRuleFirewallD(virFirewallRulePtr rule,

                               bool ignoreErrors,

                               char **output)

@@ -702,7 +702,16 @@ virFirewallApplyRule(virFirewallPtr firewall,

             return -1;

         break;

     case VIR_FIREWALL_BACKEND_FIREWALLD:

-        if (virFirewallApplyRuleFirewallD(rule, ignoreErrors, &output) < 0)

+        /* Since we are using raw iptables rules, there is no

+         * advantage to going through firewalld, so instead just add

+         * them directly rather that via dbus calls to firewalld. This

+         * has the useful side effect of eliminating extra unwanted

+         * warning messages in the system logs when trying to delete

+         * rules that don't exist (which is something that happens

+         * often when libvirtd is started, and *always* when firewalld

+         * is restarted)

+         */

+        if (virFirewallApplyRuleDirect(rule, ignoreErrors, &output) < 0)

             return -1;

         break;

diff --git a/tests/virfirewalltest.c b/tests/virfirewalltest.c

index 40e7f4f00b..1036353579 100644

--- a/tests/virfirewalltest.c

+++ b/tests/virfirewalltest.c

@@ -214,7 +214,8 @@ testFirewallSingleGroup(const void *opaque)

     if (virFirewallSetBackend(data->tryBackend) < 0)

         goto cleanup;

-    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT)

+    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT ||

+        data->expectBackend == VIR_FIREWALL_BACKEND_FIREWALLD)

         virCommandSetDryRun(&cmdbuf, NULL, NULL);

     else

         fwBuf = &cmdbuf;

@@ -271,7 +272,8 @@ testFirewallRemoveRule(const void *opaque)

     if (virFirewallSetBackend(data->tryBackend) < 0)

         goto cleanup;

-    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT)

+    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT ||

+        data->expectBackend == VIR_FIREWALL_BACKEND_FIREWALLD)

         virCommandSetDryRun(&cmdbuf, NULL, NULL);

     else

         fwBuf = &cmdbuf;

@@ -335,7 +337,8 @@ testFirewallManyGroups(const void *opaque G_GNUC_UNUSED)

     if (virFirewallSetBackend(data->tryBackend) < 0)

         goto cleanup;

-    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT)

+    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT ||

+        data->expectBackend == VIR_FIREWALL_BACKEND_FIREWALLD)

         virCommandSetDryRun(&cmdbuf, NULL, NULL);

     else

         fwBuf = &cmdbuf;

@@ -426,7 +429,8 @@ testFirewallIgnoreFailGroup(const void *opaque G_GNUC_UNUSED)

     if (virFirewallSetBackend(data->tryBackend) < 0)

         goto cleanup;

-    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT) {

+    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT ||

+        data->expectBackend == VIR_FIREWALL_BACKEND_FIREWALLD) {

         virCommandSetDryRun(&cmdbuf, testFirewallRollbackHook, NULL);

     } else {

         fwBuf = &cmdbuf;

@@ -498,7 +502,8 @@ testFirewallIgnoreFailRule(const void *opaque G_GNUC_UNUSED)

     if (virFirewallSetBackend(data->tryBackend) < 0)

         goto cleanup;

-    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT) {

+    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT ||

+        data->expectBackend == VIR_FIREWALL_BACKEND_FIREWALLD) {

         virCommandSetDryRun(&cmdbuf, testFirewallRollbackHook, NULL);

     } else {

         fwBuf = &cmdbuf;

@@ -567,7 +572,8 @@ testFirewallNoRollback(const void *opaque G_GNUC_UNUSED)

     if (virFirewallSetBackend(data->tryBackend) < 0)

         goto cleanup;

-    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT) {

+    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT ||

+        data->expectBackend == VIR_FIREWALL_BACKEND_FIREWALLD) {

         virCommandSetDryRun(&cmdbuf, testFirewallRollbackHook, NULL);

     } else {

         fwBuf = &cmdbuf;

@@ -634,7 +640,8 @@ testFirewallSingleRollback(const void *opaque G_GNUC_UNUSED)

     if (virFirewallSetBackend(data->tryBackend) < 0)

         goto cleanup;

-    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT) {

+    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT ||

+        data->expectBackend == VIR_FIREWALL_BACKEND_FIREWALLD) {

         virCommandSetDryRun(&cmdbuf, testFirewallRollbackHook, NULL);

     } else {

         fwError = true;

@@ -717,7 +724,8 @@ testFirewallManyRollback(const void *opaque G_GNUC_UNUSED)

     if (virFirewallSetBackend(data->tryBackend) < 0)

         goto cleanup;

-    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT) {

+    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT ||

+        data->expectBackend == VIR_FIREWALL_BACKEND_FIREWALLD) {

         virCommandSetDryRun(&cmdbuf, testFirewallRollbackHook, NULL);

     } else {

         fwBuf = &cmdbuf;

@@ -808,7 +816,8 @@ testFirewallChainedRollback(const void *opaque G_GNUC_UNUSED)

     if (virFirewallSetBackend(data->tryBackend) < 0)

         goto cleanup;

-    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT) {

+    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT ||

+        data->expectBackend == VIR_FIREWALL_BACKEND_FIREWALLD) {

         virCommandSetDryRun(&cmdbuf, testFirewallRollbackHook, NULL);

     } else {

         fwBuf = &cmdbuf;

@@ -1007,7 +1016,8 @@ testFirewallQuery(const void *opaque G_GNUC_UNUSED)

     if (virFirewallSetBackend(data->tryBackend) < 0)

         goto cleanup;

-    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT) {

+    if (data->expectBackend == VIR_FIREWALL_BACKEND_DIRECT ||

+        data->expectBackend == VIR_FIREWALL_BACKEND_FIREWALLD) {

         virCommandSetDryRun(&cmdbuf, testFirewallQueryHook, NULL);

     } else {

         fwBuf = &cmdbuf;

-- 

2.30.0