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util: call iptables directly rather than via firewalld

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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/1790837 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>
This commit is contained in:
Laine Stump 2020-11-17 10:55:12 -05:00
parent 070690538a
commit b19863640d
2 changed files with 31 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
src/util/virfirewall.c
View File

@ -640,7 +640,7 @@ virFirewallApplyRuleDirect(virFirewallRulePtr rule,
}
static int
static int G_GNUC_UNUSED
virFirewallApplyRuleFirewallD(virFirewallRulePtr rule,
bool ignoreErrors,
char **output)
@ -698,7 +698,16 @@ 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;

30
tests/virfirewalltest.c
View File

@ -194,7 +194,8 @@ 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;
@ -247,7 +248,8 @@ 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;
@ -307,7 +309,8 @@ 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;
@ -394,7 +397,8 @@ 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;
@ -462,7 +466,8 @@ 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;
@ -527,7 +532,8 @@ 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;
@ -590,7 +596,8 @@ 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;
@ -669,7 +676,8 @@ 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;
@ -756,7 +764,8 @@ 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;
@ -951,7 +960,8 @@ 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;