Implement NAT networking support based on the Packet Filter (pf)
firewall in FreeBSD. At this point, the implementation is very basic.
It creates:
- Essential NAT translation rules
- Basic forwarding rules
Implementation uses pf's anchor feature to group rules. All rules live
in the "libvirt" anchor and every libvirt's network has its own
sub-anchor.
Currently there are some assumptions and limitations:
- We assume that a user has created the "libvirt" (nat-)anchors. As
they cannot be created on fly, it's better not to touch global pf
configuration and let the user do the changes. If the user doesn't
have these anchors configured, the rules will still be created in
sub-anchors, but will not be effective until these anchors are
activated. Should we check if these anchors are not active to
give some runtime warning?
- Currently, rule reloading is not smart: it always deletes rules,
flushes rules and re-creates that. It would be better to do that
more gracefully.
- IPv6 configurations are currently not supported
- For NAT, pf requires explicit IP address or an interface to NAT to.
We try to obtain that from the network XML definition, and if it's
not specified, we try to determine interface corresponding to the
default route.
Signed-off-by: Roman Bogorodskiy <bogorodskiy@gmail.com>
---
meson.build | 2 +
po/POTFILES | 1 +
src/network/bridge_driver_bsd.c | 6 +
src/network/bridge_driver_conf.c | 8 +
src/network/bridge_driver_linux.c | 2 +
src/network/meson.build | 1 +
src/network/network_pf.c | 327 ++++++++++++++++++++++++++++++
src/network/network_pf.h | 26 +++
src/util/virfirewall.c | 4 +-
src/util/virfirewall.h | 2 +
10 files changed, 378 insertions(+), 1 deletion(-)
create mode 100644 src/network/network_pf.c
create mode 100644 src/network/network_pf.h
diff --git a/meson.build b/meson.build
index 37b1caa566..b8a9be25bb 100644
--- a/meson.build
+++ b/meson.build
@@ -1642,6 +1642,8 @@ if not get_option('driver_network').disabled() and conf.has('WITH_LIBVIRTD')
if firewall_backend_priority.length() == 0
if host_machine.system() == 'linux'
firewall_backend_priority = ['nftables', 'iptables']
+ elif host_machine.system() == 'freebsd'
+ firewall_backend_priority = ['pf']
else
# No firewall impl on non-Linux so far, so force 'none'
# as placeholder
diff --git a/po/POTFILES b/po/POTFILES
index 90664fe6e7..dc7293d0cd 100644
--- a/po/POTFILES
+++ b/po/POTFILES
@@ -152,6 +152,7 @@ src/network/bridge_driver_nop.c
src/network/leaseshelper.c
src/network/network_iptables.c
src/network/network_nftables.c
+src/network/network_pf.c
src/node_device/node_device_driver.c
src/node_device/node_device_udev.c
src/nwfilter/nwfilter_dhcpsnoop.c
diff --git a/src/network/bridge_driver_bsd.c b/src/network/bridge_driver_bsd.c
index 93312fe6db..ad4fbd064b 100644
--- a/src/network/bridge_driver_bsd.c
+++ b/src/network/bridge_driver_bsd.c
@@ -19,6 +19,7 @@
#include <config.h>
#include "virlog.h"
+#include "network_pf.h"
#define VIR_FROM_THIS VIR_FROM_NONE
@@ -78,6 +79,9 @@ int networkAddFirewallRules(virNetworkDef *def G_GNUC_UNUSED,
_("No firewall backend is available"));
return -1;
+ case VIR_FIREWALL_BACKEND_PF:
+ return pfAddFirewallRules(def);
+
case VIR_FIREWALL_BACKEND_IPTABLES:
case VIR_FIREWALL_BACKEND_NFTABLES:
case VIR_FIREWALL_BACKEND_LAST:
@@ -98,4 +102,6 @@ networkRemoveFirewallRules(virNetworkObj *obj,
def->name);
return;
}
+
+ pfRemoveFirewallRules(def);
}
diff --git a/src/network/bridge_driver_conf.c b/src/network/bridge_driver_conf.c
index 738652390f..280c0f9c4f 100644
--- a/src/network/bridge_driver_conf.c
+++ b/src/network/bridge_driver_conf.c
@@ -129,6 +129,14 @@ virNetworkLoadDriverConfig(virNetworkDriverConfig *cfg G_GNUC_UNUSED,
break;
}
+ case VIR_FIREWALL_BACKEND_PF: {
+ g_autofree char *pfctlInPath = virFindFileInPath(PFCTL);
+
+ if (pfctlInPath)
+ fwBackendSelected = true;
+ break;
+ }
+
case VIR_FIREWALL_BACKEND_LAST:
virReportEnumRangeError(virFirewallBackend, fwBackends[i]);
return -1;
diff --git a/src/network/bridge_driver_linux.c b/src/network/bridge_driver_linux.c
index 86f6a5915f..9077178c3e 100644
--- a/src/network/bridge_driver_linux.c
+++ b/src/network/bridge_driver_linux.c
@@ -58,6 +58,7 @@ networkFirewallSetupPrivateChains(virFirewallBackend backend,
case VIR_FIREWALL_BACKEND_NFTABLES:
return nftablesSetupPrivateChains(layer);
+ case VIR_FIREWALL_BACKEND_PF:
case VIR_FIREWALL_BACKEND_LAST:
virReportEnumRangeError(virFirewallBackend, backend);
return -1;
@@ -437,6 +438,7 @@ networkAddFirewallRules(virNetworkDef *def,
case VIR_FIREWALL_BACKEND_NFTABLES:
return nftablesAddFirewallRules(def, fwRemoval);
+ case VIR_FIREWALL_BACKEND_PF:
case VIR_FIREWALL_BACKEND_LAST:
virReportEnumRangeError(virFirewallBackend, firewallBackend);
return -1;
diff --git a/src/network/meson.build b/src/network/meson.build
index 07cd5cda55..b527bab392 100644
--- a/src/network/meson.build
+++ b/src/network/meson.build
@@ -4,6 +4,7 @@ network_driver_sources = [
'bridge_driver_platform.c',
'network_iptables.c',
'network_nftables.c',
+ 'network_pf.c',
]
driver_source_files += files(network_driver_sources)
diff --git a/src/network/network_pf.c b/src/network/network_pf.c
new file mode 100644
index 0000000000..b12ef86089
--- /dev/null
+++ b/src/network/network_pf.c
@@ -0,0 +1,327 @@
+/*
+ * network_pf.c: pf-based firewall implementation for virtual networks
+ *
+ * Copyright (C) 2025 FreeBSD Foundation
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see
+ * <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * pf(4) configuration principles/assumptions.
+ *
+ * All libvirt-managed firewall rule are configured within a pf anchor.
+ * Every libvirt network has a corresponding sub-anchor, like "libvirt/$network_name".
+ * Libvirt does not create the root anchors, so users are expected to specify them in
+ * their firewall configuration. Minimal configuration might look like:
+ *
+ * # cat /etc/pf.conf
+ * scrub all
+ *
+ * nat-anchor "libvirt\*"
+ * anchor "libvirt\*"
+ *
+ * pass all
+ * #
+ *
+ * Users are not expected to add/modify rules in the "libvirt\*" subanchors because
+ * the changes will be lost on restart.
+ *
+ * IPv6 NAT is currently not supported.
+ */
+
+#include <config.h>
+
+#include <stdarg.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/socket.h>
+#ifdef WITH_NET_IF_H
+# include <net/if.h>
+#endif
+#if defined(__FreeBSD__)
+# include <sys/sysctl.h>
+# include <net/if_dl.h>
+#endif
+#include <net/route.h>
+#include <netinet/in.h>
+
+#include "internal.h"
+#include "virfirewalld.h"
+#include "vircommand.h"
+#include "virerror.h"
+#include "virlog.h"
+#include "virhash.h"
+#include "virenum.h"
+#include "virstring.h"
+#include "network_pf.h"
+
+VIR_LOG_INIT("network.pf");
+
+#define VIR_FROM_THIS VIR_FROM_NONE
+
+
+static const char networkLocalMulticastIPv4[] = "224.0.0.0/24";
+static const char networkLocalBroadcast[] = "255.255.255.255/32";
+
+
+static char *
+findDefaultRouteInterface(void)
+{
+#if defined(__FreeBSD__)
+ int mib[6] = {CTL_NET, PF_ROUTE, 0, AF_INET, NET_RT_DUMP, 0};
+ size_t needed;
+ g_autofree char *buf = NULL;
+ char *lim, *next;
+ struct rt_msghdr *rtm;
+ struct sockaddr *sa;
+ struct sockaddr_in *sin;
+ struct sockaddr_dl *sdl;
+ char *ifname;
+ size_t ifname_len;
+ size_t i;
+
+ if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0) {
+ virReportSystemError(errno,
+ "%s",
+ _("Unable to get default interface name"));
+ return NULL;
+ }
+
+ if (posix_memalign((void **)&buf, 8, needed) != 0) {
+ virReportSystemError(errno,
+ "%s",
+ _("Unable to get default interface name"));
+ return NULL;
+ }
+
+ if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0) {
+ virReportSystemError(errno,
+ "%s",
+ _("Unable to get default interface name"));
+ return NULL;
+ }
+
+ lim = buf + needed;
+ next = buf;
+
+ while (next < lim) {
+ rtm = (struct rt_msghdr *)(void *)next;
+ if (next + rtm->rtm_msglen > lim)
+ break;
+
+ sin = (struct sockaddr_in *)(rtm + 1);
+
+ if ((rtm->rtm_flags & RTF_GATEWAY) && sin->sin_addr.s_addr == INADDR_ANY) {
+ sdl = NULL;
+ sa = (struct sockaddr *)(sin + 1);
+
+ for (i = 1; i < RTAX_MAX; i++) {
+ if (rtm->rtm_addrs & (1 << i)) {
+ if (i == RTAX_IFP && sa->sa_family == AF_LINK) {
+ sdl = (struct sockaddr_dl *)(void *)sa;
+ ifname_len = (sdl->sdl_nlen >= IFNAMSIZ) ? IFNAMSIZ - 1 : sdl->sdl_nlen;
+ ifname = g_new(char, ifname_len + 1);
+ virStrcpy(ifname, sdl->sdl_data, ifname_len + 1);
+ return ifname;
+ }
+ sa = (struct sockaddr *)((char *)sa +
+ ((sa->sa_len > 0) ? sa->sa_len : sizeof(struct sockaddr)));
+ }
+ }
+ }
+
+ next += rtm->rtm_msglen;
+ }
+#endif
+
+ return NULL;
+}
+
+static int
+pfAddNatFirewallRules(virNetworkDef *def,
+ virNetworkIPDef *ipdef)
+{
+ /*
+ * # NAT rules
+ * table <natdst> persist
+ * { 0.0.0.0/0, ! 192.168.122.0/24, !224.0.0.0/24, !255.255.255.255 }
+ * nat pass log on $ext_if from 192.168.122.0/24 to <natdst>
+ * -> ($ext_if) port 1024:65535
+ *
+ * # Filtering
+ * pass log quick on virbr0 from 192.168.122.0/24 to 192.168.122.0/24
+ * pass out log quick on virbr0 from 192.168.122.0/24 to 224.0.0.0/24
+ * pass out log quick on virbr0 from 192.168.122.0/24 to 255.255.255.255
+ * block log on virbr0
+ */
+ int prefix = virNetworkIPDefPrefix(ipdef);
+ g_autofree const char *forwardIf = g_strdup(virNetworkDefForwardIf(def, 0));
+ g_auto(virBuffer) pf_rules_buf = VIR_BUFFER_INITIALIZER;
+ g_autoptr(virCommand) cmd = virCommandNew(PFCTL);
+ virPortRange *portRange = &def->forward.port;
+ g_autofree char *portRangeStr = NULL;
+
+ if (prefix < 0) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("Invalid prefix or netmask for '%1$s'"),
+ def->bridge);
+ return -1;
+ }
+
+ if (portRange->start == 0 && portRange->end == 0) {
+ portRange->start = 1024;
+ portRange->end = 65535;
+ }
+
+ if (portRange->start < portRange->end && portRange->end < 65536) {
+ portRangeStr = g_strdup_printf("%u:%u",
+ portRange->start,
+ portRange->end);
+ } else {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("Invalid port range '%1$u-%2$u'."),
+ portRange->start, portRange->end);
+ return -1;
+ }
+
+ if (!forwardIf) {
+ forwardIf = findDefaultRouteInterface();
+ if (!forwardIf) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ "%s",
+ _("Cannot determine the default interface"));
+ return -1;
+ }
+ }
+
+ virBufferAsprintf(&pf_rules_buf,
+ "table <natdst> persist { 0.0.0.0/0, ! %s/%d, ! %s, ! %s }\n",
+ virSocketAddrFormat(&ipdef->address),
+ prefix,
+ networkLocalMulticastIPv4,
+ networkLocalBroadcast);
+ virBufferAsprintf(&pf_rules_buf,
+ "nat pass on %s from %s/%d to <natdst> -> (%s) port %s\n",
+ forwardIf,
+ virSocketAddrFormat(&ipdef->address),
+ prefix,
+ forwardIf,
+ portRangeStr);
+ virBufferAsprintf(&pf_rules_buf,
+ "pass quick on %s from %s/%d to %s/%d\n",
+ def->bridge,
+ virSocketAddrFormat(&ipdef->address),
+ prefix,
+ virSocketAddrFormat(&ipdef->address),
+ prefix);
+ virBufferAsprintf(&pf_rules_buf,
+ "pass quick on %s from %s/%d to %s\n",
+ def->bridge,
+ virSocketAddrFormat(&ipdef->address),
+ prefix,
+ networkLocalMulticastIPv4);
+ virBufferAsprintf(&pf_rules_buf,
+ "pass quick on %s from %s/%d to %s\n",
+ def->bridge,
+ virSocketAddrFormat(&ipdef->address),
+ prefix,
+ networkLocalBroadcast);
+ virBufferAsprintf(&pf_rules_buf,
+ "block on %s\n",
+ def->bridge);
+
+ /* pfctl -a libvirt/default -F all -f - */
+ virCommandAddArg(cmd, "-a");
+ virCommandAddArgFormat(cmd, "libvirt/%s", def->name);
+ virCommandAddArgList(cmd, "-F", "all", "-f", "-", NULL);
+
+ virCommandSetInputBuffer(cmd, virBufferContentAndReset(&pf_rules_buf));
+
+ if (virCommandRun(cmd, NULL) < 0) {
+ VIR_WARN("Failed to create firewall rules for network %s",
+ def->name);
+ return -1;
+ }
+ return 0;
+}
+
+
+static int
+pfAddRoutingFirewallRules(virNetworkDef *def,
+ virNetworkIPDef *ipdef G_GNUC_UNUSED)
+{
+ int prefix = virNetworkIPDefPrefix(ipdef);
+
+ if (prefix < 0) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("Invalid prefix or netmask for '%1$s'"),
+ def->bridge);
+ return -1;
+ }
+
+ /* TODO: routing rules */
+
+ return 0;
+}
+
+
+static int
+pfAddIPSpecificFirewallRules(virNetworkDef *def,
+ virNetworkIPDef *ipdef)
+{
+ if (def->forward.type == VIR_NETWORK_FORWARD_NAT) {
+ if (VIR_SOCKET_ADDR_IS_FAMILY(&ipdef->address, AF_INET))
+ return pfAddNatFirewallRules(def, ipdef);
+ else
+ return -1;
+ } else if (def->forward.type == VIR_NETWORK_FORWARD_ROUTE) {
+ return pfAddRoutingFirewallRules(def, ipdef);
+ }
+ return 0;
+}
+
+
+int
+pfAddFirewallRules(virNetworkDef *def)
+{
+ size_t i;
+ virNetworkIPDef *ipdef;
+
+ for (i = 0;
+ (ipdef = virNetworkDefGetIPByIndex(def, AF_UNSPEC, i));
+ i++) {
+ if (pfAddIPSpecificFirewallRules(def, ipdef) < 0)
+ return -1;
+ }
+
+ return 0;
+}
+
+
+void
+pfRemoveFirewallRules(virNetworkDef *def)
+{
+ /* pfctl -a libvirt/default -F all */
+ g_autoptr(virCommand) cmd = virCommandNew(PFCTL);
+ virCommandAddArg(cmd, "-a");
+ virCommandAddArgFormat(cmd, "libvirt/%s", def->name);
+ virCommandAddArgList(cmd, "-F", "all", NULL);
+
+ if (virCommandRun(cmd, NULL) < 0)
+ VIR_WARN("Failed to remove firewall rules for network %s",
+ def->name);
+}
diff --git a/src/network/network_pf.h b/src/network/network_pf.h
new file mode 100644
index 0000000000..2cf5a1a6d9
--- /dev/null
+++ b/src/network/network_pf.h
@@ -0,0 +1,26 @@
+/*
+ * network_pf.h: helper APIs for managing pf in network driver
+ *
+ * Copyright (C) 2025 FreeBSD Foundation
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see
+ * <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "network_conf.h"
+
+int pfAddFirewallRules(virNetworkDef *def);
+void pfRemoveFirewallRules(virNetworkDef *def);
diff --git a/src/util/virfirewall.c b/src/util/virfirewall.c
index 9389bcf541..69521e2b46 100644
--- a/src/util/virfirewall.c
+++ b/src/util/virfirewall.c
@@ -39,7 +39,8 @@ VIR_ENUM_IMPL(virFirewallBackend,
VIR_FIREWALL_BACKEND_LAST,
"none",
"iptables",
- "nftables");
+ "nftables",
+ "pf");
VIR_ENUM_DECL(virFirewallLayer);
VIR_ENUM_IMPL(virFirewallLayer,
@@ -847,6 +848,7 @@ virFirewallApplyCmd(virFirewall *firewall,
return -1;
break;
+ case VIR_FIREWALL_BACKEND_PF:
case VIR_FIREWALL_BACKEND_LAST:
default:
virReportEnumRangeError(virFirewallBackend,
diff --git a/src/util/virfirewall.h b/src/util/virfirewall.h
index d42e60884b..030cb2c0a4 100644
--- a/src/util/virfirewall.h
+++ b/src/util/virfirewall.h
@@ -30,6 +30,7 @@
#define IPTABLES "iptables"
#define IP6TABLES "ip6tables"
#define NFT "nft"
+#define PFCTL "pfctl"
typedef struct _virFirewall virFirewall;
@@ -48,6 +49,7 @@ typedef enum {
VIR_FIREWALL_BACKEND_NONE, /* Always fails */
VIR_FIREWALL_BACKEND_IPTABLES,
VIR_FIREWALL_BACKEND_NFTABLES,
+ VIR_FIREWALL_BACKEND_PF,
VIR_FIREWALL_BACKEND_LAST,
} virFirewallBackend;
--
2.49.0On Sat, Apr 26, 2025 at 09:42:36AM +0200, Roman Bogorodskiy wrote:
> Implement NAT networking support based on the Packet Filter (pf)
> firewall in FreeBSD. At this point, the implementation is very basic.
> It creates:
>
> - Essential NAT translation rules
> - Basic forwarding rules
>
> Implementation uses pf's anchor feature to group rules. All rules live
> in the "libvirt" anchor and every libvirt's network has its own
> sub-anchor.
>
> Currently there are some assumptions and limitations:
>
> - We assume that a user has created the "libvirt" (nat-)anchors. As
> they cannot be created on fly, it's better not to touch global pf
> configuration and let the user do the changes. If the user doesn't
> have these anchors configured, the rules will still be created in
> sub-anchors, but will not be effective until these anchors are
> activated. Should we check if these anchors are not active to
> give some runtime warning?
So IIUC a PF 'anchor' is essentially a top level namespace
under which all libvirt rules will live, so they are isolated
from other system rules ?
This sounds similar to how we deal with the new 'nft' firewall
on Linux, where we have to create top level tables to hold
all our rules
That has thrown up a tricky problem for us though around the
prioritization. A packet has to be accepted by *every* top
level table, for it to be allowed. So even if a libvirt rule
allows it, potentiallly other system rules can still block
it. This is basically unsolvable in the general case. We do
a special hack in the firewalld case to tell it to put the
bridge device into a separate libvirt "zone", which in
turn means none of the other firewalld rules will ever get
applied to those packets.
Back to PF though. You're saying we can't create anchors on
the fly - so that's saying the only way to create the anchors
is to edit the /etc/ config file, and those get applied on
system boot ?
We should probably document this in docs/drvnetwork.rst...
which I see does not actually exist :-( Probably good to
start a skeleton of a page and put the FreeBSD specific
notes there, and we can fll out Linux notes later
> - Currently, rule reloading is not smart: it always deletes rules,
> flushes rules and re-creates that. It would be better to do that
> more gracefully.
That's not especially worse than what we do on Linux either
> - IPv6 configurations are currently not supported
Probably worth reporting a fatal error if you see IPv6
config in the XML input, so attempts to use IPV6 are
not silently ignored.
> - For NAT, pf requires explicit IP address or an interface to NAT to.
> We try to obtain that from the network XML definition, and if it's
> not specified, we try to determine interface corresponding to the
> default route.
On Linux the defaults should work based on routing, so that's not
too bad as a default behaviour. The difference is that FreeBSD
would only work based on the single route, while the Linux behaviour
could use all available routes. Not the end of the world, since
most machines only have a single default route. The common exception
being people using VPN clients.
> diff --git a/src/network/network_pf.c b/src/network/network_pf.c
> new file mode 100644
> index 0000000000..b12ef86089
> --- /dev/null
> +++ b/src/network/network_pf.c
> @@ -0,0 +1,327 @@
> +/*
> + * network_pf.c: pf-based firewall implementation for virtual networks
> + *
> + * Copyright (C) 2025 FreeBSD Foundation
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library. If not, see
> + * <http://www.gnu.org/licenses/>.
> + */
> +
> +/*
> + * pf(4) configuration principles/assumptions.
> + *
> + * All libvirt-managed firewall rule are configured within a pf anchor.
> + * Every libvirt network has a corresponding sub-anchor, like "libvirt/$network_name".
> + * Libvirt does not create the root anchors, so users are expected to specify them in
> + * their firewall configuration. Minimal configuration might look like:
> + *
> + * # cat /etc/pf.conf
> + * scrub all
> + *
> + * nat-anchor "libvirt\*"
> + * anchor "libvirt\*"
> + *
> + * pass all
> + * #
> + *
> + * Users are not expected to add/modify rules in the "libvirt\*" subanchors because
> + * the changes will be lost on restart.
> + *
> + * IPv6 NAT is currently not supported.
> + */
> +
> +#include <config.h>
> +
> +#include <stdarg.h>
> +#include <unistd.h>
> +#include <fcntl.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <sys/socket.h>
> +#ifdef WITH_NET_IF_H
> +# include <net/if.h>
> +#endif
> +#if defined(__FreeBSD__)
Do you need these __FreeBSD__ conditions here ? Is 'pf' intended to be
used on anything other than FreeBSD ? If not, we should ensure that
it simply never built on any other platform at the meson level.
> +# include <sys/sysctl.h>
> +# include <net/if_dl.h>
> +#endif
> +#include <net/route.h>
> +#include <netinet/in.h>
> +
> +#include "internal.h"
> +#include "virfirewalld.h"
> +#include "vircommand.h"
> +#include "virerror.h"
> +#include "virlog.h"
> +#include "virhash.h"
> +#include "virenum.h"
> +#include "virstring.h"
> +#include "network_pf.h"
> +
> +VIR_LOG_INIT("network.pf");
> +
> +#define VIR_FROM_THIS VIR_FROM_NONE
> +
> +
> +static const char networkLocalMulticastIPv4[] = "224.0.0.0/24";
> +static const char networkLocalBroadcast[] = "255.255.255.255/32";
> +
> +
> +static char *
> +findDefaultRouteInterface(void)
> +{
> +#if defined(__FreeBSD__)
> + int mib[6] = {CTL_NET, PF_ROUTE, 0, AF_INET, NET_RT_DUMP, 0};
> + size_t needed;
> + g_autofree char *buf = NULL;
> + char *lim, *next;
> + struct rt_msghdr *rtm;
> + struct sockaddr *sa;
> + struct sockaddr_in *sin;
> + struct sockaddr_dl *sdl;
> + char *ifname;
> + size_t ifname_len;
> + size_t i;
> +
> + if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0) {
> + virReportSystemError(errno,
> + "%s",
> + _("Unable to get default interface name"));
> + return NULL;
> + }
> +
> + if (posix_memalign((void **)&buf, 8, needed) != 0) {
> + virReportSystemError(errno,
> + "%s",
> + _("Unable to get default interface name"));
> + return NULL;
> + }
> +
> + if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0) {
> + virReportSystemError(errno,
> + "%s",
> + _("Unable to get default interface name"));
> + return NULL;
> + }
> +
> + lim = buf + needed;
> + next = buf;
> +
> + while (next < lim) {
> + rtm = (struct rt_msghdr *)(void *)next;
> + if (next + rtm->rtm_msglen > lim)
> + break;
> +
> + sin = (struct sockaddr_in *)(rtm + 1);
> +
> + if ((rtm->rtm_flags & RTF_GATEWAY) && sin->sin_addr.s_addr == INADDR_ANY) {
> + sdl = NULL;
> + sa = (struct sockaddr *)(sin + 1);
> +
> + for (i = 1; i < RTAX_MAX; i++) {
> + if (rtm->rtm_addrs & (1 << i)) {
> + if (i == RTAX_IFP && sa->sa_family == AF_LINK) {
> + sdl = (struct sockaddr_dl *)(void *)sa;
> + ifname_len = (sdl->sdl_nlen >= IFNAMSIZ) ? IFNAMSIZ - 1 : sdl->sdl_nlen;
> + ifname = g_new(char, ifname_len + 1);
> + virStrcpy(ifname, sdl->sdl_data, ifname_len + 1);
> + return ifname;
> + }
> + sa = (struct sockaddr *)((char *)sa +
> + ((sa->sa_len > 0) ? sa->sa_len : sizeof(struct sockaddr)));
> + }
> + }
> + }
> +
> + next += rtm->rtm_msglen;
> + }
> +#endif
> +
> + return NULL;
> +}
> +
> +static int
> +pfAddNatFirewallRules(virNetworkDef *def,
> + virNetworkIPDef *ipdef)
> +{
> + /*
> + * # NAT rules
> + * table <natdst> persist
> + * { 0.0.0.0/0, ! 192.168.122.0/24, !224.0.0.0/24, !255.255.255.255 }
> + * nat pass log on $ext_if from 192.168.122.0/24 to <natdst>
> + * -> ($ext_if) port 1024:65535
> + *
> + * # Filtering
> + * pass log quick on virbr0 from 192.168.122.0/24 to 192.168.122.0/24
> + * pass out log quick on virbr0 from 192.168.122.0/24 to 224.0.0.0/24
> + * pass out log quick on virbr0 from 192.168.122.0/24 to 255.255.255.255
> + * block log on virbr0
> + */
> + int prefix = virNetworkIPDefPrefix(ipdef);
> + g_autofree const char *forwardIf = g_strdup(virNetworkDefForwardIf(def, 0));
> + g_auto(virBuffer) pf_rules_buf = VIR_BUFFER_INITIALIZER;
> + g_autoptr(virCommand) cmd = virCommandNew(PFCTL);
> + virPortRange *portRange = &def->forward.port;
> + g_autofree char *portRangeStr = NULL;
> +
> + if (prefix < 0) {
> + virReportError(VIR_ERR_INTERNAL_ERROR,
> + _("Invalid prefix or netmask for '%1$s'"),
> + def->bridge);
> + return -1;
> + }
> +
> + if (portRange->start == 0 && portRange->end == 0) {
> + portRange->start = 1024;
> + portRange->end = 65535;
> + }
> +
> + if (portRange->start < portRange->end && portRange->end < 65536) {
> + portRangeStr = g_strdup_printf("%u:%u",
> + portRange->start,
> + portRange->end);
> + } else {
> + virReportError(VIR_ERR_INTERNAL_ERROR,
> + _("Invalid port range '%1$u-%2$u'."),
> + portRange->start, portRange->end);
> + return -1;
> + }
> +
> + if (!forwardIf) {
> + forwardIf = findDefaultRouteInterface();
> + if (!forwardIf) {
> + virReportError(VIR_ERR_INTERNAL_ERROR,
> + "%s",
> + _("Cannot determine the default interface"));
> + return -1;
> + }
> + }
> +
> + virBufferAsprintf(&pf_rules_buf,
> + "table <natdst> persist { 0.0.0.0/0, ! %s/%d, ! %s, ! %s }\n",
> + virSocketAddrFormat(&ipdef->address),
> + prefix,
> + networkLocalMulticastIPv4,
> + networkLocalBroadcast);
> + virBufferAsprintf(&pf_rules_buf,
> + "nat pass on %s from %s/%d to <natdst> -> (%s) port %s\n",
> + forwardIf,
> + virSocketAddrFormat(&ipdef->address),
> + prefix,
> + forwardIf,
> + portRangeStr);
> + virBufferAsprintf(&pf_rules_buf,
> + "pass quick on %s from %s/%d to %s/%d\n",
> + def->bridge,
> + virSocketAddrFormat(&ipdef->address),
> + prefix,
> + virSocketAddrFormat(&ipdef->address),
> + prefix);
> + virBufferAsprintf(&pf_rules_buf,
> + "pass quick on %s from %s/%d to %s\n",
> + def->bridge,
> + virSocketAddrFormat(&ipdef->address),
> + prefix,
> + networkLocalMulticastIPv4);
> + virBufferAsprintf(&pf_rules_buf,
> + "pass quick on %s from %s/%d to %s\n",
> + def->bridge,
> + virSocketAddrFormat(&ipdef->address),
> + prefix,
> + networkLocalBroadcast);
> + virBufferAsprintf(&pf_rules_buf,
> + "block on %s\n",
> + def->bridge);
> +
> + /* pfctl -a libvirt/default -F all -f - */
> + virCommandAddArg(cmd, "-a");
> + virCommandAddArgFormat(cmd, "libvirt/%s", def->name);
> + virCommandAddArgList(cmd, "-F", "all", "-f", "-", NULL);
> +
> + virCommandSetInputBuffer(cmd, virBufferContentAndReset(&pf_rules_buf));
> +
> + if (virCommandRun(cmd, NULL) < 0) {
> + VIR_WARN("Failed to create firewall rules for network %s",
> + def->name);
> + return -1;
> + }
> + return 0;
> +}
> +
> +
> +static int
> +pfAddRoutingFirewallRules(virNetworkDef *def,
> + virNetworkIPDef *ipdef G_GNUC_UNUSED)
> +{
> + int prefix = virNetworkIPDefPrefix(ipdef);
> +
> + if (prefix < 0) {
> + virReportError(VIR_ERR_INTERNAL_ERROR,
> + _("Invalid prefix or netmask for '%1$s'"),
> + def->bridge);
> + return -1;
> + }
> +
> + /* TODO: routing rules */
> +
> + return 0;
> +}
> +
> +
> +static int
> +pfAddIPSpecificFirewallRules(virNetworkDef *def,
> + virNetworkIPDef *ipdef)
> +{
> + if (def->forward.type == VIR_NETWORK_FORWARD_NAT) {
> + if (VIR_SOCKET_ADDR_IS_FAMILY(&ipdef->address, AF_INET))
> + return pfAddNatFirewallRules(def, ipdef);
> + else
> + return -1;
Should report an error message here about lack of IPV6
> + } else if (def->forward.type == VIR_NETWORK_FORWARD_ROUTE) {
> + return pfAddRoutingFirewallRules(def, ipdef);
Should this check for IPv6 too ? The linux impl doesn't seem to
conditionalize based on IP family though.
> + }
> + return 0;
> +}
> +
> +
> +int
> +pfAddFirewallRules(virNetworkDef *def)
> +{
> + size_t i;
> + virNetworkIPDef *ipdef;
> +
> + for (i = 0;
> + (ipdef = virNetworkDefGetIPByIndex(def, AF_UNSPEC, i));
> + i++) {
> + if (pfAddIPSpecificFirewallRules(def, ipdef) < 0)
> + return -1;
> + }
> +
> + return 0;
> +}
> +
> +
> +void
> +pfRemoveFirewallRules(virNetworkDef *def)
> +{
> + /* pfctl -a libvirt/default -F all */
> + g_autoptr(virCommand) cmd = virCommandNew(PFCTL);
> + virCommandAddArg(cmd, "-a");
> + virCommandAddArgFormat(cmd, "libvirt/%s", def->name);
> + virCommandAddArgList(cmd, "-F", "all", NULL);
> +
> + if (virCommandRun(cmd, NULL) < 0)
> + VIR_WARN("Failed to remove firewall rules for network %s",
> + def->name);
> +}
> diff --git a/src/util/virfirewall.h b/src/util/virfirewall.h
> index d42e60884b..030cb2c0a4 100644
> --- a/src/util/virfirewall.h
> +++ b/src/util/virfirewall.h
> @@ -30,6 +30,7 @@
> #define IPTABLES "iptables"
> #define IP6TABLES "ip6tables"
> #define NFT "nft"
> +#define PFCTL "pfctl"
>
> typedef struct _virFirewall virFirewall;
>
> @@ -48,6 +49,7 @@ typedef enum {
> VIR_FIREWALL_BACKEND_NONE, /* Always fails */
> VIR_FIREWALL_BACKEND_IPTABLES,
> VIR_FIREWALL_BACKEND_NFTABLES,
> + VIR_FIREWALL_BACKEND_PF,
>
> VIR_FIREWALL_BACKEND_LAST,
> } virFirewallBackend;
I'd suggest adding the new backend to virfirewall as a standalone patch
behand, so this patch focuses exclusively on the freebsd pf impl in the
network driver.
With regards,
Daniel
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Daniel P. Berrangé wrote:
> On Sat, Apr 26, 2025 at 09:42:36AM +0200, Roman Bogorodskiy wrote:
> > Implement NAT networking support based on the Packet Filter (pf)
> > firewall in FreeBSD. At this point, the implementation is very basic.
> > It creates:
> >
> > - Essential NAT translation rules
> > - Basic forwarding rules
> >
> > Implementation uses pf's anchor feature to group rules. All rules live
> > in the "libvirt" anchor and every libvirt's network has its own
> > sub-anchor.
> >
> > Currently there are some assumptions and limitations:
> >
> > - We assume that a user has created the "libvirt" (nat-)anchors. As
> > they cannot be created on fly, it's better not to touch global pf
> > configuration and let the user do the changes. If the user doesn't
> > have these anchors configured, the rules will still be created in
> > sub-anchors, but will not be effective until these anchors are
> > activated. Should we check if these anchors are not active to
> > give some runtime warning?
>
> So IIUC a PF 'anchor' is essentially a top level namespace
> under which all libvirt rules will live, so they are isolated
> from other system rules ?
Yes, that's correct.
> This sounds similar to how we deal with the new 'nft' firewall
> on Linux, where we have to create top level tables to hold
> all our rules
>
> That has thrown up a tricky problem for us though around the
> prioritization. A packet has to be accepted by *every* top
> level table, for it to be allowed. So even if a libvirt rule
> allows it, potentiallly other system rules can still block
> it. This is basically unsolvable in the general case. We do
> a special hack in the firewalld case to tell it to put the
> bridge device into a separate libvirt "zone", which in
> turn means none of the other firewalld rules will ever get
> applied to those packets.
It depends. In PF, rules could be created with the "quick" keyword.
Quoting the manual page:
Matching filter and translation rules marked with the quick option are
final and abort the evaluation of the rules in other anchors and the main
ruleset. If the anchor itself is marked with the quick option, ruleset
evaluation will terminate when the anchor is exited if the packet is
matched by any rule within the anchor.
I'm using this keyword for some of the pass rules to avoid these packets
occasionally blocked.
> Back to PF though. You're saying we can't create anchors on
> the fly - so that's saying the only way to create the anchors
> is to edit the /etc/ config file, and those get applied on
> system boot ?
Yes, that's true. Well, in theory, we can edit the /etc/pf.conf, try to
find an appropriate place for anchors definitions, and reload the rules.
I saw some management software does that, but that seems to be too
invasive for me, at least for now.
> We should probably document this in docs/drvnetwork.rst...
> which I see does not actually exist :-( Probably good to
> start a skeleton of a page and put the FreeBSD specific
> notes there, and we can fll out Linux notes later
>
> > - Currently, rule reloading is not smart: it always deletes rules,
> > flushes rules and re-creates that. It would be better to do that
> > more gracefully.
>
> That's not especially worse than what we do on Linux either
>
> > - IPv6 configurations are currently not supported
>
> Probably worth reporting a fatal error if you see IPv6
> config in the XML input, so attempts to use IPV6 are
> not silently ignored.
>
> > - For NAT, pf requires explicit IP address or an interface to NAT to.
> > We try to obtain that from the network XML definition, and if it's
> > not specified, we try to determine interface corresponding to the
> > default route.
>
> On Linux the defaults should work based on routing, so that's not
> too bad as a default behaviour. The difference is that FreeBSD
> would only work based on the single route, while the Linux behaviour
> could use all available routes. Not the end of the world, since
> most machines only have a single default route. The common exception
> being people using VPN clients.
Thanks for feedback, will address the comments in the follow up series.
Roman
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