[PATCH pve-network v5 6/9] sdn: evpn: accept untracked IPv6 neighbor advertisements

[Hannes Laimer <h.laimer@proxmox.com>]

Every node of an EVPN zone has the same gateway address and MAC on a
vnet bridge. An exit node without a neighbor entry for a guest's IPv6
address floods a solicitation to the other nodes. The guest answers
to the shared gateway, so the node it runs on gets the advertisement.
That node never sent the solicitation, and with no entry for the
address its kernel ignores the advertisement by default. The exit
node is left without an entry and drops traffic from outside the zone
to the guest.

Set accept_untracked_na to 2 on vnet bridges with an IPv6 subnet [1].
The kernel then adds an entry from such an advertisement if its source
is in the subnet of an address on the bridge. From there EVPN carries
the entry to the exit node.

[1] https://docs.kernel.org/networking/ip-sysctl.html#proc-sys-net-ipv6-variables

Signed-off-by: Hannes Laimer <h.laimer@proxmox.com>
---

Notes:
    v3:
     - add the missing accept_untracked_na line to the exitnode_local_routing_ipv6 fixture

 src/PVE/Network/SDN/Zones/EvpnPlugin.pm                      | 5 +++++
 .../evpn/exitnode_local_routing_ipv6/expected_sdn_interfaces | 1 +
 src/test/zones/evpn/exitnode_snat/expected_sdn_interfaces    | 1 +
 .../zones/evpn/exitnodenullroute/expected_sdn_interfaces     | 1 +
 src/test/zones/evpn/ipv4ipv6/expected_sdn_interfaces         | 1 +
 .../zones/evpn/ipv4ipv6nogateway/expected_sdn_interfaces     | 1 +
 src/test/zones/evpn/ipv6/expected_sdn_interfaces             | 1 +
 src/test/zones/evpn/ipv6underlay/expected_sdn_interfaces     | 1 +
 8 files changed, 12 insertions(+)

diff --git a/src/PVE/Network/SDN/Zones/EvpnPlugin.pm b/src/PVE/Network/SDN/Zones/EvpnPlugin.pm
index c1d5536e09c0..96f549577b3b 100644
--- a/src/PVE/Network/SDN/Zones/EvpnPlugin.pm
+++ b/src/PVE/Network/SDN/Zones/EvpnPlugin.pm
@@ -309,6 +309,11 @@ sub generate_sdn_config {
     push @iface_config, "ip-forward on" if $enable_forward_v4;
     push @iface_config, "ip6-forward on" if $enable_forward_v6;
     push @iface_config, "arp-accept on" if $ipv4 || $ipv6;
+
+    if ($ipv6) {
+        push @iface_config,
+            "post-up echo 2 > /proc/sys/net/ipv6/conf/$vnetid/accept_untracked_na || true";
+    }
     push @iface_config, "vrf $vrf_iface" if $vrf_iface;
     push(@{ $config->{$vnetid} }, @iface_config) if !$config->{$vnetid};
 
diff --git a/src/test/zones/evpn/exitnode_local_routing_ipv6/expected_sdn_interfaces b/src/test/zones/evpn/exitnode_local_routing_ipv6/expected_sdn_interfaces
index b46d4e7b6ea0..9b268f21857f 100644
--- a/src/test/zones/evpn/exitnode_local_routing_ipv6/expected_sdn_interfaces
+++ b/src/test/zones/evpn/exitnode_local_routing_ipv6/expected_sdn_interfaces
@@ -9,6 +9,7 @@ iface myvnet
 	mtu 1450
 	ip6-forward on
 	arp-accept on
+	post-up echo 2 > /proc/sys/net/ipv6/conf/myvnet/accept_untracked_na || true
 	vrf vrf_myzone
 
 auto vrf_myzone
diff --git a/src/test/zones/evpn/exitnode_snat/expected_sdn_interfaces b/src/test/zones/evpn/exitnode_snat/expected_sdn_interfaces
index 0d7d17412f0b..3e9b8adca124 100644
--- a/src/test/zones/evpn/exitnode_snat/expected_sdn_interfaces
+++ b/src/test/zones/evpn/exitnode_snat/expected_sdn_interfaces
@@ -28,6 +28,7 @@ iface myvnet2
 	mtu 1450
 	ip6-forward on
 	arp-accept on
+	post-up echo 2 > /proc/sys/net/ipv6/conf/myvnet2/accept_untracked_na || true
 	vrf vrf_myzone
 
 auto vrf_myzone
diff --git a/src/test/zones/evpn/exitnodenullroute/expected_sdn_interfaces b/src/test/zones/evpn/exitnodenullroute/expected_sdn_interfaces
index 4bf5ccf96f91..81a3b39ed129 100644
--- a/src/test/zones/evpn/exitnodenullroute/expected_sdn_interfaces
+++ b/src/test/zones/evpn/exitnodenullroute/expected_sdn_interfaces
@@ -15,6 +15,7 @@ iface myvnet
 	ip-forward on
 	ip6-forward on
 	arp-accept on
+	post-up echo 2 > /proc/sys/net/ipv6/conf/myvnet/accept_untracked_na || true
 	vrf vrf_myzone
 
 auto myvnet2
diff --git a/src/test/zones/evpn/ipv4ipv6/expected_sdn_interfaces b/src/test/zones/evpn/ipv4ipv6/expected_sdn_interfaces
index 7a5d741b067c..7b1727bbf278 100644
--- a/src/test/zones/evpn/ipv4ipv6/expected_sdn_interfaces
+++ b/src/test/zones/evpn/ipv4ipv6/expected_sdn_interfaces
@@ -12,6 +12,7 @@ iface myvnet
 	ip-forward on
 	ip6-forward on
 	arp-accept on
+	post-up echo 2 > /proc/sys/net/ipv6/conf/myvnet/accept_untracked_na || true
 	vrf vrf_myzone
 
 auto vrf_myzone
diff --git a/src/test/zones/evpn/ipv4ipv6nogateway/expected_sdn_interfaces b/src/test/zones/evpn/ipv4ipv6nogateway/expected_sdn_interfaces
index 378fa77fa368..4d904be3fd5b 100644
--- a/src/test/zones/evpn/ipv4ipv6nogateway/expected_sdn_interfaces
+++ b/src/test/zones/evpn/ipv4ipv6nogateway/expected_sdn_interfaces
@@ -8,6 +8,7 @@ iface myvnet
 	bridge_fd 0
 	mtu 1450
 	arp-accept on
+	post-up echo 2 > /proc/sys/net/ipv6/conf/myvnet/accept_untracked_na || true
 	vrf vrf_myzone
 
 auto vrf_myzone
diff --git a/src/test/zones/evpn/ipv6/expected_sdn_interfaces b/src/test/zones/evpn/ipv6/expected_sdn_interfaces
index b2bdbfefd810..f77612293fbf 100644
--- a/src/test/zones/evpn/ipv6/expected_sdn_interfaces
+++ b/src/test/zones/evpn/ipv6/expected_sdn_interfaces
@@ -10,6 +10,7 @@ iface myvnet
 	mtu 1450
 	ip6-forward on
 	arp-accept on
+	post-up echo 2 > /proc/sys/net/ipv6/conf/myvnet/accept_untracked_na || true
 	vrf vrf_myzone
 
 auto vrf_myzone
diff --git a/src/test/zones/evpn/ipv6underlay/expected_sdn_interfaces b/src/test/zones/evpn/ipv6underlay/expected_sdn_interfaces
index 3b91f75eb3dd..ab5988fae818 100644
--- a/src/test/zones/evpn/ipv6underlay/expected_sdn_interfaces
+++ b/src/test/zones/evpn/ipv6underlay/expected_sdn_interfaces
@@ -10,6 +10,7 @@ iface myvnet
 	mtu 1450
 	ip6-forward on
 	arp-accept on
+	post-up echo 2 > /proc/sys/net/ipv6/conf/myvnet/accept_untracked_na || true
 	vrf vrf_myzone
 
 auto vrf_myzone
-- 
2.47.3