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e9e5ebe6a6
Please see the commit log for commit v10.9.0-rc1-1-g42ab0148dd for the
history and explanation of the problem that this patch is fixing.
A shorter explanation is that when a guest is connected to a libvirt
virtual network using a virtio-net adapter with in-kernel "vhost-net"
packet processing enabled, it will fail to acquire an IP address from
a DHCP seever running on the host.
In commit v10.9.0-rc1-1-g42ab0148dd we tried fixing this by *zeroing
out* the checksums of these packets with an nftables rule (nftables
can't recompute the checksum, but it can set it to 0) . This
*appeared* to work initially, but it turned out that zeroing the
checksum ends up breaking dhcp packets on *non* virtio/vhost-net guest
interfaces. That attempt was reverted in commit v10.9.0-rc2.
Fortunately, there is an existing way to recompute the checksum of a
packet as it leaves an interface - the "tc" (traffic control) utility
that libvirt already uses for bandwidth management. This patch uses a
tc filter rule to match dhcp response packets on the bridge and
recompute their checksum.
The filter rule must be attached to a tc qdisc, which may also have a
filter attached for bandwidth management (in the <bandwidth> element
of the network config). Not only must we add the qdisc only once
(which was already handled by the patch two prior to this one), but
also the filter rule for checksum fixing and the filter rule for
bandwidth management must be different priorities so they don't clash;
this is solved by adding the checksum-fix filter with "priority 2",
while the bandwidth management filter remains "priority 1" (both will
always be evaluated anyway, it's just a matter of which is evaluated
first).
So far this method has worked with every different guest we could
throw at it, including several that failed with the previous method.
Fixes: b89c4991da
Reported-by: Rich Jones <rjones@redhat.com>
Reported-by: Andrea Bolognani <abologna@redhat.com>
Fix-Suggested-by: Eric Garver <egarver@redhat.com>
Fix-Suggested-by: Phil Sutter <psutter@redhat.com>
Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
409 lines
3.8 KiB
Plaintext
409 lines
3.8 KiB
Plaintext
tc \
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qdisc \
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show \
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dev \
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virbr0 \
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handle \
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1:
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tc \
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qdisc \
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add \
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dev \
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virbr0 \
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root \
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handle \
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1: \
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htb \
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default \
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2
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tc \
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filter \
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add \
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dev \
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virbr0 \
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prio \
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2 \
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protocol \
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ip \
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parent \
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1: \
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u32 \
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match \
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ip \
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dport \
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68 \
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ffff \
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action \
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csum \
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ip \
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and \
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udp
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_output \
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iif \
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virbr0 \
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counter \
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reject
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_input \
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oif \
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virbr0 \
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counter \
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reject
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_cross \
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iif \
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virbr0 \
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oif \
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virbr0 \
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counter \
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accept
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_output \
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ip \
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saddr \
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192.168.122.0/24 \
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iif \
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virbr0 \
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counter \
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accept
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_input \
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oif \
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virbr0 \
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ip \
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daddr \
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192.168.122.0/24 \
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ct \
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state \
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related,established \
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counter \
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accept
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_nat \
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ip \
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saddr \
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192.168.122.0/24 \
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ip \
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daddr \
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'!=' \
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192.168.122.0/24 \
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counter \
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masquerade
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_nat \
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meta \
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l4proto \
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udp \
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ip \
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saddr \
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192.168.122.0/24 \
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ip \
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daddr \
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'!=' \
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192.168.122.0/24 \
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counter \
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masquerade \
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to \
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:1024-65535
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_nat \
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meta \
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l4proto \
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tcp \
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ip \
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saddr \
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192.168.122.0/24 \
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ip \
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daddr \
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'!=' \
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192.168.122.0/24 \
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counter \
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masquerade \
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to \
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:1024-65535
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_nat \
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ip \
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saddr \
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192.168.122.0/24 \
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ip \
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daddr \
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255.255.255.255/32 \
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counter \
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return
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_nat \
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ip \
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saddr \
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192.168.122.0/24 \
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ip \
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daddr \
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224.0.0.0/24 \
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counter \
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return
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_output \
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ip \
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saddr \
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192.168.128.0/24 \
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iif \
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virbr0 \
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counter \
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accept
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_input \
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oif \
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virbr0 \
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ip \
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daddr \
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192.168.128.0/24 \
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ct \
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state \
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related,established \
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counter \
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accept
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_nat \
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ip \
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saddr \
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192.168.128.0/24 \
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ip \
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daddr \
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'!=' \
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192.168.128.0/24 \
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counter \
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masquerade
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_nat \
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meta \
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l4proto \
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udp \
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ip \
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saddr \
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192.168.128.0/24 \
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ip \
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daddr \
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'!=' \
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192.168.128.0/24 \
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counter \
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masquerade \
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to \
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:1024-65535
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_nat \
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meta \
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l4proto \
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tcp \
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ip \
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saddr \
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192.168.128.0/24 \
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ip \
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daddr \
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'!=' \
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192.168.128.0/24 \
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counter \
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masquerade \
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to \
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:1024-65535
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_nat \
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ip \
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saddr \
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192.168.128.0/24 \
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ip \
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daddr \
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255.255.255.255/32 \
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counter \
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return
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_nat \
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ip \
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saddr \
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192.168.128.0/24 \
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ip \
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daddr \
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224.0.0.0/24 \
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counter \
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return
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_output \
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ip \
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saddr \
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192.168.150.0/24 \
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iif \
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virbr0 \
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counter \
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accept
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_input \
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oif \
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virbr0 \
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ip \
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daddr \
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192.168.150.0/24 \
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ct \
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state \
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related,established \
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counter \
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accept
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_nat \
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ip \
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saddr \
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192.168.150.0/24 \
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ip \
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daddr \
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'!=' \
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192.168.150.0/24 \
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counter \
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masquerade
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_nat \
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meta \
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l4proto \
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udp \
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ip \
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saddr \
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192.168.150.0/24 \
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ip \
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daddr \
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'!=' \
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192.168.150.0/24 \
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counter \
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masquerade \
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to \
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:1024-65535
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_nat \
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meta \
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l4proto \
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tcp \
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ip \
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saddr \
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192.168.150.0/24 \
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ip \
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daddr \
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'!=' \
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192.168.150.0/24 \
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counter \
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masquerade \
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to \
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:1024-65535
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_nat \
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ip \
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saddr \
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192.168.150.0/24 \
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ip \
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daddr \
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255.255.255.255/32 \
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counter \
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return
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nft \
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-ae insert \
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rule \
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ip \
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libvirt_network \
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guest_nat \
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ip \
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saddr \
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192.168.150.0/24 \
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ip \
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daddr \
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224.0.0.0/24 \
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counter \
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return
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