Hi, I have been playing with jool a bit but when using my own address space for NAT64 always gets this issue:

Jool NAT64/ba23ed80/default: ===============================================
Jool NAT64/ba23ed80/default: Packet: 2001:xxx:518f->2001:xxx::1f2f:4d04
Jool NAT64/ba23ed80/default: TCP 41168->80
Jool NAT64/ba23ed80/default: Step 1: Determining the Incoming Tuple
Jool NAT64/ba23ed80/default: Tuple: 2001:xxx:518f#41168 -> 2001:xxx::1f2f:4d04#80 (TCP)
Jool NAT64/ba23ed80/default: Done step 1.
Jool NAT64/ba23ed80/default: Step 2: Filtering and Updating
Jool NAT64/ba23ed80/default: BIB entry: 2001:xxx:518f#41168 - 194.1.1.1#22154 (TCP)
Jool NAT64/ba23ed80/default: Session entry: 2001:xxx:518f#41168 - 2001:xxx::1f2f:4d04#80 | 194.1.1.1#22154 - 31.47.77.4#80 (TCP)
Jool NAT64/ba23ed80/default: Done: Step 2.
Jool NAT64/ba23ed80/default: Step 3: Computing the Outgoing Tuple
Jool NAT64/ba23ed80/default: Tuple: 194.1.1.1#22154 -> 31.47.77.4#80 (TCP)
Jool NAT64/ba23ed80/default: Done step 3.
Jool NAT64/ba23ed80/default: Step 4: Translating the Packet
Jool NAT64/ba23ed80/default: Translating packet addresses 2001:xxx:518f->2001:xxx::1f2f:4d04...
Jool NAT64/ba23ed80/default: Result: 194.1.1.1->31.47.77.4
Jool NAT64/ba23ed80/default: Packet routed via device 'eth0'.
Jool NAT64/ba23ed80/default: Done step 4.
Jool NAT64/ba23ed80/default: Sending packet.
Jool NAT64/ba23ed80/default: dst_output() returned errcode 1.
Jool: Dropping packet.

When jool is down, the server is able to reach anything on public ipv4 space.

i have totally run out of ideas.

my jool.conf:

{
"instance": "default",
"framework": "netfilter",
"global": {
"maximum-simultaneous-opens": 1000,
"drop-externally-initiated-tcp": true,
"pool6": "2001:xxx::/96"
},
"pool4": [
{
"comment": "mark, port range and max-iterations are optional.",
"protocol": "TCP",
"prefix": "194.1.1.1",
"port range": "21001-65535"
},
{
"protocol": "UDP",
"prefix": "194.1.1.1",
"port range": "21001-65535"
},
{
"protocol": "ICMP",
"prefix": "194.1.1.1",
"port range": "21001-65535"
}
]
}

sysctl values:

net.ipv4.ip_local_port_range = 10000 20000
net.ipv4.conf.all.forwarding=1
net.ipv6.conf.all.forwarding=1

Dont know if its a bug or what:

Tried this with:

Jool 4.1.5, 4.1.8, 4.2.0-rc2
Kernels 5.10, 5.15, 5.16