Yes, you can transparently forward traffic from a specific process to mitmproxy using a combination of Linux network namespace isolation and iptables. Here’s a general approach:

1. Create a network namespace: This isolates the process's network activity.

   sudo ip netns add ns1
   

2. Create a virtual network interface pair (veth pair), connecting the default namespace to the new namespace:

   sudo ip link add veth0 type veth peer name veth1
   sudo ip link set veth1 netns ns1
   

3. Configure the network interfaces:

   sudo ip addr add 192.168.1.1/24 dev veth0
   sudo ip link set veth0 up
   
   sudo ip netns exec ns1 ip addr add 192.168.1.2/24 dev veth1
   sudo ip netns exec ns1 ip link set veth1 up
   sudo ip netns exec ns1 ip route add default via 192.168.1.1
   

4. Enable IP forwarding and set up iptables to redirect the traffic from the new namespace to mitmproxy:

   sudo sysctl -w net.ipv4.ip_forward=1
   sudo iptables -t nat -A POSTROUTING -s 192.168.1.0/24 -o <your-main-interface> -j MASQUERADE
   sudo iptables -t nat -A PREROUTING -p tcp -s 192.168.1.2 -j REDIRECT --to-port <mitmproxy-port>
   

5. Start mitmproxy on your host, listening on the specified port:

   mitmproxy --mode transparent --listen-host 0.0.0.0 --listen-port <mitmproxy-port>
   

6. Run the process in the isolated namespace:

   sudo ip netns exec ns1 <command-to-start-your-process>
   

This setup isolates the process in a separate network namespace and redirects its network traffic through mitmproxy for monitoring or manipulation. Make sure to replace placeholders like <your-main-interface> and <mitmproxy-port> with actual values relevant to your setup.