port_handler=slirp4netns not working?

[FGasper]

Hello,

I’m running this:

podman run -it --network slirp4netns:port_handler=slirp4netns --publish 10.2.65.75:8080:80 almalinux:8 /bin/bash -c 'dnf install -qy iproute; ip route get 1'

I’m expecting to see 10.2.65.75 printed since I’m using port_handler=slirp4netns, but instead I see 10.0.2.100.

Am I “holding it wrong”, or just misunderstanding what that option actually does? And, is there some way I could configure my container so that it does show 10.2.65.75 (assuming that the container runs from a machine that uses that same IP)?

Thank you!

[Luap99]

I have no idea about your perl command but I guess you are looking at the local ip (which is 10.0.2.100 by default) and not the remote ip.

[FGasper]

Hi!

That’s right: I need the container’s local IP to be 10.2.65.75, not 10.0.2.100. Is there some way I can get there?

(Updated the original post with a simpler demonstration.)

[Luap99]

This already works you are just looking at the wrong ip:
podman run -it --network slirp4netns:port_handler=slirp4netns --publish 192.168.178.119:8080:80 alpine nc -v -n -l -p 80
This works for me, when I connect I see 192.168.178.119 as remote ip.

[FGasper]

@Luap99 The local IP is what I need, actually.

Context: I have 2 httpd instances, one containerized and the other non-containerized. I’m trying to copy the host’s httpd.conf to the container. Ideally I’d like, at least for my demonstration purposes, to keep the IPs in the entries the same.

So if httpd on the host listens on 10.2.65.75:80, I’d like the containerized httpd to do the same, with podman just mapping the container’s port 80 to the host’s 8080.

[Luap99]

This is not possible the slir4netns port handler just keeps the source ip.

With slirp4netns you cannot chnage the local ip. You could change the subnet with the cidr option but it will always take the .100 from that.

I think https://passt.top/passt/about/#pasta sounds more like what you want then but this is not yet integrated into podman.