podman/slirp4netns: open("/dev/net/tun"): No such file or directory

[adelton]

With podman - 5.2.2-r1 on OpenWrt 24.10.0-rc5 r28304-6dacba30a7 installed, running

podman run --rm --network=host docker.io/library/busybox ip a

works fine.

Seeing podman package pulls in slirp4netns via

# opkg info podman | grep '^Depends:'
Depends: libc, conmon, libgpgme, libseccomp, nsenter, zoneinfo-simple, kmod-veth, slirp4netns, netavark, aardvark-dns, catatonit, crun

I then tried to use a more isolated network setup:

# podman run --rm --network=slirp4netns docker.io/library/busybox ip a
Error: /usr/bin/slirp4netns failed: "WARNING: Support for seccomp is experimental\nopen(\"/dev/net/tun\"): No such file or directory\nWARNING: Support for IPv6 is experimental\nchild failed(1)\nWARNING: Support for IPv6 is experimental\n"

The issue gets fixed by manually installing the tun kernel module:

# opkg install kmod-tun
Installing kmod-tun (6.6.69-r1) to root...
Downloading https://downloads.openwrt.org/releases/24.10.0-rc5/targets/mediatek/filogic/kmods/6.6.69-1-83c6d4e14f7353564d3cadaf38a15bef/kmod-tun_6.6.69-r1_aarch64_cortex-a53.ipk
Configuring kmod-tun.

But if slirp4netns needs that module for its basic operation, it should likely include the kmod-tun package as a dependency.