libnet/pms/nat: don't bind IPv6 ports if not supported by port driver#51616
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thaJeztah merged 2 commits intomoby:masterfrom Nov 28, 2025
Merged
libnet/pms/nat: don't bind IPv6 ports if not supported by port driver#51616thaJeztah merged 2 commits intomoby:masterfrom
thaJeztah merged 2 commits intomoby:masterfrom
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In rootless mode, the Engine needs to call the rootless port driver to know which IP address it should bind to inside of its network namespace. The slirp4netns port drivers doesn't support binding to IPv6 address, so we need to detect that before listening on the port. Before commit 201968c, this wasn't a problem because the Engine was binding the port, then calling rootless port driver to learn whether the proto/IP family was supported, and listen on the port if so. Starting with that commit, the Engine does bind + listen in one go, and then calls the port driver — this is too late. Fix the bug by checking if the port driver supports the PortBindingReq, and only allocate the port if so. Signed-off-by: Albin Kerouanton <albin.kerouanton@docker.com>
Signed-off-by: Albin Kerouanton <albin.kerouanton@docker.com>
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DOCKERD_ROOTLESS_ROOTLESSKIT_PORT_DRIVER=slirp4netns) #51591- What I did
In rootless mode, the Engine needs to call the rootless port driver to know which IP address it should bind to inside of its network namespace.
The slirp4netns port drivers doesn't support binding to IPv6 address, so we need to detect that before listening on the port.
Before commit 201968c, this wasn't a problem because the Engine was binding the port, then calling rootless port driver to learn whether the proto/IP family was supported, and listen on the port if so.
Starting with that commit, the Engine does bind + listen in one go, and then calls the port driver — this is too late. Fix the bug by checking if the port driver supports the PortBindingReq, and only allocate the port if so.
- How to verify it
Start a rootless daemon with
DOCKERD_ROOTLESS_ROOTLESSKIT_NET=slirp4netns DOCKERD_ROOTLESS_ROOTLESSKIT_PORT_DRIVER=slirp4netns, thendocker run -p 80:80 alpine.- Human readable description for the release notes