[talha7k]

Servers configured in the canonical user@host form broke deploys that
use the local registry on 2.12.0. Net::SSH.start received the raw host
from the config, so deploy@203.0.113.10 went to getaddrinfo verbatim
and resolution failed with getaddrinfo: Name or service not known before
a single image was built. SSHKit splits the user out when it connects for
the deploy commands themselves; the port forwarding setup skipped that
step. The prefix is now stripped before connecting, and authentication
still uses ssh_options[:user].

A rejected tcpip-forward also aborted the deploy. That is exactly what
happens when the remote port is already bound — for example by an
operator-managed persistent ssh -R tunnel serving the local registry.
The rejection is now logged ("Port forward rejected on ... tunnel may
already exist") and the deploy continues; a connection failure during
setup passes the same way instead of raising. If the registry really is
unreachable, the deploy still fails later with the registry error.

Repro on 2.12.0: servers: [ "deploy@<ip>" ] with a remote builder and a
local registry, then kamal deploy (or kamal app pull) — it dies with
getaddrinfo during "Setting up local registry port forwarding". With the
patch the same config forwards to the bare host and deploys.

Tests added for the PortForwarding class: the user prefix is stripped
when connecting, and both a rejected forward and a failed connection are
logged without aborting the deploy.

[Copilot]

Copilot review overview

🟡 Changes recommended

The host prefix’s username is discarded, causing canonical deploy@host configurations to authenticate as the configured default user instead.

Review effort: Balanced
Findings: 1

Open (1)

• Preserve username from user@​host when configuring SSH · New

What changed in this PR

Updates local-registry SSH port forwarding to handle user@host server addresses and tolerate tunnel setup failures.

Changes:

• Strips the user prefix before hostname resolution.
• Logs rejected forwards and connection failures without aborting immediately.
• Adds focused port-forwarding tests.

[!TIP]
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File	Description
lib/​kamal/​cli/​build/​port_forwarding.rb	Updates SSH connection and failure handling.
test/​cli/​build/​port_forwarding_test.rb	Tests hostname parsing and recoverable failures.

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