fix: SSH config ProxyJump directive parsed but never applied during connection

[inureyes]

Problem / Background

The SSH config file (~/.ssh/config) ProxyJump directive is correctly parsed but never applied during connection establishment. The get_proxy_jump() function exists in the codebase but is never called, meaning connections completely ignore the ProxyJump setting from SSH config.

This breaks compatibility with OpenSSH behavior where users expect ProxyJump directives to work automatically.

Current Behavior

• bssh parses ~/.ssh/config and reads ProxyJump directives correctly
• SshHostConfig.proxy_jump field is populated during parsing
• get_proxy_jump(hostname) method exists in src/ssh/ssh_config/mod.rs:142
• However, this method is never called anywhere in the codebase
• Connections ignore the ProxyJump setting from SSH config

Expected Behavior

When connecting to a host that has ProxyJump configured in ~/.ssh/config, bssh should automatically use that jump host. This should work similarly to OpenSSH's behavior.

Example SSH Config:

Host internal-server
    HostName 192.168.1.100
    User admin
    ProxyJump bastion.example.com

Host bastion.example.com
    User jumpuser
    Port 22

When running bssh internal-server 'ls', bssh should automatically use bastion.example.com as the jump host.

Root Cause

The function get_proxy_jump() is defined but never integrated into the connection flow:

// src/ssh/ssh_config/mod.rs:142-144
pub fn get_proxy_jump(&self, hostname: &str) -> Option<String> {
    resolver::get_proxy_jump(&self.hosts, hostname)
}

This method needs to be called during connection establishment, and the returned jump host spec should be passed to the jump host chain.

Proposed Solution

1. In src/app/initialization.rs or connection setup code, call ssh_config.get_proxy_jump(hostname)
2. Merge SSH config ProxyJump with CLI -J option (CLI should take precedence)
3. Pass the resolved jump host to the connection logic

Priority Order for Jump Host Resolution:

1. CLI -J option (highest priority)
2. SSH config ProxyJump directive
3. bssh config.yaml jump_host (when implemented - see feat: Add jump_host field support in config.yaml #115)

Acceptance Criteria

• get_proxy_jump() is called during connection setup for each target host
• ProxyJump from SSH config is used when no CLI -J option is specified
• CLI -J option takes precedence over SSH config ProxyJump
• Connections through SSH config ProxyJump work for command execution
• Connections through SSH config ProxyJump work for file transfers (upload/download)
• Add test cases for ProxyJump resolution priority

Affected Files

• src/ssh/ssh_config/mod.rs - get_proxy_jump() exists but unused
• src/ssh/ssh_config/resolver.rs - resolver function exists
• src/app/initialization.rs - needs to integrate ProxyJump resolution
• src/app/dispatcher.rs - needs to pass resolved jump host

Related Issues

• feat: Add jump_host field support in config.yaml #115 - Add jump_host support to config.yaml (different config system, lower priority)
• fix: Jump host authentication fails with empty SSH agent despite available key files #116 - Jump host auth fails with empty SSH agent (related jump host functionality)

[inureyes]

Implementation Complete

PR #119 now fully implements SSH config ProxyJump support with the following features:

Priority Order

1. CLI -J option (highest priority)
2. SSH config ProxyJump directive
3. None (direct connection)

Supported Operations

• ✅ Command execution (bssh -c cluster "command")
• ✅ File uploads (bssh upload)
• ✅ File downloads (bssh download)
• ✅ Interactive mode (bssh -c cluster -I)

Key Changes

1. Added determine_effective_jump_hosts() function with comprehensive tests
2. Integrated ProxyJump resolution in connection_manager.rs for all connection types
3. Added ssh_config parameter to all file transfer functions
4. Updated FileTransferParams to carry SSH config through command handlers
5. Modified ParallelExecutor to support ssh_config for per-node ProxyJump resolution

Example Usage

Users can now configure ProxyJump in ~/.ssh/config:

Host *.internal
    ProxyJump bastion.example.com

And bssh will automatically use this configuration:

bssh -H "user@server.internal" "hostname"  # Automatically uses ProxyJump
bssh -c cluster upload file.txt /tmp/      # Uploads through jump host
bssh -c cluster download /etc/hosts ./     # Downloads through jump host

The CLI -J option continues to override SSH config when explicitly specified.