Git Sagar
42f8333783
DHCP is on by default; use -no-dhcp to disable. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
143 lines
5 KiB
Markdown
143 lines
5 KiB
Markdown
# Usage
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```
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softether-go [flags]
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```
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## Required flags
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| Flag | Description |
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|---|---|
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| `-host` | SoftEther server hostname or IP |
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| `-user` | Authentication username |
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## Optional flags
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| Flag | Default | Description |
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|---|---|---|
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| `-pass` | `""` | Authentication password |
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| `-port` | `443` | Server port |
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| `-hub` | `DEFAULT` | Virtual hub name |
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| `-tap` | *(auto)* | TAP interface name (kernel-assigned if empty) |
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| `-mac` | *(auto)* | TAP interface MAC address (e.g. `5E:3B:6F:63:A8:3E`) |
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| `-plain-password` | `false` | Send password as plaintext (AuthType 2, for RADIUS/external auth) |
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| `-insecure` | `false` | Skip TLS certificate verification |
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| `-no-dhcp` | `false` | Disable built-in DHCP client |
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| `-accept-default-gateway` | `false` | Install DHCP-provided gateway as default route |
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| `-accept-static-routes` | `false` | Install DHCP classless static routes (option 121/249) |
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| `-accept-dns` | `false` | Set `/etc/resolv.conf` from DHCP-provided DNS servers |
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| `-policy-route-table` | `0` | Policy routing table number (0 = disabled) |
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| `-reconnect-delay` | `5s` | Delay between reconnection attempts |
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## Authentication
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Two authentication modes are supported:
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**Hashed password (AuthType 1)** — the default. Password is hashed with SHA-0 and combined with the server's random challenge to produce a `SecurePassword`. Used for local user accounts on the SoftEther server.
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```bash
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softether-go -host vpn.example.com -user admin -pass secret
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```
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**Plaintext password (AuthType 2)** — enabled with `-plain-password`. Password is sent as-is over TLS. Used when the server delegates authentication to an external system like RADIUS.
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```bash
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softether-go -host vpn.example.com -user admin -pass secret -plain-password
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```
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## Network configuration flags
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These flags control what the client does with the DHCP lease it receives from the VPN server.
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### `-mac`
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Sets a specific MAC address on the TAP interface before connecting. Useful for deterministic DHCP assignments — the server sees the same MAC across reconnects and can assign the same IP.
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```bash
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softether-go -host vpn.example.com -user admin -mac 5E:3B:6F:63:A8:3E
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```
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### `-no-dhcp`
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Disables the built-in DHCP client. Use this if the TAP interface will be configured manually or by an external DHCP client.
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### `-accept-default-gateway`
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Adds a default route via the DHCP-provided gateway on the TAP interface with metric 50. Before doing this, the client adds a `/32` host route to the VPN server via the current default gateway so the tunnel itself is not routed through the VPN.
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Without this flag, only the subnet route (implicit from the assigned IP/mask) is added.
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### `-accept-static-routes`
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Installs classless static routes from DHCP option 121 (RFC 3442) or option 249 (Microsoft variant). These are non-default routes pushed by the DHCP server, such as routes to specific subnets via the VPN gateway.
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If a static route entry has destination `0.0.0.0/0` (default route), it is only installed when `-accept-default-gateway` is also set. Per RFC 3442, when option 121 is present it takes precedence over option 3 (Router).
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### `-accept-dns`
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Overwrites `/etc/resolv.conf` with the DNS servers from the DHCP lease. The original file is backed up in memory and restored when the session ends (disconnect, reconnect, or shutdown).
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### `-policy-route-table`
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Enables policy routing for asymmetric return paths. Set to a routing table number (e.g. `200`). When enabled, the client adds:
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```
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ip rule add from <VPN_IP> table 200
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ip route replace default via <VPN_GW> dev <TAP> table 200
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```
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This ensures reply packets from the VPN IP are routed back through the VPN tunnel, not the default route. Needed when the VPN server forwards ports to the client — without it, reply packets leave via the home router and get dropped.
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Cleaned up on disconnect and shutdown.
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## Examples
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Minimal connection:
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```bash
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softether-go -host vpn.example.com -user admin -pass secret
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```
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Full setup with routing, DNS, and policy routing:
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```bash
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softether-go \
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-host vpn.example.com \
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-port 992 \
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-hub DEFAULT \
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-user admin \
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-pass secret \
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-plain-password \
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-tap vpn0 \
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-mac 5E:3B:6F:63:A8:3E \
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-insecure \
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-accept-default-gateway \
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-accept-static-routes \
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-accept-dns \
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-policy-route-table 200
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```
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No DHCP (manual configuration):
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```bash
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softether-go -host vpn.example.com -user admin -pass secret -no-dhcp -tap vpn0
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```
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## Docker
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The client works in containers with `NET_ADMIN` capability and the TUN device:
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```bash
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docker run --rm -it \
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--cap-add NET_ADMIN \
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--device /dev/net/tun \
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-v ./softether-go:/usr/bin/softether-go \
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alpine \
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softether-go -host vpn.example.com -user admin -pass secret \
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-plain-password -insecure -tap vpn0 \
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-accept-default-gateway -accept-dns
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```
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The container needs `iproute2` installed (`apk add iproute2` on Alpine) for the `ip` command.
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## Signals
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- **SIGINT / SIGTERM** — clean shutdown: closes tunnel, flushes TAP addresses, restores DNS, removes server host route, cleans up policy routes
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- During reconnect delay, a signal triggers immediate shutdown instead of waiting
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