---
name: "mptcpd"
section: "8"
platform: "linux"
package: "mptcpd"
version: "0.13-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/mptcpd"
---

# mptcpd(8)

multipath TCP daemon

## NAME

mptcpd - multipath TCP daemon

## SYNOPSIS

**mptcpd** \[**-d?V**\] \[**-l** *DEST*\] \[**--debug**\] **\[--addr-flags=***FLAGS***\]** **\[--notify-flags=***FLAGS***\]** **\[--plugin-dir=***DIR***\]** **\[--path-manager=***PLUGIN***\]** **\[--load-plugins=***PLUGINS***\]** \[**--help**\] \[**--usage**\] **\[--log=***DEST***\]** \[**--version**\]

## DESCRIPTION

**mptcpd** is a daemon for Linux based operating systems that performs multipath TCP (see IETF RFC 8684) path management related operations in the user space.  It interacts with the Linux kernel through a generic netlink connection to track per-connection information, available network interfaces, request new MPTCP subflows, handle requests for subflows, etc.

## OPTIONS

**mptcpd** accepts the following command line options:

- **-d**,**--debug**

  enable debug log messages

- **-?**,**--help**

  display **mptcpd** help information

- **--usage**

  display brief **mptcpd** usage information

- **-l** *DEST***, --log=***DEST*

  log output to *DEST*, where *DEST* can be *stderr*, *syslog* or *journal*

- **--addr-flags=***FLAGS*

  set flags for announced address, where *FLAGS* is a comma separated list containing one or more of the flags *subflow*, *signal*, *backup*, and *fullmesh* that plugins that deal with the in-kernel path manager may use when advertising addresses, e.g. **--addr-flags=subflow**

- **--notify-flags=***FLAGS*

  address notification flags, where *FLAGS* is a comma separated list containing one or more of the following flags:

  - *existing*

    notify plugins of the addresses that exist at mptcpd start

  - *skip\_link\_local*

    ignore (do not notify) \[ipv6\] link local address updates

  - *skip\_loopback*

    ignore (do not notify) host (loopback) address updates

  - *check\_route*

    notify address only if a default route is available from such address and the related device. If the route check fails, it will be re-done after a little timeout, to allow e.g. DHCP to configure the host properly. Complex policy routing configuration may confuse or circumvent this check.

These flags determine whether mptpcd plugins will be notified when related addresses are updated, e.g. **--notify-flags=existing,skip\_link\_local,skip\_loopback,check\_route**

- **--plugin-dir=***DIR*

  set plugin directory to *DIR*

- **--path-manager=***PLUGIN*

  set default path manager plugin to *PLUGIN*, overriding plugin priorities

- **--load-plugins=***PLUGINS*

  set plugins to load on startup, where *PLUGINS* is a comma separated list containing one or more plugin names

- **-V**,**--version**

  display **mptcpd** version information

## FILES

- */etc/mptcpd/mptcpd.conf*

  Location of the mptcpd system configuration file.

## REPORTING BUGS

Report bugs to ⟨mptcp@lists.linux.dev⟩.

## SEE ALSO

[ip-mptcp(8)](/ip-mptcp/8.md)