IP-MPTCP(8) Linux IP-MPTCP(8) NAME ip-mptcp - MPTCP path manager configuration SYNOPSIS ip [ OPTIONS ] mptcp { endpoint | limits | help } ip mptcp endpoint add IFADDR [ port PORT ] [ dev IFNAME ] [ id ID ] [ FLAG- LIST ] ip mptcp endpoint delete id ID [ IFADDR ] ip mptcp endpoint change [ id ID ] [ IFADDR ] [ port PORT ] CHANGE-OPT ip mptcp endpoint show [ id ID ] ip mptcp endpoint flush FLAG-LIST := [ FLAG-LIST ] FLAG FLAG := [ signal | subflow | laminar | backup | fullmesh ] CHANGE-OPT := [ backup | nobackup | fullmesh | nofullmesh ] ip mptcp limits set [ subflow SUBFLOW_NR ] [ add_addr_accepted ADD_ADDR_AC- CEPTED_NR ] ip mptcp limits show ip mptcp monitor DESCRIPTION MPTCP is a transport protocol built on top of TCP that allows TCP connec- tions to use multiple paths to maximize resource usage and increase redun- dancy. The ip-mptcp sub-commands allow configuring several aspects of the MPTCP path manager, which is in charge of subflows creation: The endpoint object specifies the IP addresses that will be used and/or an- nounced for additional subflows: l l. ip mptcp endpoint add add new MPTCP endpoint ip mptcp endpoint delete delete existing MPTCP endpoint ip mptcp endpoint show get existing MPTCP endpoint ip mptcp endpoint flush flush all existing MPTCP endpoints IFADDR An IPv4 or IPv6 address. When used with the delete id operation, an IFADDR is only included when the ID is 0. PORT When a port number is specified, incoming MPTCP subflows for already established MPTCP sockets will be accepted on the specified port, regardless the original listener port accepting the first MPTCP sub- flow and/or this peer being actually on the client side. This option has to be used in combination with the signal flag. IFNAME is the network interface name attached to the endpoint. It is impor- tant to specify this device name linked to the address to make sure the system knows how to route packets from the specified IP address to the correct network interface. Without this, it might be re- quired to add IP rules and routes to have the expected behavior. ID is a unique numeric identifier, between 0 and 255, for the given endpoint. It is not possible to add endpoints with ID 0, because this special ID is reserved for the initial subflow. For rules linked to the initial subflow, the path-manager will look at end- points matching the same address, and port if set, ignoring the ID. signal The endpoint will be announced/signalled to each peer via an MPTCP ADD_ADDR sub-option. Typically, a server would be responsible for this. Upon reception of an ADD_ADDR sub-option, the other peer, typ- ically the client side, can try to create additional subflows, see ADD_ADDR_ACCEPTED_NR. subflow If additional subflow creation is allowed by the MPTCP limits, the MPTCP path manager will try to create an additional subflow using this endpoint as the source address after the MPTCP connection is established. A client would typically do this. laminar The endpoint will be used to create new subflows from the associated address to additional addresses announced by the other peer. This will be done if allowed by the MPTCP limits, and if the associated address is not already being used by another subflow from the same MPTCP connection. Note that the fullmesh flag takes precedence over the laminar one. Without any of these two flags, the path-manager will create new subflows to additional addresses announced by the other peer by selecting the source address from the routing tables, which is harder to configure if the announced address is not known in advance. backup If this is a subflow endpoint, the subflows created using this end- point will have the backup flag set during the connection process. This flag instructs the remote peer to only send data on a given subflow when all non-backup subflows are unavailable. When using the default packet scheduler with a 'backup' endpoint, outgoing data from the local peer is also affected: packets will only be sent from this endpoint when all non-backup subflows are unavailable. fullmesh If this is a subflow endpoint and additional subflow creation is al- lowed by the MPTCP limits, the MPTCP path manager will try to create an additional subflow for each known peer address, using this end- point as the source address. This will occur after the MPTCP connec- tion is established. If the peer did not announce any additional ad- dresses using the MPTCP ADD_ADDR sub-option, this will behave the same as a plain subflow endpoint. When the peer does announce ad- dresses, each received ADD_ADDR sub-option will trigger creation of an additional subflow to generate a full mesh topology. This fullmesh flag should always be used in combination with the subflow one to be useful, except for the address used by the initial sub- flow, where subflow is then optional. implicit In some scenarios, an MPTCP subflow can use a local address mapped by an implicit endpoint created by the in-kernel path manager. Once set, the implicit flag cannot be removed, but other flags can be added to the endpoint. Implicit endpoints cannot be created from user-space. The limits object specifies the constraints for subflow creations: l l. ip mptcp limits show get current MPTCP subflow creation limits ip mptcp limits set change the MPTCP subflow creation limits SUBFLOW_NR specifies the maximum number of additional subflows allowed for each MPTCP connection. Additional subflows can be created due to: incom- ing accepted ADD_ADDR sub-option, local subflow endpoints, addi- tional subflows started by the peer. ADD_ADDR_ACCEPTED_NR specifies the maximum number of incoming ADD_ADDR sub-options ac- cepted for each MPTCP connection. After receiving the specified num- ber of ADD_ADDR sub-options, any other incoming one will be ignored for the MPTCP connection lifetime. When an ADD_ADDR sub-option is accepted and there are no local fullmesh endpoints, the MPTCP path manager will try to create a new subflow using the address in the ADD_ADDR sub-option as the destination address and a source address determined using local routing resolution When fullmesh endpoints are available, the MPTCP path manager will try to create new sub- flows using each fullmesh endpoint as a source address and the peer's ADD_ADDR address as the destination. In both cases the SUB- FLOW_NR limit is enforced. monitor displays creation and deletion of MPTCP connections as well as ad- dition or removal of remote addresses and subflows. AUTHOR Original Manpage by Paolo Abeni iproute2 4 Apr 2020 IP-MPTCP(8)