Hi Alan, Thanks for your reply.
On Fri, 2025-09-05 at 10:28 +0100, Alan Bateman wrote: > > On 05/09/2025 09:43, Geliang Tang wrote: > > > > > > : > > > > 3. Proposed Java API Changes > > > > The goal is to allow Java applications to opt-in to using MPTCP > > when > > creating sockets, without breaking existing code. The proposed > > changes > > are additive and backward-compatible. > > > > The core idea is to add a boolean mptcp parameter through the API > > layers, from the public Socket class down to the native system > > call. > > > > (moving the discussion to nio-dev and net-dev). > > Adding new constructors to legacy Socket/ServerSocket may work for > your initial prototype but would be problematic to propose as it > would bake non-standard features into the standard API. Also many > high performance servers use SocketChannel rather than Socket. > > One suggestion for a next prototype is to model the enablement of > MultiPath TCP as as a JDK-specific socket option (see > jdk.net.ExtendingSocketOptions). All of the standard APIs for > networking sockets define a setOption method for setting socket I was initially concerned that calling setOption() after Socket() creation to convert TCP to MPTCP was too late. Creating an MPTCP socket must be done during the socket() system call. > options. If modeled as a socket option then enabling can create a new > AF_INET6/SOCK_STREAM/IPPROTO_MPTCP socket and then dup2 it into place Until I saw here, it should be feasible if the socket can be created again and dup when calling setOption(). I will try to reimplement MPTCP support using jdk.net.ExtendingSocketOptions soon and give you feedback. Thanks, -Geliang > so that the original AF_INET6/SOCK_STREAM/0 socket is closed. > Enabling can be made to fail if the socket is already bound. It could > copy over existing socket options if needed. Look at the built-in > (and no longer used) SDP support for an example that does similar > with AF_INET_SDP/SOCK_STREAM/0. The only API surface would be a > socket option defined in jdk.net.ExtendingSocketOptions. > > -Alan > >
