mptcp_subflow_info
mfi.size_sfinfo_kernel = sizeof(struct mptcp_subflow_info);
sizeof(struct mptcp_subflow_info));
struct mptcp_subflow_info sfinfo;
offsetof(struct mptcp_subflow_info, addrs))
struct mptcp_subflow_info sfinfo[2];
mfi.size_sfinfo_user = sizeof(struct mptcp_subflow_info);
MIN(mfi.size_sfinfo_kernel, sizeof(struct mptcp_subflow_info)));