Calls write(fd, buf, size) sendto(socket, …) sendmsg(socket, …) sendfile(to_fd, from_fd, …) read(fd, buf, size) readfrom(socket, …) readmsg(socket, …) int sock_sendmsg( struct socket *sock, struct msghdr *msg ) int sock_recvmsg( struct socket *sock, struct msghdr *msg, int flags ) user space kernel space