usr/src/sys/sys/unpcb.h

/*
 * Copyright (c) 1982 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 *
 *      @(#)unpcb.h     6.3 (Berkeley) %G%
 */

/*
 * Protocol control block for an active
 * instance of a UNIX internal protocol.
 *
 * A socket may be associated with an inode in the
 * file system.  If so, the unp_inode pointer holds
 * a reference count to this inode, which should be irele'd
 * when the socket goes away.
 *
 * A socket may be connected to another socket, in which
 * case the control block of the socket to which it is connected
 * is given by unp_conn.
 *
 * A socket may be referenced by a number of sockets (e.g. several
 * sockets may be connected to a datagram socket.)  These sockets
 * are in a linked list starting with unp_refs, linked through
 * unp_nextref and null-terminated.  Note that a socket may be referenced
 * by a number of other sockets and may also reference a socket (not
 * necessarily one which is referencing it).  This generates
 * the need for unp_refs and unp_nextref to be separate fields.
 *
 * Stream sockets keep copies of receive sockbuf sb_cc and sb_mbcnt
 * so that changes in the sockbuf may be computed to modify
 * back pressure on the sender accordingly.
 */
struct  unpcb {
        struct  socket *unp_socket;     /* pointer back to socket */
        struct  inode *unp_inode;       /* if associated with file */
        ino_t   unp_ino;                /* fake inode number */
        struct  unpcb *unp_conn;        /* control block of connected socket */
        struct  unpcb *unp_refs;        /* referencing socket linked list */
        struct  unpcb *unp_nextref;     /* link in unp_refs list */
        struct  mbuf *unp_addr;         /* bound address of socket */
        int     unp_cc;                 /* copy of rcv.sb_cc */
        int     unp_mbcnt;              /* copy of rcv.sb_mbcnt */
};

#define sotounpcb(so)   ((struct unpcb *)((so)->so_pcb))