usr/src/sys/kern/uipc_socket2.c

/*
 * Copyright (c) 1982, 1986 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 *
 *      @(#)uipc_socket2.c      7.1 (Berkeley) %G%
 */

#include "param.h"
#include "systm.h"
#include "dir.h"
#include "user.h"
#include "proc.h"
#include "file.h"
#include "inode.h"
#include "buf.h"
#include "mbuf.h"
#include "protosw.h"
#include "socket.h"
#include "socketvar.h"

/*
 * Primitive routines for operating on sockets and socket buffers
 */

/*
 * Procedures to manipulate state flags of socket
 * and do appropriate wakeups.  Normal sequence from the
 * active (originating) side is that soisconnecting() is
 * called during processing of connect() call,
 * resulting in an eventual call to soisconnected() if/when the
 * connection is established.  When the connection is torn down
 * soisdisconnecting() is called during processing of disconnect() call,
 * and soisdisconnected() is called when the connection to the peer
 * is totally severed.  The semantics of these routines are such that
 * connectionless protocols can call soisconnected() and soisdisconnected()
 * only, bypassing the in-progress calls when setting up a ``connection''
 * takes no time.
 *
 * From the passive side, a socket is created with
 * two queues of sockets: so_q0 for connections in progress
 * and so_q for connections already made and awaiting user acceptance.
 * As a protocol is preparing incoming connections, it creates a socket
 * structure queued on so_q0 by calling sonewconn().  When the connection
 * is established, soisconnected() is called, and transfers the
 * socket structure to so_q, making it available to accept().
 *
 * If a socket is closed with sockets on either
 * so_q0 or so_q, these sockets are dropped.
 *
 * If higher level protocols are implemented in
 * the kernel, the wakeups done here will sometimes
 * cause software-interrupt process scheduling.
 */

soisconnecting(so)
        register struct socket *so;
{

        so->so_state &= ~(SS_ISCONNECTED|SS_ISDISCONNECTING);
        so->so_state |= SS_ISCONNECTING;
        wakeup((caddr_t)&so->so_timeo);
}

soisconnected(so)
        register struct socket *so;
{
        register struct socket *head = so->so_head;

        if (head) {
                if (soqremque(so, 0) == 0)
                        panic("soisconnected");
                soqinsque(head, so, 1);
                sorwakeup(head);
                wakeup((caddr_t)&head->so_timeo);
        }
        so->so_state &= ~(SS_ISCONNECTING|SS_ISDISCONNECTING);
        so->so_state |= SS_ISCONNECTED;
        wakeup((caddr_t)&so->so_timeo);
        sorwakeup(so);
        sowwakeup(so);
}

soisdisconnecting(so)
        register struct socket *so;
{

        so->so_state &= ~SS_ISCONNECTING;
        so->so_state |= (SS_ISDISCONNECTING|SS_CANTRCVMORE|SS_CANTSENDMORE);
        wakeup((caddr_t)&so->so_timeo);
        sowwakeup(so);
        sorwakeup(so);
}

soisdisconnected(so)
        register struct socket *so;
{

        so->so_state &= ~(SS_ISCONNECTING|SS_ISCONNECTED|SS_ISDISCONNECTING);
        so->so_state |= (SS_CANTRCVMORE|SS_CANTSENDMORE);
        wakeup((caddr_t)&so->so_timeo);
        sowwakeup(so);
        sorwakeup(so);
}

/*
 * When an attempt at a new connection is noted on a socket
 * which accepts connections, sonewconn is called.  If the
 * connection is possible (subject to space constraints, etc.)
 * then we allocate a new structure, propoerly linked into the
 * data structure of the original socket, and return this.
 */
struct socket *
sonewconn(head)
        register struct socket *head;
{
        register struct socket *so;
        register struct mbuf *m;

        if (head->so_qlen + head->so_q0len > 3 * head->so_qlimit / 2)
                goto bad;
        m = m_getclr(M_DONTWAIT, MT_SOCKET);
        if (m == NULL)
                goto bad;
        so = mtod(m, struct socket *);
        so->so_type = head->so_type;
        so->so_options = head->so_options &~ SO_ACCEPTCONN;
        so->so_linger = head->so_linger;
        so->so_state = head->so_state | SS_NOFDREF;
        so->so_proto = head->so_proto;
        so->so_timeo = head->so_timeo;
        so->so_pgrp = head->so_pgrp;
        soqinsque(head, so, 0);
        if ((*so->so_proto->pr_usrreq)(so, PRU_ATTACH,
            (struct mbuf *)0, (struct mbuf *)0, (struct mbuf *)0)) {
                (void) soqremque(so, 0);
                (void) m_free(m);
                goto bad;
        }
        return (so);
bad:
        return ((struct socket *)0);
}

soqinsque(head, so, q)
        register struct socket *head, *so;
        int q;
{

        so->so_head = head;
        if (q == 0) {
                head->so_q0len++;
                so->so_q0 = head->so_q0;
                head->so_q0 = so;
        } else {
                head->so_qlen++;
                so->so_q = head->so_q;
                head->so_q = so;
        }
}

soqremque(so, q)
        register struct socket *so;
        int q;
{
        register struct socket *head, *prev, *next;

        head = so->so_head;
        prev = head;
        for (;;) {
                next = q ? prev->so_q : prev->so_q0;
                if (next == so)
                        break;
                if (next == head)
                        return (0);
                prev = next;
        }
        if (q == 0) {
                prev->so_q0 = next->so_q0;
                head->so_q0len--;
        } else {
                prev->so_q = next->so_q;
                head->so_qlen--;
        }
        next->so_q0 = next->so_q = 0;
        next->so_head = 0;
        return (1);
}

/*
 * Socantsendmore indicates that no more data will be sent on the
 * socket; it would normally be applied to a socket when the user
 * informs the system that no more data is to be sent, by the protocol
 * code (in case PRU_SHUTDOWN).  Socantrcvmore indicates that no more data
 * will be received, and will normally be applied to the socket by a
 * protocol when it detects that the peer will send no more data.
 * Data queued for reading in the socket may yet be read.
 */

socantsendmore(so)
        struct socket *so;
{

        so->so_state |= SS_CANTSENDMORE;
        sowwakeup(so);
}

socantrcvmore(so)
        struct socket *so;
{

        so->so_state |= SS_CANTRCVMORE;
        sorwakeup(so);
}

/*
 * Socket select/wakeup routines.
 */

/*
 * Queue a process for a select on a socket buffer.
 */
sbselqueue(sb)
        struct sockbuf *sb;
{
        register struct proc *p;

        if ((p = sb->sb_sel) && p->p_wchan == (caddr_t)&selwait)
                sb->sb_flags |= SB_COLL;
        else
                sb->sb_sel = u.u_procp;
}

/*
 * Wait for data to arrive at/drain from a socket buffer.
 */
sbwait(sb)
        struct sockbuf *sb;
{

        sb->sb_flags |= SB_WAIT;
        sleep((caddr_t)&sb->sb_cc, PZERO+1);
}

/*
 * Wakeup processes waiting on a socket buffer.
 */
sbwakeup(sb)
        register struct sockbuf *sb;
{

        if (sb->sb_sel) {
                selwakeup(sb->sb_sel, sb->sb_flags & SB_COLL);
                sb->sb_sel = 0;
                sb->sb_flags &= ~SB_COLL;
        }
        if (sb->sb_flags & SB_WAIT) {
                sb->sb_flags &= ~SB_WAIT;
                wakeup((caddr_t)&sb->sb_cc);
        }
}

/*
 * Wakeup socket readers and writers.
 * Do asynchronous notification via SIGIO
 * if the socket has the SS_ASYNC flag set.
 */
sowakeup(so, sb)
        register struct socket *so;
        struct sockbuf *sb;
{
        register struct proc *p;

        sbwakeup(sb);
        if (so->so_state & SS_ASYNC) {
                if (so->so_pgrp < 0)
                        gsignal(-so->so_pgrp, SIGIO);
                else if (so->so_pgrp > 0 && (p = pfind(so->so_pgrp)) != 0)
                        psignal(p, SIGIO);
        }
}

/*
 * Socket buffer (struct sockbuf) utility routines.
 *
 * Each socket contains two socket buffers: one for sending data and
 * one for receiving data.  Each buffer contains a queue of mbufs,
 * information about the number of mbufs and amount of data in the
 * queue, and other fields allowing select() statements and notification
 * on data availability to be implemented.
 *
 * Data stored in a socket buffer is maintained as a list of records.
 * Each record is a list of mbufs chained together with the m_next
 * field.  Records are chained together with the m_act field. The upper
 * level routine soreceive() expects the following conventions to be
 * observed when placing information in the receive buffer:
 *
 * 1. If the protocol requires each message be preceded by the sender's
 *    name, then a record containing that name must be present before
 *    any associated data (mbuf's must be of type MT_SONAME).
 * 2. If the protocol supports the exchange of ``access rights'' (really
 *    just additional data associated with the message), and there are
 *    ``rights'' to be received, then a record containing this data
 *    should be present (mbuf's must be of type MT_RIGHTS).
 * 3. If a name or rights record exists, then it must be followed by
 *    a data record, perhaps of zero length.
 *
 * Before using a new socket structure it is first necessary to reserve
 * buffer space to the socket, by calling sbreserve().  This commits
 * some of the available buffer space in the system buffer pool for the
 * socket.  The space should be released by calling sbrelease() when the
 * socket is destroyed.
 */

soreserve(so, sndcc, rcvcc)
        register struct socket *so;
        int sndcc, rcvcc;
{

        if (sbreserve(&so->so_snd, sndcc) == 0)
                goto bad;
        if (sbreserve(&so->so_rcv, rcvcc) == 0)
                goto bad2;
        return (0);
bad2:
        sbrelease(&so->so_snd);
bad:
        return (ENOBUFS);
}

/*
 * Allot mbufs to a sockbuf.
 * Attempt to scale cc so that mbcnt doesn't become limiting
 * if buffering efficiency is near the normal case.
 */
sbreserve(sb, cc)
        struct sockbuf *sb;
{

        if ((unsigned) cc > (unsigned)SB_MAX * CLBYTES / (2 * MSIZE + CLBYTES))
                return (0);
        sb->sb_hiwat = cc;
        sb->sb_mbmax = MIN(cc * 2, SB_MAX);
        return (1);
}

/*
 * Free mbufs held by a socket, and reserved mbuf space.
 */
sbrelease(sb)
        struct sockbuf *sb;
{

        sbflush(sb);
        sb->sb_hiwat = sb->sb_mbmax = 0;
}

/*
 * Routines to add and remove
 * data from an mbuf queue.
 *
 * The routines sbappend() or sbappendrecord() are normally called to
 * append new mbufs to a socket buffer, after checking that adequate
 * space is available, comparing the function sbspace() with the amount
 * of data to be added.  sbappendrecord() differs from sbappend() in
 * that data supplied is treated as the beginning of a new record.
 * To place a sender's address, optional access rights, and data in a
 * socket receive buffer, sbappendaddr() should be used.  To place
 * access rights and data in a socket receive buffer, sbappendrights()
 * should be used.  In either case, the new data begins a new record.
 * Note that unlike sbappend() and sbappendrecord(), these routines check
 * for the caller that there will be enough space to store the data.
 * Each fails if there is not enough space, or if it cannot find mbufs
 * to store additional information in.
 *
 * Reliable protocols may use the socket send buffer to hold data
 * awaiting acknowledgement.  Data is normally copied from a socket
 * send buffer in a protocol with m_copy for output to a peer,
 * and then removing the data from the socket buffer with sbdrop()
 * or sbdroprecord() when the data is acknowledged by the peer.
 */

/*
 * Append mbuf chain m to the last record in the
 * socket buffer sb.  The additional space associated
 * the mbuf chain is recorded in sb.  Empty mbufs are
 * discarded and mbufs are compacted where possible.
 */
sbappend(sb, m)
        struct sockbuf *sb;
        struct mbuf *m;
{
        register struct mbuf *n;

        if (m == 0)
                return;
        if (n = sb->sb_mb) {
                while (n->m_act)
                        n = n->m_act;
                while (n->m_next)
                        n = n->m_next;
        }
        sbcompress(sb, m, n);
}

/*
 * As above, except the mbuf chain
 * begins a new record.
 */
sbappendrecord(sb, m0)
        register struct sockbuf *sb;
        register struct mbuf *m0;
{
        register struct mbuf *m;

        if (m0 == 0)
                return;
        if (m = sb->sb_mb)
                while (m->m_act)
                        m = m->m_act;
        /*
         * Put the first mbuf on the queue.
         * Note this permits zero length records.
         */
        sballoc(sb, m0);
        if (m)
                m->m_act = m0;
        else
                sb->sb_mb = m0;
        m = m0->m_next;
        m0->m_next = 0;
        sbcompress(sb, m, m0);
}

/*
 * Append address and data, and optionally, rights
 * to the receive queue of a socket.  Return 0 if
 * no space in sockbuf or insufficient mbufs.
 */
sbappendaddr(sb, asa, m0, rights0)
        register struct sockbuf *sb;
        struct sockaddr *asa;
        struct mbuf *rights0, *m0;
{
        register struct mbuf *m, *n;
        int space = sizeof (*asa);

        for (m = m0; m; m = m->m_next)
                space += m->m_len;
        if (rights0)
                space += rights0->m_len;
        if (space > sbspace(sb))
                return (0);
        MGET(m, M_DONTWAIT, MT_SONAME);
        if (m == 0)
                return (0);
        *mtod(m, struct sockaddr *) = *asa;
        m->m_len = sizeof (*asa);
        if (rights0 && rights0->m_len) {
                m->m_next = m_copy(rights0, 0, rights0->m_len);
                if (m->m_next == 0) {
                        m_freem(m);
                        return (0);
                }
                sballoc(sb, m->m_next);
        }
        sballoc(sb, m);
        if (n = sb->sb_mb) {
                while (n->m_act)
                        n = n->m_act;
                n->m_act = m;
        } else
                sb->sb_mb = m;
        if (m->m_next)
                m = m->m_next;
        if (m0)
                sbcompress(sb, m0, m);
        return (1);
}

sbappendrights(sb, m0, rights)
        struct sockbuf *sb;
        struct mbuf *rights, *m0;
{
        register struct mbuf *m, *n;
        int space = 0;

        if (rights == 0)
                panic("sbappendrights");
        for (m = m0; m; m = m->m_next)
                space += m->m_len;
        space += rights->m_len;
        if (space > sbspace(sb))
                return (0);
        m = m_copy(rights, 0, rights->m_len);
        if (m == 0)
                return (0);
        sballoc(sb, m);
        if (n = sb->sb_mb) {
                while (n->m_act)
                        n = n->m_act;
                n->m_act = m;
        } else
                sb->sb_mb = m;
        if (m0)
                sbcompress(sb, m0, m);
        return (1);
}

/*
 * Compress mbuf chain m into the socket
 * buffer sb following mbuf n.  If n
 * is null, the buffer is presumed empty.
 */
sbcompress(sb, m, n)
        register struct sockbuf *sb;
        register struct mbuf *m, *n;
{

        while (m) {
                if (m->m_len == 0) {
                        m = m_free(m);
                        continue;
                }
                if (n && n->m_off <= MMAXOFF && m->m_off <= MMAXOFF &&
                    (n->m_off + n->m_len + m->m_len) <= MMAXOFF &&
                    n->m_type == m->m_type) {
                        bcopy(mtod(m, caddr_t), mtod(n, caddr_t) + n->m_len,
                            (unsigned)m->m_len);
                        n->m_len += m->m_len;
                        sb->sb_cc += m->m_len;
                        m = m_free(m);
                        continue;
                }
                sballoc(sb, m);
                if (n)
                        n->m_next = m;
                else
                        sb->sb_mb = m;
                n = m;
                m = m->m_next;
                n->m_next = 0;
        }
}

/*
 * Free all mbufs in a sockbuf.
 * Check that all resources are reclaimed.
 */
sbflush(sb)
        register struct sockbuf *sb;
{

        if (sb->sb_flags & SB_LOCK)
                panic("sbflush");
        while (sb->sb_mbcnt)
                sbdrop(sb, (int)sb->sb_cc);
        if (sb->sb_cc || sb->sb_mbcnt || sb->sb_mb)
                panic("sbflush 2");
}

/*
 * Drop data from (the front of) a sockbuf.
 */
sbdrop(sb, len)
        register struct sockbuf *sb;
        register int len;
{
        register struct mbuf *m, *mn;
        struct mbuf *next;

        next = (m = sb->sb_mb) ? m->m_act : 0;
        while (len > 0) {
                if (m == 0) {
                        if (next == 0)
                                panic("sbdrop");
                        m = next;
                        next = m->m_act;
                        continue;
                }
                if (m->m_len > len) {
                        m->m_len -= len;
                        m->m_off += len;
                        sb->sb_cc -= len;
                        break;
                }
                len -= m->m_len;
                sbfree(sb, m);
                MFREE(m, mn);
                m = mn;
        }
        while (m && m->m_len == 0) {
                sbfree(sb, m);
                MFREE(m, mn);
                m = mn;
        }
        if (m) {
                sb->sb_mb = m;
                m->m_act = next;
        } else
                sb->sb_mb = next;
}

/*
 * Drop a record off the front of a sockbuf
 * and move the next record to the front.
 */
sbdroprecord(sb)
        register struct sockbuf *sb;
{
        register struct mbuf *m, *mn;

        m = sb->sb_mb;
        if (m) {
                sb->sb_mb = m->m_act;
                do {
                        sbfree(sb, m);
                        MFREE(m, mn);
                } while (m = mn);
        }
}