slirp/sbuf.c

/*
 * Copyright (c) 1995 Danny Gasparovski.
 *
 * Please read the file COPYRIGHT for the
 * terms and conditions of the copyright.
 */

#include <slirp.h>
#include <qemu/main-loop.h>

static void sbappendsb(struct sbuf *sb, struct mbuf *m);

void
sbfree(struct sbuf *sb)
{
        free(sb->sb_data);
}

void
sbdrop(struct sbuf *sb, int num)
{
    u_int limit = sb->sb_datalen / 2;

        /*
         * We can only drop how much we have
         * This should never succeed
         */
        if((u_int)num > sb->sb_cc)
                num = sb->sb_cc;
        sb->sb_cc -= num;
        sb->sb_rptr += num;
        if(sb->sb_rptr >= sb->sb_data + sb->sb_datalen)
                sb->sb_rptr -= sb->sb_datalen;

    if (sb->sb_cc < limit && sb->sb_cc + num >= limit) {
        qemu_notify_event();
    }
}

void
sbreserve(struct sbuf *sb, int size)
{
        if (sb->sb_data) {
                /* Already alloced, realloc if necessary */
                if (sb->sb_datalen != size) {
                        sb->sb_wptr = sb->sb_rptr = sb->sb_data = (char *)realloc(sb->sb_data, size);
                        sb->sb_cc = 0;
                        if (sb->sb_wptr)
                           sb->sb_datalen = size;
                        else
                           sb->sb_datalen = 0;
                }
        } else {
                sb->sb_wptr = sb->sb_rptr = sb->sb_data = (char *)malloc(size);
                sb->sb_cc = 0;
                if (sb->sb_wptr)
                   sb->sb_datalen = size;
                else
                   sb->sb_datalen = 0;
        }
}

/*
 * Try and write() to the socket, whatever doesn't get written
 * append to the buffer... for a host with a fast net connection,
 * this prevents an unnecessary copy of the data
 * (the socket is non-blocking, so we won't hang)
 */
void
sbappend(struct socket *so, struct mbuf *m)
{
        int ret = 0;

        DEBUG_CALL("sbappend");
        DEBUG_ARG("so = %lx", (long)so);
        DEBUG_ARG("m = %lx", (long)m);
        DEBUG_ARG("m->m_len = %d", m->m_len);

        /* Shouldn't happen, but...  e.g. foreign host closes connection */
        if (m->m_len <= 0) {
                m_free(m);
                return;
        }

        /*
         * If there is urgent data, call sosendoob
         * if not all was sent, sowrite will take care of the rest
         * (The rest of this function is just an optimisation)
         */
        if (so->so_urgc) {
                sbappendsb(&so->so_rcv, m);
                m_free(m);
                sosendoob(so);
                return;
        }

        /*
         * We only write if there's nothing in the buffer,
         * ottherwise it'll arrive out of order, and hence corrupt
         */
        if (!so->so_rcv.sb_cc)
           ret = slirp_send(so, m->m_data, m->m_len, 0);

        if (ret <= 0) {
                /*
                 * Nothing was written
                 * It's possible that the socket has closed, but
                 * we don't need to check because if it has closed,
                 * it will be detected in the normal way by soread()
                 */
                sbappendsb(&so->so_rcv, m);
        } else if (ret != m->m_len) {
                /*
                 * Something was written, but not everything..
                 * sbappendsb the rest
                 */
                m->m_len -= ret;
                m->m_data += ret;
                sbappendsb(&so->so_rcv, m);
        } /* else */
        /* Whatever happened, we free the mbuf */
        m_free(m);
}

/*
 * Copy the data from m into sb
 * The caller is responsible to make sure there's enough room
 */
static void
sbappendsb(struct sbuf *sb, struct mbuf *m)
{
        int len, n,  nn;

        len = m->m_len;

        if (sb->sb_wptr < sb->sb_rptr) {
                n = sb->sb_rptr - sb->sb_wptr;
                if (n > len) n = len;
                memcpy(sb->sb_wptr, m->m_data, n);
        } else {
                /* Do the right edge first */
                n = sb->sb_data + sb->sb_datalen - sb->sb_wptr;
                if (n > len) n = len;
                memcpy(sb->sb_wptr, m->m_data, n);
                len -= n;
                if (len) {
                        /* Now the left edge */
                        nn = sb->sb_rptr - sb->sb_data;
                        if (nn > len) nn = len;
                        memcpy(sb->sb_data,m->m_data+n,nn);
                        n += nn;
                }
        }

        sb->sb_cc += n;
        sb->sb_wptr += n;
        if (sb->sb_wptr >= sb->sb_data + sb->sb_datalen)
                sb->sb_wptr -= sb->sb_datalen;
}

/*
 * Copy data from sbuf to a normal, straight buffer
 * Don't update the sbuf rptr, this will be
 * done in sbdrop when the data is acked
 */
void
sbcopy(struct sbuf *sb, int off, int len, char *to)
{
        char *from;

        from = sb->sb_rptr + off;
        if (from >= sb->sb_data + sb->sb_datalen)
                from -= sb->sb_datalen;

        if (from < sb->sb_wptr) {
                if ((u_int)len > sb->sb_cc) len = sb->sb_cc;
                memcpy(to,from,len);
        } else {
                /* re-use off */
                off = (sb->sb_data + sb->sb_datalen) - from;
                if (off > len) off = len;
                memcpy(to,from,off);
                len -= off;
                if (len)
                   memcpy(to+off,sb->sb_data,len);
        }
}