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Annotation of qemu/slirp/ip_output.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1982, 1986, 1988, 1990, 1993
        !             3:  *     The Regents of the University of California.  All rights reserved.
        !             4:  *
        !             5:  * Redistribution and use in source and binary forms, with or without
        !             6:  * modification, are permitted provided that the following conditions
        !             7:  * are met:
        !             8:  * 1. Redistributions of source code must retain the above copyright
        !             9:  *    notice, this list of conditions and the following disclaimer.
        !            10:  * 2. Redistributions in binary form must reproduce the above copyright
        !            11:  *    notice, this list of conditions and the following disclaimer in the
        !            12:  *    documentation and/or other materials provided with the distribution.
        !            13:  * 3. All advertising materials mentioning features or use of this software
        !            14:  *    must display the following acknowledgement:
        !            15:  *     This product includes software developed by the University of
        !            16:  *     California, Berkeley and its contributors.
        !            17:  * 4. Neither the name of the University nor the names of its contributors
        !            18:  *    may be used to endorse or promote products derived from this software
        !            19:  *    without specific prior written permission.
        !            20:  *
        !            21:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            22:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            23:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            24:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            25:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            26:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            27:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            28:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            29:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            30:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            31:  * SUCH DAMAGE.
        !            32:  *
        !            33:  *     @(#)ip_output.c 8.3 (Berkeley) 1/21/94
        !            34:  * ip_output.c,v 1.9 1994/11/16 10:17:10 jkh Exp
        !            35:  */
        !            36: 
        !            37: /*
        !            38:  * Changes and additions relating to SLiRP are
        !            39:  * Copyright (c) 1995 Danny Gasparovski.
        !            40:  *
        !            41:  * Please read the file COPYRIGHT for the
        !            42:  * terms and conditions of the copyright.
        !            43:  */
        !            44: 
        !            45: #include <slirp.h>
        !            46: 
        !            47: u_int16_t ip_id;
        !            48: 
        !            49: /*
        !            50:  * IP output.  The packet in mbuf chain m contains a skeletal IP
        !            51:  * header (with len, off, ttl, proto, tos, src, dst).
        !            52:  * The mbuf chain containing the packet will be freed.
        !            53:  * The mbuf opt, if present, will not be freed.
        !            54:  */
        !            55: int
        !            56: ip_output(so, m0)
        !            57:        struct socket *so;
        !            58:        struct mbuf *m0;
        !            59: {
        !            60:        register struct ip *ip;
        !            61:        register struct mbuf *m = m0;
        !            62:        register int hlen = sizeof(struct ip );
        !            63:        int len, off, error = 0;
        !            64: 
        !            65:        DEBUG_CALL("ip_output");
        !            66:        DEBUG_ARG("so = %lx", (long)so);
        !            67:        DEBUG_ARG("m0 = %lx", (long)m0);
        !            68:        
        !            69:        /* We do no options */
        !            70: /*     if (opt) {
        !            71:  *             m = ip_insertoptions(m, opt, &len);
        !            72:  *             hlen = len;
        !            73:  *     }
        !            74:  */
        !            75:        ip = mtod(m, struct ip *);
        !            76:        /*
        !            77:         * Fill in IP header.
        !            78:         */
        !            79:        ip->ip_v = IPVERSION;
        !            80:        ip->ip_off &= IP_DF;
        !            81:        ip->ip_id = htons(ip_id++);
        !            82:        ip->ip_hl = hlen >> 2;
        !            83:        ipstat.ips_localout++;
        !            84: 
        !            85:        /*
        !            86:         * Verify that we have any chance at all of being able to queue
        !            87:         *      the packet or packet fragments
        !            88:         */
        !            89:        /* XXX Hmmm... */
        !            90: /*     if (if_queued > if_thresh && towrite <= 0) {
        !            91:  *             error = ENOBUFS;
        !            92:  *             goto bad;
        !            93:  *     }
        !            94:  */
        !            95:        
        !            96:        /*
        !            97:         * If small enough for interface, can just send directly.
        !            98:         */
        !            99:        if ((u_int16_t)ip->ip_len <= if_mtu) {
        !           100:                ip->ip_len = htons((u_int16_t)ip->ip_len);
        !           101:                ip->ip_off = htons((u_int16_t)ip->ip_off);
        !           102:                ip->ip_sum = 0;
        !           103:                ip->ip_sum = cksum(m, hlen);
        !           104: 
        !           105:                if_output(so, m);
        !           106:                goto done;
        !           107:        }
        !           108: 
        !           109:        /*
        !           110:         * Too large for interface; fragment if possible.
        !           111:         * Must be able to put at least 8 bytes per fragment.
        !           112:         */
        !           113:        if (ip->ip_off & IP_DF) {
        !           114:                error = -1;
        !           115:                ipstat.ips_cantfrag++;
        !           116:                goto bad;
        !           117:        }
        !           118:        
        !           119:        len = (if_mtu - hlen) &~ 7;       /* ip databytes per packet */
        !           120:        if (len < 8) {
        !           121:                error = -1;
        !           122:                goto bad;
        !           123:        }
        !           124: 
        !           125:     {
        !           126:        int mhlen, firstlen = len;
        !           127:        struct mbuf **mnext = &m->m_nextpkt;
        !           128: 
        !           129:        /*
        !           130:         * Loop through length of segment after first fragment,
        !           131:         * make new header and copy data of each part and link onto chain.
        !           132:         */
        !           133:        m0 = m;
        !           134:        mhlen = sizeof (struct ip);
        !           135:        for (off = hlen + len; off < (u_int16_t)ip->ip_len; off += len) {
        !           136:          register struct ip *mhip;
        !           137:          m = m_get();
        !           138:          if (m == 0) {
        !           139:            error = -1;
        !           140:            ipstat.ips_odropped++;
        !           141:            goto sendorfree;
        !           142:          }
        !           143:          m->m_data += if_maxlinkhdr;
        !           144:          mhip = mtod(m, struct ip *);
        !           145:          *mhip = *ip;
        !           146:                
        !           147:                /* No options */
        !           148: /*             if (hlen > sizeof (struct ip)) {
        !           149:  *                     mhlen = ip_optcopy(ip, mhip) + sizeof (struct ip);
        !           150:  *                     mhip->ip_hl = mhlen >> 2;
        !           151:  *             }
        !           152:  */
        !           153:          m->m_len = mhlen;
        !           154:          mhip->ip_off = ((off - hlen) >> 3) + (ip->ip_off & ~IP_MF);
        !           155:          if (ip->ip_off & IP_MF)
        !           156:            mhip->ip_off |= IP_MF;
        !           157:          if (off + len >= (u_int16_t)ip->ip_len)
        !           158:            len = (u_int16_t)ip->ip_len - off;
        !           159:          else 
        !           160:            mhip->ip_off |= IP_MF;
        !           161:          mhip->ip_len = htons((u_int16_t)(len + mhlen));
        !           162:          
        !           163:          if (m_copy(m, m0, off, len) < 0) {
        !           164:            error = -1;
        !           165:            goto sendorfree;
        !           166:          }
        !           167:          
        !           168:          mhip->ip_off = htons((u_int16_t)mhip->ip_off);
        !           169:          mhip->ip_sum = 0;
        !           170:          mhip->ip_sum = cksum(m, mhlen);
        !           171:          *mnext = m;
        !           172:          mnext = &m->m_nextpkt;
        !           173:          ipstat.ips_ofragments++;
        !           174:        }
        !           175:        /*
        !           176:         * Update first fragment by trimming what's been copied out
        !           177:         * and updating header, then send each fragment (in order).
        !           178:         */
        !           179:        m = m0;
        !           180:        m_adj(m, hlen + firstlen - (u_int16_t)ip->ip_len);
        !           181:        ip->ip_len = htons((u_int16_t)m->m_len);
        !           182:        ip->ip_off = htons((u_int16_t)(ip->ip_off | IP_MF));
        !           183:        ip->ip_sum = 0;
        !           184:        ip->ip_sum = cksum(m, hlen);
        !           185: sendorfree:
        !           186:        for (m = m0; m; m = m0) {
        !           187:                m0 = m->m_nextpkt;
        !           188:                m->m_nextpkt = 0;
        !           189:                if (error == 0)
        !           190:                        if_output(so, m);
        !           191:                else
        !           192:                        m_freem(m);
        !           193:        }
        !           194: 
        !           195:        if (error == 0)
        !           196:                ipstat.ips_fragmented++;
        !           197:     }
        !           198: 
        !           199: done:
        !           200:        return (error);
        !           201: 
        !           202: bad:
        !           203:        m_freem(m0);
        !           204:        goto done;
        !           205: }

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