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      1 /* $NetBSD: ip.c,v 1.5 2022/07/08 07:02:47 skrll Exp $ */
      2 
      3 /*
      4  * Copyright (c) 1992 Regents of the University of California.
      5  * Copyright (c) 2010 Zoltan Arnold NAGY
      6  * All rights reserved.
      7  *
      8  * This software was developed by the Computer Systems Engineering group
      9  * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
     10  * contributed to Berkeley.
     11  *
     12  * Redistribution and use in source and binary forms, with or without
     13  * modification, are permitted provided that the following conditions
     14  * are met:
     15  * 1. Redistributions of source code must retain the above copyright
     16  *    notice, this list of conditions and the following disclaimer.
     17  * 2. Redistributions in binary form must reproduce the above copyright
     18  *    notice, this list of conditions and the following disclaimer in the
     19  *    documentation and/or other materials provided with the distribution.
     20  * 3. All advertising materials mentioning features or use of this software
     21  *    must display the following acknowledgement:
     22  *	This product includes software developed by the University of
     23  *	California, Lawrence Berkeley Laboratory and its contributors.
     24  * 4. Neither the name of the University nor the names of its contributors
     25  *    may be used to endorse or promote products derived from this software
     26  *    without specific prior written permission.
     27  *
     28  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     29  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     30  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     31  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     32  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     33  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     34  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     35  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     36  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     37  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     38  * SUCH DAMAGE.
     39  */
     40 
     41 #include <sys/param.h>
     42 #include <sys/socket.h>
     43 #include <net/if.h>
     44 #include <net/if_ether.h>
     45 #include <netinet/in.h>
     46 #include <netinet/in_systm.h>
     47 #include <netinet/ip.h>
     48 #include <netinet/ip_var.h>
     49 #include <netinet/udp.h>
     50 #include <netinet/udp_var.h>
     51 
     52 #ifdef _STANDALONE
     53 #include <lib/libkern/libkern.h>
     54 #else
     55 #include <string.h>
     56 #endif
     57 
     58 #include "stand.h"
     59 #include "net.h"
     60 
     61 /*
     62  * sends an IP packet, if it's already constructed
     63 */
     64 static ssize_t
     65 _sendip(struct iodesc *d, struct ip *ip, size_t len)
     66 {
     67 	u_char *ea;
     68 
     69 	if (ip->ip_dst.s_addr == INADDR_BROADCAST || ip->ip_src.s_addr == 0 ||
     70 	    netmask == 0 || SAMENET(ip->ip_src, ip->ip_dst, netmask)) {
     71 		ea = arpwhohas(d, ip->ip_dst);
     72 	} else {
     73 		ea = arpwhohas(d, gateip);
     74 	}
     75 
     76 	return sendether(d, ip, len, ea, ETHERTYPE_IP);
     77 }
     78 
     79 /*
     80  * fills out the IP header
     81  * Caller must leave room for ethernet, ip and udp headers in front!
     82 */
     83 ssize_t
     84 sendip(struct iodesc *d, void *pkt, size_t len, u_int8_t proto)
     85 {
     86 	ssize_t cc;
     87 	struct ip *ip;
     88 
     89 	ip = (struct ip *)pkt - 1;
     90 	len += sizeof(*ip);
     91 
     92 	memset(ip, 0, sizeof(*ip));
     93 
     94 	ip->ip_v = IPVERSION;
     95 	ip->ip_hl = sizeof(*ip) >> 2;
     96 	ip->ip_len = htons(len);
     97 	ip->ip_p = proto;
     98 	ip->ip_ttl = IPDEFTTL;
     99 	ip->ip_src = d->myip;
    100 	ip->ip_dst = d->destip;
    101 	ip->ip_sum = ip_cksum(ip, sizeof(*ip));
    102 
    103 	cc = _sendip(d, ip, len);
    104 
    105 	if (cc == -1)
    106 		return -1;
    107 	if ((size_t)cc != len)
    108 		panic("%s: bad write (%zd != %zu)", __func__, cc, len);
    109 	return (cc - (sizeof(*ip)));
    110 }
    111 
    112 /*
    113  * reads an IP packet
    114  * WARNING: the old version stripped the IP options, if there were
    115  * any. Because we have absolutely no idea if the upper layer needs
    116  * these or not, it's best to leave them there.
    117  *
    118  * The size returned is the size indicated in the header.
    119  */
    120 ssize_t
    121 readip(struct iodesc *d, void *pkt, size_t len, time_t tleft, u_int8_t proto)
    122 {
    123 	ssize_t n;
    124 	size_t hlen;
    125 	struct ip *ip;
    126 	u_int16_t etype;
    127 
    128 	ip = (struct ip *)pkt - 1;
    129 
    130 	n = readether(d, ip, len + sizeof(*ip), tleft, &etype);
    131 	if (n == -1 || (size_t)n < sizeof(*ip))
    132 		return -1;
    133 
    134 	if (etype == ETHERTYPE_ARP) {
    135 		struct arphdr *ah = (void *)ip;
    136 		if (n < (ssize_t)(sizeof(*ah) + 2 * (ah->ar_hln + ah->ar_pln))) {
    137 			return -1;
    138 		}
    139 		if (ah->ar_op == htons(ARPOP_REQUEST)) {
    140 			/* Send ARP reply */
    141 			arp_reply(d, ah);
    142 		}
    143 		return -1;
    144 	}
    145 	if (etype != ETHERTYPE_IP) {
    146 		return -1;
    147 	}
    148 
    149 	if (ip->ip_v != IPVERSION || ip->ip_p != proto) {
    150 		return -1;
    151 	}
    152 
    153 	hlen = ip->ip_hl << 2;
    154 	if (hlen != sizeof(*ip) || ip_cksum(ip, hlen) != 0) {
    155 		return -1;
    156 	}
    157 	if (ntohs(ip->ip_len) < hlen) {
    158 		return -1;
    159 	}
    160 	if (n < ntohs(ip->ip_len)) {
    161 		return -1;
    162 	}
    163 	if (d->myip.s_addr && ip->ip_dst.s_addr != d->myip.s_addr) {
    164 		return -1;
    165 	}
    166 
    167 	return (ntohs(ip->ip_len) - hlen);
    168 }
    169