/* $NetBSD: ip.c,v 1.4 2018/02/04 08:19:42 mrg Exp $ */ /* * ip.c (C) 1995-1998 Darren Reed * * See the IPFILTER.LICENCE file for details on licencing. */ #if !defined(lint) static __attribute__((__used__)) const char sccsid[] = "%W% %G% (C)1995"; static __attribute__((__used__)) const char rcsid[] = "@(#)Id: ip.c,v 1.1.1.2 2012/07/22 13:44:36 darrenr"; #endif #include #include #include #include #include #include #include #include #ifndef linux # include # include # include # if __FreeBSD_version >= 300000 # include # endif #endif #include #include #include #include #include #include "ipsend.h" static char *ipbuf = NULL, *ethbuf = NULL; u_short chksum(buf,len) u_short *buf; int len; { u_long sum = 0; int nwords = len >> 1; for(; nwords > 0; nwords--) sum += *buf++; sum = (sum>>16) + (sum & 0xffff); sum += (sum >>16); return (~sum); } int send_ether(nfd, buf, len, gwip) int nfd, len; char *buf; struct in_addr gwip; { static struct in_addr last_gw; static char last_arp[6] = { 0, 0, 0, 0, 0, 0}; ether_header_t *eh; char *s; int err; if (!ethbuf) ethbuf = (char *)calloc(1, 65536+1024); s = ethbuf; eh = (ether_header_t *)s; bcopy((char *)buf, s + sizeof(*eh), len); if (gwip.s_addr == last_gw.s_addr) { bcopy(last_arp, (char *)A_A eh->ether_dhost, 6); } else if (arp((char *)&gwip, (char *)A_A eh->ether_dhost) == -1) { perror("arp"); return -2; } eh->ether_type = htons(ETHERTYPE_IP); last_gw.s_addr = gwip.s_addr; err = sendip(nfd, s, sizeof(*eh) + len); return err; } /* */ int send_ip(nfd, mtu, ip, gwip, frag) int nfd, mtu; ip_t *ip; struct in_addr gwip; int frag; { static struct in_addr last_gw, local_ip; static char local_arp[6] = { 0, 0, 0, 0, 0, 0}; static char last_arp[6] = { 0, 0, 0, 0, 0, 0}; static u_short id = 0; ether_header_t *eh; ip_t ipsv; int err, iplen; if (!ipbuf) { ipbuf = (char *)malloc(65536); if (!ipbuf) { perror("malloc failed"); return -2; } } eh = (ether_header_t *)ipbuf; bzero((char *)A_A eh->ether_shost, sizeof(eh->ether_shost)); if (last_gw.s_addr && (gwip.s_addr == last_gw.s_addr)) { bcopy(last_arp, (char *)A_A eh->ether_dhost, 6); } else if (arp((char *)&gwip, (char *)A_A eh->ether_dhost) == -1) { perror("arp"); return -2; } bcopy((char *)A_A eh->ether_dhost, last_arp, sizeof(last_arp)); eh->ether_type = htons(ETHERTYPE_IP); bcopy((char *)ip, (char *)&ipsv, sizeof(*ip)); last_gw.s_addr = gwip.s_addr; iplen = ip->ip_len; ip->ip_len = htons(iplen); if (!(frag & 2)) { if (!IP_V(ip)) IP_V_A(ip, IPVERSION); if (!ip->ip_id) ip->ip_id = htons(id++); if (!ip->ip_ttl) ip->ip_ttl = 60; } if (ip->ip_src.s_addr != local_ip.s_addr) { (void) arp((char *)&ip->ip_src, (char *)A_A local_arp); bcopy(local_arp, (char *)A_A eh->ether_shost,sizeof(last_arp)); local_ip = ip->ip_src; } else bcopy(local_arp, (char *)A_A eh->ether_shost, 6); if (!frag || (sizeof(*eh) + iplen < mtu)) { ip->ip_sum = 0; ip->ip_sum = chksum((u_short *)ip, IP_HL(ip) << 2); bcopy((char *)ip, ipbuf + sizeof(*eh), iplen); err = sendip(nfd, ipbuf, sizeof(*eh) + iplen); } else { /* * Actually, this is bogus because we're putting all IP * options in every packet, which isn't always what should be * done. Will do for now. */ ether_header_t eth; char optcpy[48], ol; char *s; int i, sent = 0, ts, hlen, olen; hlen = IP_HL(ip) << 2; if (mtu < (hlen + 8)) { fprintf(stderr, "mtu (%d) < ip header size (%d) + 8\n", mtu, hlen); fprintf(stderr, "can't fragment data\n"); return -2; } ol = (IP_HL(ip) << 2) - sizeof(*ip); for (i = 0, s = (char*)(ip + 1); ol > 0; ) if (*s == IPOPT_EOL) { optcpy[i++] = *s; break; } else if (*s == IPOPT_NOP) { s++; ol--; } else { olen = (int)(*(u_char *)(s + 1)); ol -= olen; if (IPOPT_COPIED(*s)) { bcopy(s, optcpy + i, olen); i += olen; s += olen; } } if (i) { /* * pad out */ while ((i & 3) && (i & 3) != 3) optcpy[i++] = IPOPT_NOP; if ((i & 3) == 3) optcpy[i++] = IPOPT_EOL; } bcopy((char *)eh, (char *)ð, sizeof(eth)); s = (char *)ip + hlen; iplen = ntohs(ip->ip_len) - hlen; ip->ip_off |= htons(IP_MF); while (1) { if ((sent + (mtu - hlen)) >= iplen) { ip->ip_off ^= htons(IP_MF); ts = iplen - sent; } else ts = (mtu - hlen); ip->ip_off &= htons(0xe000); ip->ip_off |= htons(sent >> 3); ts += hlen; ip->ip_len = htons(ts); ip->ip_sum = 0; ip->ip_sum = chksum((u_short *)ip, hlen); bcopy((char *)ip, ipbuf + sizeof(*eh), hlen); bcopy(s + sent, ipbuf + sizeof(*eh) + hlen, ts - hlen); err = sendip(nfd, ipbuf, sizeof(*eh) + ts); bcopy((char *)ð, ipbuf, sizeof(eth)); sent += (ts - hlen); if (!(ntohs(ip->ip_off) & IP_MF)) break; else if (!(ip->ip_off & htons(0x1fff))) { hlen = i + sizeof(*ip); IP_HL_A(ip, (sizeof(*ip) + i) >> 2); bcopy(optcpy, (char *)(ip + 1), i); } } } bcopy((char *)&ipsv, (char *)ip, sizeof(*ip)); return err; } /* * send a tcp packet. */ int send_tcp(nfd, mtu, ip, gwip) int nfd, mtu; ip_t *ip; struct in_addr gwip; { static tcp_seq iss = 2; tcphdr_t *t, *t2; int thlen, i, iplen, hlen; u_32_t lbuf[20]; ip_t *ip2; iplen = ip->ip_len; hlen = IP_HL(ip) << 2; t = (tcphdr_t *)((char *)ip + hlen); ip2 = (struct ip *)lbuf; t2 = (tcphdr_t *)((char *)ip2 + sizeof(ip_t)); thlen = TCP_OFF(t) << 2; if (!thlen) thlen = sizeof(tcphdr_t); bzero((char *)ip2, sizeof(*ip2) + sizeof(*t2)); ip->ip_p = IPPROTO_TCP; ip2->ip_p = ip->ip_p; ip2->ip_src = ip->ip_src; ip2->ip_dst = ip->ip_dst; bcopy((char *)ip + hlen, (char *)t2, thlen); if (!t2->th_win) t2->th_win = htons(4096); iss += 63; i = sizeof(struct tcpiphdr) / sizeof(long); if ((t2->th_flags == TH_SYN) && !ntohs(ip->ip_off) && (lbuf[i] != htonl(0x020405b4))) { lbuf[i] = htonl(0x020405b4); bcopy((char *)ip + hlen + thlen, (char *)ip + hlen + thlen + 4, iplen - thlen - hlen); thlen += 4; } TCP_OFF_A(t2, thlen >> 2); ip2->ip_len = htons(thlen); ip->ip_len = hlen + thlen; t2->th_sum = 0; t2->th_sum = chksum((u_short *)ip2, thlen + sizeof(ip_t)); bcopy((char *)t2, (char *)ip + hlen, thlen); return send_ip(nfd, mtu, ip, gwip, 1); } /* * send a udp packet. */ int send_udp(nfd, mtu, ip, gwip) int nfd, mtu; ip_t *ip; struct in_addr gwip; { struct tcpiphdr *ti; int thlen; u_long lbuf[20]; ti = (struct tcpiphdr *)lbuf; bzero((char *)ti, sizeof(*ti)); thlen = sizeof(udphdr_t); ti->ti_pr = ip->ip_p; ti->ti_src = ip->ip_src; ti->ti_dst = ip->ip_dst; bcopy((char *)ip + (IP_HL(ip) << 2), (char *)&ti->ti_sport, sizeof(udphdr_t)); ti->ti_len = htons(thlen); ip->ip_len = (IP_HL(ip) << 2) + thlen; ti->ti_sum = 0; ti->ti_sum = chksum((u_short *)ti, thlen + sizeof(ip_t)); bcopy((char *)&ti->ti_sport, (char *)ip + (IP_HL(ip) << 2), sizeof(udphdr_t)); return send_ip(nfd, mtu, ip, gwip, 1); } /* * send an icmp packet. */ int send_icmp(nfd, mtu, ip, gwip) int nfd, mtu; ip_t *ip; struct in_addr gwip; { struct icmp *ic; ic = (struct icmp *)((char *)ip + (IP_HL(ip) << 2)); ic->icmp_cksum = 0; ic->icmp_cksum = chksum((u_short *)ic, sizeof(struct icmp)); return send_ip(nfd, mtu, ip, gwip, 1); } int send_packet(nfd, mtu, ip, gwip) int nfd, mtu; ip_t *ip; struct in_addr gwip; { switch (ip->ip_p) { case IPPROTO_TCP : return send_tcp(nfd, mtu, ip, gwip); case IPPROTO_UDP : return send_udp(nfd, mtu, ip, gwip); case IPPROTO_ICMP : return send_icmp(nfd, mtu, ip, gwip); default : return send_ip(nfd, mtu, ip, gwip, 1); } }