1 /* $NetBSD: npf_sendpkt.c,v 1.7 2011/11/06 02:49:03 rmind Exp $ */ 2 3 /*- 4 * Copyright (c) 2010 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This material is based upon work partially supported by The 8 * NetBSD Foundation under a contract with Mindaugas Rasiukevicius. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 /* 33 * NPF module for packet construction routines. 34 */ 35 36 #include <sys/cdefs.h> 37 __KERNEL_RCSID(0, "$NetBSD: npf_sendpkt.c,v 1.7 2011/11/06 02:49:03 rmind Exp $"); 38 39 #include <sys/param.h> 40 #include <sys/kernel.h> 41 42 #include <netinet/in_systm.h> 43 #include <netinet/in.h> 44 #include <netinet/ip.h> 45 #include <netinet/ip_icmp.h> 46 #include <netinet/ip_var.h> 47 #include <netinet/tcp.h> 48 #include <netinet/ip6.h> 49 #include <netinet/icmp6.h> 50 #include <netinet6/ip6_var.h> 51 #include <sys/mbuf.h> 52 53 #include "npf_impl.h" 54 55 #define DEFAULT_IP_TTL (ip_defttl) 56 57 /* 58 * npf_return_tcp: return a TCP reset (RST) packet. 59 */ 60 static int 61 npf_return_tcp(npf_cache_t *npc, nbuf_t *nbuf) 62 { 63 struct mbuf *m; 64 struct ip *ip = NULL; 65 struct ip6_hdr *ip6 = NULL; 66 struct tcphdr *oth, *th; 67 tcp_seq seq, ack; 68 int tcpdlen, len; 69 uint32_t win; 70 71 /* Fetch relevant data. */ 72 KASSERT(npf_iscached(npc, NPC_IP46)); 73 KASSERT(npf_iscached(npc, NPC_LAYER4)); 74 tcpdlen = npf_tcpsaw(npc, nbuf, &seq, &ack, &win); 75 oth = &npc->npc_l4.tcp; 76 77 if (oth->th_flags & TH_RST) { 78 return 0; 79 } 80 81 /* Create and setup a network buffer. */ 82 if (npf_iscached(npc, NPC_IP4)) 83 len = sizeof(struct ip) + sizeof(struct tcphdr); 84 else { 85 KASSERT(npf_iscached(npc, NPC_IP6)); 86 len = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 87 } 88 89 m = m_gethdr(M_DONTWAIT, MT_HEADER); 90 if (m == NULL) { 91 return ENOMEM; 92 } 93 m->m_data += max_linkhdr; 94 m->m_len = len; 95 m->m_pkthdr.len = len; 96 97 if (npf_iscached(npc, NPC_IP4)) { 98 struct ip *oip = &npc->npc_ip.v4; 99 100 ip = mtod(m, struct ip *); 101 memset(ip, 0, len); 102 103 /* 104 * First fill of IPv4 header, for TCP checksum. 105 * Note: IP length contains TCP header length. 106 */ 107 ip->ip_p = IPPROTO_TCP; 108 ip->ip_src.s_addr = oip->ip_dst.s_addr; 109 ip->ip_dst.s_addr = oip->ip_src.s_addr; 110 ip->ip_len = htons(sizeof(struct tcphdr)); 111 112 th = (struct tcphdr *)(ip + 1); 113 } else { 114 struct ip6_hdr *oip = &npc->npc_ip.v6; 115 116 KASSERT(npf_iscached(npc, NPC_IP6)); 117 ip6 = mtod(m, struct ip6_hdr *); 118 memset(ip6, 0, len); 119 120 ip6->ip6_nxt = IPPROTO_TCP; 121 ip6->ip6_hlim = IPV6_DEFHLIM; 122 memcpy(&ip6->ip6_src, &oip->ip6_dst, sizeof(struct in6_addr)); 123 memcpy(&ip6->ip6_dst, &oip->ip6_src, sizeof(struct in6_addr)); 124 ip6->ip6_plen = htons(len); 125 ip6->ip6_vfc = IPV6_VERSION; 126 127 th = (struct tcphdr *)(ip6 + 1); 128 } 129 130 /* Construct TCP header and compute the checksum. */ 131 th->th_sport = oth->th_dport; 132 th->th_dport = oth->th_sport; 133 th->th_seq = htonl(ack); 134 if (oth->th_flags & TH_SYN) { 135 tcpdlen++; 136 } 137 th->th_ack = htonl(seq + tcpdlen); 138 th->th_off = sizeof(struct tcphdr) >> 2; 139 th->th_flags = TH_ACK | TH_RST; 140 141 if (npf_iscached(npc, NPC_IP4)) { 142 th->th_sum = in_cksum(m, len); 143 144 /* Second fill of IPv4 header, fill correct IP length. */ 145 ip->ip_v = IPVERSION; 146 ip->ip_hl = sizeof(struct ip) >> 2; 147 ip->ip_tos = IPTOS_LOWDELAY; 148 ip->ip_len = htons(len); 149 ip->ip_ttl = DEFAULT_IP_TTL; 150 } else { 151 KASSERT(npf_iscached(npc, NPC_IP6)); 152 #ifdef INET6 153 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 154 sizeof(struct tcphdr)); 155 #else 156 KASSERT(false); 157 #endif 158 } 159 160 /* Pass to IP layer. */ 161 if (npc->npc_info & NPC_IP4) { 162 return ip_output(m, NULL, NULL, IP_FORWARDING, NULL, NULL); 163 } else { 164 #ifdef INET6 165 return ip6_output(m, NULL, NULL, IPV6_FORWARDING, NULL, NULL, NULL); 166 #else 167 return 0; 168 #endif 169 } 170 } 171 172 /* 173 * npf_return_icmp: return an ICMP error. 174 */ 175 static int 176 npf_return_icmp(npf_cache_t *npc, nbuf_t *nbuf) 177 { 178 struct mbuf *m = nbuf; 179 180 if (npf_iscached(npc, NPC_IP4)) { 181 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_ADMIN_PROHIBIT, 0, 0); 182 } else { 183 KASSERT(npf_iscached(npc, NPC_IP6)); 184 #ifdef INET6 185 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN, 0); 186 #endif 187 } 188 return 0; 189 } 190 191 /* 192 * npf_return_block: return TCP reset or ICMP host unreachable packet. 193 * TODO: user should be able to specify exact ICMP error codes in config 194 */ 195 void 196 npf_return_block(npf_cache_t *npc, nbuf_t *nbuf, const int retfl) 197 { 198 void *n_ptr = nbuf_dataptr(nbuf); 199 200 if (!npf_iscached(npc, NPC_IP46) && !npf_fetch_ip(npc, nbuf, n_ptr)) { 201 return; 202 } 203 switch (npf_cache_ipproto(npc)) { 204 case IPPROTO_TCP: 205 if (retfl & NPF_RULE_RETRST) { 206 if (!npf_fetch_tcp(npc, nbuf, n_ptr)) { 207 return; 208 } 209 (void)npf_return_tcp(npc, nbuf); 210 } 211 break; 212 case IPPROTO_UDP: 213 if (retfl & NPF_RULE_RETICMP) { 214 (void)npf_return_icmp(npc, nbuf); 215 } 216 break; 217 } 218 } 219