1 /* $NetBSD: npf_sendpkt.c,v 1.16 2016/12/26 23:05:06 christos Exp $ */ 2 3 /*- 4 * Copyright (c) 2010-2011 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 #ifdef _KERNEL 37 #include <sys/cdefs.h> 38 __KERNEL_RCSID(0, "$NetBSD: npf_sendpkt.c,v 1.16 2016/12/26 23:05:06 christos Exp $"); 39 40 #include <sys/param.h> 41 #include <sys/types.h> 42 43 #include <netinet/in_systm.h> 44 #include <netinet/in.h> 45 #include <netinet/ip.h> 46 #include <netinet/ip_icmp.h> 47 #include <netinet/ip_var.h> 48 #include <netinet/tcp.h> 49 #include <netinet/ip6.h> 50 #include <netinet/icmp6.h> 51 #include <netinet6/ip6_var.h> 52 #include <sys/mbuf.h> 53 #endif 54 55 #include "npf_impl.h" 56 57 #define DEFAULT_IP_TTL (ip_defttl) 58 59 #if defined(_NPF_STANDALONE) 60 #define m_gethdr(t, f) npf->mbufops->alloc(0, 0) 61 #define m_freem(m) npc->npc_ctx->mbufops->free(m) 62 #define mtod(m,t) ((t)((npf)->mbufops->getdata(m))) 63 #endif 64 65 #if !defined(INET6) || defined(_NPF_STANDALONE) 66 #define in6_cksum(...) 0 67 #define ip6_output(...) 0 68 #define icmp6_error(m, ...) m_freem(m) 69 #endif 70 71 /* 72 * npf_return_tcp: return a TCP reset (RST) packet. 73 */ 74 static int 75 npf_return_tcp(npf_cache_t *npc) 76 { 77 npf_t *npf = npc->npc_ctx; 78 struct mbuf *m; 79 struct ip *ip = NULL; 80 struct ip6_hdr *ip6 = NULL; 81 struct tcphdr *oth, *th; 82 tcp_seq seq, ack; 83 int tcpdlen, len; 84 uint32_t win; 85 86 /* Fetch relevant data. */ 87 KASSERT(npf_iscached(npc, NPC_IP46)); 88 KASSERT(npf_iscached(npc, NPC_LAYER4)); 89 tcpdlen = npf_tcpsaw(npc, &seq, &ack, &win); 90 oth = npc->npc_l4.tcp; 91 92 if (oth->th_flags & TH_RST) { 93 return 0; 94 } 95 96 /* Create and setup a network buffer. */ 97 if (npf_iscached(npc, NPC_IP4)) { 98 len = sizeof(struct ip) + sizeof(struct tcphdr); 99 } else if (npf_iscached(npc, NPC_IP6)) { 100 len = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 101 } else { 102 return EINVAL; 103 } 104 105 m = m_gethdr(M_DONTWAIT, MT_HEADER); 106 if (m == NULL) { 107 return ENOMEM; 108 } 109 #if !defined(_NPF_STANDALONE) 110 m->m_data += max_linkhdr; 111 m->m_len = len; 112 m->m_pkthdr.len = len; 113 (void)npf; 114 #endif 115 if (npf_iscached(npc, NPC_IP4)) { 116 struct ip *oip = npc->npc_ip.v4; 117 118 ip = mtod(m, struct ip *); 119 memset(ip, 0, len); 120 121 /* 122 * First, partially fill IPv4 header for TCP checksum. 123 * Note: IP length contains TCP header length. 124 */ 125 ip->ip_p = IPPROTO_TCP; 126 ip->ip_src.s_addr = oip->ip_dst.s_addr; 127 ip->ip_dst.s_addr = oip->ip_src.s_addr; 128 ip->ip_len = htons(sizeof(struct tcphdr)); 129 130 th = (struct tcphdr *)(ip + 1); 131 } else { 132 struct ip6_hdr *oip = npc->npc_ip.v6; 133 134 KASSERT(npf_iscached(npc, NPC_IP6)); 135 ip6 = mtod(m, struct ip6_hdr *); 136 memset(ip6, 0, len); 137 138 ip6->ip6_nxt = IPPROTO_TCP; 139 ip6->ip6_hlim = IPV6_DEFHLIM; 140 memcpy(&ip6->ip6_src, &oip->ip6_dst, sizeof(struct in6_addr)); 141 memcpy(&ip6->ip6_dst, &oip->ip6_src, sizeof(struct in6_addr)); 142 ip6->ip6_plen = htons(len); 143 ip6->ip6_vfc = IPV6_VERSION; 144 145 th = (struct tcphdr *)(ip6 + 1); 146 } 147 148 /* 149 * Construct TCP header and compute the checksum. 150 */ 151 th->th_sport = oth->th_dport; 152 th->th_dport = oth->th_sport; 153 th->th_seq = htonl(ack); 154 if (oth->th_flags & TH_SYN) { 155 tcpdlen++; 156 } 157 th->th_ack = htonl(seq + tcpdlen); 158 th->th_off = sizeof(struct tcphdr) >> 2; 159 th->th_flags = TH_ACK | TH_RST; 160 161 if (npf_iscached(npc, NPC_IP4)) { 162 th->th_sum = in_cksum(m, len); 163 164 /* 165 * Second, fill the rest of IPv4 header and correct IP length. 166 */ 167 ip->ip_v = IPVERSION; 168 ip->ip_hl = sizeof(struct ip) >> 2; 169 ip->ip_tos = IPTOS_LOWDELAY; 170 ip->ip_len = htons(len); 171 ip->ip_ttl = DEFAULT_IP_TTL; 172 } else { 173 KASSERT(npf_iscached(npc, NPC_IP6)); 174 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 175 sizeof(struct tcphdr)); 176 } 177 178 /* Pass to IP layer. */ 179 if (npf_iscached(npc, NPC_IP4)) { 180 return ip_output(m, NULL, NULL, IP_FORWARDING, NULL, NULL); 181 } 182 return ip6_output(m, NULL, NULL, IPV6_FORWARDING, NULL, NULL, NULL); 183 } 184 185 /* 186 * npf_return_icmp: return an ICMP error. 187 */ 188 static int 189 npf_return_icmp(const npf_cache_t *npc) 190 { 191 struct mbuf *m = nbuf_head_mbuf(npc->npc_nbuf); 192 193 if (npf_iscached(npc, NPC_IP4)) { 194 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_ADMIN_PROHIBIT, 0, 0); 195 return 0; 196 } else if (npf_iscached(npc, NPC_IP6)) { 197 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN, 0); 198 return 0; 199 } 200 return EINVAL; 201 } 202 203 /* 204 * npf_return_block: return TCP reset or ICMP host unreachable packet. 205 * 206 * => Returns true if the buffer was consumed (freed) and false otherwise. 207 */ 208 bool 209 npf_return_block(npf_cache_t *npc, const int retfl) 210 { 211 if (!npf_iscached(npc, NPC_IP46) || !npf_iscached(npc, NPC_LAYER4)) { 212 return false; 213 } 214 switch (npc->npc_proto) { 215 case IPPROTO_TCP: 216 if (retfl & NPF_RULE_RETRST) { 217 (void)npf_return_tcp(npc); 218 } 219 break; 220 case IPPROTO_UDP: 221 if (retfl & NPF_RULE_RETICMP) 222 if (npf_return_icmp(npc) == 0) 223 return true; 224 break; 225 } 226 return false; 227 } 228