1/* $OpenBSD: ip_ecn.c,v 1.9 2018/11/14 23:55:04 dlg Exp $ */ 2/* $KAME: ip_ecn.c,v 1.9 2000/10/01 12:44:48 itojun Exp $ */ 3 4/* 5 * Copyright (C) 1999 WIDE Project. 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the project nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 */ 33/* 34 * ECN consideration on tunnel ingress/egress operation. 35 * http://www.aciri.org/floyd/papers/draft-ipsec-ecn-00.txt 36 */ 37 38#include <sys/param.h> 39#include <sys/systm.h> 40#include <sys/mbuf.h> 41 42#include <netinet/in.h> 43#include <netinet/ip.h> 44 45#ifdef INET6 46#include <netinet/ip6.h> 47#endif 48 49#include <netinet/ip_ecn.h> 50 51/* 52 * ECN and TOS (or TCLASS) processing rules at tunnel encapsulation and 53 * decapsulation from RFC3168: 54 * 55 * Outer Hdr at Inner Hdr at 56 * Encapsulator Decapsulator 57 * Header fields: -------------------- ------------ 58 * DS Field copied from inner hdr no change 59 * ECN Field constructed by (I) constructed by (E) 60 * 61 * ECN_ALLOWED (full functionality): 62 * (I) if the ECN field in the inner header is set to CE, then set the 63 * ECN field in the outer header to ECT(0). 64 * otherwise, copy the ECN field to the outer header. 65 * 66 * (E) if the ECN field in the outer header is set to CE and the ECN 67 * field of the inner header is not-ECT, drop the packet. 68 * if the ECN field in the inner header is set to ECT(0) or ECT(1) 69 * and the ECN field in the outer header is set to CE, then copy CE to 70 * the inner header. otherwise, make no change to the inner header. 71 * 72 * ECN_FORBIDDEN (limited functionality): 73 * (I) set the ECN field to not-ECT in the outer header. 74 * 75 * (E) if the ECN field in the outer header is set to CE, drop the packet. 76 * otherwise, make no change to the ECN field in the inner header. 77 * 78 * the drop rule is for backward compatibility and protection against 79 * erasure of CE. 80 */ 81 82/* 83 * modify outer ECN (TOS) field on ingress operation (tunnel encapsulation). 84 * call it after you've done the default initialization/copy for the outer. 85 */ 86void 87ip_ecn_ingress(int mode, u_int8_t *outer, u_int8_t *inner) 88{ 89 if (!outer || !inner) 90 panic("NULL pointer passed to ip_ecn_ingress"); 91 92 *outer = *inner; 93 switch (mode) { 94 case ECN_ALLOWED: /* ECN allowed */ 95 case ECN_ALLOWED_IPSEC: 96 /* 97 * full-functionality: if the inner is CE, set ECT(0) 98 * to the outer. otherwise, copy the ECN field. 99 */ 100 if ((*inner & IPTOS_ECN_MASK) == IPTOS_ECN_CE) 101 *outer &= ~IPTOS_ECN_ECT1; 102 break; 103 case ECN_FORBIDDEN: /* ECN forbidden */ 104 /* 105 * limited-functionality: set not-ECT to the outer 106 */ 107 *outer &= ~IPTOS_ECN_MASK; 108 break; 109 case ECN_NOCARE: /* no consideration to ECN */ 110 break; 111 } 112} 113 114/* 115 * modify inner ECN (TOS) field on egress operation (tunnel decapsulation). 116 * call it after you've done the default initialization/copy for the inner. 117 * the caller should drop the packet if the return value is 0. 118 */ 119int 120ip_ecn_egress(int mode, u_int8_t *outer, u_int8_t *inner) 121{ 122 if (!outer || !inner) 123 panic("NULL pointer passed to ip_ecn_egress"); 124 125 switch (mode) { 126 case ECN_ALLOWED: 127 case ECN_ALLOWED_IPSEC: 128 /* 129 * full-functionality: if the outer is CE and the inner is 130 * not-ECT, should drop it. otherwise, copy CE. 131 * However, according to RFC4301, we should just leave the 132 * inner as non-ECT for IPsec. 133 */ 134 if ((*outer & IPTOS_ECN_MASK) == IPTOS_ECN_CE) { 135 if ((*inner & IPTOS_ECN_MASK) == IPTOS_ECN_NOTECT) { 136 if (mode == ECN_ALLOWED_IPSEC) 137 return (1); 138 else 139 return (0); 140 } 141 *inner |= IPTOS_ECN_CE; 142 } 143 break; 144 case ECN_FORBIDDEN: /* ECN forbidden */ 145 /* 146 * limited-functionality: if the outer is CE, should drop it. 147 * otherwise, leave the inner. 148 */ 149 if ((*outer & IPTOS_ECN_MASK) == IPTOS_ECN_CE) 150 return (0); 151 break; 152 case ECN_NOCARE: /* no consideration to ECN */ 153 break; 154 } 155 return (1); 156} 157 158/* 159 * Patch the checksum with the difference between the old and new tos. 160 * The patching is based on what pf_patch_8() and pf_cksum_fixkup() do, 161 * but they're in pf, so we can't rely on them being available. 162 */ 163void 164ip_tos_patch(struct ip *ip, uint8_t tos) 165{ 166 uint16_t old; 167 uint16_t new; 168 uint32_t x; 169 170 old = htons(ip->ip_tos); 171 new = htons(tos); 172 173 ip->ip_tos = tos; 174 175 x = ip->ip_sum + old - new; 176 ip->ip_sum = (x) + (x >> 16); 177} 178