/* $OpenBSD: ip_ecn.c,v 1.10 2025/07/08 00:47:41 jsg Exp $ */ /* $KAME: ip_ecn.c,v 1.9 2000/10/01 12:44:48 itojun Exp $ */ /* * Copyright (C) 1999 WIDE Project. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the project nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * */ /* * ECN consideration on tunnel ingress/egress operation. * http://www.aciri.org/floyd/papers/draft-ipsec-ecn-00.txt */ #include <sys/param.h> #include <sys/systm.h> #include <netinet/in.h> #include <netinet/ip.h> #include <netinet/ip_ecn.h> /* * ECN and TOS (or TCLASS) processing rules at tunnel encapsulation and * decapsulation from RFC3168: * * Outer Hdr at Inner Hdr at * Encapsulator Decapsulator * Header fields: -------------------- ------------ * DS Field copied from inner hdr no change * ECN Field constructed by (I) constructed by (E) * * ECN_ALLOWED (full functionality): * (I) if the ECN field in the inner header is set to CE, then set the * ECN field in the outer header to ECT(0). * otherwise, copy the ECN field to the outer header. * * (E) if the ECN field in the outer header is set to CE and the ECN * field of the inner header is not-ECT, drop the packet. * if the ECN field in the inner header is set to ECT(0) or ECT(1) * and the ECN field in the outer header is set to CE, then copy CE to * the inner header. otherwise, make no change to the inner header. * * ECN_FORBIDDEN (limited functionality): * (I) set the ECN field to not-ECT in the outer header. * * (E) if the ECN field in the outer header is set to CE, drop the packet. * otherwise, make no change to the ECN field in the inner header. * * the drop rule is for backward compatibility and protection against * erasure of CE. */ /* * modify outer ECN (TOS) field on ingress operation (tunnel encapsulation). * call it after you've done the default initialization/copy for the outer. */ void ip_ecn_ingress(int mode, u_int8_t *outer, u_int8_t *inner) { if (!outer || !inner) panic("NULL pointer passed to ip_ecn_ingress"); *outer = *inner; switch (mode) { case ECN_ALLOWED: /* ECN allowed */ case ECN_ALLOWED_IPSEC: /* * full-functionality: if the inner is CE, set ECT(0) * to the outer. otherwise, copy the ECN field. */ if ((*inner & IPTOS_ECN_MASK) == IPTOS_ECN_CE) *outer &= ~IPTOS_ECN_ECT1; break; case ECN_FORBIDDEN: /* ECN forbidden */ /* * limited-functionality: set not-ECT to the outer */ *outer &= ~IPTOS_ECN_MASK; break; case ECN_NOCARE: /* no consideration to ECN */ break; } } /* * modify inner ECN (TOS) field on egress operation (tunnel decapsulation). * call it after you've done the default initialization/copy for the inner. * the caller should drop the packet if the return value is 0. */ int ip_ecn_egress(int mode, u_int8_t *outer, u_int8_t *inner) { if (!outer || !inner) panic("NULL pointer passed to ip_ecn_egress"); switch (mode) { case ECN_ALLOWED: case ECN_ALLOWED_IPSEC: /* * full-functionality: if the outer is CE and the inner is * not-ECT, should drop it. otherwise, copy CE. * However, according to RFC4301, we should just leave the * inner as non-ECT for IPsec. */ if ((*outer & IPTOS_ECN_MASK) == IPTOS_ECN_CE) { if ((*inner & IPTOS_ECN_MASK) == IPTOS_ECN_NOTECT) { if (mode == ECN_ALLOWED_IPSEC) return (1); else return (0); } *inner |= IPTOS_ECN_CE; } break; case ECN_FORBIDDEN: /* ECN forbidden */ /* * limited-functionality: if the outer is CE, should drop it. * otherwise, leave the inner. */ if ((*outer & IPTOS_ECN_MASK) == IPTOS_ECN_CE) return (0); break; case ECN_NOCARE: /* no consideration to ECN */ break; } return (1); } /* * Patch the checksum with the difference between the old and new tos. * The patching is based on what pf_patch_8() and pf_cksum_fixkup() do, * but they're in pf, so we can't rely on them being available. */ void ip_tos_patch(struct ip *ip, uint8_t tos) { uint16_t old; uint16_t new; uint32_t x; old = htons(ip->ip_tos); new = htons(tos); ip->ip_tos = tos; x = ip->ip_sum + old - new; ip->ip_sum = (x) + (x >> 16); }
