FreeBSD/Linux Kernel Cross Reference
sys/netinet/ip_ecn.c

     /*      $OpenBSD: ip_ecn.c,v 1.9 2018/11/14 23:55:04 dlg 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 <sys/mbuf.h>
    
    #include <netinet/in.h>
    #include <netinet/ip.h>
    
    #ifdef INET6
    #include <netinet/ip6.h>
    #endif
    
    #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);
   }

Cache object: 42ecbd411704155cd74214092b2a154a