The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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

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    1 /*      $KAME: ip_encap.c,v 1.41 2001/03/15 08:35:08 itojun Exp $       */
    2 
    3 /*-
    4  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. Neither the name of the project nor the names of its contributors
   16  *    may be used to endorse or promote products derived from this software
   17  *    without specific prior written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
   20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
   23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  */
   31 /*
   32  * My grandfather said that there's a devil inside tunnelling technology...
   33  *
   34  * We have surprisingly many protocols that want packets with IP protocol
   35  * #4 or #41.  Here's a list of protocols that want protocol #41:
   36  *      RFC1933 configured tunnel
   37  *      RFC1933 automatic tunnel
   38  *      RFC2401 IPsec tunnel
   39  *      RFC2473 IPv6 generic packet tunnelling
   40  *      RFC2529 6over4 tunnel
   41  *      mobile-ip6 (uses RFC2473)
   42  *      RFC3056 6to4 tunnel
   43  *      isatap tunnel
   44  * Here's a list of protocol that want protocol #4:
   45  *      RFC1853 IPv4-in-IPv4 tunnelling
   46  *      RFC2003 IPv4 encapsulation within IPv4
   47  *      RFC2344 reverse tunnelling for mobile-ip4
   48  *      RFC2401 IPsec tunnel
   49  * Well, what can I say.  They impose different en/decapsulation mechanism
   50  * from each other, so they need separate protocol handler.  The only one
   51  * we can easily determine by protocol # is IPsec, which always has
   52  * AH/ESP/IPComp header right after outer IP header.
   53  *
   54  * So, clearly good old protosw does not work for protocol #4 and #41.
   55  * The code will let you match protocol via src/dst address pair.
   56  */
   57 /* XXX is M_NETADDR correct? */
   58 
   59 #include <sys/cdefs.h>
   60 __FBSDID("$FreeBSD$");
   61 
   62 #include "opt_mrouting.h"
   63 #include "opt_inet.h"
   64 #include "opt_inet6.h"
   65 
   66 #include <sys/param.h>
   67 #include <sys/systm.h>
   68 #include <sys/lock.h>
   69 #include <sys/mutex.h>
   70 #include <sys/socket.h>
   71 #include <sys/sockio.h>
   72 #include <sys/mbuf.h>
   73 #include <sys/errno.h>
   74 #include <sys/protosw.h>
   75 #include <sys/queue.h>
   76 
   77 #include <net/if.h>
   78 #include <net/route.h>
   79 
   80 #include <netinet/in.h>
   81 #include <netinet/in_systm.h>
   82 #include <netinet/ip.h>
   83 #include <netinet/ip_var.h>
   84 #include <netinet/ip_encap.h>
   85 
   86 #ifdef INET6
   87 #include <netinet/ip6.h>
   88 #include <netinet6/ip6_var.h>
   89 #endif
   90 
   91 #include <machine/stdarg.h>
   92 
   93 #include <sys/kernel.h>
   94 #include <sys/malloc.h>
   95 static MALLOC_DEFINE(M_NETADDR, "encap_export_host", "Export host address structure");
   96 
   97 static void encap_add(struct encaptab *);
   98 static int mask_match(const struct encaptab *, const struct sockaddr *,
   99                 const struct sockaddr *);
  100 static void encap_fillarg(struct mbuf *, void *);
  101 
  102 /*
  103  * All global variables in ip_encap.c are locked using encapmtx.
  104  */
  105 static struct mtx encapmtx;
  106 MTX_SYSINIT(encapmtx, &encapmtx, "encapmtx", MTX_DEF);
  107 static LIST_HEAD(, encaptab) encaptab = LIST_HEAD_INITIALIZER(encaptab);
  108 
  109 #ifdef INET
  110 int
  111 encap4_input(struct mbuf **mp, int *offp, int proto)
  112 {
  113         struct ip *ip;
  114         struct mbuf *m;
  115         struct sockaddr_in s, d;
  116         const struct protosw *psw;
  117         struct encaptab *ep, *match;
  118         void *arg;
  119         int matchprio, off, prio;
  120 
  121         m = *mp;
  122         off = *offp;
  123         ip = mtod(m, struct ip *);
  124 
  125         bzero(&s, sizeof(s));
  126         s.sin_family = AF_INET;
  127         s.sin_len = sizeof(struct sockaddr_in);
  128         s.sin_addr = ip->ip_src;
  129         bzero(&d, sizeof(d));
  130         d.sin_family = AF_INET;
  131         d.sin_len = sizeof(struct sockaddr_in);
  132         d.sin_addr = ip->ip_dst;
  133 
  134         arg = NULL;
  135         psw = NULL;
  136         match = NULL;
  137         matchprio = 0;
  138         mtx_lock(&encapmtx);
  139         LIST_FOREACH(ep, &encaptab, chain) {
  140                 if (ep->af != AF_INET)
  141                         continue;
  142                 if (ep->proto >= 0 && ep->proto != proto)
  143                         continue;
  144                 if (ep->func)
  145                         prio = (*ep->func)(m, off, proto, ep->arg);
  146                 else {
  147                         /*
  148                          * it's inbound traffic, we need to match in reverse
  149                          * order
  150                          */
  151                         prio = mask_match(ep, (struct sockaddr *)&d,
  152                             (struct sockaddr *)&s);
  153                 }
  154 
  155                 /*
  156                  * We prioritize the matches by using bit length of the
  157                  * matches.  mask_match() and user-supplied matching function
  158                  * should return the bit length of the matches (for example,
  159                  * if both src/dst are matched for IPv4, 64 should be returned).
  160                  * 0 or negative return value means "it did not match".
  161                  *
  162                  * The question is, since we have two "mask" portion, we
  163                  * cannot really define total order between entries.
  164                  * For example, which of these should be preferred?
  165                  * mask_match() returns 48 (32 + 16) for both of them.
  166                  *      src=3ffe::/16, dst=3ffe:501::/32
  167                  *      src=3ffe:501::/32, dst=3ffe::/16
  168                  *
  169                  * We need to loop through all the possible candidates
  170                  * to get the best match - the search takes O(n) for
  171                  * n attachments (i.e. interfaces).
  172                  */
  173                 if (prio <= 0)
  174                         continue;
  175                 if (prio > matchprio) {
  176                         matchprio = prio;
  177                         match = ep;
  178                 }
  179         }
  180         if (match != NULL) {
  181                 psw = match->psw;
  182                 arg = match->arg;
  183         }
  184         mtx_unlock(&encapmtx);
  185 
  186         if (match != NULL) {
  187                 /* found a match, "match" has the best one */
  188                 if (psw != NULL && psw->pr_input != NULL) {
  189                         encap_fillarg(m, arg);
  190                         (*psw->pr_input)(mp, offp, proto);
  191                 } else
  192                         m_freem(m);
  193                 return (IPPROTO_DONE);
  194         }
  195 
  196         /* last resort: inject to raw socket */
  197         return (rip_input(mp, offp, proto));
  198 }
  199 #endif
  200 
  201 #ifdef INET6
  202 int
  203 encap6_input(struct mbuf **mp, int *offp, int proto)
  204 {
  205         struct mbuf *m = *mp;
  206         struct ip6_hdr *ip6;
  207         struct sockaddr_in6 s, d;
  208         const struct protosw *psw;
  209         struct encaptab *ep, *match;
  210         void *arg;
  211         int prio, matchprio;
  212 
  213         ip6 = mtod(m, struct ip6_hdr *);
  214 
  215         bzero(&s, sizeof(s));
  216         s.sin6_family = AF_INET6;
  217         s.sin6_len = sizeof(struct sockaddr_in6);
  218         s.sin6_addr = ip6->ip6_src;
  219         bzero(&d, sizeof(d));
  220         d.sin6_family = AF_INET6;
  221         d.sin6_len = sizeof(struct sockaddr_in6);
  222         d.sin6_addr = ip6->ip6_dst;
  223 
  224         arg = NULL;
  225         psw = NULL;
  226         match = NULL;
  227         matchprio = 0;
  228         mtx_lock(&encapmtx);
  229         LIST_FOREACH(ep, &encaptab, chain) {
  230                 if (ep->af != AF_INET6)
  231                         continue;
  232                 if (ep->proto >= 0 && ep->proto != proto)
  233                         continue;
  234                 if (ep->func)
  235                         prio = (*ep->func)(m, *offp, proto, ep->arg);
  236                 else {
  237                         /*
  238                          * it's inbound traffic, we need to match in reverse
  239                          * order
  240                          */
  241                         prio = mask_match(ep, (struct sockaddr *)&d,
  242                             (struct sockaddr *)&s);
  243                 }
  244 
  245                 /* see encap4_input() for issues here */
  246                 if (prio <= 0)
  247                         continue;
  248                 if (prio > matchprio) {
  249                         matchprio = prio;
  250                         match = ep;
  251                 }
  252         }
  253         if (match != NULL) {
  254                 psw = match->psw;
  255                 arg = match->arg;
  256         }
  257         mtx_unlock(&encapmtx);
  258 
  259         if (match != NULL) {
  260                 /* found a match */
  261                 if (psw != NULL && psw->pr_input != NULL) {
  262                         encap_fillarg(m, arg);
  263                         return (*psw->pr_input)(mp, offp, proto);
  264                 } else {
  265                         m_freem(m);
  266                         return (IPPROTO_DONE);
  267                 }
  268         }
  269 
  270         /* last resort: inject to raw socket */
  271         return rip6_input(mp, offp, proto);
  272 }
  273 #endif
  274 
  275 /*lint -sem(encap_add, custodial(1)) */
  276 static void
  277 encap_add(struct encaptab *ep)
  278 {
  279 
  280         mtx_assert(&encapmtx, MA_OWNED);
  281         LIST_INSERT_HEAD(&encaptab, ep, chain);
  282 }
  283 
  284 /*
  285  * sp (src ptr) is always my side, and dp (dst ptr) is always remote side.
  286  * length of mask (sm and dm) is assumed to be same as sp/dp.
  287  * Return value will be necessary as input (cookie) for encap_detach().
  288  */
  289 const struct encaptab *
  290 encap_attach(int af, int proto, const struct sockaddr *sp,
  291     const struct sockaddr *sm, const struct sockaddr *dp,
  292     const struct sockaddr *dm, const struct protosw *psw, void *arg)
  293 {
  294         struct encaptab *ep;
  295 
  296         /* sanity check on args */
  297         if (sp->sa_len > sizeof(ep->src) || dp->sa_len > sizeof(ep->dst))
  298                 return (NULL);
  299         if (sp->sa_len != dp->sa_len)
  300                 return (NULL);
  301         if (af != sp->sa_family || af != dp->sa_family)
  302                 return (NULL);
  303 
  304         /* check if anyone have already attached with exactly same config */
  305         mtx_lock(&encapmtx);
  306         LIST_FOREACH(ep, &encaptab, chain) {
  307                 if (ep->af != af)
  308                         continue;
  309                 if (ep->proto != proto)
  310                         continue;
  311                 if (ep->src.ss_len != sp->sa_len ||
  312                     bcmp(&ep->src, sp, sp->sa_len) != 0 ||
  313                     bcmp(&ep->srcmask, sm, sp->sa_len) != 0)
  314                         continue;
  315                 if (ep->dst.ss_len != dp->sa_len ||
  316                     bcmp(&ep->dst, dp, dp->sa_len) != 0 ||
  317                     bcmp(&ep->dstmask, dm, dp->sa_len) != 0)
  318                         continue;
  319 
  320                 mtx_unlock(&encapmtx);
  321                 return (NULL);
  322         }
  323 
  324         ep = malloc(sizeof(*ep), M_NETADDR, M_NOWAIT);  /*XXX*/
  325         if (ep == NULL) {
  326                 mtx_unlock(&encapmtx);
  327                 return (NULL);
  328         }
  329         bzero(ep, sizeof(*ep));
  330 
  331         ep->af = af;
  332         ep->proto = proto;
  333         bcopy(sp, &ep->src, sp->sa_len);
  334         bcopy(sm, &ep->srcmask, sp->sa_len);
  335         bcopy(dp, &ep->dst, dp->sa_len);
  336         bcopy(dm, &ep->dstmask, dp->sa_len);
  337         ep->psw = psw;
  338         ep->arg = arg;
  339 
  340         encap_add(ep);
  341         mtx_unlock(&encapmtx);
  342         return (ep);
  343 }
  344 
  345 const struct encaptab *
  346 encap_attach_func(int af, int proto,
  347     int (*func)(const struct mbuf *, int, int, void *),
  348     const struct protosw *psw, void *arg)
  349 {
  350         struct encaptab *ep;
  351 
  352         /* sanity check on args */
  353         if (!func)
  354                 return (NULL);
  355 
  356         ep = malloc(sizeof(*ep), M_NETADDR, M_NOWAIT);  /*XXX*/
  357         if (ep == NULL)
  358                 return (NULL);
  359         bzero(ep, sizeof(*ep));
  360 
  361         ep->af = af;
  362         ep->proto = proto;
  363         ep->func = func;
  364         ep->psw = psw;
  365         ep->arg = arg;
  366 
  367         mtx_lock(&encapmtx);
  368         encap_add(ep);
  369         mtx_unlock(&encapmtx);
  370         return (ep);
  371 }
  372 
  373 int
  374 encap_detach(const struct encaptab *cookie)
  375 {
  376         const struct encaptab *ep = cookie;
  377         struct encaptab *p;
  378 
  379         mtx_lock(&encapmtx);
  380         LIST_FOREACH(p, &encaptab, chain) {
  381                 if (p == ep) {
  382                         LIST_REMOVE(p, chain);
  383                         mtx_unlock(&encapmtx);
  384                         free(p, M_NETADDR);     /*XXX*/
  385                         return 0;
  386                 }
  387         }
  388         mtx_unlock(&encapmtx);
  389 
  390         return EINVAL;
  391 }
  392 
  393 static int
  394 mask_match(const struct encaptab *ep, const struct sockaddr *sp,
  395     const struct sockaddr *dp)
  396 {
  397         struct sockaddr_storage s;
  398         struct sockaddr_storage d;
  399         int i;
  400         const u_int8_t *p, *q;
  401         u_int8_t *r;
  402         int matchlen;
  403 
  404         if (sp->sa_len > sizeof(s) || dp->sa_len > sizeof(d))
  405                 return 0;
  406         if (sp->sa_family != ep->af || dp->sa_family != ep->af)
  407                 return 0;
  408         if (sp->sa_len != ep->src.ss_len || dp->sa_len != ep->dst.ss_len)
  409                 return 0;
  410 
  411         matchlen = 0;
  412 
  413         p = (const u_int8_t *)sp;
  414         q = (const u_int8_t *)&ep->srcmask;
  415         r = (u_int8_t *)&s;
  416         for (i = 0 ; i < sp->sa_len; i++) {
  417                 r[i] = p[i] & q[i];
  418                 /* XXX estimate */
  419                 matchlen += (q[i] ? 8 : 0);
  420         }
  421 
  422         p = (const u_int8_t *)dp;
  423         q = (const u_int8_t *)&ep->dstmask;
  424         r = (u_int8_t *)&d;
  425         for (i = 0 ; i < dp->sa_len; i++) {
  426                 r[i] = p[i] & q[i];
  427                 /* XXX rough estimate */
  428                 matchlen += (q[i] ? 8 : 0);
  429         }
  430 
  431         /* need to overwrite len/family portion as we don't compare them */
  432         s.ss_len = sp->sa_len;
  433         s.ss_family = sp->sa_family;
  434         d.ss_len = dp->sa_len;
  435         d.ss_family = dp->sa_family;
  436 
  437         if (bcmp(&s, &ep->src, ep->src.ss_len) == 0 &&
  438             bcmp(&d, &ep->dst, ep->dst.ss_len) == 0) {
  439                 return matchlen;
  440         } else
  441                 return 0;
  442 }
  443 
  444 static void
  445 encap_fillarg(struct mbuf *m, void *arg)
  446 {
  447         struct m_tag *tag;
  448 
  449         if (arg != NULL) {
  450                 tag = m_tag_get(PACKET_TAG_ENCAP, sizeof(void *), M_NOWAIT);
  451                 if (tag != NULL) {
  452                         *(void**)(tag+1) = arg;
  453                         m_tag_prepend(m, tag);
  454                 }
  455         }
  456 }
  457 
  458 void *
  459 encap_getarg(struct mbuf *m)
  460 {
  461         void *p = NULL;
  462         struct m_tag *tag;
  463 
  464         tag = m_tag_find(m, PACKET_TAG_ENCAP, NULL);
  465         if (tag) {
  466                 p = *(void**)(tag+1);
  467                 m_tag_delete(m, tag);
  468         }
  469         return p;
  470 }

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