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_divert.c

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    1 /*
    2  * Copyright (c) 1982, 1986, 1988, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 3. All advertising materials mentioning features or use of this software
   14  *    must display the following acknowledgement:
   15  *      This product includes software developed by the University of
   16  *      California, Berkeley and its contributors.
   17  * 4. Neither the name of the University nor the names of its contributors
   18  *    may be used to endorse or promote products derived from this software
   19  *    without specific prior written permission.
   20  *
   21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31  * SUCH DAMAGE.
   32  *
   33  * $FreeBSD$
   34  */
   35 
   36 #include "opt_inet.h"
   37 #include "opt_ipfw.h"
   38 #include "opt_ipdivert.h"
   39 #include "opt_ipsec.h"
   40 
   41 #ifndef INET
   42 #error "IPDIVERT requires INET."
   43 #endif
   44 
   45 #include <sys/param.h>
   46 #include <sys/kernel.h>
   47 #include <sys/malloc.h>
   48 #include <sys/mbuf.h>
   49 #include <sys/socket.h>
   50 #include <sys/protosw.h>
   51 #include <sys/socketvar.h>
   52 #include <sys/sysctl.h>
   53 #include <sys/systm.h>
   54 #include <sys/proc.h>
   55 
   56 #include <vm/vm_zone.h>
   57 
   58 #include <net/if.h>
   59 #include <net/route.h>
   60 
   61 #include <netinet/in.h>
   62 #include <netinet/in_systm.h>
   63 #include <netinet/ip.h>
   64 #include <netinet/in_pcb.h>
   65 #include <netinet/in_var.h>
   66 #include <netinet/ip_var.h>
   67 
   68 /*
   69  * Divert sockets
   70  */
   71 
   72 /*
   73  * Allocate enough space to hold a full IP packet
   74  */
   75 #define DIVSNDQ         (65536 + 100)
   76 #define DIVRCVQ         (65536 + 100)
   77 
   78 /*
   79  * Divert sockets work in conjunction with ipfw, see the divert(4)
   80  * manpage for features.
   81  * Internally, packets selected by ipfw in ip_input() or ip_output(),
   82  * and never diverted before, are passed to the input queue of the
   83  * divert socket with a given 'divert_port' number (as specified in
   84  * the matching ipfw rule), and they are tagged with a 16 bit cookie
   85  * (representing the rule number of the matching ipfw rule), which
   86  * is passed to process reading from the socket.
   87  *
   88  * Packets written to the divert socket are again tagged with a cookie
   89  * (usually the same as above) and a destination address.
   90  * If the destination address is INADDR_ANY then the packet is
   91  * treated as outgoing and sent to ip_output(), otherwise it is
   92  * treated as incoming and sent to ip_input().
   93  * In both cases, the packet is tagged with the cookie.
   94  *
   95  * On reinjection, processing in ip_input() and ip_output()
   96  * will be exactly the same as for the original packet, except that
   97  * ipfw processing will start at the rule number after the one
   98  * written in the cookie (so, tagging a packet with a cookie of 0
   99  * will cause it to be effectively considered as a standard packet).
  100  */
  101 
  102 /* Internal variables */
  103 static struct inpcbhead divcb;
  104 static struct inpcbinfo divcbinfo;
  105 
  106 static u_long   div_sendspace = DIVSNDQ;        /* XXX sysctl ? */
  107 static u_long   div_recvspace = DIVRCVQ;        /* XXX sysctl ? */
  108 
  109 /* Optimization: have this preinitialized */
  110 static struct sockaddr_in divsrc = { sizeof(divsrc), AF_INET };
  111 
  112 /*
  113  * Initialize divert connection block queue.
  114  */
  115 void
  116 div_init(void)
  117 {
  118         LIST_INIT(&divcb);
  119         divcbinfo.listhead = &divcb;
  120         /*
  121          * XXX We don't use the hash list for divert IP, but it's easier
  122          * to allocate a one entry hash list than it is to check all
  123          * over the place for hashbase == NULL.
  124          */
  125         divcbinfo.hashbase = hashinit(1, M_PCB, &divcbinfo.hashmask);
  126         divcbinfo.porthashbase = hashinit(1, M_PCB, &divcbinfo.porthashmask);
  127         divcbinfo.ipi_zone = zinit("divcb", sizeof(struct inpcb),
  128                                    maxsockets, ZONE_INTERRUPT, 0);
  129 }
  130 
  131 /*
  132  * IPPROTO_DIVERT is not a real IP protocol; don't allow any packets
  133  * with that protocol number to enter the system from the outside.
  134  */
  135 void
  136 div_input(struct mbuf *m, int off, int proto)
  137 {
  138         ipstat.ips_noproto++;
  139         m_freem(m);
  140 }
  141 
  142 /*
  143  * Divert a packet by passing it up to the divert socket at port 'port'.
  144  *
  145  * Setup generic address and protocol structures for div_input routine,
  146  * then pass them along with mbuf chain.
  147  */
  148 void
  149 divert_packet(struct mbuf *m, int incoming, int port, int rule)
  150 {
  151         struct ip *ip;
  152         struct inpcb *inp;
  153         struct socket *sa;
  154         u_int16_t nport;
  155 
  156         /* Sanity check */
  157         KASSERT(port != 0, ("%s: port=0", __FUNCTION__));
  158 
  159         divsrc.sin_port = rule;         /* record matching rule */
  160 
  161         /* Assure header */
  162         if (m->m_len < sizeof(struct ip) &&
  163             (m = m_pullup(m, sizeof(struct ip))) == 0)
  164                 return;
  165         ip = mtod(m, struct ip *);
  166 
  167         /*
  168          * Record receive interface address, if any.
  169          * But only for incoming packets.
  170          */
  171         divsrc.sin_addr.s_addr = 0;
  172         if (incoming) {
  173                 struct ifaddr *ifa;
  174 
  175                 /* Sanity check */
  176                 KASSERT((m->m_flags & M_PKTHDR), ("%s: !PKTHDR", __FUNCTION__));
  177 
  178                 /* Find IP address for receive interface */
  179                 TAILQ_FOREACH(ifa, &m->m_pkthdr.rcvif->if_addrhead, ifa_link) {
  180                         if (ifa->ifa_addr == NULL)
  181                                 continue;
  182                         if (ifa->ifa_addr->sa_family != AF_INET)
  183                                 continue;
  184                         divsrc.sin_addr =
  185                             ((struct sockaddr_in *) ifa->ifa_addr)->sin_addr;
  186                         break;
  187                 }
  188         }
  189         /*
  190          * Record the incoming interface name whenever we have one.
  191          */
  192         bzero(&divsrc.sin_zero, sizeof(divsrc.sin_zero));
  193         if (m->m_pkthdr.rcvif) {
  194                 /*
  195                  * Hide the actual interface name in there in the 
  196                  * sin_zero array. XXX This needs to be moved to a
  197                  * different sockaddr type for divert, e.g.
  198                  * sockaddr_div with multiple fields like 
  199                  * sockaddr_dl. Presently we have only 7 bytes
  200                  * but that will do for now as most interfaces
  201                  * are 4 or less + 2 or less bytes for unit.
  202                  * There is probably a faster way of doing this,
  203                  * possibly taking it from the sockaddr_dl on the iface.
  204                  * This solves the problem of a P2P link and a LAN interface
  205                  * having the same address, which can result in the wrong
  206                  * interface being assigned to the packet when fed back
  207                  * into the divert socket. Theoretically if the daemon saves
  208                  * and re-uses the sockaddr_in as suggested in the man pages,
  209                  * this iface name will come along for the ride.
  210                  * (see div_output for the other half of this.)
  211                  */ 
  212                 snprintf(divsrc.sin_zero, sizeof(divsrc.sin_zero),
  213                         "%s%d", m->m_pkthdr.rcvif->if_name,
  214                         m->m_pkthdr.rcvif->if_unit);
  215         }
  216 
  217         /* Put packet on socket queue, if any */
  218         sa = NULL;
  219         nport = htons((u_int16_t)port);
  220         LIST_FOREACH(inp, &divcb, inp_list) {
  221                 if (inp->inp_lport == nport)
  222                         sa = inp->inp_socket;
  223         }
  224         if (sa) {
  225                 if (sbappendaddr(&sa->so_rcv, (struct sockaddr *)&divsrc,
  226                                 m, (struct mbuf *)0) == 0)
  227                         m_freem(m);
  228                 else
  229                         sorwakeup(sa);
  230         } else {
  231                 m_freem(m);
  232                 ipstat.ips_noproto++;
  233                 ipstat.ips_delivered--;
  234         }
  235 }
  236 
  237 /*
  238  * Deliver packet back into the IP processing machinery.
  239  *
  240  * If no address specified, or address is 0.0.0.0, send to ip_output();
  241  * otherwise, send to ip_input() and mark as having been received on
  242  * the interface with that address.
  243  */
  244 static int
  245 div_output(struct socket *so, struct mbuf *m,
  246         struct sockaddr_in *sin, struct mbuf *control)
  247 {
  248         int error = 0;
  249         struct m_hdr divert_tag;
  250 
  251         /*
  252          * Prepare the tag for divert info. Note that a packet
  253          * with a 0 tag in mh_data is effectively untagged,
  254          * so we could optimize that case.
  255          */
  256         divert_tag.mh_type = MT_TAG;
  257         divert_tag.mh_flags = PACKET_TAG_DIVERT;
  258         divert_tag.mh_next = m;
  259         divert_tag.mh_data = 0;         /* the matching rule # */
  260         m->m_pkthdr.rcvif = NULL;       /* XXX is it necessary ? */
  261 
  262         if (control)
  263                 m_freem(control);               /* XXX */
  264 
  265         /* Loopback avoidance and state recovery */
  266         if (sin) {
  267                 int i;
  268 
  269                 divert_tag.mh_data = (caddr_t)(int)sin->sin_port;
  270                 /*
  271                  * Find receive interface with the given name, stuffed
  272                  * (if it exists) in the sin_zero[] field.
  273                  * The name is user supplied data so don't trust its size
  274                  * or that it is zero terminated.
  275                  */
  276                 for (i = 0; sin->sin_zero[i] && i < sizeof(sin->sin_zero); i++)
  277                         ;
  278                 if ( i > 0 && i < sizeof(sin->sin_zero))
  279                         m->m_pkthdr.rcvif = ifunit(sin->sin_zero);
  280         }
  281 
  282         /* Reinject packet into the system as incoming or outgoing */
  283         if (!sin || sin->sin_addr.s_addr == 0) {
  284                 struct inpcb *const inp = sotoinpcb(so);
  285                 struct ip *const ip = mtod(m, struct ip *);
  286 
  287                 /*
  288                  * Don't allow both user specified and setsockopt options,
  289                  * and don't allow packet length sizes that will crash
  290                  */
  291                 if (((ip->ip_hl != (sizeof (*ip) >> 2)) && inp->inp_options) ||
  292                      ((u_short)ntohs(ip->ip_len) > m->m_pkthdr.len)) {
  293                         error = EINVAL;
  294                         goto cantsend;
  295                 }
  296 
  297                 /* Convert fields to host order for ip_output() */
  298                 ip->ip_len = ntohs(ip->ip_len);
  299                 ip->ip_off = ntohs(ip->ip_off);
  300 
  301                 /* Send packet to output processing */
  302                 ipstat.ips_rawout++;                    /* XXX */
  303                 error = ip_output((struct mbuf *)&divert_tag,
  304                             inp->inp_options, &inp->inp_route,
  305                             (so->so_options & SO_DONTROUTE) |
  306                             IP_ALLOWBROADCAST | IP_RAWOUTPUT,
  307                             inp->inp_moptions, NULL);
  308         } else {
  309                 if (m->m_pkthdr.rcvif == NULL) {
  310                         /*
  311                          * No luck with the name, check by IP address.
  312                          * Clear the port and the ifname to make sure
  313                          * there are no distractions for ifa_ifwithaddr.
  314                          */
  315                         struct  ifaddr *ifa;
  316 
  317                         bzero(sin->sin_zero, sizeof(sin->sin_zero));
  318                         sin->sin_port = 0;
  319                         ifa = ifa_ifwithaddr((struct sockaddr *) sin);
  320                         if (ifa == NULL) {
  321                                 error = EADDRNOTAVAIL;
  322                                 goto cantsend;
  323                         }
  324                         m->m_pkthdr.rcvif = ifa->ifa_ifp;
  325                 }
  326                 /* Send packet to input processing */
  327                 ip_input((struct mbuf *)&divert_tag);
  328         }
  329 
  330         return error;
  331 
  332 cantsend:
  333         m_freem(m);
  334         return error;
  335 }
  336 
  337 static int
  338 div_attach(struct socket *so, int proto, struct proc *p)
  339 {
  340         struct inpcb *inp;
  341         int error, s;
  342 
  343         inp  = sotoinpcb(so);
  344         if (inp)
  345                 panic("div_attach");
  346         if (p && (error = suser(p)) != 0)
  347                 return error;
  348 
  349         error = soreserve(so, div_sendspace, div_recvspace);
  350         if (error)
  351                 return error;
  352         s = splnet();
  353         error = in_pcballoc(so, &divcbinfo, p);
  354         splx(s);
  355         if (error)
  356                 return error;
  357         inp = (struct inpcb *)so->so_pcb;
  358         inp->inp_ip_p = proto;
  359         inp->inp_vflag |= INP_IPV4;
  360         inp->inp_flags |= INP_HDRINCL;
  361         return 0;
  362 }
  363 
  364 static int
  365 div_detach(struct socket *so)
  366 {
  367         struct inpcb *inp;
  368 
  369         inp = sotoinpcb(so);
  370         if (inp == 0)
  371                 panic("div_detach");
  372         in_pcbdetach(inp);
  373         return 0;
  374 }
  375 
  376 static int
  377 div_bind(struct socket *so, struct sockaddr *nam, struct proc *p)
  378 {
  379         struct inpcb *inp;
  380         int s;
  381         int error;
  382 
  383         s = splnet();
  384         inp = sotoinpcb(so);
  385         /* in_pcbbind assumes that nam is a sockaddr_in
  386          * and in_pcbbind requires a valid address. Since divert
  387          * sockets don't we need to make sure the address is
  388          * filled in properly.
  389          * XXX -- divert should not be abusing in_pcbind
  390          * and should probably have its own family.
  391          */
  392         if (nam->sa_family != AF_INET)
  393                 error = EAFNOSUPPORT;
  394         else {
  395                 ((struct sockaddr_in *)nam)->sin_addr.s_addr = INADDR_ANY;
  396                 error = in_pcbbind(inp, nam, p);
  397         }
  398         splx(s);
  399         return error;
  400 }
  401 
  402 static int
  403 div_shutdown(struct socket *so)
  404 {
  405         socantsendmore(so);
  406         return 0;
  407 }
  408 
  409 static int
  410 div_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
  411          struct mbuf *control, struct proc *p)
  412 {
  413         /* Packet must have a header (but that's about it) */
  414         if (m->m_len < sizeof (struct ip) &&
  415             (m = m_pullup(m, sizeof (struct ip))) == 0) {
  416                 ipstat.ips_toosmall++;
  417                 m_freem(m);
  418                 return EINVAL;
  419         }
  420 
  421         /* Send packet */
  422         return div_output(so, m, (struct sockaddr_in *)nam, control);
  423 }
  424 
  425 static int
  426 div_pcblist(SYSCTL_HANDLER_ARGS)
  427 {
  428         int error, i, n, s;
  429         struct inpcb *inp, **inp_list;
  430         inp_gen_t gencnt;
  431         struct xinpgen xig;
  432 
  433         /*
  434          * The process of preparing the TCB list is too time-consuming and
  435          * resource-intensive to repeat twice on every request.
  436          */
  437         if (req->oldptr == 0) {
  438                 n = divcbinfo.ipi_count;
  439                 req->oldidx = 2 * (sizeof xig)
  440                         + (n + n/8) * sizeof(struct xinpcb);
  441                 return 0;
  442         }
  443 
  444         if (req->newptr != 0)
  445                 return EPERM;
  446 
  447         /*
  448          * OK, now we're committed to doing something.
  449          */
  450         s = splnet();
  451         gencnt = divcbinfo.ipi_gencnt;
  452         n = divcbinfo.ipi_count;
  453         splx(s);
  454 
  455         xig.xig_len = sizeof xig;
  456         xig.xig_count = n;
  457         xig.xig_gen = gencnt;
  458         xig.xig_sogen = so_gencnt;
  459         error = SYSCTL_OUT(req, &xig, sizeof xig);
  460         if (error)
  461                 return error;
  462 
  463         inp_list = malloc(n * sizeof *inp_list, M_TEMP, M_WAITOK);
  464         if (inp_list == 0)
  465                 return ENOMEM;
  466         
  467         s = splnet();
  468         for (inp = LIST_FIRST(divcbinfo.listhead), i = 0; inp && i < n;
  469              inp = LIST_NEXT(inp, inp_list)) {
  470                 if (inp->inp_gencnt <= gencnt && !prison_xinpcb(req->p, inp))
  471                         inp_list[i++] = inp;
  472         }
  473         splx(s);
  474         n = i;
  475 
  476         error = 0;
  477         for (i = 0; i < n; i++) {
  478                 inp = inp_list[i];
  479                 if (inp->inp_gencnt <= gencnt) {
  480                         struct xinpcb xi;
  481                         bzero(&xi, sizeof(xi));
  482                         xi.xi_len = sizeof xi;
  483                         /* XXX should avoid extra copy */
  484                         bcopy(inp, &xi.xi_inp, sizeof *inp);
  485                         if (inp->inp_socket)
  486                                 sotoxsocket(inp->inp_socket, &xi.xi_socket);
  487                         error = SYSCTL_OUT(req, &xi, sizeof xi);
  488                 }
  489         }
  490         if (!error) {
  491                 /*
  492                  * Give the user an updated idea of our state.
  493                  * If the generation differs from what we told
  494                  * her before, she knows that something happened
  495                  * while we were processing this request, and it
  496                  * might be necessary to retry.
  497                  */
  498                 s = splnet();
  499                 xig.xig_gen = divcbinfo.ipi_gencnt;
  500                 xig.xig_sogen = so_gencnt;
  501                 xig.xig_count = divcbinfo.ipi_count;
  502                 splx(s);
  503                 error = SYSCTL_OUT(req, &xig, sizeof xig);
  504         }
  505         free(inp_list, M_TEMP);
  506         return error;
  507 }
  508 
  509 SYSCTL_DECL(_net_inet_divert);
  510 SYSCTL_PROC(_net_inet_divert, OID_AUTO, pcblist, CTLFLAG_RD, 0, 0,
  511             div_pcblist, "S,xinpcb", "List of active divert sockets");
  512 
  513 struct pr_usrreqs div_usrreqs = {
  514         NULL, pru_accept_notsupp, div_attach, div_bind,
  515         pru_connect_notsupp, pru_connect2_notsupp, in_control, div_detach,
  516         NULL, pru_listen_notsupp, in_setpeeraddr, pru_rcvd_notsupp,
  517         pru_rcvoob_notsupp, div_send, pru_sense_null, div_shutdown,
  518         in_setsockaddr, sosend, soreceive, sopoll
  519 };

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