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

     /*
      * Copyright (c) 1982, 1986, 1988, 1993
      *      The Regents of the University of California.  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. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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.
     *
     * $FreeBSD$
     */
    
    #include "opt_inet.h"
    #include "opt_ipfw.h"
    #include "opt_ipdivert.h"
    
    #ifndef INET
    #error "IPDIVERT requires INET."
    #endif
    
    #include <sys/param.h>
    #include <sys/malloc.h>
    #include <sys/mbuf.h>
    #include <sys/socket.h>
    #include <sys/protosw.h>
    #include <sys/socketvar.h>
    #include <sys/systm.h>
    #include <sys/proc.h>
    
    #include <vm/vm_zone.h>
    
    #include <net/if.h>
    #include <net/route.h>
    
    #include <netinet/in.h>
    #include <netinet/in_systm.h>
    #include <netinet/ip.h>
    #include <netinet/in_pcb.h>
    #include <netinet/in_var.h>
    #include <netinet/ip_var.h>
    
    /*
     * Divert sockets
     */
    
    /*
     * Allocate enough space to hold a full IP packet
     */
    #define DIVSNDQ         (65536 + 100)
    #define DIVRCVQ         (65536 + 100)
    
    /* Global variables */
    
    /*
     * ip_input() and ip_output() set this secret value before calling us to
     * let us know which divert port to divert a packet to; this is done so
     * we can use the existing prototype for struct protosw's pr_input().
     * This is stored in host order.
     */
    u_short ip_divert_port;
    
    /*
     * A 16 bit cookie is passed to the user process.
     * The user process can send it back to help the caller know something
     * about where the packet came from.
     *
     * If IPFW is the caller then the cookie is the rule that sent
     * us here. On reinjection is is the rule after which processing
     * should continue. Leaving it the same will make processing start
     * at the rule number after that which sent it here. Setting it to
     * 0 will restart processing at the beginning. 
     */
    u_int16_t ip_divert_cookie;
    
    /* Internal variables */
    
   static struct inpcbhead divcb;
   static struct inpcbinfo divcbinfo;
   
   static u_long   div_sendspace = DIVSNDQ;        /* XXX sysctl ? */
   static u_long   div_recvspace = DIVRCVQ;        /* XXX sysctl ? */
   
   /* Optimization: have this preinitialized */
   static struct sockaddr_in divsrc = { sizeof(divsrc), AF_INET };
   
   /* Internal functions */
   
   static int div_output(struct socket *so,
                   struct mbuf *m, struct sockaddr *addr, struct mbuf *control);
   
   /*
    * Initialize divert connection block queue.
    */
   void
   div_init(void)
   {
           LIST_INIT(&divcb);
           divcbinfo.listhead = &divcb;
           /*
            * XXX We don't use the hash list for divert IP, but it's easier
            * to allocate a one entry hash list than it is to check all
            * over the place for hashbase == NULL.
            */
           divcbinfo.hashbase = hashinit(1, M_PCB, &divcbinfo.hashmask);
           divcbinfo.porthashbase = hashinit(1, M_PCB, &divcbinfo.porthashmask);
           divcbinfo.ipi_zone = zinit("divcb", sizeof(struct inpcb),
                                      maxsockets, ZONE_INTERRUPT, 0);
   }
   
   /*
    * Setup generic address and protocol structures
    * for div_input routine, then pass them along with
    * mbuf chain. ip->ip_len is assumed to have had
    * the header length (hlen) subtracted out already.
    * We tell whether the packet was incoming or outgoing
    * by seeing if hlen == 0, which is a hack.
    */
   void
   div_input(struct mbuf *m, int hlen)
   {
           struct ip *ip;
           struct inpcb *inp;
           struct socket *sa;
   
           /* Sanity check */
           if (ip_divert_port == 0)
                   panic("div_input: port is 0");
   
           /* Assure header */
           if (m->m_len < sizeof(struct ip) &&
               (m = m_pullup(m, sizeof(struct ip))) == 0) {
                   return;
           }
           ip = mtod(m, struct ip *);
   
           /* Record divert cookie */
           divsrc.sin_port = ip_divert_cookie;
           ip_divert_cookie = 0;
   
           /* Restore packet header fields */
           ip->ip_len += hlen;
           HTONS(ip->ip_len);
           HTONS(ip->ip_off);
   
           /*
            * Record receive interface address, if any
            * But only for incoming packets.
            */
           divsrc.sin_addr.s_addr = 0;
           if (hlen) {
                   struct ifaddr *ifa;
   
   #ifdef DIAGNOSTIC
                   /* Sanity check */
                   if (!(m->m_flags & M_PKTHDR))
                           panic("div_input: no pkt hdr");
   #endif
   
                   /* More fields affected by ip_input() */
                   HTONS(ip->ip_id);
   
                   /* Find IP address for receive interface */
                   for (ifa = m->m_pkthdr.rcvif->if_addrhead.tqh_first;
                       ifa != NULL; ifa = ifa->ifa_link.tqe_next) {
                           if (ifa->ifa_addr == NULL)
                                   continue;
                           if (ifa->ifa_addr->sa_family != AF_INET)
                                   continue;
                           divsrc.sin_addr =
                               ((struct sockaddr_in *) ifa->ifa_addr)->sin_addr;
                           break;
                   }
           }
           /*
            * Record the incoming interface name whenever we have one.
            */
           bzero(&divsrc.sin_zero, sizeof(divsrc.sin_zero));
           if (m->m_pkthdr.rcvif) {
                   /*
                    * Hide the actual interface name in there in the 
                    * sin_zero array. XXX This needs to be moved to a
                    * different sockaddr type for divert, e.g.
                    * sockaddr_div with multiple fields like 
                    * sockaddr_dl. Presently we have only 7 bytes
                    * but that will do for now as most interfaces
                    * are 4 or less + 2 or less bytes for unit.
                    * There is probably a faster way of doing this,
                    * possibly taking it from the sockaddr_dl on the iface.
                    * This solves the problem of a P2P link and a LAN interface
                    * having the same address, which can result in the wrong
                    * interface being assigned to the packet when fed back
                    * into the divert socket. Theoretically if the daemon saves
                    * and re-uses the sockaddr_in as suggested in the man pages,
                    * this iface name will come along for the ride.
                    * (see div_output for the other half of this.)
                    */ 
                   snprintf(divsrc.sin_zero, sizeof(divsrc.sin_zero),
                           "%s%d", m->m_pkthdr.rcvif->if_name,
                           m->m_pkthdr.rcvif->if_unit);
           }
   
           /* Put packet on socket queue, if any */
           sa = NULL;
           for (inp = divcb.lh_first; inp != NULL; inp = inp->inp_list.le_next) {
                   if (inp->inp_lport == htons(ip_divert_port))
                           sa = inp->inp_socket;
           }
           ip_divert_port = 0;
           if (sa) {
                   if (sbappendaddr(&sa->so_rcv, (struct sockaddr *)&divsrc,
                                   m, (struct mbuf *)0) == 0)
                           m_freem(m);
                   else
                           sorwakeup(sa);
           } else {
                   m_freem(m);
                   ipstat.ips_noproto++;
                   ipstat.ips_delivered--;
           }
   }
   
   /*
    * Deliver packet back into the IP processing machinery.
    *
    * If no address specified, or address is 0.0.0.0, send to ip_output();
    * otherwise, send to ip_input() and mark as having been received on
    * the interface with that address.
    */
   static int
   div_output(so, m, addr, control)
           struct socket *so;
           register struct mbuf *m;
           struct sockaddr *addr;
           struct mbuf *control;
   {
           register struct inpcb *const inp = sotoinpcb(so);
           register struct ip *const ip = mtod(m, struct ip *);
           struct sockaddr_in *sin = (struct sockaddr_in *)addr;
           int error = 0;
   
           if (control)
                   m_freem(control);               /* XXX */
   
           /* Loopback avoidance and state recovery */
           if (sin) {
                   int     len = 0;
                   char    *c = sin->sin_zero;
   
                   ip_divert_cookie = sin->sin_port;
   
                   /*
                    * Find receive interface with the given name or IP address.
                    * The name is user supplied data so don't trust it's size or 
                    * that it is zero terminated. The name has priority.
                    * We are presently assuming that the sockaddr_in 
                    * has not been replaced by a sockaddr_div, so we limit it
                    * to 16 bytes in total. the name is stuffed (if it exists)
                    * in the sin_zero[] field.
                    */
                   while (*c++ && (len++ < sizeof(sin->sin_zero)));
                   if ((len > 0) && (len < sizeof(sin->sin_zero)))
                           m->m_pkthdr.rcvif = ifunit(sin->sin_zero);
           } else {
                   ip_divert_cookie = 0;
           }
   
           /* Reinject packet into the system as incoming or outgoing */
           if (!sin || sin->sin_addr.s_addr == 0) {
                   /*
                    * Don't allow both user specified and setsockopt options,
                    * and don't allow packet length sizes that will crash
                    */
                   if (((ip->ip_hl != (sizeof (*ip) >> 2)) && inp->inp_options) ||
                        ((u_short)ntohs(ip->ip_len) > m->m_pkthdr.len)) {
                           error = EINVAL;
                           goto cantsend;
                   }
   
                   /* Convert fields to host order for ip_output() */
                   NTOHS(ip->ip_len);
                   NTOHS(ip->ip_off);
   
                   /* Send packet to output processing */
                   ipstat.ips_rawout++;                    /* XXX */
                   error = ip_output(m, inp->inp_options, &inp->inp_route,
                           (so->so_options & SO_DONTROUTE) |
                           IP_ALLOWBROADCAST | IP_RAWOUTPUT, inp->inp_moptions);
           } else {
                   struct  ifaddr *ifa;
   
                   /* If no luck with the name above. check by IP address.  */
                   if (m->m_pkthdr.rcvif == NULL) {
                           /*
                            * Make sure there are no distractions
                            * for ifa_ifwithaddr. Clear the port and the ifname.
                            * Maybe zap all 8 bytes at once using a 64bit write?
                            */
                           bzero(sin->sin_zero, sizeof(sin->sin_zero));
                           /* *((u_int64_t *)sin->sin_zero) = 0; */ /* XXX ?? */
                           sin->sin_port = 0;
                           if (!(ifa = ifa_ifwithaddr((struct sockaddr *) sin))) {
                                   error = EADDRNOTAVAIL;
                                   goto cantsend;
                           }
                           m->m_pkthdr.rcvif = ifa->ifa_ifp;
                   }
   
                   /* Send packet to input processing */
                   ip_input(m);
           }
   
           /* paranoid: Reset for next time (and other packets) */
           /* almost definitly already done in the ipfw filter but.. */
           ip_divert_cookie = 0;
           return error;
   
   cantsend:
           ip_divert_cookie = 0;
           m_freem(m);
           return error;
   }
   
   static int
   div_attach(struct socket *so, int proto, struct proc *p)
   {
           struct inpcb *inp;
           int error, s;
   
           inp  = sotoinpcb(so);
           if (inp)
                   panic("div_attach");
           if (p && (error = suser(p->p_ucred, &p->p_acflag)) != 0)
                   return error;
   
           s = splnet();
           error = in_pcballoc(so, &divcbinfo, p);
           splx(s);
           if (error)
                   return error;
           error = soreserve(so, div_sendspace, div_recvspace);
           if (error)
                   return error;
           inp = (struct inpcb *)so->so_pcb;
           inp->inp_ip_p = proto;
           inp->inp_flags |= INP_HDRINCL;
           /* The socket is always "connected" because
              we always know "where" to send the packet */
           so->so_state |= SS_ISCONNECTED;
           return 0;
   }
   
   static int
   div_detach(struct socket *so)
   {
           struct inpcb *inp;
   
           inp = sotoinpcb(so);
           if (inp == 0)
                   panic("div_detach");
           in_pcbdetach(inp);
           return 0;
   }
   
   static int
   div_abort(struct socket *so)
   {
           soisdisconnected(so);
           return div_detach(so);
   }
   
   static int
   div_disconnect(struct socket *so)
   {
           if ((so->so_state & SS_ISCONNECTED) == 0)
                   return ENOTCONN;
           return div_abort(so);
   }
   
   static int
   div_bind(struct socket *so, struct sockaddr *nam, struct proc *p)
   {
           struct inpcb *inp;
           int s;
           int error;
   
           s = splnet();
           inp = sotoinpcb(so);
           error = in_pcbbind(inp, nam, p);
           splx(s);
           return 0;
   }
   
   static int
   div_shutdown(struct socket *so)
   {
           socantsendmore(so);
           return 0;
   }
   
   static int
   div_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
            struct mbuf *control, struct proc *p)
   {
           /* Packet must have a header (but that's about it) */
           if (m->m_len < sizeof (struct ip) ||
               (m = m_pullup(m, sizeof (struct ip))) == 0) {
                   ipstat.ips_toosmall++;
                   m_freem(m);
                   return EINVAL;
           }
   
           /* Send packet */
           return div_output(so, m, nam, control);
   }
   
   struct pr_usrreqs div_usrreqs = {
           div_abort, pru_accept_notsupp, div_attach, div_bind,
           pru_connect_notsupp, pru_connect2_notsupp, in_control, div_detach,
           div_disconnect, pru_listen_notsupp, in_setpeeraddr, pru_rcvd_notsupp,
           pru_rcvoob_notsupp, div_send, pru_sense_null, div_shutdown,
           in_setsockaddr, sosend, soreceive, sopoll
   };

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