nit.c

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/* nit.c
 
   Network Interface Tap (NIT) network interface code, by Ted Lemon
   with one crucial tidbit of help from Stu Grossmen. */
 
/*
 * Copyright (c) 2004,2007,2009,2014 by Internet Systems Consortium, Inc. ("ISC")
 * Copyright (c) 1996-2003 by Internet Software Consortium
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 *   Internet Systems Consortium, Inc.
 *   950 Charter Street
 *   Redwood City, CA 94063
 *   <info@isc.org>
 *   https://www.isc.org/
 *
 */
 
#include "dhcpd.h"
#if defined (USE_NIT_SEND) || defined (USE_NIT_RECEIVE)
#include <sys/ioctl.h>
#include <sys/uio.h>
 
#include <sys/time.h>
#include <net/nit.h>
#include <net/nit_if.h>
#include <net/nit_pf.h>
#include <net/nit_buf.h>
#include <sys/stropts.h>
#include <net/packetfilt.h>
 
#include <netinet/in_systm.h>
#include "includes/netinet/ip.h"
#include "includes/netinet/udp.h"
#include "includes/netinet/if_ether.h"
 
/* Reinitializes the specified interface after an address change.   This
   is not required for packet-filter APIs. */
 
#ifdef USE_NIT_SEND
void if_reinitialize_send (info)
        struct interface_info *info;
{
}
#endif
 
#ifdef USE_NIT_RECEIVE
void if_reinitialize_receive (info)
        struct interface_info *info;
{
}
#endif
 
/* Called by get_interface_list for each interface that's discovered.
   Opens a packet filter for each interface and adds it to the select
   mask. */
 
int if_register_nit (info)
        struct interface_info *info;
{
        int sock;
        char filename[50];
        struct ifreq ifr;
        struct strioctl sio;
 
        /* Open a NIT device */
        sock = open ("/dev/nit", O_RDWR | O_CLOEXEC);
        if (sock < 0)
                log_fatal ("Can't open NIT device for %s: %m", info -> name);
 
        /* Set the NIT device to point at this interface. */
        sio.ic_cmd = NIOCBIND;
        sio.ic_len = sizeof *(info -> ifp);
        sio.ic_dp = (char *)(info -> ifp);
        sio.ic_timout = INFTIM;
        if (ioctl (sock, I_STR, &sio) < 0)
                log_fatal ("Can't attach interface %s to nit device: %m",
                       info -> name);
 
        /* Get the low-level address... */
        sio.ic_cmd = SIOCGIFADDR;
        sio.ic_len = sizeof ifr;
        sio.ic_dp = (char *)&ifr;
        sio.ic_timout = INFTIM;
        if (ioctl (sock, I_STR, &sio) < 0)
                log_fatal ("Can't get physical layer address for %s: %m",
                       info -> name);
 
        /* XXX code below assumes ethernet interface! */
        info -> hw_address.hlen = 7;
        info -> hw_address.hbuf [0] = ARPHRD_ETHER;
        memcpy (&info -> hw_address.hbuf [1],
                ifr.ifr_ifru.ifru_addr.sa_data, 6);
 
        if (ioctl (sock, I_PUSH, "pf") < 0)
                log_fatal ("Can't push packet filter onto NIT for %s: %m",
                       info -> name);
 
        return sock;
}
#endif /* USE_NIT_SEND || USE_NIT_RECEIVE */
 
#ifdef USE_NIT_SEND
void if_register_send (info)
        struct interface_info *info;
{
        /* If we're using the nit API for sending and receiving,
           we don't need to register this interface twice. */
#ifndef USE_NIT_RECEIVE
        struct packetfilt pf;
        struct strioctl sio;
 
        info -> wfdesc = if_register_nit (info);
 
        pf.Pf_Priority = 0;
        pf.Pf_FilterLen = 1;
        pf.Pf_Filter [0] = ENF_PUSHZERO;
 
        /* Set up an NIT filter that rejects everything... */
        sio.ic_cmd = NIOCSETF;
        sio.ic_len = sizeof pf;
        sio.ic_dp = (char *)&pf;
        sio.ic_timout = INFTIM;
        if (ioctl (info -> wfdesc, I_STR, &sio) < 0)
                log_fatal ("Can't set NIT filter: %m");
#else
        info -> wfdesc = info -> rfdesc;
#endif
        if (!quiet_interface_discovery)
                log_info ("Sending on   NIT/%s%s%s",
                      print_hw_addr (info -> hw_address.hbuf [0],
                                     info -> hw_address.hlen - 1,
                                     &info -> hw_address.hbuf [1]),
                      (info -> shared_network ? "/" : ""),
                      (info -> shared_network ?
                       info -> shared_network -> name : ""));
}
 
void if_deregister_send (info)
        struct interface_info *info;
{
        /* If we're using the nit API for sending and receiving,
           we don't need to register this interface twice. */
#ifndef USE_NIT_RECEIVE
        close (info -> wfdesc);
#endif
        info -> wfdesc = -1;
        if (!quiet_interface_discovery)
                log_info ("Disabling output on NIT/%s%s%s",
                      print_hw_addr (info -> hw_address.hbuf [0],
                                     info -> hw_address.hlen - 1,
                                     &info -> hw_address.hbuf [1]),
                      (info -> shared_network ? "/" : ""),
                      (info -> shared_network ?
                       info -> shared_network -> name : ""));
}
#endif /* USE_NIT_SEND */
 
#ifdef USE_NIT_RECEIVE
/* Packet filter program...
   XXX Changes to the filter program may require changes to the constant
   offsets used in if_register_send to patch the NIT program! XXX */
 
void if_register_receive (info)
        struct interface_info *info;
{
        int flag = 1;
        u_int32_t x;
        struct packetfilt pf;
        struct strioctl sio;
        u_int16_t addr [2];
        struct timeval t;
 
        /* Open a NIT device and hang it on this interface... */
        info -> rfdesc = if_register_nit (info);
 
        /* Set the snap length to 0, which means always take the whole
           packet. */
        x = 0;
        if (ioctl (info -> rfdesc, NIOCSSNAP, &x) < 0)
                log_fatal ("Can't set NIT snap length on %s: %m", info -> name);
 
        /* Set the stream to byte stream mode */
        if (ioctl (info -> rfdesc, I_SRDOPT, RMSGN) != 0)
                log_info ("I_SRDOPT failed on %s: %m", info -> name);
 
#if 0
        /* Push on the chunker... */
        if (ioctl (info -> rfdesc, I_PUSH, "nbuf") < 0)
                log_fatal ("Can't push chunker onto NIT STREAM: %m");
 
        /* Set the timeout to zero. */
        t.tv_sec = 0;
        t.tv_usec = 0;
        if (ioctl (info -> rfdesc, NIOCSTIME, &t) < 0)
                log_fatal ("Can't set chunk timeout: %m");
#endif
 
        /* Ask for no header... */
        x = 0;
        if (ioctl (info -> rfdesc, NIOCSFLAGS, &x) < 0)
                log_fatal ("Can't set NIT flags on %s: %m", info -> name);
 
        /* Set up the NIT filter program. */
        /* XXX Unlike the BPF filter program, this one won't work if the
           XXX IP packet is fragmented or if there are options on the IP
           XXX header. */
        pf.Pf_Priority = 0;
        pf.Pf_FilterLen = 0;
 
        pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_PUSHWORD + 6;
        pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_PUSHLIT + ENF_CAND;
        pf.Pf_Filter [pf.Pf_FilterLen++] = htons (ETHERTYPE_IP);
        pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_PUSHLIT;
        pf.Pf_Filter [pf.Pf_FilterLen++] = htons (IPPROTO_UDP);
        pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_PUSHWORD + 11;
        pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_PUSHLIT + ENF_AND;
        pf.Pf_Filter [pf.Pf_FilterLen++] = htons (0xFF);
        pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_CAND;
        pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_PUSHWORD + 18;
        pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_PUSHLIT + ENF_CAND;
        pf.Pf_Filter [pf.Pf_FilterLen++] = local_port;
 
        /* Install the filter... */
        sio.ic_cmd = NIOCSETF;
        sio.ic_len = sizeof pf;
        sio.ic_dp = (char *)&pf;
        sio.ic_timout = INFTIM;
        if (ioctl (info -> rfdesc, I_STR, &sio) < 0)
                log_fatal ("Can't set NIT filter on %s: %m", info -> name);
 
        if (!quiet_interface_discovery)
                log_info ("Listening on NIT/%s%s%s",
                      print_hw_addr (info -> hw_address.hbuf [0],
                                     info -> hw_address.hlen - 1,
                                     &info -> hw_address.hbuf [1]),
                      (info -> shared_network ? "/" : ""),
                      (info -> shared_network ?
                       info -> shared_network -> name : ""));
}
 
void if_deregister_receive (info)
        struct interface_info *info;
{
        /* If we're using the nit API for sending and receiving,
           we don't need to register this interface twice. */
        close (info -> rfdesc);
        info -> rfdesc = -1;
 
        if (!quiet_interface_discovery)
                log_info ("Disabling input on NIT/%s%s%s",
                      print_hw_addr (info -> hw_address.hbuf [0],
                                     info -> hw_address.hlen - 1,
                                     &info -> hw_address.hbuf [1]),
                      (info -> shared_network ? "/" : ""),
                      (info -> shared_network ?
                       info -> shared_network -> name : ""));
}
#endif /* USE_NIT_RECEIVE */
 
#ifdef USE_NIT_SEND
ssize_t send_packet (interface, packet, raw, len, from, to, hto)
        struct interface_info *interface;
        struct packet *packet;
        struct dhcp_packet *raw;
        size_t len;
        struct in_addr from;
        struct sockaddr_in *to;
        struct hardware *hto;
{
        unsigned hbufp, ibufp;
        double hh [16];
        double ih [1536 / sizeof (double)];
        unsigned char *buf = (unsigned char *)ih;
        struct sockaddr *junk;
        struct strbuf ctl, data;
        struct sockaddr_in foo;
        int result;
 
        if (!strcmp (interface -> name, "fallback"))
                return send_fallback (interface, packet, raw,
                                      len, from, to, hto);
 
        if (hto == NULL && interface->anycast_mac_addr.hlen)
                hto = &interface->anycast_mac_addr;
 
        /* Start with the sockaddr struct... */
        junk = (struct sockaddr *)&hh [0];
        hbufp = (((unsigned char *)&junk -> sa_data [0]) -
                 (unsigned char *)&hh[0]);
        ibufp = 0;
 
        /* Assemble the headers... */
        assemble_hw_header (interface, (unsigned char *)junk, &hbufp, hto);
        assemble_udp_ip_header (interface, buf, &ibufp,
                                from.s_addr, to -> sin_addr.s_addr,
                                to -> sin_port, (unsigned char *)raw, len);
 
        /* Copy the data into the buffer (yuk). */
        memcpy (buf + ibufp, raw, len);
 
        /* Set up the sockaddr structure... */
#if USE_SIN_LEN
        junk -> sa_len = hbufp - 2; /* XXX */
#endif
        junk -> sa_family = AF_UNSPEC;
 
        /* Set up the msg_buf structure... */
        ctl.buf = (char *)&hh [0];
        ctl.maxlen = ctl.len = hbufp;
        data.buf = (char *)&ih [0];
        data.maxlen = data.len = ibufp + len;
 
        result = putmsg (interface -> wfdesc, &ctl, &data, 0);
        if (result < 0)
                log_error ("send_packet: %m");
        return result;
}
#endif /* USE_NIT_SEND */
 
#ifdef USE_NIT_RECEIVE
ssize_t receive_packet (interface, buf, len, from, hfrom)
        struct interface_info *interface;
        unsigned char *buf;
        size_t len;
        struct sockaddr_in *from;
        struct hardware *hfrom;
{
        int nread;
        int length = 0;
        int offset = 0;
        unsigned char ibuf [1536];
        int bufix = 0;
        unsigned paylen;
 
        length = read (interface -> rfdesc, ibuf, sizeof ibuf);
        if (length <= 0)
                return length;
 
        /* Decode the physical header... */
        offset = decode_hw_header (interface, ibuf, bufix, hfrom);
 
        /* If a physical layer checksum failed (dunno of any
           physical layer that supports this, but WTH), skip this
           packet. */
        if (offset < 0) {
                return 0;
        }
 
        bufix += offset;
        length -= offset;
 
        /* Decode the IP and UDP headers... */
        offset = decode_udp_ip_header (interface, ibuf, bufix,
                                       from, length, &paylen, 1);
 
        /* If the IP or UDP checksum was bad, skip the packet... */
        if (offset < 0)
                return 0;
 
        bufix += offset;
        length -= offset;
 
        if (length < paylen)
                log_fatal("Internal inconsistency at %s:%d.", MDL);
 
        /* Copy out the data in the packet... */
        memcpy(buf, &ibuf[bufix], paylen);
        return paylen;
}
 
int can_unicast_without_arp (ip)
        struct interface_info *ip;
{
        return 1;
}
 
int can_receive_unicast_unconfigured (ip)
        struct interface_info *ip;
{
        return 1;
}
 
int supports_multiple_interfaces (ip)
        struct interface_info *ip;
{
        return 1;
}
 
void maybe_setup_fallback ()
{
        isc_result_t status;
        struct interface_info *fbi = (struct interface_info *)0;
        if (setup_fallback (&fbi, MDL)) {
                if_register_fallback (fbi);
                status = omapi_register_io_object ((omapi_object_t *)fbi,
                                                   if_readsocket, 0,
                                                   fallback_discard, 0, 0);
                if (status != ISC_R_SUCCESS)
                        log_fatal ("Can't register I/O handle for %s: %s",
                                   fbi -> name, isc_result_totext (status));
                interface_dereference (&fbi, MDL);
        }
}
#endif