autoip.c

00001 /**
00002  * @file
00003  * AutoIP Automatic LinkLocal IP Configuration
00004  *
00005  */
00006 
00007 /*
00008  *
00009  * Copyright (c) 2007 Dominik Spies <kontakt@dspies.de>
00010  * All rights reserved.
00011  *
00012  * Redistribution and use in source and binary forms, with or without modification,
00013  * are permitted provided that the following conditions are met:
00014  *
00015  * 1. Redistributions of source code must retain the above copyright notice,
00016  *    this list of conditions and the following disclaimer.
00017  * 2. Redistributions in binary form must reproduce the above copyright notice,
00018  *    this list of conditions and the following disclaimer in the documentation
00019  *    and/or other materials provided with the distribution.
00020  * 3. The name of the author may not be used to endorse or promote products
00021  *    derived from this software without specific prior written permission.
00022  *
00023  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
00024  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
00025  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
00026  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
00027  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
00028  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
00029  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
00030  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
00031  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
00032  * OF SUCH DAMAGE.
00033  *
00034  * Author: Dominik Spies <kontakt@dspies.de>
00035  *
00036  * This is a AutoIP implementation for the lwIP TCP/IP stack. It aims to conform
00037  * with RFC 3927.
00038  *
00039  *
00040  * Please coordinate changes and requests with Dominik Spies
00041  * <kontakt@dspies.de>
00042  */
00043 
00044 /*******************************************************************************
00045  * USAGE:
00046  * 
00047  * define LWIP_AUTOIP 1  in your lwipopts.h
00048  * 
00049  * If you don't use tcpip.c (so, don't call, you don't call tcpip_init):
00050  * - First, call autoip_init().
00051  * - call autoip_tmr() all AUTOIP_TMR_INTERVAL msces,
00052  *   that should be defined in autoip.h.
00053  *   I recommend a value of 100. The value must divide 1000 with a remainder almost 0.
00054  *   Possible values are 1000, 500, 333, 250, 200, 166, 142, 125, 111, 100 ....
00055  *
00056  * Without DHCP:
00057  * - Call autoip_start() after netif_add().
00058  * 
00059  * With DHCP:
00060  * - define LWIP_DHCP_AUTOIP_COOP 1 in your lwipopts.h.
00061  * - Configure your DHCP Client.
00062  *
00063  */
00064 
00065 #include "lwip/opt.h"
00066 
00067 #if LWIP_AUTOIP /* don't build if not configured for use in lwipopts.h */
00068 
00069 #include "lwip/mem.h"
00070 #include "lwip/udp.h"
00071 #include "lwip/ip_addr.h"
00072 #include "lwip/netif.h"
00073 #include "lwip/autoip.h"
00074 #include "netif/etharp.h"
00075 
00076 #include <stdlib.h>
00077 #include <string.h>
00078 
00079 /* 169.254.0.0 */
00080 #define AUTOIP_NET         0xA9FE0000
00081 /* 169.254.1.0 */
00082 #define AUTOIP_RANGE_START (AUTOIP_NET | 0x0100)
00083 /* 169.254.254.255 */
00084 #define AUTOIP_RANGE_END   (AUTOIP_NET | 0xFEFF)
00085 
00086 
00087 /** Pseudo random macro based on netif informations.
00088  * You could use "rand()" from the C Library if you define LWIP_AUTOIP_RAND in lwipopts.h */
00089 #ifndef LWIP_AUTOIP_RAND
00090 #define LWIP_AUTOIP_RAND(netif) ( (((u32_t)((netif->hwaddr[5]) & 0xff) << 24) | \
00091                                    ((u32_t)((netif->hwaddr[3]) & 0xff) << 16) | \
00092                                    ((u32_t)((netif->hwaddr[2]) & 0xff) << 8) | \
00093                                    ((u32_t)((netif->hwaddr[4]) & 0xff))) + \
00094                                    (netif->autoip?netif->autoip->tried_llipaddr:0))
00095 #endif /* LWIP_AUTOIP_RAND */
00096 
00097 /**
00098  * Macro that generates the initial IP address to be tried by AUTOIP.
00099  * If you want to override this, define it to something else in lwipopts.h.
00100  */
00101 #ifndef LWIP_AUTOIP_CREATE_SEED_ADDR
00102 #define LWIP_AUTOIP_CREATE_SEED_ADDR(netif) \
00103   htonl(AUTOIP_RANGE_START + ((u32_t)(((u8_t)(netif->hwaddr[4])) | \
00104                  ((u32_t)((u8_t)(netif->hwaddr[5]))) << 8)))
00105 #endif /* LWIP_AUTOIP_CREATE_SEED_ADDR */
00106 
00107 /* static functions */
00108 static void autoip_handle_arp_conflict(struct netif *netif);
00109 
00110 /* creates a pseudo random LL IP-Address for a network interface */
00111 static void autoip_create_addr(struct netif *netif, struct ip_addr *ipaddr);
00112 
00113 /* sends an ARP probe */
00114 static err_t autoip_arp_probe(struct netif *netif);
00115 
00116 /* sends an ARP announce */
00117 static err_t autoip_arp_announce(struct netif *netif);
00118 
00119 /* configure interface for use with current LL IP-Address */
00120 static err_t autoip_bind(struct netif *netif);
00121 
00122 /* start sending probes for llipaddr */
00123 static void autoip_start_probing(struct netif *netif);
00124 
00125 /**
00126  * Initialize this module
00127  */
00128 void
00129 autoip_init(void)
00130 {
00131   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | 3, ("autoip_init()\n"));
00132 }
00133 
00134 /**
00135  * Handle a IP address conflict after an ARP conflict detection
00136  */
00137 static void
00138 autoip_handle_arp_conflict(struct netif *netif)
00139 {
00140   /* Somehow detect if we are defending or retreating */
00141   unsigned char defend = 1; /* tbd */
00142 
00143   if(defend) {
00144     if(netif->autoip->lastconflict > 0) {
00145       /* retreat, there was a conflicting ARP in the last
00146        * DEFEND_INTERVAL seconds
00147        */
00148       LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | 1,
00149         ("autoip_handle_arp_conflict(): we are defending, but in DEFEND_INTERVAL, retreating\n"));
00150 
00151       /* TODO: close all TCP sessions */
00152       autoip_start(netif);
00153     } else {
00154       LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | 1,
00155         ("autoip_handle_arp_conflict(): we are defend, send ARP Announce\n"));
00156       autoip_arp_announce(netif);
00157       netif->autoip->lastconflict = DEFEND_INTERVAL * AUTOIP_TICKS_PER_SECOND;
00158     }
00159   } else {
00160     LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | 1,
00161       ("autoip_handle_arp_conflict(): we do not defend, retreating\n"));
00162     /* TODO: close all TCP sessions */
00163     autoip_start(netif);
00164   }
00165 }
00166 
00167 /**
00168  * Create an IP-Address out of range 169.254.1.0 to 169.254.254.255
00169  *
00170  * @param netif network interface on which create the IP-Address
00171  * @param ipaddr ip address to initialize
00172  */
00173 static void
00174 autoip_create_addr(struct netif *netif, struct ip_addr *ipaddr)
00175 {
00176   /* Here we create an IP-Address out of range 169.254.1.0 to 169.254.254.255
00177    * compliant to RFC 3927 Section 2.1
00178    * We have 254 * 256 possibilities */
00179 
00180   u32_t addr = ntohl(LWIP_AUTOIP_CREATE_SEED_ADDR(netif));
00181   addr += netif->autoip->tried_llipaddr;
00182   addr = AUTOIP_NET | (addr & 0xffff);
00183   /* Now, 169.254.0.0 <= addr <= 169.254.255.255 */ 
00184 
00185   if (addr < AUTOIP_RANGE_START) {
00186     addr += AUTOIP_RANGE_END - AUTOIP_RANGE_START + 1;
00187   }
00188   if (addr > AUTOIP_RANGE_END) {
00189     addr -= AUTOIP_RANGE_END - AUTOIP_RANGE_START + 1;
00190   }
00191   LWIP_ASSERT("AUTOIP address not in range", (addr >= AUTOIP_RANGE_START) &&
00192     (addr <= AUTOIP_RANGE_END));
00193   ipaddr->addr = htonl(addr);
00194   
00195   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | 1,
00196     ("autoip_create_addr(): tried_llipaddr=%"U16_F", 0x%08"X32_F"\n",
00197     (u16_t)(netif->autoip->tried_llipaddr), (u32_t)(ipaddr->addr)));
00198 }
00199 
00200 /**
00201  * Sends an ARP probe from a network interface
00202  *
00203  * @param netif network interface used to send the probe
00204  */
00205 static err_t
00206 autoip_arp_probe(struct netif *netif)
00207 {
00208   return etharp_raw(netif, (struct eth_addr *)netif->hwaddr, &ethbroadcast,
00209     (struct eth_addr *)netif->hwaddr, IP_ADDR_ANY, &ethzero,
00210     &netif->autoip->llipaddr, ARP_REQUEST);
00211 }
00212 
00213 /**
00214  * Sends an ARP announce from a network interface
00215  *
00216  * @param netif network interface used to send the announce
00217  */
00218 static err_t
00219 autoip_arp_announce(struct netif *netif)
00220 {
00221   return etharp_raw(netif, (struct eth_addr *)netif->hwaddr, &ethbroadcast,
00222     (struct eth_addr *)netif->hwaddr, &netif->autoip->llipaddr, &ethzero,
00223     &netif->autoip->llipaddr, ARP_REQUEST);
00224 }
00225 
00226 /**
00227  * Configure interface for use with current LL IP-Address
00228  *
00229  * @param netif network interface to configure with current LL IP-Address
00230  */
00231 static err_t
00232 autoip_bind(struct netif *netif)
00233 {
00234   struct autoip *autoip = netif->autoip;
00235   struct ip_addr sn_mask, gw_addr;
00236 
00237   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | 3,
00238     ("autoip_bind(netif=%p) %c%c%"U16_F" 0x%08"X32_F"\n",
00239     (void*)netif, netif->name[0], netif->name[1], (u16_t)netif->num, autoip->llipaddr.addr));
00240 
00241   IP4_ADDR(&sn_mask, 255, 255, 0, 0);
00242   IP4_ADDR(&gw_addr, 0, 0, 0, 0);
00243 
00244   netif_set_ipaddr(netif, &autoip->llipaddr);
00245   netif_set_netmask(netif, &sn_mask);
00246   netif_set_gw(netif, &gw_addr);  
00247 
00248   /* bring the interface up */
00249   netif_set_up(netif);
00250 
00251   return ERR_OK;
00252 }
00253 
00254 /**
00255  * Start AutoIP client
00256  *
00257  * @param netif network interface on which start the AutoIP client
00258  */
00259 err_t
00260 autoip_start(struct netif *netif)
00261 {
00262   struct autoip *autoip = netif->autoip;
00263   err_t result = ERR_OK;
00264 
00265   if(netif_is_up(netif)) {
00266     netif_set_down(netif);
00267   }
00268 
00269   /* Set IP-Address, Netmask and Gateway to 0 to make sure that
00270    * ARP Packets are formed correctly
00271    */
00272   netif->ip_addr.addr = 0;
00273   netif->netmask.addr = 0;
00274   netif->gw.addr      = 0;
00275 
00276   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
00277     ("autoip_start(netif=%p) %c%c%"U16_F"\n", (void*)netif, netif->name[0],
00278     netif->name[1], (u16_t)netif->num));
00279   if(autoip == NULL) {
00280     /* no AutoIP client attached yet? */
00281     LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
00282       ("autoip_start(): starting new AUTOIP client\n"));
00283     autoip = mem_malloc(sizeof(struct autoip));
00284     if(autoip == NULL) {
00285       LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
00286         ("autoip_start(): could not allocate autoip\n"));
00287       return ERR_MEM;
00288     }
00289     memset( autoip, 0, sizeof(struct autoip));
00290     /* store this AutoIP client in the netif */
00291     netif->autoip = autoip;
00292     LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE, ("autoip_start(): allocated autoip"));
00293   } else {
00294     autoip->state = AUTOIP_STATE_OFF;
00295     autoip->ttw = 0;
00296     autoip->sent_num = 0;
00297     memset(&autoip->llipaddr, 0, sizeof(struct ip_addr));
00298     autoip->lastconflict = 0;
00299   }
00300 
00301   autoip_create_addr(netif, &(autoip->llipaddr));
00302   autoip->tried_llipaddr++;
00303   autoip_start_probing(netif);
00304 
00305   return result;
00306 }
00307 
00308 static void
00309 autoip_start_probing(struct netif *netif)
00310 {
00311   struct autoip *autoip = netif->autoip;
00312 
00313   autoip->state = AUTOIP_STATE_PROBING;
00314   autoip->sent_num = 0;
00315 
00316   /* time to wait to first probe, this is randomly
00317    * choosen out of 0 to PROBE_WAIT seconds.
00318    * compliant to RFC 3927 Section 2.2.1
00319    */
00320   autoip->ttw = (u16_t)(LWIP_AUTOIP_RAND(netif) % (PROBE_WAIT * AUTOIP_TICKS_PER_SECOND));
00321 
00322   /*
00323    * if we tried more then MAX_CONFLICTS we must limit our rate for
00324    * accquiring and probing address
00325    * compliant to RFC 3927 Section 2.2.1
00326    */
00327   if(autoip->tried_llipaddr > MAX_CONFLICTS) {
00328     autoip->ttw = RATE_LIMIT_INTERVAL * AUTOIP_TICKS_PER_SECOND;
00329   }
00330 }
00331 
00332 /**
00333  * Handle a possible change in the network configuration.
00334  *
00335  * If there is an AutoIP address configured, take the interface down
00336  * and begin probing with the same address.
00337  */
00338 void
00339 autoip_network_changed(struct netif *netif)
00340 {
00341   if (netif->autoip && netif->autoip->state != AUTOIP_STATE_OFF) {
00342     netif_set_down(netif);
00343     autoip_start_probing(netif);
00344   }
00345 }
00346 
00347 /**
00348  * Stop AutoIP client
00349  *
00350  * @param netif network interface on which stop the AutoIP client
00351  */
00352 err_t
00353 autoip_stop(struct netif *netif)
00354 {
00355   netif->autoip->state = AUTOIP_STATE_OFF;
00356   netif_set_down(netif);
00357   return ERR_OK;
00358 }
00359 
00360 /**
00361  * Has to be called in loop every AUTOIP_TMR_INTERVAL milliseconds
00362  */
00363 void
00364 autoip_tmr()
00365 {
00366   struct netif *netif = netif_list;
00367   /* loop through netif's */
00368   while (netif != NULL) {
00369     /* only act on AutoIP configured interfaces */
00370     if (netif->autoip != NULL) {
00371       if(netif->autoip->lastconflict > 0) {
00372         netif->autoip->lastconflict--;
00373       }
00374 
00375       LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
00376         ("autoip_tmr() AutoIP-State: %"U16_F", ttw=%"U16_F"\n",
00377         (u16_t)(netif->autoip->state), netif->autoip->ttw));
00378 
00379       switch(netif->autoip->state) {
00380         case AUTOIP_STATE_PROBING:
00381           if(netif->autoip->ttw > 0) {
00382             netif->autoip->ttw--;
00383           } else {
00384             if(netif->autoip->sent_num >= PROBE_NUM) {
00385               netif->autoip->state = AUTOIP_STATE_ANNOUNCING;
00386               netif->autoip->sent_num = 0;
00387               netif->autoip->ttw = ANNOUNCE_WAIT * AUTOIP_TICKS_PER_SECOND;
00388             } else {
00389               autoip_arp_probe(netif);
00390               LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | 3,
00391                 ("autoip_tmr() PROBING Sent Probe\n"));
00392               netif->autoip->sent_num++;
00393               /* calculate time to wait to next probe */
00394               netif->autoip->ttw = (u16_t)((LWIP_AUTOIP_RAND(netif) %
00395                 ((PROBE_MAX - PROBE_MIN) * AUTOIP_TICKS_PER_SECOND) ) +
00396                 PROBE_MIN * AUTOIP_TICKS_PER_SECOND);
00397             }
00398           }
00399           break;
00400 
00401         case AUTOIP_STATE_ANNOUNCING:
00402           if(netif->autoip->ttw > 0) {
00403             netif->autoip->ttw--;
00404           } else {
00405             if(netif->autoip->sent_num == 0) {
00406              /* We are here the first time, so we waited ANNOUNCE_WAIT seconds
00407               * Now we can bind to an IP address and use it.
00408               *
00409               * autoip_bind calls netif_set_up. This triggers a gratuitous ARP
00410               * which counts as an announcement.
00411               */
00412               autoip_bind(netif);
00413             } else {
00414               autoip_arp_announce(netif);
00415               LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | 3,
00416                 ("autoip_tmr() ANNOUNCING Sent Announce\n"));
00417             }
00418             netif->autoip->ttw = ANNOUNCE_INTERVAL * AUTOIP_TICKS_PER_SECOND;
00419             netif->autoip->sent_num++;
00420 
00421             if(netif->autoip->sent_num >= ANNOUNCE_NUM) {
00422                 netif->autoip->state = AUTOIP_STATE_BOUND;
00423                 netif->autoip->sent_num = 0;
00424                 netif->autoip->ttw = 0;
00425             }
00426           }
00427           break;
00428       }
00429     }
00430     /* proceed to next network interface */
00431     netif = netif->next;
00432   }
00433 }
00434 
00435 /**
00436  * Handles every incoming ARP Packet, called by etharp_arp_input.
00437  *
00438  * @param netif network interface to use for autoip processing
00439  * @param hdr Incoming ARP packet
00440  */
00441 void
00442 autoip_arp_reply(struct netif *netif, struct etharp_hdr *hdr)
00443 {
00444   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | 3, ("autoip_arp_reply()\n"));
00445   if ((netif->autoip != NULL) && (netif->autoip->state != AUTOIP_STATE_OFF)) {
00446    /* when ip.src == llipaddr && hw.src != netif->hwaddr
00447     *
00448     * when probing  ip.dst == llipaddr && hw.src != netif->hwaddr
00449     * we have a conflict and must solve it
00450     */
00451     struct ip_addr sipaddr, dipaddr;
00452     struct eth_addr netifaddr;
00453     netifaddr.addr[0] = netif->hwaddr[0];
00454     netifaddr.addr[1] = netif->hwaddr[1];
00455     netifaddr.addr[2] = netif->hwaddr[2];
00456     netifaddr.addr[3] = netif->hwaddr[3];
00457     netifaddr.addr[4] = netif->hwaddr[4];
00458     netifaddr.addr[5] = netif->hwaddr[5];
00459 
00460     /* Copy struct ip_addr2 to aligned ip_addr, to support compilers without
00461      * structure packing (not using structure copy which breaks strict-aliasing rules).
00462      */
00463     SMEMCPY(&sipaddr, &hdr->sipaddr, sizeof(sipaddr));
00464     SMEMCPY(&dipaddr, &hdr->dipaddr, sizeof(dipaddr));
00465       
00466     if ((netif->autoip->state == AUTOIP_STATE_PROBING) ||
00467         ((netif->autoip->state == AUTOIP_STATE_ANNOUNCING) &&
00468          (netif->autoip->sent_num == 0))) {
00469      /* RFC 3927 Section 2.2.1:
00470       * from beginning to after ANNOUNCE_WAIT
00471       * seconds we have a conflict if
00472       * ip.src == llipaddr OR
00473       * ip.dst == llipaddr && hw.src != own hwaddr
00474       */
00475       if ((ip_addr_cmp(&sipaddr, &netif->autoip->llipaddr)) ||
00476           (ip_addr_cmp(&dipaddr, &netif->autoip->llipaddr) &&
00477            !eth_addr_cmp(&netifaddr, &hdr->shwaddr))) {
00478         LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | 1,
00479           ("autoip_arp_reply(): Probe Conflict detected\n"));
00480         autoip_start(netif);
00481       }
00482     } else {
00483      /* RFC 3927 Section 2.5:
00484       * in any state we have a conflict if
00485       * ip.src == llipaddr && hw.src != own hwaddr
00486       */
00487       if (ip_addr_cmp(&sipaddr, &netif->autoip->llipaddr) &&
00488           !eth_addr_cmp(&netifaddr, &hdr->shwaddr)) {
00489         LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | 1,
00490           ("autoip_arp_reply(): Conflicting ARP-Packet detected\n"));
00491         autoip_handle_arp_conflict(netif);
00492       }
00493     }
00494   }
00495 }
00496 
00497 #endif /* LWIP_AUTOIP */