/**************************************************************************** * net/uip/uip-arp.c * Implementation of the ARP Address Resolution Protocol. * * Copyright (C) 2007 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * Based on uIP which also has a BSD style license: * * Author: Adam Dunkels * Copyright (c) 2001-2003, Adam Dunkels. * 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. The name of the author may not be used to endorse or promote * products derived from this software without specific prior * written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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. * ****************************************************************************/ /* The Address Resolution Protocol ARP is used for mapping between IP * addresses and link level addresses such as the Ethernet MAC * addresses. ARP uses broadcast queries to ask for the link level * address of a known IP address and the host which is configured with * the IP address for which the query was meant, will respond with its * link level address. * * Note: This ARP implementation only supports Ethernet. */ /**************************************************************************** * Included Files ****************************************************************************/ #include #ifdef CONFIG_NET #include #include #include #include #include #include #include /**************************************************************************** * Definitions ****************************************************************************/ #define ARP_REQUEST 1 #define ARP_REPLY 2 #define ARP_HWTYPE_ETH 1 #define ETHBUF ((struct uip_eth_hdr *)&dev->d_buf[0]) #define ARPBUF ((struct arp_hdr *)&dev->d_buf[UIP_LLH_LEN]) #define IPBUF ((struct ethip_hdr *)&dev->d_buf[UIP_LLH_LEN]) /**************************************************************************** * Private Types ****************************************************************************/ /* ARP header -- Size 28 bytes */ struct arp_hdr { uint16 ah_hwtype; /* 16-bit Hardware type (Ethernet=0x001) */ uint16 ah_protocol; /* 16-bit Protocoal type (IP=0x0800 */ uint8 ah_hwlen; /* 8-bit Hardware address size (6) */ uint8 ah_protolen; /* 8-bit Procotol address size (4) */ uint16 ah_opcode; /* 16-bit Operation */ uint8 ah_shwaddr[6]; /* 48-bit Sender hardware address */ uint16 ah_sipaddr[2]; /* 32-bit Sender IP adress */ uint8 ah_dhwaddr[6]; /* 48-bit Target hardware address */ uint16 ah_dipaddr[2]; /* 32-bit Target IP address */ }; /* IP header -- Size 20 or 24 bytes */ struct ethip_hdr { uint8 eh_vhl; /* 8-bit Version (4) and header length (5 or 6) */ uint8 eh_tos; /* 8-bit Type of service (e.g., 6=TCP) */ uint8 eh_len[2]; /* 16-bit Total length */ uint8 eh_ipid[2]; /* 16-bit Identification */ uint8 eh_ipoffset[2]; /* 16-bit IP flags + fragment offset */ uint8 eh_ttl; /* 8-bit Time to Live */ uint8 eh_proto; /* 8-bit Protocol */ uint16 eh_ipchksum; /* 16-bit Header checksum */ uint16 eh_srcipaddr[2]; /* 32-bit Source IP address */ uint16 eh_destipaddr[2]; /* 32-bit Destination IP address */ uint16 eh_ipoption[2]; /* (optional) */ }; struct arp_entry { in_addr_t at_ipaddr; struct uip_eth_addr at_ethaddr; uint8 at_time; }; /**************************************************************************** * Private Data ****************************************************************************/ static const struct uip_eth_addr broadcast_ethaddr = {{0xff, 0xff, 0xff, 0xff, 0xff, 0xff}}; static const uint16 broadcast_ipaddr[2] = {0xffff, 0xffff}; static struct arp_entry arp_table[CONFIG_NET_ARPTAB_SIZE]; static uint8 g_arptime; /**************************************************************************** * Private Functions ****************************************************************************/ #if defined(CONFIG_NET_DUMPARP) && defined(CONFIG_DEBUG) static void uip_arp_dump(struct arp_hdr *arp) { dbg(" HW type: %04x Protocol: %04x\n", arp->ah_hwtype, arp->ah_protocol);\ dbg(" HW len: %02x Proto len: %02x Operation: %04x\n", arp->ah_hwlen, arp->ah_protolen, arp->ah_opcode); dbg(" Sender MAC: %02x:%02x:%02x:%02x:%02x:%02x IP: %d.%d.%d.%d\n", arp->ah_shwaddr[0], arp->ah_shwaddr[1], arp->ah_shwaddr[2], arp->ah_shwaddr[3], arp->ah_shwaddr[4], arp->ah_shwaddr[5], arp->ah_sipaddr[0] & 0xff, arp->ah_sipaddr[0] >> 8, arp->ah_sipaddr[1] & 0xff, arp->ah_sipaddr[1] >> 8); dbg(" Dest MAC: %02x:%02x:%02x:%02x:%02x:%02x IP: %d.%d.%d.%d\n", arp->ah_dhwaddr[0], arp->ah_dhwaddr[1], arp->ah_dhwaddr[2], arp->ah_dhwaddr[3], arp->ah_dhwaddr[4], arp->ah_dhwaddr[5], arp->ah_dipaddr[0] & 0xff, arp->ah_dipaddr[0] >> 8, arp->ah_dipaddr[1] & 0xff, arp->ah_dipaddr[1] >> 8); } #else # define uip_arp_dump(arp) #endif static void uip_arp_update(uint16 *pipaddr, uint8 *ethaddr) { struct arp_entry *tabptr; in_addr_t ipaddr = uip_ip4addr_conv(pipaddr); int i; /* Walk through the ARP mapping table and try to find an entry to * update. If none is found, the IP -> MAC address mapping is * inserted in the ARP table. */ for (i = 0; i < CONFIG_NET_ARPTAB_SIZE; ++i) { tabptr = &arp_table[i]; /* Only check those entries that are actually in use. */ if (tabptr->at_ipaddr != 0) { /* Check if the source IP address of the incoming packet matches * the IP address in this ARP table entry. */ if (uip_ipaddr_cmp(ipaddr, tabptr->at_ipaddr)) { /* An old entry found, update this and return. */ memcpy(tabptr->at_ethaddr.addr, ethaddr, IFHWADDRLEN); tabptr->at_time = g_arptime; return; } } } /* If we get here, no existing ARP table entry was found, so we create one. */ /* First, we try to find an unused entry in the ARP table. */ for (i = 0; i < CONFIG_NET_ARPTAB_SIZE; ++i) { tabptr = &arp_table[i]; if (tabptr->at_ipaddr == 0) { break; } } /* If no unused entry is found, we try to find the oldest entry and * throw it away. */ if (i == CONFIG_NET_ARPTAB_SIZE) { uint8 tmpage = 0; int j = 0; for (i = 0; i < CONFIG_NET_ARPTAB_SIZE; ++i) { tabptr = &arp_table[i]; if (g_arptime - tabptr->at_time > tmpage) { tmpage = g_arptime - tabptr->at_time; j = i; } } i = j; tabptr = &arp_table[i]; } /* Now, i is the ARP table entry which we will fill with the new * information. */ tabptr->at_ipaddr = ipaddr; memcpy(tabptr->at_ethaddr.addr, ethaddr, IFHWADDRLEN); tabptr->at_time = g_arptime; } /**************************************************************************** * Public Functions ****************************************************************************/ /* Initialize the ARP module. */ void uip_arp_init(void) { int i; for (i = 0; i < CONFIG_NET_ARPTAB_SIZE; ++i) { memset(&arp_table[i].at_ipaddr, 0, sizeof(in_addr_t)); } } /* Periodic ARP processing function. * * This function performs periodic timer processing in the ARP module * and should be called at regular intervals. The recommended interval * is 10 seconds between the calls. */ void uip_arp_timer(void) { struct arp_entry *tabptr; int i; ++g_arptime; for (i = 0; i < CONFIG_NET_ARPTAB_SIZE; ++i) { tabptr = &arp_table[i]; if (tabptr->at_ipaddr != 0 && g_arptime - tabptr->at_time >= UIP_ARP_MAXAGE) { tabptr->at_ipaddr = 0; } } } /* ARP processing for incoming IP packets * * This function should be called by the device driver when an IP * packet has been received. The function will check if the address is * in the ARP cache, and if so the ARP cache entry will be * refreshed. If no ARP cache entry was found, a new one is created. * * This function expects an IP packet with a prepended Ethernet header * in the d_buf[] buffer, and the length of the packet in the field * d_len. */ #if 0 void uip_arp_ipin(void) { /* Only insert/update an entry if the source IP address of the * incoming IP packet comes from a host on the local network. */ if ((IPBUF->eh_srcipaddr & dev->d_netmask) != (dev->d_ipaddr & dev->d_netmask)) { return; } uip_arp_update(IPBUF->eh_srcipaddr, ETHBUF->eh_ethhdr.src); } #endif /* 0 */ /* ARP processing for incoming ARP packets. * * This function should be called by the device driver when an ARP * packet has been received. The function will act differently * depending on the ARP packet type: if it is a reply for a request * that we previously sent out, the ARP cache will be filled in with * the values from the ARP reply. If the incoming ARP packet is an ARP * request for our IP address, an ARP reply packet is created and put * into the d_buf[] buffer. * * When the function returns, the value of the field d_len * indicates whether the device driver should send out a packet or * not. If d_len is zero, no packet should be sent. If d_len is * non-zero, it contains the length of the outbound packet that is * present in the d_buf[] buffer. * * This function expects an ARP packet with a prepended Ethernet * header in the d_buf[] buffer, and the length of the packet in the * global variable d_len. */ void uip_arp_arpin(struct uip_driver_s *dev) { in_addr_t ipaddr; if (dev->d_len < (sizeof(struct arp_hdr) + UIP_LLH_LEN)) { dev->d_len = 0; return; } dev->d_len = 0; ipaddr = uip_ip4addr_conv(ARPBUF->ah_dipaddr); switch(ARPBUF->ah_opcode) { case HTONS(ARP_REQUEST): /* ARP request. If it asked for our address, we send out a reply. */ if (uip_ipaddr_cmp(ipaddr, dev->d_ipaddr)) { /* First, we register the one who made the request in our ARP * table, since it is likely that we will do more communication * with this host in the future. */ uip_arp_update(ARPBUF->ah_sipaddr, ARPBUF->ah_shwaddr); /* The reply opcode is 2. */ ARPBUF->ah_opcode = HTONS(2); memcpy(ARPBUF->ah_dhwaddr, ARPBUF->ah_shwaddr, IFHWADDRLEN); memcpy(ARPBUF->ah_shwaddr, dev->d_mac.addr, IFHWADDRLEN); memcpy(ETHBUF->src, dev->d_mac.addr, IFHWADDRLEN); memcpy(ETHBUF->dest, ARPBUF->ah_dhwaddr, IFHWADDRLEN); ARPBUF->ah_dipaddr[0] = ARPBUF->ah_sipaddr[0]; ARPBUF->ah_dipaddr[1] = ARPBUF->ah_sipaddr[1]; uiphdr_ipaddr_copy(ARPBUF->ah_sipaddr, &dev->d_ipaddr); uip_arp_dump(ARPBUF); ETHBUF->type = HTONS(UIP_ETHTYPE_ARP); dev->d_len = sizeof(struct arp_hdr) + UIP_LLH_LEN; } break; case HTONS(ARP_REPLY): /* ARP reply. We insert or update the ARP table if it was meant * for us. */ if (uip_ipaddr_cmp(ipaddr, dev->d_ipaddr)) { uip_arp_update(ARPBUF->ah_sipaddr, ARPBUF->ah_shwaddr); } break; } } /* Prepend Ethernet header to an outbound IP packet and see if we need * to send out an ARP request. * * This function should be called before sending out an IP packet. The * function checks the destination IP address of the IP packet to see * what Ethernet MAC address that should be used as a destination MAC * address on the Ethernet. * * If the destination IP address is in the local network (determined * by logical ANDing of netmask and our IP address), the function * checks the ARP cache to see if an entry for the destination IP * address is found. If so, an Ethernet header is prepended and the * function returns. If no ARP cache entry is found for the * destination IP address, the packet in the d_buf[] is replaced by * an ARP request packet for the IP address. The IP packet is dropped * and it is assumed that they higher level protocols (e.g., TCP) * eventually will retransmit the dropped packet. * * If the destination IP address is not on the local network, the IP * address of the default router is used instead. * * When the function returns, a packet is present in the d_buf[] * buffer, and the length of the packet is in the field d_len. */ void uip_arp_out(struct uip_driver_s *dev) { struct arp_entry *tabptr; in_addr_t ipaddr; in_addr_t destipaddr; int i; /* Find the destination IP address in the ARP table and construct * the Ethernet header. If the destination IP addres isn't on the * local network, we use the default router's IP address instead. * * If not ARP table entry is found, we overwrite the original IP * packet with an ARP request for the IP address. */ /* First check if destination is a local broadcast. */ if (uiphdr_ipaddr_cmp(IPBUF->eh_destipaddr, broadcast_ipaddr)) { memcpy(ETHBUF->dest, broadcast_ethaddr.addr, IFHWADDRLEN); } else { /* Check if the destination address is on the local network. */ destipaddr = uip_ip4addr_conv(IPBUF->eh_destipaddr); if (!uip_ipaddr_maskcmp(destipaddr, dev->d_ipaddr, dev->d_netmask)) { /* Destination address was not on the local network, so we need to * use the default router's IP address instead of the destination * address when determining the MAC address. */ uip_ipaddr_copy(ipaddr, dev->d_draddr); } else { /* Else, we use the destination IP address. */ uip_ipaddr_copy(ipaddr, destipaddr); } /* Check if we already have this destination address in the ARP table */ for (i = 0; i < CONFIG_NET_ARPTAB_SIZE; ++i) { tabptr = &arp_table[i]; if (uip_ipaddr_cmp(ipaddr, tabptr->at_ipaddr)) { break; } } if (i == CONFIG_NET_ARPTAB_SIZE) { /* The destination address was not in our ARP table, so we * overwrite the IP packet with an ARP request. */ memset(ETHBUF->dest, 0xff, IFHWADDRLEN); memset(ARPBUF->ah_dhwaddr, 0x00, IFHWADDRLEN); memcpy(ETHBUF->src, dev->d_mac.addr, IFHWADDRLEN); memcpy(ARPBUF->ah_shwaddr, dev->d_mac.addr, IFHWADDRLEN); uiphdr_ipaddr_copy(ARPBUF->ah_dipaddr, &ipaddr); uiphdr_ipaddr_copy(ARPBUF->ah_sipaddr, &dev->d_ipaddr); ARPBUF->ah_opcode = HTONS(ARP_REQUEST); ARPBUF->ah_hwtype = HTONS(ARP_HWTYPE_ETH); ARPBUF->ah_protocol = HTONS(UIP_ETHTYPE_IP); ARPBUF->ah_hwlen = IFHWADDRLEN; ARPBUF->ah_protolen = 4; uip_arp_dump(ARPBUF); ETHBUF->type = HTONS(UIP_ETHTYPE_ARP); dev->d_appdata = &dev->d_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN]; dev->d_len = sizeof(struct arp_hdr) + UIP_LLH_LEN; return; } /* Build an ethernet header. */ memcpy(ETHBUF->dest, tabptr->at_ethaddr.addr, IFHWADDRLEN); } /* Finish populating the ethernet header */ memcpy(ETHBUF->src, dev->d_mac.addr, IFHWADDRLEN); ETHBUF->type = HTONS(UIP_ETHTYPE_IP); dev->d_len += UIP_LLH_LEN; } #endif /* CONFIG_NET */