| /** |
| * \file |
| * uIP packet forwarding. |
| * \author Adam Dunkels <adam@sics.se> |
| * |
| * This file implements a number of simple functions which do packet |
| * forwarding over multiple network interfaces with uIP. |
| * |
| */ |
| |
| #include "uip.h" |
| #include "uip-fw.h" |
| |
| /** |
| * \internal |
| * The list of registered network interfaces. |
| */ |
| static struct uip_fw_netif *netifs = NULL; |
| |
| /** |
| * \internal |
| * A pointer to the default network interface. |
| */ |
| static struct uip_fw_netif *defaultnetif = NULL; |
| |
| struct tcpip_hdr { |
| /* IP header. */ |
| u8_t vhl, |
| tos; |
| u16_t len, |
| ipid, |
| ipoffset; |
| u8_t ttl, |
| proto; |
| u16_t ipchksum; |
| u16_t srcipaddr[2], |
| destipaddr[2]; |
| |
| /* TCP header. */ |
| u16_t srcport, |
| destport; |
| u8_t seqno[4], |
| ackno[4], |
| tcpoffset, |
| flags, |
| wnd[2]; |
| u16_t tcpchksum; |
| u8_t urgp[2]; |
| u8_t optdata[4]; |
| }; |
| |
| /** |
| * \internal |
| * Pointer to the TCP/IP headers of the packet in the uip_buf buffer. |
| */ |
| #define BUF ((struct tcpip_hdr *)&uip_buf[UIP_LLH_LEN]) |
| |
| /** |
| * \internal |
| * Certain fields of an IP packet that are used for identifying |
| * duplicate packets. |
| */ |
| struct fwcache_entry { |
| u16_t timestamp; |
| |
| u16_t len, offset, ipid; |
| u16_t srcipaddr[2]; |
| u16_t destipaddr[2]; |
| u16_t payload[2]; |
| }; |
| |
| /** |
| * \internal |
| * The number of packets to remember when looking for duplicates. |
| */ |
| #define FWCACHE_SIZE 2 |
| |
| /** |
| * \internal |
| * A cache of packet header fields which are used for |
| * identifying duplicate packets. |
| */ |
| static struct fwcache_entry fwcache[FWCACHE_SIZE]; |
| |
| /*------------------------------------------------------------------------------*/ |
| /** |
| * Initialize the uIP packet forwarding module. |
| */ |
| /*------------------------------------------------------------------------------*/ |
| void |
| uip_fw_init(void) |
| { |
| defaultnetif = netifs = NULL; |
| } |
| /*------------------------------------------------------------------------------*/ |
| /** |
| * \internal |
| * Check if an IP address is within the network defined by an IP |
| * address and a netmask. |
| * |
| * \param ipaddr The IP address to be checked. |
| * \param netipaddr The IP address of the network. |
| * \param netmask The netmask of the network. |
| * |
| * \return Non-zero if IP address is in network, zero otherwise. |
| */ |
| /*------------------------------------------------------------------------------*/ |
| static unsigned char |
| ipaddr_maskcmp(u16_t *ipaddr, u16_t *netipaddr, u16_t *netmask) |
| { |
| return (ipaddr[0] & netmask [0]) == (netipaddr[0] & netmask[0]) && |
| (ipaddr[1] & netmask[1]) == (netipaddr[1] & netmask[1]); |
| } |
| /*------------------------------------------------------------------------------*/ |
| /** |
| * \internal |
| * Register a packet in the forwarding cache so that it won't be |
| * forwarded again. |
| */ |
| /*------------------------------------------------------------------------------*/ |
| static void |
| fwcache_register(void) |
| { |
| struct fwcache_entry *fw; |
| |
| /* Register packet in forwarding cache. */ |
| fw = &fwcache[0]; |
| fw->len = BUF->len; |
| fw->offset = BUF->ipoffset; |
| fw->ipid = BUF->ipid; |
| fw->srcipaddr[0] = BUF->srcipaddr[0]; |
| fw->srcipaddr[1] = BUF->srcipaddr[1]; |
| fw->destipaddr[0] = BUF->destipaddr[0]; |
| fw->destipaddr[1] = BUF->destipaddr[1]; |
| fw->payload[0] = BUF->srcport; |
| fw->payload[1] = BUF->destport; |
| } |
| /*------------------------------------------------------------------------------*/ |
| /** |
| * Output an IP packet on the correct network interface. |
| * |
| * The IP packet should be present in the uip_buf buffer and its |
| * length in the global uip_len variable. |
| */ |
| /*------------------------------------------------------------------------------*/ |
| void |
| uip_fw_output(void) |
| { |
| struct uip_fw_netif *netif; |
| |
| /* Walk through every network interface to check for a match. */ |
| for(netif = netifs; netif != NULL; netif = netif->next) { |
| if(ipaddr_maskcmp(BUF->destipaddr, netif->ipaddr, |
| netif->netmask)) { |
| /* If there was a match, we break the loop. */ |
| break; |
| } |
| } |
| |
| /* If no matching netif was found, we use default netif. */ |
| if(netif == NULL) { |
| netif = defaultnetif; |
| } |
| |
| /* If we now have found a suitable network interface, we call its |
| output function to send out the packet. */ |
| if(netif != NULL && uip_len > 0) { |
| fwcache_register(); |
| netif->output(); |
| } |
| } |
| /*------------------------------------------------------------------------------*/ |
| /** |
| * Forward an IP packet in the uip_buf buffer. |
| * |
| * |
| * |
| * \return Non-zero if the packet was forwarded, zero if the packet |
| * should be processed locally. |
| */ |
| /*------------------------------------------------------------------------------*/ |
| unsigned char |
| uip_fw_forward(void) |
| { |
| struct uip_fw_netif *netif; |
| struct fwcache_entry *fw; |
| |
| /* First check if the packet is destined for ourselves and return 0 |
| to indicate that the packet should be processed locally. */ |
| if(BUF->destipaddr[0] == uip_hostaddr[0] && |
| BUF->destipaddr[1] == uip_hostaddr[1]) { |
| return 0; |
| } |
| |
| /* Check if the packet is in the forwarding cache already, and if so |
| we drop it. */ |
| /* for(fw = fwcache; fw <= &fwcache[FWCACHE_SIZE]; ++fw) {*/ |
| fw = &fwcache[0]; |
| { |
| if(fw->len == BUF->len && |
| fw->offset == BUF->ipoffset && |
| fw->ipid == BUF->ipid && |
| fw->srcipaddr[0] == BUF->srcipaddr[0] && |
| fw->srcipaddr[1] == BUF->srcipaddr[1] && |
| fw->destipaddr[0] == BUF->destipaddr[0] && |
| fw->destipaddr[1] == BUF->destipaddr[1] && |
| fw->payload[0] == BUF->srcport && |
| fw->payload[1] == BUF->destport) { |
| /* Drop packet. */ |
| return 1; |
| } |
| } |
| |
| |
| /* Walk through every network interface to check for a match. */ |
| for(netif = netifs; netif != NULL; netif = netif->next) { |
| if(ipaddr_maskcmp(BUF->destipaddr, netif->ipaddr, |
| netif->netmask)) { |
| /* If there was a match, we break the loop. */ |
| break; |
| } |
| } |
| |
| /* If no matching netif was found, we use default netif. */ |
| if(netif == NULL) { |
| netif = defaultnetif; |
| } |
| |
| /* Decrement the TTL (time-to-live) value in the IP header */ |
| BUF->ttl = htons(htons(BUF->ttl) - 1); |
| |
| /* We should really send an ICMP message if TTL == 0, but we skip it |
| for now... Instead, we just drop the packet (and pretend that it |
| was forwarded by returning 1). */ |
| if(BUF->ttl == 0) { |
| return 1; |
| } |
| |
| /* Incrementally update the IP checksum. */ |
| if(BUF->ipchksum >= htons(0xffff - 0x0100)) { |
| BUF->ipchksum = BUF->ipchksum + HTONS(0x0100) + 1; |
| } else { |
| BUF->ipchksum = BUF->ipchksum + HTONS(0x0100); |
| } |
| |
| /* If we now have found a suitable network interface, we call its |
| output function to send out the packet. */ |
| if(netif != NULL && uip_len > 0) { |
| uip_appdata = &uip_buf[UIP_LLH_LEN + 40]; |
| fwcache_register(); |
| netif->output(); |
| } |
| |
| /* Return non-zero to indicate that the packet was forwarded and that no |
| other processing should be made. */ |
| return 1; |
| } |
| /*------------------------------------------------------------------------------*/ |
| /** |
| * Register a network interface with the forwarding module. |
| * |
| * \param netif A pointer to the network interface that is to be |
| * registered. |
| */ |
| /*------------------------------------------------------------------------------*/ |
| void |
| uip_fw_register(struct uip_fw_netif *netif) |
| { |
| netif->next = netifs; |
| netifs = netif; |
| } |
| /*------------------------------------------------------------------------------*/ |
| /** |
| * Register a default network interface. |
| * |
| * All packets that don't go out on any of the other interfaces will |
| * be routed to the default interface. |
| * |
| * \param netif A pointer to the network interface that is to be |
| * registered. |
| */ |
| /*------------------------------------------------------------------------------*/ |
| void |
| uip_fw_default(struct uip_fw_netif *netif) |
| { |
| defaultnetif = netif; |
| } |
| /*------------------------------------------------------------------------------*/ |