/* vi: set sw=4 ts=4: */ /* * packet.c -- packet ops * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001 * * Licensed under GPLv2, see file LICENSE in this tarball for details. */ #include <netinet/in.h> #if (defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 1) || defined _NEWLIB_VERSION #include <netpacket/packet.h> #include <net/ethernet.h> #else #include <asm/types.h> #include <linux/if_packet.h> #include <linux/if_ether.h> #endif #include "common.h" #include "dhcpd.h" #include "options.h" void FAST_FUNC udhcp_init_header(struct dhcpMessage *packet, char type) { memset(packet, 0, sizeof(struct dhcpMessage)); packet->op = BOOTREQUEST; /* if client to a server */ switch (type) { case DHCPOFFER: case DHCPACK: case DHCPNAK: packet->op = BOOTREPLY; /* if server to client */ } packet->htype = ETH_10MB; packet->hlen = ETH_10MB_LEN; packet->cookie = htonl(DHCP_MAGIC); packet->options[0] = DHCP_END; add_simple_option(packet->options, DHCP_MESSAGE_TYPE, type); } /* read a packet from socket fd, return -1 on read error, -2 on packet error */ int FAST_FUNC udhcp_recv_kernel_packet(struct dhcpMessage *packet, int fd) { int bytes; unsigned char *vendor; memset(packet, 0, sizeof(*packet)); bytes = safe_read(fd, packet, sizeof(*packet)); if (bytes < 0) { DEBUG("cannot read on listening socket, ignoring"); return bytes; /* returns -1 */ } if (packet->cookie != htonl(DHCP_MAGIC)) { bb_error_msg("received bogus message, ignoring"); return -2; } DEBUG("Received a packet"); if (packet->op == BOOTREQUEST) { vendor = get_option(packet, DHCP_VENDOR); if (vendor) { #if 0 static const char broken_vendors[][8] = { "MSFT 98", "" }; int i; for (i = 0; broken_vendors[i][0]; i++) { if (vendor[OPT_LEN - 2] == (uint8_t)strlen(broken_vendors[i]) && !strncmp((char*)vendor, broken_vendors[i], vendor[OPT_LEN - 2]) ) { DEBUG("broken client (%s), forcing broadcast replies", broken_vendors[i]); packet->flags |= htons(BROADCAST_FLAG); } } #else if (vendor[OPT_LEN - 2] == (uint8_t)(sizeof("MSFT 98")-1) && memcmp(vendor, "MSFT 98", sizeof("MSFT 98")-1) == 0 ) { DEBUG("broken client (%s), forcing broadcast replies", "MSFT 98"); packet->flags |= htons(BROADCAST_FLAG); } #endif } } return bytes; } uint16_t FAST_FUNC udhcp_checksum(void *addr, int count) { /* Compute Internet Checksum for "count" bytes * beginning at location "addr". */ int32_t sum = 0; uint16_t *source = (uint16_t *) addr; while (count > 1) { /* This is the inner loop */ sum += *source++; count -= 2; } /* Add left-over byte, if any */ if (count > 0) { /* Make sure that the left-over byte is added correctly both * with little and big endian hosts */ uint16_t tmp = 0; *(uint8_t*)&tmp = *(uint8_t*)source; sum += tmp; } /* Fold 32-bit sum to 16 bits */ while (sum >> 16) sum = (sum & 0xffff) + (sum >> 16); return ~sum; } /* Construct a ip/udp header for a packet, send packet */ int FAST_FUNC udhcp_send_raw_packet(struct dhcpMessage *payload, uint32_t source_ip, int source_port, uint32_t dest_ip, int dest_port, const uint8_t *dest_arp, int ifindex) { struct sockaddr_ll dest; struct udp_dhcp_packet packet; int fd; int result = -1; const char *msg; enum { IP_UPD_DHCP_SIZE = sizeof(struct udp_dhcp_packet) - CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS, UPD_DHCP_SIZE = IP_UPD_DHCP_SIZE - offsetof(struct udp_dhcp_packet, udp), }; fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP)); if (fd < 0) { msg = "socket(%s)"; goto ret_msg; } memset(&dest, 0, sizeof(dest)); memset(&packet, 0, sizeof(packet)); packet.data = *payload; /* struct copy */ dest.sll_family = AF_PACKET; dest.sll_protocol = htons(ETH_P_IP); dest.sll_ifindex = ifindex; dest.sll_halen = 6; memcpy(dest.sll_addr, dest_arp, 6); if (bind(fd, (struct sockaddr *)&dest, sizeof(dest)) < 0) { msg = "bind(%s)"; goto ret_close; } packet.ip.protocol = IPPROTO_UDP; packet.ip.saddr = source_ip; packet.ip.daddr = dest_ip; packet.udp.source = htons(source_port); packet.udp.dest = htons(dest_port); /* size, excluding IP header: */ packet.udp.len = htons(UPD_DHCP_SIZE); /* for UDP checksumming, ip.len is set to UDP packet len */ packet.ip.tot_len = packet.udp.len; packet.udp.check = udhcp_checksum(&packet, IP_UPD_DHCP_SIZE); /* but for sending, it is set to IP packet len */ packet.ip.tot_len = htons(IP_UPD_DHCP_SIZE); packet.ip.ihl = sizeof(packet.ip) >> 2; packet.ip.version = IPVERSION; packet.ip.ttl = IPDEFTTL; packet.ip.check = udhcp_checksum(&packet.ip, sizeof(packet.ip)); /* Currently we send full-sized DHCP packets (zero padded). * If you need to change this: last byte of the packet is * packet.data.options[end_option(packet.data.options)] */ result = sendto(fd, &packet, IP_UPD_DHCP_SIZE, 0, (struct sockaddr *) &dest, sizeof(dest)); msg = "sendto"; ret_close: close(fd); if (result < 0) { ret_msg: bb_perror_msg(msg, "PACKET"); } return result; } /* Let the kernel do all the work for packet generation */ int FAST_FUNC udhcp_send_kernel_packet(struct dhcpMessage *payload, uint32_t source_ip, int source_port, uint32_t dest_ip, int dest_port) { struct sockaddr_in client; int fd; int result = -1; const char *msg; enum { DHCP_SIZE = sizeof(struct dhcpMessage) - CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS, }; fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP); if (fd < 0) { msg = "socket(%s)"; goto ret_msg; } setsockopt_reuseaddr(fd); memset(&client, 0, sizeof(client)); client.sin_family = AF_INET; client.sin_port = htons(source_port); client.sin_addr.s_addr = source_ip; if (bind(fd, (struct sockaddr *)&client, sizeof(client)) == -1) { msg = "bind(%s)"; goto ret_close; } memset(&client, 0, sizeof(client)); client.sin_family = AF_INET; client.sin_port = htons(dest_port); client.sin_addr.s_addr = dest_ip; if (connect(fd, (struct sockaddr *)&client, sizeof(client)) == -1) { msg = "connect"; goto ret_close; } /* Currently we send full-sized DHCP packets (see above) */ result = safe_write(fd, payload, DHCP_SIZE); msg = "write"; ret_close: close(fd); if (result < 0) { ret_msg: bb_perror_msg(msg, "UDP"); } return result; }