/* vi: set sw=4 ts=4: */ #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 udhcp_init_header(struct dhcpMessage *packet, char type) { memset(packet, 0, sizeof(struct dhcpMessage)); switch (type) { case DHCPDISCOVER: case DHCPREQUEST: case DHCPRELEASE: case DHCPINFORM: packet->op = BOOTREQUEST; break; case DHCPOFFER: case DHCPACK: case DHCPNAK: packet->op = BOOTREPLY; } 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 udhcp_get_packet(struct dhcpMessage *packet, int fd) { static const char broken_vendors[][8] = { "MSFT 98", "" }; int bytes; int i; char unsigned *vendor; memset(packet, 0, sizeof(struct dhcpMessage)); bytes = read(fd, packet, sizeof(struct dhcpMessage)); if (bytes < 0) { DEBUG("cannot read on listening socket, ignoring"); return -1; } if (ntohl(packet->cookie) != 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))) { 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", broken_vendors[i]); packet->flags |= htons(BROADCAST_FLAG); } } } return bytes; } uint16_t 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, and specify the source and dest hardware address */ void BUG_sizeof_struct_udp_dhcp_packet_must_be_576(void); int udhcp_raw_packet(struct dhcpMessage *payload, uint32_t source_ip, int source_port, uint32_t dest_ip, int dest_port, uint8_t *dest_arp, int ifindex) { int fd; int result; struct sockaddr_ll dest; struct udp_dhcp_packet packet; fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP)); if (fd < 0) { bb_perror_msg("socket"); return -1; } memset(&dest, 0, sizeof(dest)); memset(&packet, 0, sizeof(packet)); 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(struct sockaddr_ll)) < 0) { bb_perror_msg("bind"); close(fd); return -1; } 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); packet.udp.len = htons(sizeof(packet.udp) + sizeof(struct dhcpMessage)); /* cheat on the psuedo-header */ packet.ip.tot_len = packet.udp.len; memcpy(&(packet.data), payload, sizeof(struct dhcpMessage)); packet.udp.check = udhcp_checksum(&packet, sizeof(struct udp_dhcp_packet)); packet.ip.tot_len = htons(sizeof(struct udp_dhcp_packet)); 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)); if (sizeof(struct udp_dhcp_packet) != 576) BUG_sizeof_struct_udp_dhcp_packet_must_be_576(); result = sendto(fd, &packet, sizeof(struct udp_dhcp_packet), 0, (struct sockaddr *) &dest, sizeof(dest)); if (result <= 0) { bb_perror_msg("sendto"); } close(fd); return result; } /* Let the kernel do all the work for packet generation */ int udhcp_kernel_packet(struct dhcpMessage *payload, uint32_t source_ip, int source_port, uint32_t dest_ip, int dest_port) { int fd, result; struct sockaddr_in client; fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP); if (fd < 0) return -1; if (setsockopt_reuseaddr(fd) == -1) { close(fd); return -1; } 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(struct sockaddr)) == -1) { close(fd); return -1; } 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(struct sockaddr)) == -1) { close(fd); return -1; } result = write(fd, payload, sizeof(struct dhcpMessage)); close(fd); return result; }