diff options
Diffstat (limited to 'networking/udhcp/packet.c')
-rw-r--r-- | networking/udhcp/packet.c | 238 |
1 files changed, 238 insertions, 0 deletions
diff --git a/networking/udhcp/packet.c b/networking/udhcp/packet.c new file mode 100644 index 0000000..1a6f7e6 --- /dev/null +++ b/networking/udhcp/packet.c @@ -0,0 +1,238 @@ +/* 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 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; +} |