diff options
Diffstat (limited to 'networking/udhcp/packet.c')
| -rw-r--r-- | networking/udhcp/packet.c | 207 |
1 files changed, 207 insertions, 0 deletions
diff --git a/networking/udhcp/packet.c b/networking/udhcp/packet.c new file mode 100644 index 000000000..ae06d53cc --- /dev/null +++ b/networking/udhcp/packet.c @@ -0,0 +1,207 @@ +#include <unistd.h> +#include <string.h> +#include <netinet/in.h> +#include <sys/types.h> +#include <sys/socket.h> +#include <features.h> +#if (__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 <errno.h> + +#include "common.h" +#include "packet.h" +#include "dhcpd.h" +#include "options.h" + + +void 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 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(LOG_INFO, "couldn't read on listening socket, ignoring"); + return -1; + } + + if (ntohl(packet->cookie) != DHCP_MAGIC) { + LOG(LOG_ERR, "received bogus message, ignoring"); + return -2; + } + DEBUG(LOG_INFO, "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(LOG_INFO, "broken client (%s), forcing broadcast", + broken_vendors[i]); + packet->flags |= htons(BROADCAST_FLAG); + } + } + } + + return bytes; +} + + +uint16_t checksum(void *addr, int count) +{ + /* Compute Internet Checksum for "count" bytes + * beginning at location "addr". + */ + register 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 */ +int 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; + + if ((fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP))) < 0) { + DEBUG(LOG_ERR, "socket call failed: %m"); + 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) { + DEBUG(LOG_ERR, "bind call failed: %m"); + 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 = 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 = checksum(&(packet.ip), sizeof(packet.ip)); + + result = sendto(fd, &packet, sizeof(struct udp_dhcp_packet), 0, (struct sockaddr *) &dest, sizeof(dest)); + if (result <= 0) { + DEBUG(LOG_ERR, "write on socket failed: %m"); + } + close(fd); + return result; +} + + +/* Let the kernel do all the work for packet generation */ +int kernel_packet(struct dhcpMessage *payload, uint32_t source_ip, int source_port, + uint32_t dest_ip, int dest_port) +{ + int n = 1; + int fd, result; + struct sockaddr_in client; + + if ((fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) + return -1; + + if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char *) &n, sizeof(n)) == -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; +} |