/* Let the kernel do all the work for packet generation */
int FAST_FUNC udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
uint32_t source_nip, int source_port,
uint32_t dest_nip, int dest_port)
{
struct sockaddr_in client;
unsigned padding;
int fd;
int result = -1;
const char *msg;
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_nip;
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_nip;
if (connect(fd, (struct sockaddr *)&client, sizeof(client)) == -1) {
msg = "connect";
goto ret_close;
}
udhcp_dump_packet(dhcp_pkt);
padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(dhcp_pkt->options);
result = safe_write(fd, dhcp_pkt, DHCP_SIZE - padding);
msg = "write";
ret_close:
close(fd);
if (result < 0) {
ret_msg:
bb_perror_msg(msg, "UDP");
}
return result;
}
/* Add an option (supplied in binary form) to the options.
* Option format: [code][len][data1][data2]..[dataLEN]
*/
void FAST_FUNC udhcp_add_binary_option(struct dhcp_packet *packet, uint8_t *addopt)
{
unsigned len;
uint8_t *optionptr = packet->options;
unsigned end = udhcp_end_option(optionptr);
len = OPT_DATA + addopt[OPT_LEN];
/* end position + (option code/length + addopt length) + end option */
if (end + len + 1 >= DHCP_OPTIONS_BUFSIZE) {
//TODO: learn how to use overflow option if we exhaust packet->options[]
bb_error_msg("option 0x%02x did not fit into the packet",
addopt[OPT_CODE]);
return;
}
log_option("adding option", addopt);
memcpy(optionptr + end, addopt, len);
optionptr[end + len] = DHCP_END;
}
/* Construct a ip/udp header for a packet, send packet */
int FAST_FUNC udhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
uint32_t source_nip, int source_port,
uint32_t dest_nip, int dest_port, const uint8_t *dest_arp,
int ifindex)
{
struct sockaddr_ll dest_sll;
struct ip_udp_dhcp_packet packet;
unsigned padding;
int fd;
int result = -1;
const char *msg;
fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
if (fd < 0) {
msg = "socket(%s)";
goto ret_msg;
}
memset(&dest_sll, 0, sizeof(dest_sll));
memset(&packet, 0, offsetof(struct ip_udp_dhcp_packet, data));
packet.data = *dhcp_pkt; /* struct copy */
dest_sll.sll_family = AF_PACKET;
dest_sll.sll_protocol = htons(ETH_P_IP);
dest_sll.sll_ifindex = ifindex;
dest_sll.sll_halen = 6;
memcpy(dest_sll.sll_addr, dest_arp, 6);
if (bind(fd, (struct sockaddr *)&dest_sll, sizeof(dest_sll)) < 0) {
msg = "bind(%s)";
goto ret_close;
}
/* We were sending full-sized DHCP packets (zero padded),
* but some badly configured servers were seen dropping them.
* Apparently they drop all DHCP packets >576 *ethernet* octets big,
* whereas they may only drop packets >576 *IP* octets big
* (which for typical Ethernet II means 590 octets: 6+6+2 + 576).
*
* In order to work with those buggy servers,
* we truncate packets after end option byte.
*/
padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(packet.data.options);
packet.ip.protocol = IPPROTO_UDP;
packet.ip.saddr = source_nip;
packet.ip.daddr = dest_nip;
packet.udp.source = htons(source_port);
packet.udp.dest = htons(dest_port);
/* size, excluding IP header: */
packet.udp.len = htons(UDP_DHCP_SIZE - padding);
/* for UDP checksumming, ip.len is set to UDP packet len */
packet.ip.tot_len = packet.udp.len;
packet.udp.check = inet_cksum((uint16_t *)&packet,
IP_UDP_DHCP_SIZE - padding);
/* but for sending, it is set to IP packet len */
packet.ip.tot_len = htons(IP_UDP_DHCP_SIZE - padding);
packet.ip.ihl = sizeof(packet.ip) >> 2;
packet.ip.version = IPVERSION;
packet.ip.ttl = IPDEFTTL;
packet.ip.check = inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip));
udhcp_dump_packet(dhcp_pkt);
result = sendto(fd, &packet, IP_UDP_DHCP_SIZE - padding, /*flags:*/ 0,
(struct sockaddr *) &dest_sll, sizeof(dest_sll));
msg = "sendto";
ret_close:
close(fd);
if (result < 0) {
ret_msg:
bb_perror_msg(msg, "PACKET");
}
return result;
}
