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/* vi: set sw=4 ts=4: */
/*
* Packet ops
*
* Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
*
* Licensed under GPLv2, see file LICENSE in this source tree.
*/
#include "common.h"
#include "dhcpd.h"
#include <netinet/in.h>
#include <netinet/if_ether.h>
#include <netpacket/packet.h>
#if ENABLE_UDHCPC || ENABLE_UDHCPD
void FAST_FUNC udhcp_init_header(struct dhcp_packet *packet, char type)
{
memset(packet, 0, sizeof(*packet));
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 = 1; /* ethernet */
packet->hlen = 6;
packet->cookie = htonl(DHCP_MAGIC);
if (DHCP_END != 0)
packet->options[0] = DHCP_END;
udhcp_add_simple_option(packet, DHCP_MESSAGE_TYPE, type);
}
#endif
#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2
void FAST_FUNC udhcp_dump_packet(struct dhcp_packet *packet)
{
char buf[sizeof(packet->chaddr)*2 + 1];
if (dhcp_verbose < 2)
return;
bb_info_msg(
//" op %x"
//" htype %x"
" hlen %x"
//" hops %x"
" xid %x"
//" secs %x"
//" flags %x"
" ciaddr %x"
" yiaddr %x"
" siaddr %x"
" giaddr %x"
//" sname %s"
//" file %s"
//" cookie %x"
//" options %s"
//, packet->op
//, packet->htype
, packet->hlen
//, packet->hops
, packet->xid
//, packet->secs
//, packet->flags
, packet->ciaddr
, packet->yiaddr
, packet->siaddr_nip
, packet->gateway_nip
//, packet->sname[64]
//, packet->file[128]
//, packet->cookie
//, packet->options[]
);
*bin2hex(buf, (void *) packet->chaddr, sizeof(packet->chaddr)) = '\0';
bb_info_msg(" chaddr %s", buf);
}
#endif
/* Read a packet from socket fd, return -1 on read error, -2 on packet error */
int FAST_FUNC udhcp_recv_kernel_packet(struct dhcp_packet *packet, int fd)
{
int bytes;
memset(packet, 0, sizeof(*packet));
bytes = safe_read(fd, packet, sizeof(*packet));
if (bytes < 0) {
log1s("packet read error, ignoring");
return bytes; /* returns -1 */
}
if (bytes < offsetof(struct dhcp_packet, options)
|| packet->cookie != htonl(DHCP_MAGIC)
) {
bb_simple_info_msg("packet with bad magic, ignoring");
return -2;
}
log1("received %s", "a packet");
udhcp_dump_packet(packet);
return bytes;
}
/* 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_hatype = ARPHRD_???;*/
/*dest_sll.sll_pkttype = PACKET_???;*/
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.
*
* However, RFC 1542 says "The IP Total Length and UDP Length
* must be large enough to contain the minimal BOOTP header of 300 octets".
* Thus, we retain enough padding to not go below 300 BOOTP bytes.
* Some devices have filters which drop DHCP packets shorter than that.
*/
padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(packet.data.options);
if (padding > DHCP_SIZE - 300)
padding = DHCP_SIZE - 300;
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(&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(&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;
}
/* 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,
const char *ifname)
{
struct sockaddr_in sa;
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);
/* If interface carrier goes down, unless we
* bind socket to a particular netdev, the packet
* can go out through another interface, eg. via
* default route despite being bound to a specific
* source IP. As such, bind to device hard and fail
* otherwise. Sending renewal packets on foreign
* interfaces makes no sense.
*/
if (ifname) {
if (setsockopt_bindtodevice(fd, ifname) < 0) {
msg = "bindtodevice";
goto ret_close;
}
}
memset(&sa, 0, sizeof(sa));
sa.sin_family = AF_INET;
sa.sin_port = htons(source_port);
sa.sin_addr.s_addr = source_nip;
if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
msg = "bind(%s)";
goto ret_close;
}
memset(&sa, 0, sizeof(sa));
sa.sin_family = AF_INET;
sa.sin_port = htons(dest_port);
sa.sin_addr.s_addr = dest_nip;
if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
msg = "connect";
goto ret_close;
}
udhcp_dump_packet(dhcp_pkt);
padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(dhcp_pkt->options);
if (padding > DHCP_SIZE - 300)
padding = DHCP_SIZE - 300;
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;
}
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