289 lines
7.1 KiB
C
289 lines
7.1 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* packet.c -- packet ops
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* Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
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*
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* Licensed under GPLv2, see file LICENSE in this tarball for details.
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*/
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#include <netinet/in.h>
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#if (defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 1) || defined _NEWLIB_VERSION
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#include <netpacket/packet.h>
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#include <net/ethernet.h>
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#else
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#include <asm/types.h>
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#include <linux/if_packet.h>
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#include <linux/if_ether.h>
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#endif
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#include "common.h"
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#include "dhcpd.h"
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#include "options.h"
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void FAST_FUNC udhcp_init_header(struct dhcp_packet *packet, char type)
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{
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memset(packet, 0, sizeof(struct dhcp_packet));
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packet->op = BOOTREQUEST; /* if client to a server */
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switch (type) {
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case DHCPOFFER:
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case DHCPACK:
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case DHCPNAK:
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packet->op = BOOTREPLY; /* if server to client */
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}
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packet->htype = ETH_10MB;
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packet->hlen = ETH_10MB_LEN;
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packet->cookie = htonl(DHCP_MAGIC);
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packet->options[0] = DHCP_END;
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add_simple_option(packet->options, DHCP_MESSAGE_TYPE, type);
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}
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#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
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void FAST_FUNC udhcp_dump_packet(struct dhcp_packet *packet)
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{
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char buf[sizeof(packet->chaddr)*2 + 1];
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if (dhcp_verbose < 2)
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return;
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bb_info_msg(
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//" op %x"
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//" htype %x"
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" hlen %x"
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//" hops %x"
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" xid %x"
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//" secs %x"
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//" flags %x"
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" ciaddr %x"
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" yiaddr %x"
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" siaddr %x"
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" giaddr %x"
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//" chaddr %s"
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//" sname %s"
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//" file %s"
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//" cookie %x"
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//" options %s"
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//, packet->op
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//, packet->htype
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, packet->hlen
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//, packet->hops
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, packet->xid
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//, packet->secs
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//, packet->flags
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, packet->ciaddr
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, packet->yiaddr
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, packet->siaddr_nip
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, packet->gateway_nip
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//, packet->chaddr[16]
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//, packet->sname[64]
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//, packet->file[128]
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//, packet->cookie
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//, packet->options[]
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);
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*bin2hex(buf, (void *) packet->chaddr, sizeof(packet->chaddr)) = '\0';
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bb_info_msg(" chaddr %s", buf);
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}
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#endif
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/* Read a packet from socket fd, return -1 on read error, -2 on packet error */
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int FAST_FUNC udhcp_recv_kernel_packet(struct dhcp_packet *packet, int fd)
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{
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int bytes;
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unsigned char *vendor;
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memset(packet, 0, sizeof(*packet));
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bytes = safe_read(fd, packet, sizeof(*packet));
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if (bytes < 0) {
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log1("Packet read error, ignoring");
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return bytes; /* returns -1 */
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}
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if (packet->cookie != htonl(DHCP_MAGIC)) {
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bb_info_msg("Packet with bad magic, ignoring");
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return -2;
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}
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log1("Received a packet");
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udhcp_dump_packet(packet);
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if (packet->op == BOOTREQUEST) {
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vendor = get_option(packet, DHCP_VENDOR);
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if (vendor) {
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#if 0
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static const char broken_vendors[][8] = {
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"MSFT 98",
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""
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};
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int i;
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for (i = 0; broken_vendors[i][0]; i++) {
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if (vendor[OPT_LEN - 2] == (uint8_t)strlen(broken_vendors[i])
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&& !strncmp((char*)vendor, broken_vendors[i], vendor[OPT_LEN - 2])
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) {
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log1("Broken client (%s), forcing broadcast replies",
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broken_vendors[i]);
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packet->flags |= htons(BROADCAST_FLAG);
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}
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}
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#else
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if (vendor[OPT_LEN - 2] == (uint8_t)(sizeof("MSFT 98")-1)
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&& memcmp(vendor, "MSFT 98", sizeof("MSFT 98")-1) == 0
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) {
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log1("Broken client (%s), forcing broadcast replies", "MSFT 98");
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packet->flags |= htons(BROADCAST_FLAG);
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}
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#endif
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}
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}
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return bytes;
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}
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uint16_t FAST_FUNC udhcp_checksum(void *addr, int count)
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{
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/* Compute Internet Checksum for "count" bytes
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* beginning at location "addr".
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*/
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int32_t sum = 0;
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uint16_t *source = (uint16_t *) addr;
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while (count > 1) {
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/* This is the inner loop */
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sum += *source++;
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count -= 2;
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}
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/* Add left-over byte, if any */
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if (count > 0) {
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/* Make sure that the left-over byte is added correctly both
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* with little and big endian hosts */
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uint16_t tmp = 0;
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*(uint8_t*)&tmp = *(uint8_t*)source;
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sum += tmp;
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}
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/* Fold 32-bit sum to 16 bits */
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while (sum >> 16)
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sum = (sum & 0xffff) + (sum >> 16);
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return ~sum;
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}
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/* Construct a ip/udp header for a packet, send packet */
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int FAST_FUNC udhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
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uint32_t source_ip, int source_port,
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uint32_t dest_ip, int dest_port, const uint8_t *dest_arp,
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int ifindex)
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{
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struct sockaddr_ll dest;
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struct ip_udp_dhcp_packet packet;
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int fd;
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int result = -1;
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const char *msg;
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enum {
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IP_UPD_DHCP_SIZE = sizeof(struct ip_udp_dhcp_packet) - CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS,
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UPD_DHCP_SIZE = IP_UPD_DHCP_SIZE - offsetof(struct ip_udp_dhcp_packet, udp),
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};
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fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
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if (fd < 0) {
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msg = "socket(%s)";
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goto ret_msg;
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}
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memset(&dest, 0, sizeof(dest));
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memset(&packet, 0, sizeof(packet));
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packet.data = *dhcp_pkt; /* struct copy */
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dest.sll_family = AF_PACKET;
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dest.sll_protocol = htons(ETH_P_IP);
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dest.sll_ifindex = ifindex;
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dest.sll_halen = 6;
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memcpy(dest.sll_addr, dest_arp, 6);
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if (bind(fd, (struct sockaddr *)&dest, sizeof(dest)) < 0) {
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msg = "bind(%s)";
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goto ret_close;
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}
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packet.ip.protocol = IPPROTO_UDP;
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packet.ip.saddr = source_ip;
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packet.ip.daddr = dest_ip;
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packet.udp.source = htons(source_port);
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packet.udp.dest = htons(dest_port);
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/* size, excluding IP header: */
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packet.udp.len = htons(UPD_DHCP_SIZE);
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/* for UDP checksumming, ip.len is set to UDP packet len */
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packet.ip.tot_len = packet.udp.len;
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packet.udp.check = udhcp_checksum(&packet, IP_UPD_DHCP_SIZE);
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/* but for sending, it is set to IP packet len */
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packet.ip.tot_len = htons(IP_UPD_DHCP_SIZE);
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packet.ip.ihl = sizeof(packet.ip) >> 2;
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packet.ip.version = IPVERSION;
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packet.ip.ttl = IPDEFTTL;
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packet.ip.check = udhcp_checksum(&packet.ip, sizeof(packet.ip));
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/* Currently we send full-sized DHCP packets (zero padded).
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* If you need to change this: last byte of the packet is
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* packet.data.options[end_option(packet.data.options)]
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*/
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udhcp_dump_packet(dhcp_pkt);
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result = sendto(fd, &packet, IP_UPD_DHCP_SIZE, 0,
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(struct sockaddr *) &dest, sizeof(dest));
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msg = "sendto";
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ret_close:
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close(fd);
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if (result < 0) {
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ret_msg:
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bb_perror_msg(msg, "PACKET");
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}
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return result;
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}
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/* Let the kernel do all the work for packet generation */
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int FAST_FUNC udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
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uint32_t source_ip, int source_port,
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uint32_t dest_ip, int dest_port)
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{
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struct sockaddr_in client;
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int fd;
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int result = -1;
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const char *msg;
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enum {
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DHCP_SIZE = sizeof(struct dhcp_packet) - CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS,
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};
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fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
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if (fd < 0) {
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msg = "socket(%s)";
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goto ret_msg;
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}
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setsockopt_reuseaddr(fd);
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memset(&client, 0, sizeof(client));
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client.sin_family = AF_INET;
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client.sin_port = htons(source_port);
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client.sin_addr.s_addr = source_ip;
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if (bind(fd, (struct sockaddr *)&client, sizeof(client)) == -1) {
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msg = "bind(%s)";
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goto ret_close;
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}
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memset(&client, 0, sizeof(client));
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client.sin_family = AF_INET;
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client.sin_port = htons(dest_port);
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client.sin_addr.s_addr = dest_ip;
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if (connect(fd, (struct sockaddr *)&client, sizeof(client)) == -1) {
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msg = "connect";
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goto ret_close;
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}
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/* Currently we send full-sized DHCP packets (see above) */
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udhcp_dump_packet(dhcp_pkt);
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result = safe_write(fd, dhcp_pkt, DHCP_SIZE);
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msg = "write";
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ret_close:
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close(fd);
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if (result < 0) {
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ret_msg:
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bb_perror_msg(msg, "UDP");
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}
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return result;
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}
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