257 lines
6.8 KiB
C
257 lines
6.8 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* Packet ops
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*
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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 source tree.
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*/
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#include "common.h"
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#include "dhcpd.h"
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#include <netinet/in.h>
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#include <netinet/if_ether.h>
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#include <netpacket/packet.h>
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#if ENABLE_UDHCPC || ENABLE_UDHCPD
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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(*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 = 1; /* ethernet */
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packet->hlen = 6;
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packet->cookie = htonl(DHCP_MAGIC);
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if (DHCP_END != 0)
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packet->options[0] = DHCP_END;
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udhcp_add_simple_option(packet, DHCP_MESSAGE_TYPE, type);
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}
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#endif
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#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2
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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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//" 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->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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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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log1s("packet read error, ignoring");
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return bytes; /* returns -1 */
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}
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if (bytes < offsetof(struct dhcp_packet, options)
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|| packet->cookie != htonl(DHCP_MAGIC)
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) {
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bb_simple_info_msg("packet with bad magic, ignoring");
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return -2;
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}
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log2("received %s", "a packet");
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/* log2 because more informative msg for valid packets is printed later at log1 level */
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udhcp_dump_packet(packet);
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return bytes;
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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_nip, int source_port,
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uint32_t dest_nip, 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_sll;
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struct ip_udp_dhcp_packet packet;
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unsigned padding;
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int fd;
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int result = -1;
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const char *msg;
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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_sll, 0, sizeof(dest_sll));
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memset(&packet, 0, offsetof(struct ip_udp_dhcp_packet, data));
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packet.data = *dhcp_pkt; /* struct copy */
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dest_sll.sll_family = AF_PACKET;
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dest_sll.sll_protocol = htons(ETH_P_IP);
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dest_sll.sll_ifindex = ifindex;
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/*dest_sll.sll_hatype = ARPHRD_???;*/
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/*dest_sll.sll_pkttype = PACKET_???;*/
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dest_sll.sll_halen = 6;
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memcpy(dest_sll.sll_addr, dest_arp, 6);
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//TODO: is bind() necessary? we sendto() to this destination, should work anyway
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if (bind(fd, (struct sockaddr *)&dest_sll, sizeof(dest_sll)) < 0) {
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msg = "bind(%s)";
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goto ret_close;
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}
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/* We were sending full-sized DHCP packets (zero padded),
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* but some badly configured servers were seen dropping them.
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* Apparently they drop all DHCP packets >576 *ethernet* octets big,
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* whereas they may only drop packets >576 *IP* octets big
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* (which for typical Ethernet II means 590 octets: 6+6+2 + 576).
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*
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* In order to work with those buggy servers,
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* we truncate packets after end option byte.
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*
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* However, RFC 1542 says "The IP Total Length and UDP Length
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* must be large enough to contain the minimal BOOTP header of 300 octets".
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* Thus, we retain enough padding to not go below 300 BOOTP bytes.
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* Some devices have filters which drop DHCP packets shorter than that.
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*/
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padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(packet.data.options);
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if (padding > DHCP_SIZE - 300)
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padding = DHCP_SIZE - 300;
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packet.ip.protocol = IPPROTO_UDP;
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packet.ip.saddr = source_nip;
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packet.ip.daddr = dest_nip;
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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(UDP_DHCP_SIZE - padding);
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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 = inet_cksum(&packet,
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IP_UDP_DHCP_SIZE - padding);
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/* but for sending, it is set to IP packet len */
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packet.ip.tot_len = htons(IP_UDP_DHCP_SIZE - padding);
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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 = inet_cksum(&packet.ip, sizeof(packet.ip));
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udhcp_dump_packet(dhcp_pkt);
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result = sendto(fd, &packet, IP_UDP_DHCP_SIZE - padding, /*flags:*/ 0,
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(struct sockaddr *) &dest_sll, sizeof(dest_sll));
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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_nip, int source_port,
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uint32_t dest_nip, int dest_port,
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const char *ifname)
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{
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struct sockaddr_in sa;
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unsigned padding;
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int fd;
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int result = -1;
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const char *msg;
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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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/* If interface carrier goes down, unless we
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* bind socket to a particular netdev, the packet
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* can go out through another interface, eg. via
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* default route despite being bound to a specific
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* source IP. As such, bind to device hard and fail
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* otherwise. Sending renewal packets on foreign
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* interfaces makes no sense.
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*/
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if (ifname) {
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if (setsockopt_bindtodevice(fd, ifname) < 0) {
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msg = "bindtodevice";
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goto ret_close;
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}
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}
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memset(&sa, 0, sizeof(sa));
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sa.sin_family = AF_INET;
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sa.sin_port = htons(source_port);
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sa.sin_addr.s_addr = source_nip;
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if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
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msg = "bind(%s)";
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goto ret_close;
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}
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memset(&sa, 0, sizeof(sa));
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sa.sin_family = AF_INET;
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sa.sin_port = htons(dest_port);
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sa.sin_addr.s_addr = dest_nip;
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if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
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msg = "connect";
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goto ret_close;
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}
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udhcp_dump_packet(dhcp_pkt);
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padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(dhcp_pkt->options);
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if (padding > DHCP_SIZE - 300)
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padding = DHCP_SIZE - 300;
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result = safe_write(fd, dhcp_pkt, DHCP_SIZE - padding);
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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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