/* 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((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; } /* 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 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); 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; }