diff options
Diffstat (limited to 'src/libsystemd-network/sd-dhcp-server.c')
| -rw-r--r-- | src/libsystemd-network/sd-dhcp-server.c | 1222 |
1 files changed, 1222 insertions, 0 deletions
diff --git a/src/libsystemd-network/sd-dhcp-server.c b/src/libsystemd-network/sd-dhcp-server.c new file mode 100644 index 0000000..dfced72 --- /dev/null +++ b/src/libsystemd-network/sd-dhcp-server.c @@ -0,0 +1,1222 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/*** + Copyright © 2013 Intel Corporation. All rights reserved. +***/ + +#include <net/if_arp.h> +#include <sys/ioctl.h> + +#include "sd-dhcp-server.h" +#include "sd-id128.h" + +#include "alloc-util.h" +#include "dhcp-internal.h" +#include "dhcp-server-internal.h" +#include "fd-util.h" +#include "in-addr-util.h" +#include "io-util.h" +#include "siphash24.h" +#include "string-util.h" +#include "unaligned.h" + +#define DHCP_DEFAULT_LEASE_TIME_USEC USEC_PER_HOUR +#define DHCP_MAX_LEASE_TIME_USEC (USEC_PER_HOUR*12) + +static DHCPLease *dhcp_lease_free(DHCPLease *lease) { + if (!lease) + return NULL; + + free(lease->client_id.data); + return mfree(lease); +} + +/* configures the server's address and subnet, and optionally the pool's size and offset into the subnet + * the whole pool must fit into the subnet, and may not contain the first (any) nor last (broadcast) address + * moreover, the server's own address may be in the pool, and is in that case reserved in order not to + * accidentally hand it out */ +int sd_dhcp_server_configure_pool( + sd_dhcp_server *server, + const struct in_addr *address, + unsigned char prefixlen, + uint32_t offset, + uint32_t size) { + + struct in_addr netmask_addr; + be32_t netmask; + uint32_t server_off, broadcast_off, size_max; + + assert_return(server, -EINVAL); + assert_return(address, -EINVAL); + assert_return(address->s_addr != INADDR_ANY, -EINVAL); + assert_return(prefixlen <= 32, -ERANGE); + + assert_se(in4_addr_prefixlen_to_netmask(&netmask_addr, prefixlen)); + netmask = netmask_addr.s_addr; + + server_off = be32toh(address->s_addr & ~netmask); + broadcast_off = be32toh(~netmask); + + /* the server address cannot be the subnet address */ + assert_return(server_off != 0, -ERANGE); + + /* nor the broadcast address */ + assert_return(server_off != broadcast_off, -ERANGE); + + /* 0 offset means we should set a default, we skip the first (subnet) address + and take the next one */ + if (offset == 0) + offset = 1; + + size_max = (broadcast_off + 1) /* the number of addresses in the subnet */ + - offset /* exclude the addresses before the offset */ + - 1; /* exclude the last (broadcast) address */ + + /* The pool must contain at least one address */ + assert_return(size_max >= 1, -ERANGE); + + if (size != 0) + assert_return(size <= size_max, -ERANGE); + else + size = size_max; + + if (server->address != address->s_addr || server->netmask != netmask || server->pool_size != size || server->pool_offset != offset) { + + free(server->bound_leases); + server->bound_leases = new0(DHCPLease*, size); + if (!server->bound_leases) + return -ENOMEM; + + server->pool_offset = offset; + server->pool_size = size; + + server->address = address->s_addr; + server->netmask = netmask; + server->subnet = address->s_addr & netmask; + + if (server_off >= offset && server_off - offset < size) + server->bound_leases[server_off - offset] = &server->invalid_lease; + + /* Drop any leases associated with the old address range */ + hashmap_clear(server->leases_by_client_id); + + if (server->callback) + server->callback(server, SD_DHCP_SERVER_EVENT_LEASE_CHANGED, server->callback_userdata); + } + + return 0; +} + +int sd_dhcp_server_is_running(sd_dhcp_server *server) { + assert_return(server, false); + + return !!server->receive_message; +} + +void client_id_hash_func(const DHCPClientId *id, struct siphash *state) { + assert(id); + assert(id->length); + assert(id->data); + + siphash24_compress(&id->length, sizeof(id->length), state); + siphash24_compress(id->data, id->length, state); +} + +int client_id_compare_func(const DHCPClientId *a, const DHCPClientId *b) { + int r; + + assert(!a->length || a->data); + assert(!b->length || b->data); + + r = CMP(a->length, b->length); + if (r != 0) + return r; + + return memcmp(a->data, b->data, a->length); +} + +DEFINE_PRIVATE_HASH_OPS_WITH_VALUE_DESTRUCTOR(dhcp_lease_hash_ops, DHCPClientId, client_id_hash_func, client_id_compare_func, + DHCPLease, dhcp_lease_free); + +static sd_dhcp_server *dhcp_server_free(sd_dhcp_server *server) { + assert(server); + + log_dhcp_server(server, "UNREF"); + + sd_dhcp_server_stop(server); + + sd_event_unref(server->event); + + free(server->timezone); + + for (sd_dhcp_lease_server_type i = 0; i < _SD_DHCP_LEASE_SERVER_TYPE_MAX; i++) + free(server->servers[i].addr); + + hashmap_free(server->leases_by_client_id); + + ordered_hashmap_free(server->extra_options); + ordered_hashmap_free(server->vendor_options); + + free(server->bound_leases); + return mfree(server); +} + +DEFINE_TRIVIAL_REF_UNREF_FUNC(sd_dhcp_server, sd_dhcp_server, dhcp_server_free); + +int sd_dhcp_server_new(sd_dhcp_server **ret, int ifindex) { + _cleanup_(sd_dhcp_server_unrefp) sd_dhcp_server *server = NULL; + + assert_return(ret, -EINVAL); + assert_return(ifindex > 0, -EINVAL); + + server = new0(sd_dhcp_server, 1); + if (!server) + return -ENOMEM; + + server->n_ref = 1; + server->fd_raw = -1; + server->fd = -1; + server->address = htobe32(INADDR_ANY); + server->netmask = htobe32(INADDR_ANY); + server->ifindex = ifindex; + + server->leases_by_client_id = hashmap_new(&dhcp_lease_hash_ops); + if (!server->leases_by_client_id) + return -ENOMEM; + + server->default_lease_time = DIV_ROUND_UP(DHCP_DEFAULT_LEASE_TIME_USEC, USEC_PER_SEC); + server->max_lease_time = DIV_ROUND_UP(DHCP_MAX_LEASE_TIME_USEC, USEC_PER_SEC); + + *ret = TAKE_PTR(server); + + return 0; +} + +int sd_dhcp_server_attach_event(sd_dhcp_server *server, sd_event *event, int64_t priority) { + int r; + + assert_return(server, -EINVAL); + assert_return(!server->event, -EBUSY); + + if (event) + server->event = sd_event_ref(event); + else { + r = sd_event_default(&server->event); + if (r < 0) + return r; + } + + server->event_priority = priority; + + return 0; +} + +int sd_dhcp_server_detach_event(sd_dhcp_server *server) { + assert_return(server, -EINVAL); + + server->event = sd_event_unref(server->event); + + return 0; +} + +sd_event *sd_dhcp_server_get_event(sd_dhcp_server *server) { + assert_return(server, NULL); + + return server->event; +} + +int sd_dhcp_server_stop(sd_dhcp_server *server) { + if (!server) + return 0; + + server->receive_message = + sd_event_source_unref(server->receive_message); + + server->fd_raw = safe_close(server->fd_raw); + server->fd = safe_close(server->fd); + + log_dhcp_server(server, "STOPPED"); + + return 0; +} + +static int dhcp_server_send_unicast_raw(sd_dhcp_server *server, + DHCPPacket *packet, size_t len) { + union sockaddr_union link = { + .ll.sll_family = AF_PACKET, + .ll.sll_protocol = htobe16(ETH_P_IP), + .ll.sll_ifindex = server->ifindex, + .ll.sll_halen = ETH_ALEN, + }; + + assert(server); + assert(server->ifindex > 0); + assert(server->address); + assert(packet); + assert(len > sizeof(DHCPPacket)); + + memcpy(&link.ll.sll_addr, &packet->dhcp.chaddr, ETH_ALEN); + + dhcp_packet_append_ip_headers(packet, server->address, DHCP_PORT_SERVER, + packet->dhcp.yiaddr, + DHCP_PORT_CLIENT, len, -1); + + return dhcp_network_send_raw_socket(server->fd_raw, &link, packet, len); +} + +static int dhcp_server_send_udp(sd_dhcp_server *server, be32_t destination, + uint16_t destination_port, + DHCPMessage *message, size_t len) { + union sockaddr_union dest = { + .in.sin_family = AF_INET, + .in.sin_port = htobe16(destination_port), + .in.sin_addr.s_addr = destination, + }; + struct iovec iov = { + .iov_base = message, + .iov_len = len, + }; + CMSG_BUFFER_TYPE(CMSG_SPACE(sizeof(struct in_pktinfo))) control = {}; + struct msghdr msg = { + .msg_name = &dest, + .msg_namelen = sizeof(dest.in), + .msg_iov = &iov, + .msg_iovlen = 1, + .msg_control = &control, + .msg_controllen = sizeof(control), + }; + struct cmsghdr *cmsg; + struct in_pktinfo *pktinfo; + + assert(server); + assert(server->fd >= 0); + assert(message); + assert(len > sizeof(DHCPMessage)); + + cmsg = CMSG_FIRSTHDR(&msg); + assert(cmsg); + + cmsg->cmsg_level = IPPROTO_IP; + cmsg->cmsg_type = IP_PKTINFO; + cmsg->cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo)); + + /* we attach source interface and address info to the message + rather than binding the socket. This will be mostly useful + when we gain support for arbitrary number of server addresses + */ + pktinfo = (struct in_pktinfo*) CMSG_DATA(cmsg); + assert(pktinfo); + + pktinfo->ipi_ifindex = server->ifindex; + pktinfo->ipi_spec_dst.s_addr = server->address; + + if (sendmsg(server->fd, &msg, 0) < 0) + return -errno; + + return 0; +} + +static bool requested_broadcast(DHCPRequest *req) { + assert(req); + + return req->message->flags & htobe16(0x8000); +} + +int dhcp_server_send_packet(sd_dhcp_server *server, + DHCPRequest *req, DHCPPacket *packet, + int type, size_t optoffset) { + be32_t destination = INADDR_ANY; + uint16_t destination_port = DHCP_PORT_CLIENT; + int r; + + assert(server); + assert(req); + assert(req->max_optlen); + assert(optoffset <= req->max_optlen); + assert(packet); + + r = dhcp_option_append(&packet->dhcp, req->max_optlen, &optoffset, 0, + SD_DHCP_OPTION_SERVER_IDENTIFIER, + 4, &server->address); + if (r < 0) + return r; + + r = dhcp_option_append(&packet->dhcp, req->max_optlen, &optoffset, 0, + SD_DHCP_OPTION_END, 0, NULL); + if (r < 0) + return r; + + /* RFC 2131 Section 4.1 + + If the ’giaddr’ field in a DHCP message from a client is non-zero, + the server sends any return messages to the ’DHCP server’ port on the + BOOTP relay agent whose address appears in ’giaddr’. If the ’giaddr’ + field is zero and the ’ciaddr’ field is nonzero, then the server + unicasts DHCPOFFER and DHCPACK messages to the address in ’ciaddr’. + If ’giaddr’ is zero and ’ciaddr’ is zero, and the broadcast bit is + set, then the server broadcasts DHCPOFFER and DHCPACK messages to + 0xffffffff. If the broadcast bit is not set and ’giaddr’ is zero and + ’ciaddr’ is zero, then the server unicasts DHCPOFFER and DHCPACK + messages to the client’s hardware address and ’yiaddr’ address. In + all cases, when ’giaddr’ is zero, the server broadcasts any DHCPNAK + messages to 0xffffffff. + + Section 4.3.2 + + If ’giaddr’ is set in the DHCPREQUEST message, the client is on a + different subnet. The server MUST set the broadcast bit in the + DHCPNAK, so that the relay agent will broadcast the DHCPNAK to the + client, because the client may not have a correct network address + or subnet mask, and the client may not be answering ARP requests. + */ + if (req->message->giaddr) { + destination = req->message->giaddr; + destination_port = DHCP_PORT_SERVER; + if (type == DHCP_NAK) + packet->dhcp.flags = htobe16(0x8000); + } else if (req->message->ciaddr && type != DHCP_NAK) + destination = req->message->ciaddr; + + if (destination != INADDR_ANY) + return dhcp_server_send_udp(server, destination, + destination_port, &packet->dhcp, + sizeof(DHCPMessage) + optoffset); + else if (requested_broadcast(req) || type == DHCP_NAK) + return dhcp_server_send_udp(server, INADDR_BROADCAST, + destination_port, &packet->dhcp, + sizeof(DHCPMessage) + optoffset); + else + /* we cannot send UDP packet to specific MAC address when the + address is not yet configured, so must fall back to raw + packets */ + return dhcp_server_send_unicast_raw(server, packet, + sizeof(DHCPPacket) + optoffset); +} + +static int server_message_init(sd_dhcp_server *server, DHCPPacket **ret, + uint8_t type, size_t *_optoffset, + DHCPRequest *req) { + _cleanup_free_ DHCPPacket *packet = NULL; + size_t optoffset = 0; + int r; + + assert(server); + assert(ret); + assert(_optoffset); + assert(IN_SET(type, DHCP_OFFER, DHCP_ACK, DHCP_NAK)); + + packet = malloc0(sizeof(DHCPPacket) + req->max_optlen); + if (!packet) + return -ENOMEM; + + r = dhcp_message_init(&packet->dhcp, BOOTREPLY, + be32toh(req->message->xid), type, ARPHRD_ETHER, + req->max_optlen, &optoffset); + if (r < 0) + return r; + + packet->dhcp.flags = req->message->flags; + packet->dhcp.giaddr = req->message->giaddr; + memcpy(&packet->dhcp.chaddr, &req->message->chaddr, ETH_ALEN); + + *_optoffset = optoffset; + *ret = TAKE_PTR(packet); + + return 0; +} + +static int server_send_offer(sd_dhcp_server *server, DHCPRequest *req, + be32_t address) { + _cleanup_free_ DHCPPacket *packet = NULL; + size_t offset; + be32_t lease_time; + int r; + + r = server_message_init(server, &packet, DHCP_OFFER, &offset, req); + if (r < 0) + return r; + + packet->dhcp.yiaddr = address; + + lease_time = htobe32(req->lifetime); + r = dhcp_option_append(&packet->dhcp, req->max_optlen, &offset, 0, + SD_DHCP_OPTION_IP_ADDRESS_LEASE_TIME, 4, + &lease_time); + if (r < 0) + return r; + + r = dhcp_option_append(&packet->dhcp, req->max_optlen, &offset, 0, + SD_DHCP_OPTION_SUBNET_MASK, 4, &server->netmask); + if (r < 0) + return r; + + if (server->emit_router) { + r = dhcp_option_append(&packet->dhcp, req->max_optlen, &offset, 0, + SD_DHCP_OPTION_ROUTER, 4, &server->address); + if (r < 0) + return r; + } + + r = dhcp_server_send_packet(server, req, packet, DHCP_OFFER, offset); + if (r < 0) + return r; + + return 0; +} + +static int server_send_ack( + sd_dhcp_server *server, + DHCPRequest *req, + be32_t address) { + + static const uint8_t option_map[_SD_DHCP_LEASE_SERVER_TYPE_MAX] = { + [SD_DHCP_LEASE_DNS] = SD_DHCP_OPTION_DOMAIN_NAME_SERVER, + [SD_DHCP_LEASE_NTP] = SD_DHCP_OPTION_NTP_SERVER, + [SD_DHCP_LEASE_SIP] = SD_DHCP_OPTION_SIP_SERVER, + [SD_DHCP_LEASE_POP3] = SD_DHCP_OPTION_POP3_SERVER, + [SD_DHCP_LEASE_SMTP] = SD_DHCP_OPTION_SMTP_SERVER, + [SD_DHCP_LEASE_LPR] = SD_DHCP_OPTION_LPR_SERVER, + }; + + _cleanup_free_ DHCPPacket *packet = NULL; + be32_t lease_time; + sd_dhcp_option *j; + size_t offset; + int r; + + r = server_message_init(server, &packet, DHCP_ACK, &offset, req); + if (r < 0) + return r; + + packet->dhcp.yiaddr = address; + + lease_time = htobe32(req->lifetime); + r = dhcp_option_append(&packet->dhcp, req->max_optlen, &offset, 0, + SD_DHCP_OPTION_IP_ADDRESS_LEASE_TIME, 4, + &lease_time); + if (r < 0) + return r; + + r = dhcp_option_append(&packet->dhcp, req->max_optlen, &offset, 0, + SD_DHCP_OPTION_SUBNET_MASK, 4, &server->netmask); + if (r < 0) + return r; + + if (server->emit_router) { + r = dhcp_option_append(&packet->dhcp, req->max_optlen, &offset, 0, + SD_DHCP_OPTION_ROUTER, 4, &server->address); + if (r < 0) + return r; + } + + for (sd_dhcp_lease_server_type k = 0; k < _SD_DHCP_LEASE_SERVER_TYPE_MAX; k++) { + + if (server->servers[k].size <= 0) + continue; + + r = dhcp_option_append( + &packet->dhcp, req->max_optlen, &offset, 0, + option_map[k], + sizeof(struct in_addr) * server->servers[k].size, server->servers[k].addr); + if (r < 0) + return r; + } + + + if (server->timezone) { + r = dhcp_option_append( + &packet->dhcp, req->max_optlen, &offset, 0, + SD_DHCP_OPTION_NEW_TZDB_TIMEZONE, + strlen(server->timezone), server->timezone); + if (r < 0) + return r; + } + + ORDERED_HASHMAP_FOREACH(j, server->extra_options) { + r = dhcp_option_append(&packet->dhcp, req->max_optlen, &offset, 0, + j->option, j->length, j->data); + if (r < 0) + return r; + } + + if (!ordered_hashmap_isempty(server->vendor_options)) { + r = dhcp_option_append( + &packet->dhcp, req->max_optlen, &offset, 0, + SD_DHCP_OPTION_VENDOR_SPECIFIC, + ordered_hashmap_size(server->vendor_options), server->vendor_options); + if (r < 0) + return r; + } + + r = dhcp_server_send_packet(server, req, packet, DHCP_ACK, offset); + if (r < 0) + return r; + + return 0; +} + +static int server_send_nak(sd_dhcp_server *server, DHCPRequest *req) { + _cleanup_free_ DHCPPacket *packet = NULL; + size_t offset; + int r; + + r = server_message_init(server, &packet, DHCP_NAK, &offset, req); + if (r < 0) + return r; + + return dhcp_server_send_packet(server, req, packet, DHCP_NAK, offset); +} + +static int server_send_forcerenew(sd_dhcp_server *server, be32_t address, + be32_t gateway, const uint8_t chaddr[]) { + _cleanup_free_ DHCPPacket *packet = NULL; + size_t optoffset = 0; + int r; + + assert(server); + assert(address != INADDR_ANY); + assert(chaddr); + + packet = malloc0(sizeof(DHCPPacket) + DHCP_MIN_OPTIONS_SIZE); + if (!packet) + return -ENOMEM; + + r = dhcp_message_init(&packet->dhcp, BOOTREPLY, 0, + DHCP_FORCERENEW, ARPHRD_ETHER, + DHCP_MIN_OPTIONS_SIZE, &optoffset); + if (r < 0) + return r; + + r = dhcp_option_append(&packet->dhcp, DHCP_MIN_OPTIONS_SIZE, + &optoffset, 0, SD_DHCP_OPTION_END, 0, NULL); + if (r < 0) + return r; + + memcpy(&packet->dhcp.chaddr, chaddr, ETH_ALEN); + + r = dhcp_server_send_udp(server, address, DHCP_PORT_CLIENT, + &packet->dhcp, + sizeof(DHCPMessage) + optoffset); + if (r < 0) + return r; + + return 0; +} + +static int parse_request(uint8_t code, uint8_t len, const void *option, void *userdata) { + DHCPRequest *req = userdata; + + assert(req); + + switch(code) { + case SD_DHCP_OPTION_IP_ADDRESS_LEASE_TIME: + if (len == 4) + req->lifetime = unaligned_read_be32(option); + + break; + case SD_DHCP_OPTION_REQUESTED_IP_ADDRESS: + if (len == 4) + memcpy(&req->requested_ip, option, sizeof(be32_t)); + + break; + case SD_DHCP_OPTION_SERVER_IDENTIFIER: + if (len == 4) + memcpy(&req->server_id, option, sizeof(be32_t)); + + break; + case SD_DHCP_OPTION_CLIENT_IDENTIFIER: + if (len >= 2) { + uint8_t *data; + + data = memdup(option, len); + if (!data) + return -ENOMEM; + + free(req->client_id.data); + req->client_id.data = data; + req->client_id.length = len; + } + + break; + case SD_DHCP_OPTION_MAXIMUM_MESSAGE_SIZE: + + if (len == 2 && unaligned_read_be16(option) >= sizeof(DHCPPacket)) + req->max_optlen = unaligned_read_be16(option) - sizeof(DHCPPacket); + + break; + } + + return 0; +} + +static void dhcp_request_free(DHCPRequest *req) { + if (!req) + return; + + free(req->client_id.data); + free(req); +} + +DEFINE_TRIVIAL_CLEANUP_FUNC(DHCPRequest*, dhcp_request_free); + +static int ensure_sane_request(sd_dhcp_server *server, DHCPRequest *req, DHCPMessage *message) { + assert(req); + assert(message); + + req->message = message; + + /* set client id based on MAC address if client did not send an explicit + one */ + if (!req->client_id.data) { + void *data; + + data = malloc0(ETH_ALEN + 1); + if (!data) + return -ENOMEM; + + ((uint8_t*) data)[0] = 0x01; + memcpy((uint8_t*) data + 1, &message->chaddr, ETH_ALEN); + + req->client_id.length = ETH_ALEN + 1; + req->client_id.data = data; + } + + if (req->max_optlen < DHCP_MIN_OPTIONS_SIZE) + req->max_optlen = DHCP_MIN_OPTIONS_SIZE; + + if (req->lifetime <= 0) + req->lifetime = MAX(1ULL, server->default_lease_time); + + if (server->max_lease_time > 0 && req->lifetime > server->max_lease_time) + req->lifetime = server->max_lease_time; + + return 0; +} + +static int get_pool_offset(sd_dhcp_server *server, be32_t requested_ip) { + assert(server); + + if (!server->pool_size) + return -EINVAL; + + if (be32toh(requested_ip) < (be32toh(server->subnet) | server->pool_offset) || + be32toh(requested_ip) >= (be32toh(server->subnet) | (server->pool_offset + server->pool_size))) + return -ERANGE; + + return be32toh(requested_ip & ~server->netmask) - server->pool_offset; +} + +#define HASH_KEY SD_ID128_MAKE(0d,1d,fe,bd,f1,24,bd,b3,47,f1,dd,6e,73,21,93,30) + +int dhcp_server_handle_message(sd_dhcp_server *server, DHCPMessage *message, + size_t length) { + _cleanup_(dhcp_request_freep) DHCPRequest *req = NULL; + _cleanup_free_ char *error_message = NULL; + DHCPLease *existing_lease; + int type, r; + + assert(server); + assert(message); + + if (message->op != BOOTREQUEST || + message->htype != ARPHRD_ETHER || + message->hlen != ETHER_ADDR_LEN) + return 0; + + req = new0(DHCPRequest, 1); + if (!req) + return -ENOMEM; + + type = dhcp_option_parse(message, length, parse_request, req, &error_message); + if (type < 0) + return 0; + + r = ensure_sane_request(server, req, message); + if (r < 0) + /* this only fails on critical errors */ + return r; + + existing_lease = hashmap_get(server->leases_by_client_id, + &req->client_id); + + switch(type) { + + case DHCP_DISCOVER: { + be32_t address = INADDR_ANY; + unsigned i; + + log_dhcp_server(server, "DISCOVER (0x%x)", + be32toh(req->message->xid)); + + if (!server->pool_size) + /* no pool allocated */ + return 0; + + /* for now pick a random free address from the pool */ + if (existing_lease) + address = existing_lease->address; + else { + struct siphash state; + uint64_t hash; + uint32_t next_offer; + + /* even with no persistence of leases, we try to offer the same client + the same IP address. we do this by using the hash of the client id + as the offset into the pool of leases when finding the next free one */ + + siphash24_init(&state, HASH_KEY.bytes); + client_id_hash_func(&req->client_id, &state); + hash = htole64(siphash24_finalize(&state)); + next_offer = hash % server->pool_size; + + for (i = 0; i < server->pool_size; i++) { + if (!server->bound_leases[next_offer]) { + address = server->subnet | htobe32(server->pool_offset + next_offer); + break; + } + + next_offer = (next_offer + 1) % server->pool_size; + } + } + + if (address == INADDR_ANY) + /* no free addresses left */ + return 0; + + r = server_send_offer(server, req, address); + if (r < 0) + /* this only fails on critical errors */ + return log_dhcp_server_errno(server, r, "Could not send offer: %m"); + + log_dhcp_server(server, "OFFER (0x%x)", be32toh(req->message->xid)); + return DHCP_OFFER; + } + case DHCP_DECLINE: + log_dhcp_server(server, "DECLINE (0x%x): %s", be32toh(req->message->xid), strna(error_message)); + + /* TODO: make sure we don't offer this address again */ + + return 1; + + case DHCP_REQUEST: { + be32_t address; + bool init_reboot = false; + int pool_offset; + + /* see RFC 2131, section 4.3.2 */ + + if (req->server_id) { + log_dhcp_server(server, "REQUEST (selecting) (0x%x)", + be32toh(req->message->xid)); + + /* SELECTING */ + if (req->server_id != server->address) + /* client did not pick us */ + return 0; + + if (req->message->ciaddr) + /* this MUST be zero */ + return 0; + + if (!req->requested_ip) + /* this must be filled in with the yiaddr + from the chosen OFFER */ + return 0; + + address = req->requested_ip; + } else if (req->requested_ip) { + log_dhcp_server(server, "REQUEST (init-reboot) (0x%x)", + be32toh(req->message->xid)); + + /* INIT-REBOOT */ + if (req->message->ciaddr) + /* this MUST be zero */ + return 0; + + /* TODO: check more carefully if IP is correct */ + address = req->requested_ip; + init_reboot = true; + } else { + log_dhcp_server(server, "REQUEST (rebinding/renewing) (0x%x)", + be32toh(req->message->xid)); + + /* REBINDING / RENEWING */ + if (!req->message->ciaddr) + /* this MUST be filled in with clients IP address */ + return 0; + + address = req->message->ciaddr; + } + + pool_offset = get_pool_offset(server, address); + + /* verify that the requested address is from the pool, and either + owned by the current client or free */ + if (pool_offset >= 0 && + server->bound_leases[pool_offset] == existing_lease) { + DHCPLease *lease; + usec_t time_now = 0; + + if (!existing_lease) { + lease = new0(DHCPLease, 1); + if (!lease) + return -ENOMEM; + lease->address = address; + lease->client_id.data = memdup(req->client_id.data, + req->client_id.length); + if (!lease->client_id.data) { + free(lease); + return -ENOMEM; + } + lease->client_id.length = req->client_id.length; + memcpy(&lease->chaddr, &req->message->chaddr, + ETH_ALEN); + lease->gateway = req->message->giaddr; + } else + lease = existing_lease; + + r = sd_event_now(server->event, + clock_boottime_or_monotonic(), + &time_now); + if (r < 0) { + if (!existing_lease) + dhcp_lease_free(lease); + return r; + } + + lease->expiration = req->lifetime * USEC_PER_SEC + time_now; + + r = server_send_ack(server, req, address); + if (r < 0) { + /* this only fails on critical errors */ + log_dhcp_server_errno(server, r, "Could not send ack: %m"); + + if (!existing_lease) + dhcp_lease_free(lease); + + return r; + } else { + log_dhcp_server(server, "ACK (0x%x)", + be32toh(req->message->xid)); + + server->bound_leases[pool_offset] = lease; + hashmap_put(server->leases_by_client_id, + &lease->client_id, lease); + + if (server->callback) + server->callback(server, SD_DHCP_SERVER_EVENT_LEASE_CHANGED, server->callback_userdata); + + return DHCP_ACK; + } + + } else if (init_reboot) { + r = server_send_nak(server, req); + if (r < 0) + /* this only fails on critical errors */ + return log_dhcp_server_errno(server, r, "Could not send nak: %m"); + + log_dhcp_server(server, "NAK (0x%x)", be32toh(req->message->xid)); + return DHCP_NAK; + } + + break; + } + + case DHCP_RELEASE: { + int pool_offset; + + log_dhcp_server(server, "RELEASE (0x%x)", + be32toh(req->message->xid)); + + if (!existing_lease) + return 0; + + if (existing_lease->address != req->message->ciaddr) + return 0; + + pool_offset = get_pool_offset(server, req->message->ciaddr); + if (pool_offset < 0) + return 0; + + if (server->bound_leases[pool_offset] == existing_lease) { + server->bound_leases[pool_offset] = NULL; + hashmap_remove(server->leases_by_client_id, existing_lease); + dhcp_lease_free(existing_lease); + + if (server->callback) + server->callback(server, SD_DHCP_SERVER_EVENT_LEASE_CHANGED, server->callback_userdata); + } + + return 0; + }} + + return 0; +} + +static int server_receive_message(sd_event_source *s, int fd, + uint32_t revents, void *userdata) { + _cleanup_free_ DHCPMessage *message = NULL; + CMSG_BUFFER_TYPE(CMSG_SPACE(sizeof(struct in_pktinfo))) control; + sd_dhcp_server *server = userdata; + struct iovec iov = {}; + struct msghdr msg = { + .msg_iov = &iov, + .msg_iovlen = 1, + .msg_control = &control, + .msg_controllen = sizeof(control), + }; + struct cmsghdr *cmsg; + ssize_t buflen, len; + int r; + + assert(server); + + buflen = next_datagram_size_fd(fd); + if (buflen < 0) + return buflen; + + message = malloc(buflen); + if (!message) + return -ENOMEM; + + iov = IOVEC_MAKE(message, buflen); + + len = recvmsg_safe(fd, &msg, 0); + if (IN_SET(len, -EAGAIN, -EINTR)) + return 0; + if (len < 0) + return len; + if ((size_t) len < sizeof(DHCPMessage)) + return 0; + + CMSG_FOREACH(cmsg, &msg) { + if (cmsg->cmsg_level == IPPROTO_IP && + cmsg->cmsg_type == IP_PKTINFO && + cmsg->cmsg_len == CMSG_LEN(sizeof(struct in_pktinfo))) { + struct in_pktinfo *info = (struct in_pktinfo*)CMSG_DATA(cmsg); + + /* TODO figure out if this can be done as a filter on + * the socket, like for IPv6 */ + if (server->ifindex != info->ipi_ifindex) + return 0; + + break; + } + } + + r = dhcp_server_handle_message(server, message, (size_t) len); + if (r < 0) + log_dhcp_server_errno(server, r, "Couldn't process incoming message: %m"); + + return 0; +} + +int sd_dhcp_server_start(sd_dhcp_server *server) { + int r; + + assert_return(server, -EINVAL); + assert_return(server->event, -EINVAL); + assert_return(!server->receive_message, -EBUSY); + assert_return(server->fd_raw < 0, -EBUSY); + assert_return(server->fd < 0, -EBUSY); + assert_return(server->address != htobe32(INADDR_ANY), -EUNATCH); + + r = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0); + if (r < 0) { + r = -errno; + sd_dhcp_server_stop(server); + return r; + } + server->fd_raw = r; + + r = dhcp_network_bind_udp_socket(server->ifindex, INADDR_ANY, DHCP_PORT_SERVER, -1); + if (r < 0) { + sd_dhcp_server_stop(server); + return r; + } + server->fd = r; + + r = sd_event_add_io(server->event, &server->receive_message, + server->fd, EPOLLIN, + server_receive_message, server); + if (r < 0) { + sd_dhcp_server_stop(server); + return r; + } + + r = sd_event_source_set_priority(server->receive_message, + server->event_priority); + if (r < 0) { + sd_dhcp_server_stop(server); + return r; + } + + log_dhcp_server(server, "STARTED"); + + return 0; +} + +int sd_dhcp_server_forcerenew(sd_dhcp_server *server) { + unsigned i; + int r = 0; + + assert_return(server, -EINVAL); + assert(server->bound_leases); + + for (i = 0; i < server->pool_size; i++) { + DHCPLease *lease = server->bound_leases[i]; + + if (!lease || lease == &server->invalid_lease) + continue; + + r = server_send_forcerenew(server, lease->address, + lease->gateway, + lease->chaddr); + if (r < 0) + return r; + + log_dhcp_server(server, "FORCERENEW"); + } + + return r; +} + +int sd_dhcp_server_set_timezone(sd_dhcp_server *server, const char *tz) { + int r; + + assert_return(server, -EINVAL); + assert_return(timezone_is_valid(tz, LOG_DEBUG), -EINVAL); + + if (streq_ptr(tz, server->timezone)) + return 0; + + r = free_and_strdup(&server->timezone, tz); + if (r < 0) + return r; + + return 1; +} + +int sd_dhcp_server_set_max_lease_time(sd_dhcp_server *server, uint32_t t) { + assert_return(server, -EINVAL); + + if (t == server->max_lease_time) + return 0; + + server->max_lease_time = t; + return 1; +} + +int sd_dhcp_server_set_default_lease_time(sd_dhcp_server *server, uint32_t t) { + assert_return(server, -EINVAL); + + if (t == server->default_lease_time) + return 0; + + server->default_lease_time = t; + return 1; +} + +int sd_dhcp_server_set_servers( + sd_dhcp_server *server, + sd_dhcp_lease_server_type what, + const struct in_addr addresses[], + size_t n_addresses) { + + struct in_addr *c = NULL; + + assert_return(server, -EINVAL); + assert_return(addresses || n_addresses == 0, -EINVAL); + assert_return(what >= 0, -EINVAL); + assert_return(what < _SD_DHCP_LEASE_SERVER_TYPE_MAX, -EINVAL); + + if (server->servers[what].size == n_addresses && + memcmp(server->servers[what].addr, addresses, sizeof(struct in_addr) * n_addresses) == 0) + return 0; + + if (n_addresses > 0) { + c = newdup(struct in_addr, addresses, n_addresses); + if (!c) + return -ENOMEM; + } + + free(server->servers[what].addr); + server->servers[what].addr = c; + server->servers[what].size = n_addresses; + return 1; +} + +int sd_dhcp_server_set_dns(sd_dhcp_server *server, const struct in_addr dns[], size_t n) { + return sd_dhcp_server_set_servers(server, SD_DHCP_LEASE_DNS, dns, n); +} +int sd_dhcp_server_set_ntp(sd_dhcp_server *server, const struct in_addr ntp[], size_t n) { + return sd_dhcp_server_set_servers(server, SD_DHCP_LEASE_NTP, ntp, n); +} +int sd_dhcp_server_set_sip(sd_dhcp_server *server, const struct in_addr sip[], size_t n) { + return sd_dhcp_server_set_servers(server, SD_DHCP_LEASE_SIP, sip, n); +} +int sd_dhcp_server_set_pop3(sd_dhcp_server *server, const struct in_addr pop3[], size_t n) { + return sd_dhcp_server_set_servers(server, SD_DHCP_LEASE_POP3, pop3, n); +} +int sd_dhcp_server_set_smtp(sd_dhcp_server *server, const struct in_addr smtp[], size_t n) { + return sd_dhcp_server_set_servers(server, SD_DHCP_LEASE_SMTP, smtp, n); +} +int sd_dhcp_server_set_lpr(sd_dhcp_server *server, const struct in_addr lpr[], size_t n) { + return sd_dhcp_server_set_servers(server, SD_DHCP_LEASE_LPR, lpr, n); +} + +int sd_dhcp_server_set_emit_router(sd_dhcp_server *server, int enabled) { + assert_return(server, -EINVAL); + + if (enabled == server->emit_router) + return 0; + + server->emit_router = enabled; + + return 1; +} + +int sd_dhcp_server_add_option(sd_dhcp_server *server, sd_dhcp_option *v) { + int r; + + assert_return(server, -EINVAL); + assert_return(v, -EINVAL); + + r = ordered_hashmap_ensure_allocated(&server->extra_options, &dhcp_option_hash_ops); + if (r < 0) + return r; + + r = ordered_hashmap_put(server->extra_options, UINT_TO_PTR(v->option), v); + if (r < 0) + return r; + + sd_dhcp_option_ref(v); + return 0; +} + +int sd_dhcp_server_add_vendor_option(sd_dhcp_server *server, sd_dhcp_option *v) { + int r; + + assert_return(server, -EINVAL); + assert_return(v, -EINVAL); + + r = ordered_hashmap_ensure_allocated(&server->vendor_options, &dhcp_option_hash_ops); + if (r < 0) + return -ENOMEM; + + r = ordered_hashmap_put(server->vendor_options, v, v); + if (r < 0) + return r; + + sd_dhcp_option_ref(v); + + return 1; +} + +int sd_dhcp_server_set_callback(sd_dhcp_server *server, sd_dhcp_server_callback_t cb, void *userdata) { + assert_return(server, -EINVAL); + + server->callback = cb; + server->callback_userdata = userdata; + + return 0; +} |