sd-network: add new library

[elogind.git] / src / libsystemd-network / dhcp-packet.c

diff --git a/src/libsystemd-network/dhcp-packet.c b/src/libsystemd-network/dhcp-packet.c
new file mode 100644 (file)
index 0000000..95c4277
--- /dev/null
+++ b/src/libsystemd-network/dhcp-packet.c
@@ -0,0 +1,191 @@
+/***
+  This file is part of systemd.
+
+  Copyright (C) 2013 Intel Corporation. All rights reserved.
+  Copyright (C) 2014 Tom Gundersen
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <stdio.h>
+#include <net/ethernet.h>
+#include <net/if_arp.h>
+#include <sys/param.h>
+
+#include "util.h"
+#include "list.h"
+
+#include "dhcp-protocol.h"
+#include "dhcp-lease-internal.h"
+#include "dhcp-internal.h"
+#include "sd-dhcp-lease.h"
+#include "sd-dhcp-client.h"
+
+#define DHCP_CLIENT_MIN_OPTIONS_SIZE            312
+
+int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid,
+                      uint8_t type, uint8_t **opt, size_t *optlen) {
+        int err;
+
+        assert(op == BOOTREQUEST || op == BOOTREPLY);
+
+        *opt = (uint8_t *)(message + 1);
+
+        if (*optlen < 4)
+                return -ENOBUFS;
+        *optlen -= 4;
+
+        message->op = op;
+        message->htype = ARPHRD_ETHER;
+        message->hlen = ETHER_ADDR_LEN;
+        message->xid = htobe32(xid);
+
+        (*opt)[0] = 0x63;
+        (*opt)[1] = 0x82;
+        (*opt)[2] = 0x53;
+        (*opt)[3] = 0x63;
+
+        *opt += 4;
+
+        err = dhcp_option_append(opt, optlen, DHCP_OPTION_MESSAGE_TYPE, 1,
+                                 &type);
+        if (err < 0)
+                return err;
+
+        return 0;
+}
+
+static uint16_t dhcp_checksum(void *buf, int len) {
+        uint32_t sum;
+        uint16_t *check;
+        int i;
+        uint8_t *odd;
+
+        sum = 0;
+        check = buf;
+
+        for (i = 0; i < len / 2 ; i++)
+                sum += check[i];
+
+        if (len & 0x01) {
+                odd = buf;
+                sum += odd[len - 1];
+        }
+
+        while (sum >> 16)
+                sum = (sum & 0xffff) + (sum >> 16);
+
+        return ~sum;
+}
+
+void dhcp_packet_append_ip_headers(DHCPPacket *packet, uint16_t len) {
+        packet->ip.version = IPVERSION;
+        packet->ip.ihl = DHCP_IP_SIZE / 4;
+        packet->ip.tot_len = htobe16(len);
+
+        packet->ip.protocol = IPPROTO_UDP;
+        packet->ip.saddr = INADDR_ANY;
+        packet->ip.daddr = INADDR_BROADCAST;
+
+        packet->udp.source = htobe16(DHCP_PORT_CLIENT);
+        packet->udp.dest = htobe16(DHCP_PORT_SERVER);
+
+        packet->udp.len = htobe16(len - DHCP_IP_SIZE);
+
+        packet->ip.check = packet->udp.len;
+        packet->udp.check = dhcp_checksum(&packet->ip.ttl, len - 8);
+
+        packet->ip.ttl = IPDEFTTL;
+        packet->ip.check = 0;
+        packet->ip.check = dhcp_checksum(&packet->ip, DHCP_IP_SIZE);
+}
+
+int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum) {
+        size_t hdrlen;
+
+        assert(packet);
+
+        /* IP */
+
+        if (len < DHCP_IP_SIZE) {
+                log_dhcp_client(client, "ignoring packet: packet (%zu bytes) "
+                                " smaller than IP header (%u bytes)", len,
+                                DHCP_IP_SIZE);
+                return -EINVAL;
+        }
+
+        if (packet->ip.ihl < 5) {
+                log_dhcp_client(client, "ignoring packet: IPv4 IHL (%u words) invalid",
+                                packet->ip.ihl);
+                return -EINVAL;
+        }
+
+        hdrlen = packet->ip.ihl * 4;
+        if (hdrlen < 20) {
+                log_dhcp_client(client, "ignoring packet: IPv4 IHL (%zu bytes) "
+                                "smaller than minimum (20 bytes)", hdrlen);
+                return -EINVAL;
+        }
+
+        if (len < hdrlen) {
+                log_dhcp_client(client, "ignoring packet: packet (%zu bytes) "
+                                "smaller than expected (%zu) by IP header", len,
+                                hdrlen);
+                return -EINVAL;
+        }
+
+        if (dhcp_checksum(&packet->ip, hdrlen)) {
+                log_dhcp_client(client, "ignoring packet: invalid IP checksum");
+                return -EINVAL;
+        }
+
+        /* UDP */
+
+        if (len < DHCP_IP_UDP_SIZE) {
+                log_dhcp_client(client, "ignoring packet: packet (%zu bytes) "
+                                " smaller than IP+UDP header (%u bytes)", len,
+                                DHCP_IP_UDP_SIZE);
+                return -EINVAL;
+        }
+
+        if (len < hdrlen + be16toh(packet->udp.len)) {
+                log_dhcp_client(client, "ignoring packet: packet (%zu bytes) "
+                                "smaller than expected (%zu) by UDP header", len,
+                                hdrlen + be16toh(packet->udp.len));
+                return -EINVAL;
+        }
+
+        if (checksum && packet->udp.check) {
+                packet->ip.check = packet->udp.len;
+                packet->ip.ttl = 0;
+
+                if (dhcp_checksum(&packet->ip.ttl,
+                                  be16toh(packet->udp.len) + 12)) {
+                        log_dhcp_client(client, "ignoring packet: invalid UDP checksum");
+                        return -EINVAL;
+                }
+        }
+
+        if (be16toh(packet->udp.dest) != DHCP_PORT_CLIENT) {
+                log_dhcp_client(client, "ignoring packet: to port %u, which "
+                                "is not the DHCP client port (%u)",
+                                be16toh(packet->udp.dest), DHCP_PORT_CLIENT);
+                return -EINVAL;
+        }
+
+        return 0;
+}