dhcp: Add DHCP discover sending
On starting the client, use the supplied interface mac address and create
a transaction id. Puzzle together an IP/UDP/DHCP Discover message, compute
checksums and send it out as a raw packet.
Create an additional function that constructs default options common to
all DHCP messages.
Set the DHCP Client ID option as noticed by Grant Erickson in ConnMan
commit b18d9798b3a0ae46ed87d6d2be8d5a474bf3ab1e:
"Some Internet gateways and Wi-Fi access points are unhappy when the
DHCPv4 client-id option (61) is missing and will refuse to issue a
DHCP lease."
This commit is contained in:
Patrik Flykt
Zbigniew Jędrzejewski-Szmek
parent
8b4a96932d
commit
46a66b794a
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@ -21,19 +21,25 @@
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#include <errno.h>
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#include <string.h>
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#include <stdio.h>
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#include <net/ethernet.h>
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#include "util.h"
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#include "list.h"
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#include "dhcp-protocol.h"
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#include "dhcp-internal.h"
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#include "sd-dhcp-client.h"
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#define DHCP_CLIENT_MIN_OPTIONS_SIZE 312
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struct sd_dhcp_client {
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DHCPState state;
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int index;
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uint8_t *req_opts;
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size_t req_opts_size;
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uint32_t last_addr;
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struct ether_addr mac_addr;
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uint32_t xid;
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};
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static const uint8_t default_req_opts[] = {
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@ -102,6 +108,157 @@ int sd_dhcp_client_set_index(sd_dhcp_client *client, int interface_index)
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return 0;
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}
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int sd_dhcp_client_set_mac(sd_dhcp_client *client,
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const struct ether_addr *addr)
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{
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assert_return(client, -EINVAL);
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assert_return(client->state == DHCP_STATE_INIT, -EBUSY);
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memcpy(&client->mac_addr, addr, ETH_ALEN);
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return 0;
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}
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static int client_packet_init(sd_dhcp_client *client, uint8_t type,
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DHCPMessage *message, uint8_t **opt,
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size_t *optlen)
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{
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int err;
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*opt = (uint8_t *)(message + 1);
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if (*optlen < 4)
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return -ENOBUFS;
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*optlen -= 4;
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message->op = BOOTREQUEST;
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message->htype = 1;
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message->hlen = ETHER_ADDR_LEN;
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message->xid = htobe32(client->xid);
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memcpy(&message->chaddr, &client->mac_addr, ETH_ALEN);
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(*opt)[0] = 0x63;
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(*opt)[1] = 0x82;
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(*opt)[2] = 0x53;
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(*opt)[3] = 0x63;
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*opt += 4;
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err = dhcp_option_append(opt, optlen, DHCP_OPTION_MESSAGE_TYPE, 1,
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&type);
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if (err < 0)
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return err;
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/* Some DHCP servers will refuse to issue an DHCP lease if the Cliient
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Identifier option is not set */
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err = dhcp_option_append(opt, optlen, DHCP_OPTION_CLIENT_IDENTIFIER,
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ETH_ALEN, &client->mac_addr);
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if (err < 0)
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return err;
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if (type == DHCP_DISCOVER || type == DHCP_REQUEST) {
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err = dhcp_option_append(opt, optlen,
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DHCP_OPTION_PARAMETER_REQUEST_LIST,
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client->req_opts_size,
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client->req_opts);
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if (err < 0)
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return err;
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}
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return 0;
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}
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static uint16_t client_checksum(void *buf, int len)
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{
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uint32_t sum;
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uint16_t *check;
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int i;
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uint8_t *odd;
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sum = 0;
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check = buf;
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for (i = 0; i < len / 2 ; i++)
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sum += check[i];
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if (len & 0x01) {
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odd = buf;
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sum += odd[len];
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}
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return ~((sum & 0xffff) + (sum >> 16));
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}
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static int client_send_discover(sd_dhcp_client *client)
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{
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int err = 0;
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_cleanup_free_ DHCPPacket *discover;
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size_t optlen, len;
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uint8_t *opt;
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optlen = DHCP_CLIENT_MIN_OPTIONS_SIZE;
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len = sizeof(DHCPPacket) + optlen;
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discover = malloc0(len);
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if (!discover)
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return -ENOMEM;
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err = client_packet_init(client, DHCP_DISCOVER, &discover->dhcp,
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&opt, &optlen);
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if (err < 0)
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return err;
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if (client->last_addr != INADDR_ANY) {
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err = dhcp_option_append(&opt, &optlen,
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DHCP_OPTION_REQUESTED_IP_ADDRESS,
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4, &client->last_addr);
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if (err < 0)
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return err;
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}
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err = dhcp_option_append(&opt, &optlen, DHCP_OPTION_END, 0, NULL);
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if (err < 0)
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return err;
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discover->ip.version = IPVERSION;
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discover->ip.ihl = sizeof(discover->ip) >> 2;
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discover->ip.tot_len = htobe16(len);
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discover->ip.protocol = IPPROTO_UDP;
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discover->ip.saddr = INADDR_ANY;
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discover->ip.daddr = INADDR_BROADCAST;
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discover->udp.source = htobe16(DHCP_PORT_CLIENT);
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discover->udp.dest = htobe16(DHCP_PORT_SERVER);
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discover->udp.len = htobe16(len - sizeof(discover->ip));
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discover->ip.check = discover->udp.len;
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discover->udp.check = client_checksum(&discover->ip.ttl,
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len - 8);
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discover->ip.ttl = IPDEFTTL;
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discover->ip.check = 0;
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discover->ip.check = client_checksum(&discover->ip,
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sizeof(discover->ip));
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err = dhcp_network_send_raw_packet(client->index, discover, len);
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return 0;
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}
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int sd_dhcp_client_start(sd_dhcp_client *client)
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{
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assert_return(client, -EINVAL);
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assert_return(client->index >= 0, -EINVAL);
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assert_return(client->state == DHCP_STATE_INIT ||
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client->state == DHCP_STATE_INIT_REBOOT, -EBUSY);
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client->xid = random_u();
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return client_send_discover(client);
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}
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sd_dhcp_client *sd_dhcp_client_new(void)
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{
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sd_dhcp_client *client;
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@ -55,6 +55,11 @@ struct DHCPPacket {
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typedef struct DHCPPacket DHCPPacket;
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enum {
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DHCP_PORT_SERVER = 67,
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DHCP_PORT_CLIENT = 68,
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};
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enum DHCPState {
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DHCP_STATE_INIT = 0,
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DHCP_STATE_SELECTING = 1,
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@ -100,5 +105,6 @@ enum {
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DHCP_OPTION_OVERLOAD = 52,
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DHCP_OPTION_MESSAGE_TYPE = 53,
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DHCP_OPTION_PARAMETER_REQUEST_LIST = 55,
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DHCP_OPTION_CLIENT_IDENTIFIER = 61,
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DHCP_OPTION_END = 255,
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};
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@ -23,6 +23,7 @@
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***/
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#include <netinet/in.h>
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#include <net/ethernet.h>
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typedef struct sd_dhcp_client sd_dhcp_client;
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@ -30,7 +31,10 @@ int sd_dhcp_client_set_request_option(sd_dhcp_client *client, uint8_t option);
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int sd_dhcp_client_set_request_address(sd_dhcp_client *client,
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const struct in_addr *last_address);
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int sd_dhcp_client_set_index(sd_dhcp_client *client, int interface_index);
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int sd_dhcp_client_set_mac(sd_dhcp_client *client,
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const struct ether_addr *addr);
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int sd_dhcp_client_start(sd_dhcp_client *client);
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sd_dhcp_client *sd_dhcp_client_new(void);
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#endif
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