[systemd-devel] [PATCH v3 13/26] dhcp: Add DHCP discover sending
Patrik Flykt
patrik.flykt at linux.intel.com
Mon Dec 9 13:43:19 PST 2013
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."
---
src/dhcp/client.c | 157 ++++++++++++++++++++++++++++++++++++++++++
src/dhcp/protocol.h | 6 ++
src/systemd/sd-dhcp-client.h | 4 ++
3 files changed, 167 insertions(+)
diff --git a/src/dhcp/client.c b/src/dhcp/client.c
index dc4e409..4d0034f 100644
--- a/src/dhcp/client.c
+++ b/src/dhcp/client.c
@@ -21,19 +21,25 @@
#include <errno.h>
#include <string.h>
#include <stdio.h>
+#include <net/ethernet.h>
#include "util.h"
#include "list.h"
#include "protocol.h"
+#include "internal.h"
#include "sd-dhcp-client.h"
+#define DHCP_CLIENT_MIN_OPTIONS_SIZE 312
+
struct sd_dhcp_client {
DHCPState state;
int index;
uint8_t *req_opts;
size_t req_opts_size;
uint32_t last_addr;
+ struct ether_addr mac_addr;
+ uint32_t xid;
};
static const uint8_t default_req_opts[] = {
@@ -102,6 +108,157 @@ int sd_dhcp_client_set_index(sd_dhcp_client *client, int interface_index)
return 0;
}
+int sd_dhcp_client_set_mac(sd_dhcp_client *client,
+ const struct ether_addr *addr)
+{
+ assert_return(client, -EINVAL);
+ assert_return(client->state == DHCP_STATE_INIT, -EBUSY);
+
+ memcpy(&client->mac_addr, addr, ETH_ALEN);
+
+ return 0;
+}
+
+static int client_packet_init(sd_dhcp_client *client, uint8_t type,
+ DHCPMessage *message, uint8_t **opt,
+ size_t *optlen)
+{
+ int err;
+
+ *opt = (uint8_t *)(message + 1);
+
+ if (*optlen < 4)
+ return -ENOBUFS;
+ *optlen -= 4;
+
+ message->op = BOOTREQUEST;
+ message->htype = 1;
+ message->hlen = ETHER_ADDR_LEN;
+ message->xid = htobe32(client->xid);
+
+ memcpy(&message->chaddr, &client->mac_addr, ETH_ALEN);
+ (*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;
+
+ /* Some DHCP servers will refuse to issue an DHCP lease if the Cliient
+ Identifier option is not set */
+ err = dhcp_option_append(opt, optlen, DHCP_OPTION_CLIENT_IDENTIFIER,
+ ETH_ALEN, &client->mac_addr);
+ if (err < 0)
+ return err;
+
+ if (type == DHCP_DISCOVER || type == DHCP_REQUEST) {
+ err = dhcp_option_append(opt, optlen,
+ DHCP_OPTION_PARAMETER_REQUEST_LIST,
+ client->req_opts_size,
+ client->req_opts);
+ if (err < 0)
+ return err;
+ }
+
+ return 0;
+}
+
+static uint16_t client_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];
+ }
+
+ return ~((sum & 0xffff) + (sum >> 16));
+}
+
+static int client_send_discover(sd_dhcp_client *client)
+{
+ int err = 0;
+ _cleanup_free_ DHCPPacket *discover;
+ size_t optlen, len;
+ uint8_t *opt;
+
+ optlen = DHCP_CLIENT_MIN_OPTIONS_SIZE;
+ len = sizeof(DHCPPacket) + optlen;
+
+ discover = malloc0(len);
+
+ if (!discover)
+ return -ENOMEM;
+
+ err = client_packet_init(client, DHCP_DISCOVER, &discover->dhcp,
+ &opt, &optlen);
+ if (err < 0)
+ return err;
+
+ if (client->last_addr != INADDR_ANY) {
+ err = dhcp_option_append(&opt, &optlen,
+ DHCP_OPTION_REQUESTED_IP_ADDRESS,
+ 4, &client->last_addr);
+ if (err < 0)
+ return err;
+ }
+
+ err = dhcp_option_append(&opt, &optlen, DHCP_OPTION_END, 0, NULL);
+ if (err < 0)
+ return err;
+
+ discover->ip.version = IPVERSION;
+ discover->ip.ihl = sizeof(discover->ip) >> 2;
+ discover->ip.tot_len = htobe16(len);
+
+ discover->ip.protocol = IPPROTO_UDP;
+ discover->ip.saddr = INADDR_ANY;
+ discover->ip.daddr = INADDR_BROADCAST;
+
+ discover->udp.source = htobe16(DHCP_PORT_CLIENT);
+ discover->udp.dest = htobe16(DHCP_PORT_SERVER);
+ discover->udp.len = htobe16(len - sizeof(discover->ip));
+
+ discover->ip.check = discover->udp.len;
+ discover->udp.check = client_checksum(&discover->ip.ttl,
+ len - 8);
+
+ discover->ip.ttl = IPDEFTTL;
+ discover->ip.check = 0;
+ discover->ip.check = client_checksum(&discover->ip,
+ sizeof(discover->ip));
+
+ err = dhcp_network_send_raw_packet(client->index, discover, len);
+
+ return 0;
+}
+
+int sd_dhcp_client_start(sd_dhcp_client *client)
+{
+ assert_return(client, -EINVAL);
+ assert_return(client->index >= 0, -EINVAL);
+ assert_return(client->state == DHCP_STATE_INIT ||
+ client->state == DHCP_STATE_INIT_REBOOT, -EBUSY);
+
+ client->xid = random_u();
+
+ return client_send_discover(client);
+}
+
sd_dhcp_client *sd_dhcp_client_new(void)
{
sd_dhcp_client *client;
diff --git a/src/dhcp/protocol.h b/src/dhcp/protocol.h
index d375467..fa077fb 100644
--- a/src/dhcp/protocol.h
+++ b/src/dhcp/protocol.h
@@ -55,6 +55,11 @@ struct DHCPPacket {
typedef struct DHCPPacket DHCPPacket;
+enum {
+ DHCP_PORT_SERVER = 67,
+ DHCP_PORT_CLIENT = 68,
+};
+
enum DHCPState {
DHCP_STATE_INIT = 0,
DHCP_STATE_SELECTING = 1,
@@ -100,5 +105,6 @@ enum {
DHCP_OPTION_OVERLOAD = 52,
DHCP_OPTION_MESSAGE_TYPE = 53,
DHCP_OPTION_PARAMETER_REQUEST_LIST = 55,
+ DHCP_OPTION_CLIENT_IDENTIFIER = 61,
DHCP_OPTION_END = 255,
};
diff --git a/src/systemd/sd-dhcp-client.h b/src/systemd/sd-dhcp-client.h
index 9b19a1d..acfa3fa 100644
--- a/src/systemd/sd-dhcp-client.h
+++ b/src/systemd/sd-dhcp-client.h
@@ -23,6 +23,7 @@
***/
#include <netinet/in.h>
+#include <net/ethernet.h>
typedef struct sd_dhcp_client sd_dhcp_client;
@@ -30,7 +31,10 @@ int sd_dhcp_client_set_request_option(sd_dhcp_client *client, uint8_t option);
int sd_dhcp_client_set_request_address(sd_dhcp_client *client,
const struct in_addr *last_address);
int sd_dhcp_client_set_index(sd_dhcp_client *client, int interface_index);
+int sd_dhcp_client_set_mac(sd_dhcp_client *client,
+ const struct ether_addr *addr);
+int sd_dhcp_client_start(sd_dhcp_client *client);
sd_dhcp_client *sd_dhcp_client_new(void);
#endif
--
1.7.10.4
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