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sd-dhcp-client: document message creation a bit more

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Also reshuffle some code to make the correspondence with the RFC a bit more
obvious.

Small functional change: fail if we try to send a message from the wrong state.
This commit is contained in:
Tom Gundersen 2014-04-11 21:02:16 +02:00
parent 8a9e761600
commit 50d6810ea8
1 changed files with 79 additions and 25 deletions
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104
src/libsystemd-network/sd-dhcp-client.c
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@ -261,12 +261,12 @@ static int client_message_init(sd_dhcp_client *client, DHCPMessage *message,
refuse to issue an DHCP lease if 'secs' is set to zero */
message->secs = htobe16(client->secs);
/* RFC2132 section 4.1.1:
The client MUST include its hardware address in the ’chaddr’ field, if
necessary for delivery of DHCP reply messages.
*/
memcpy(&message->chaddr, &client->client_id.mac_addr, ETH_ALEN);
if (client->state == DHCP_STATE_RENEWING ||
client->state == DHCP_STATE_REBINDING)
message->ciaddr = client->lease->address;
/* Some DHCP servers will refuse to issue an DHCP lease if the Client
Identifier option is not set */
r = dhcp_option_append(opt, optlen, DHCP_OPTION_CLIENT_IDENTIFIER,
@ -274,6 +274,15 @@ static int client_message_init(sd_dhcp_client *client, DHCPMessage *message,
if (r < 0)
return r;
/* RFC2131 section 3.5:
in its initial DHCPDISCOVER or DHCPREQUEST message, a
client may provide the server with a list of specific
parameters the client is interested in. If the client
includes a list of parameters in a DHCPDISCOVER message,
it MUST include that list in any subsequent DHCPREQUEST
messages.
*/
r = dhcp_option_append(opt, optlen,
DHCP_OPTION_PARAMETER_REQUEST_LIST,
client->req_opts_size,
@ -281,9 +290,14 @@ static int client_message_init(sd_dhcp_client *client, DHCPMessage *message,
if (r < 0)
return r;
/* Some DHCP servers will send bigger DHCP packets than the
defined default size unless the Maximum Messge Size option
is explicitely set */
/* RFC2131 section 3.5:
The client SHOULD include the ’maximum DHCP message size’ option to
let the server know how large the server may make its DHCP messages.
Note (from ConnMan): Some DHCP servers will send bigger DHCP packets
than the defined default size unless the Maximum Messge Size option
is explicitely set
*/
max_size = htobe16(DHCP_IP_UDP_SIZE + DHCP_MESSAGE_SIZE +
DHCP_MIN_OPTIONS_SIZE);
r = dhcp_option_append(opt, optlen,
@ -312,6 +326,10 @@ static int client_send_discover(sd_dhcp_client *client) {
int r;
assert(client);
assert(client->state == DHCP_STATE_INIT ||
client->state == DHCP_STATE_SELECTING);
/* See RFC2131 section 4.4.1 */
r = sd_event_now(client->event, CLOCK_MONOTONIC, &time_now);
if (r < 0)
@ -334,6 +352,12 @@ static int client_send_discover(sd_dhcp_client *client) {
if (r < 0)
return r;
/* the client may suggest values for the network address
and lease time in the DHCPDISCOVER message. The client may include
the ’requested IP address’ option to suggest that a particular IP
address be assigned, and may include the ’IP address lease time’
option to suggest the lease time it would like.
*/
if (client->last_addr != INADDR_ANY) {
r = dhcp_option_append(&opt, &optlen,
DHCP_OPTION_REQUESTED_IP_ADDRESS,
@ -346,6 +370,10 @@ static int client_send_discover(sd_dhcp_client *client) {
if (r < 0)
return r;
/* We currently ignore:
The client SHOULD wait a random time between one and ten seconds to
desynchronize the use of DHCP at startup.
*/
r = dhcp_client_send_raw(client, discover, len - optlen);
if (r < 0)
return r;
@ -374,38 +402,64 @@ static int client_send_request(sd_dhcp_client *client) {
return r;
switch (client->state) {
case DHCP_STATE_INIT_REBOOT:
r = dhcp_option_append(&opt, &optlen,
DHCP_OPTION_REQUESTED_IP_ADDRESS,
4, &client->last_addr);
if (r < 0)
return r;
break;
/* See RFC2131 section 4.3.2 (note that there is a typo in the RFC,
SELECTING should be REQUESTING)
*/
case DHCP_STATE_REQUESTING:
r = dhcp_option_append(&opt, &optlen,
DHCP_OPTION_REQUESTED_IP_ADDRESS,
4, &client->lease->address);
if (r < 0)
return r;
/* Client inserts the address of the selected server in ’server
identifier’, ’ciaddr’ MUST be zero, ’requested IP address’ MUST be
filled in with the yiaddr value from the chosen DHCPOFFER.
*/
r = dhcp_option_append(&opt, &optlen,
DHCP_OPTION_SERVER_IDENTIFIER,
4, &client->lease->server_address);
if (r < 0)
return r;
r = dhcp_option_append(&opt, &optlen,
DHCP_OPTION_REQUESTED_IP_ADDRESS,
4, &client->lease->address);
if (r < 0)
return r;
break;
case DHCP_STATE_INIT_REBOOT:
/* ’server identifier’ MUST NOT be filled in, ’requested IP address’
option MUST be filled in with client’s notion of its previously
assigned address. ’ciaddr’ MUST be zero.
*/
r = dhcp_option_append(&opt, &optlen,
DHCP_OPTION_REQUESTED_IP_ADDRESS,
4, &client->last_addr);
if (r < 0)
return r;
break;
case DHCP_STATE_RENEWING:
/* ’server identifier’ MUST NOT be filled in, ’requested IP address’
option MUST NOT be filled in, ’ciaddr’ MUST be filled in with
client’s IP address.
*/
/* fall through */
case DHCP_STATE_REBINDING:
/* ’server identifier’ MUST NOT be filled in, ’requested IP address’
option MUST NOT be filled in, ’ciaddr’ MUST be filled in with
client’s IP address.
This message MUST be broadcast to the 0xffffffff IP broadcast address.
*/
request->dhcp.ciaddr = client->lease->address;
break;
case DHCP_STATE_INIT:
case DHCP_STATE_SELECTING:
case DHCP_STATE_REBOOTING:
case DHCP_STATE_BOUND:
case DHCP_STATE_RENEWING:
case DHCP_STATE_REBINDING:
break;
case DHCP_STATE_STOPPED:
return -EINVAL;
}