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authorTom Gundersen <teg@jklm.no>2014-04-11 21:02:16 +0200
committerTom Gundersen <teg@jklm.no>2014-04-11 22:24:26 +0200
commit50d6810ea8117bbfcf7007ae779d1a98a7300b5f (patch)
tree1a6361ef649d1d8f7b4f77c07f50b914ebdb6ebd /src
parent8a9e761600d0d44bcc2e665e4fe1fda30e3e4749 (diff)
sd-dhcp-client: document message creation a bit more
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.
Diffstat (limited to 'src')
-rw-r--r--src/libsystemd-network/sd-dhcp-client.c90
1 files changed, 72 insertions, 18 deletions
diff --git a/src/libsystemd-network/sd-dhcp-client.c b/src/libsystemd-network/sd-dhcp-client.c
index e690f6785f..0adcf1328f 100644
--- a/src/libsystemd-network/sd-dhcp-client.c
+++ b/src/libsystemd-network/sd-dhcp-client.c
@@ -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) {
+ /* See RFC2131 section 4.3.2 (note that there is a typo in the RFC,
+ SELECTING should be REQUESTING)
+ */
+
+ case DHCP_STATE_REQUESTING:
+ /* 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.
+ */
- case DHCP_STATE_INIT_REBOOT:
r = dhcp_option_append(&opt, &optlen,
- DHCP_OPTION_REQUESTED_IP_ADDRESS,
- 4, &client->last_addr);
+ DHCP_OPTION_SERVER_IDENTIFIER,
+ 4, &client->lease->server_address);
if (r < 0)
return r;
- break;
- case DHCP_STATE_REQUESTING:
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_SERVER_IDENTIFIER,
- 4, &client->lease->server_address);
+ DHCP_OPTION_REQUESTED_IP_ADDRESS,
+ 4, &client->last_addr);
if (r < 0)
return r;
break;
- case DHCP_STATE_INIT:
- case DHCP_STATE_SELECTING:
- case DHCP_STATE_REBOOTING:
- case DHCP_STATE_BOUND:
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_STOPPED:
return -EINVAL;
}