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sd-dhcp-client: several fixlets for sending RELEASE or DECLINE

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- Extract common logic to client_send_release_or_decline().
- Do not send DECLINE message on BOOTP protocol.
- Drop redundant assignment of chaddr, as it is already set by
  client_message_init() -> dhcp_message_init().
- Do not assign acquired address in ciaddr field of DECLINE message,
  but use Requested IP Address option.
- Broadcast DECLINE message, rather than unicast.
- Set server identifier in both cases.

Fixes #39299.
This commit is contained in:
Yu Watanabe
2026-03-11 08:45:24 +09:00
parent b27e17d762
commit 6eaa5ba322
1 changed files with 73 additions and 55 deletions
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src/libsystemd-network/sd-dhcp-client.c
+73 -55
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@@ -876,7 +876,7 @@ static int client_message_init(
MAY contain the Parameter Request List option. */
/* NOTE: in case that there would be an option to do not send
* any PRL at all, the size should be checked before sending */
if (!set_isempty(client->req_opts) && type != DHCP_RELEASE) {
if (!set_isempty(client->req_opts) && IN_SET(type, DHCP_DISCOVER, DHCP_REQUEST)) {
_cleanup_free_ uint8_t *opts = NULL;
size_t n_opts, i = 0;
void *val;
@@ -2356,70 +2356,93 @@ int sd_dhcp_client_start(sd_dhcp_client *client) {
return r;
}
static int client_send_release(sd_dhcp_client *client) {
_cleanup_free_ DHCPPacket *release = NULL;
size_t optoffset, optlen;
static int client_send_release_or_decline(sd_dhcp_client *client, uint8_t type) {
int r;
assert(client);
assert(IN_SET(type, DHCP_RELEASE, DHCP_DECLINE));
if (!client->send_release)
return 0; /* disabled */
if (!sd_dhcp_client_is_running(client) || !client->lease || client->bootp)
return 0; /* there is nothing to release or decline */
if (!client->lease || client->bootp)
return 0; /* there is nothing to be released */
const char *name = type == DHCP_RELEASE ? "RELEASE" : "DECLINE";
r = client_message_init(client, DHCP_RELEASE, &release, &optlen, &optoffset);
_cleanup_free_ DHCPPacket *packet = NULL;
size_t optoffset, optlen;
r = client_message_init(client, type, &packet, &optlen, &optoffset);
if (r < 0)
return r;
return log_dhcp_client_errno(client, r, "Failed to initialize DHCP %s message: %m", name);
/* Fill up release IP and MAC */
release->dhcp.ciaddr = client->lease->address;
memcpy(&release->dhcp.chaddr, client->hw_addr.bytes, client->hw_addr.length);
/* See RFC 2131, Table 5 */
switch (type) {
case DHCP_RELEASE:
/* On release, the acquired address must be set in ciaddr. */
packet->dhcp.ciaddr = client->lease->address;
break;
r = dhcp_option_append(&release->dhcp, optlen, &optoffset, 0,
SD_DHCP_OPTION_END, 0, NULL);
case DHCP_DECLINE:
/* On decline, the acquired address must be set in Requested IP Address option. */
r = dhcp_option_append(&packet->dhcp, optlen, &optoffset, /* overload= */ 0,
SD_DHCP_OPTION_REQUESTED_IP_ADDRESS,
4, &client->lease->address);
if (r < 0)
return log_dhcp_client_errno(
client, r,
"Failed to append Requested IP Address option to DHCP %s message: %m",
name);
break;
default:
assert_not_reached();
}
/* In both cases, the server identifier must be set. */
r = dhcp_option_append(&packet->dhcp, optlen, &optoffset, /* overload= */ 0,
SD_DHCP_OPTION_SERVER_IDENTIFIER,
4, &client->lease->server_address);
if (r < 0)
return r;
return log_dhcp_client_errno(
client, r,
"Failed to append Server Identifier option to DHCP %s message: %m",
name);
r = dhcp_network_send_udp_socket(client->fd,
client->lease->server_address,
client->server_port,
&release->dhcp,
sizeof(DHCPMessage) + optoffset);
r = dhcp_option_append(&packet->dhcp, optlen, &optoffset, /* overload= */ 0,
SD_DHCP_OPTION_END, /* optlen= */ 0, /* optval= */ NULL);
if (r < 0)
return r;
return log_dhcp_client_errno(
client, r,
"Failed to finalize DHCP %s message: %m",
name);
log_dhcp_client(client, "RELEASE");
return 0;
switch (type) {
case DHCP_RELEASE:
r = dhcp_network_send_udp_socket(
client->fd,
client->lease->server_address,
client->server_port,
&packet->dhcp,
sizeof(DHCPMessage) + optoffset);
break;
case DHCP_DECLINE:
r = dhcp_client_send_raw(client, packet, sizeof(DHCPPacket) + optoffset);
break;
default:
assert_not_reached();
}
if (r < 0)
return log_dhcp_client_errno(
client, r,
"Failed to send DHCP %s message: %m",
name);
log_dhcp_client(client, "%s", name);
return 1; /* sent */
}
int sd_dhcp_client_send_decline(sd_dhcp_client *client) {
_cleanup_free_ DHCPPacket *release = NULL;
size_t optoffset, optlen;
int r;
if (!sd_dhcp_client_is_running(client) || !client->lease)
return 0; /* do nothing */
r = client_message_init(client, DHCP_DECLINE, &release, &optlen, &optoffset);
if (r < 0)
return r;
release->dhcp.ciaddr = client->lease->address;
memcpy(&release->dhcp.chaddr, client->hw_addr.bytes, client->hw_addr.length);
r = dhcp_option_append(&release->dhcp, optlen, &optoffset, 0,
SD_DHCP_OPTION_END, 0, NULL);
if (r < 0)
return r;
r = dhcp_network_send_udp_socket(client->fd,
client->lease->server_address,
client->server_port,
&release->dhcp,
sizeof(DHCPMessage) + optoffset);
if (r < 0)
r = client_send_release_or_decline(client, DHCP_DECLINE);
if (r <= 0)
return r;
log_dhcp_client(client, "DECLINE");
@@ -2434,20 +2457,15 @@ int sd_dhcp_client_send_decline(sd_dhcp_client *client) {
}
int sd_dhcp_client_stop(sd_dhcp_client *client) {
int r;
if (!client)
return 0;
DHCP_CLIENT_DONT_DESTROY(client);
r = client_send_release(client);
if (r < 0)
log_dhcp_client_errno(client, r,
"Failed to send DHCP release message, ignoring: %m");
if (client->send_release)
(void) client_send_release_or_decline(client, DHCP_RELEASE);
client_stop(client, SD_DHCP_CLIENT_EVENT_STOP);
return 0;
}