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network/address: acquire address from DHCP server lease file

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If the DHCP server on an interface is configured with its server
address is null, then let's reuse the previous server address if
possible.

Otherwise, if networkd is restarted or the host is rebooted, then
possibly new subnet is picked, and clients that already have addresses
in the previous subnet cannot access the server.

Prompted by https://github.com/systemd/systemd/pull/30021#discussion_r1518478633.
This commit is contained in:
Yu Watanabe
2024-03-18 22:33:14 +09:00
parent 88123aa21c
commit 7a89aeb138
4 changed files with 54 additions and 1 deletions
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src/network/networkd-dhcp-server.c
+46
View File
@@ -7,6 +7,7 @@
#include "sd-dhcp-server.h"
#include "dhcp-protocol.h"
#include "dhcp-server-lease-internal.h"
#include "fd-util.h"
#include "fileio.h"
#include "network-common.h"
@@ -82,6 +83,7 @@ int network_adjust_dhcp_server(Network *network, Set **addresses) {
/* TODO: check if the prefix length is small enough for the pool. */
network->dhcp_server_address = address;
address->used_by_dhcp_server = true;
break;
}
if (!network->dhcp_server_address) {
@@ -128,6 +130,7 @@ int network_adjust_dhcp_server(Network *network, Set **addresses) {
a->prefixlen = network->dhcp_server_address_prefixlen;
a->in_addr.in = network->dhcp_server_address_in_addr;
a->requested_as_null = !in4_addr_is_set(&network->dhcp_server_address_in_addr);
a->used_by_dhcp_server = true;
r = address_section_verify(a);
if (r < 0)
@@ -144,6 +147,49 @@ int network_adjust_dhcp_server(Network *network, Set **addresses) {
return 0;
}
int address_acquire_from_dhcp_server_leases_file(Link *link, const Address *address, union in_addr_union *ret) {
struct in_addr a;
uint8_t prefixlen;
int r;
assert(link);
assert(link->manager);
assert(address);
assert(ret);
/* If the DHCP server address is configured as a null address, reuse the server address of the
* previous instance. */
if (address->family != AF_INET)
return -ENOENT;
if (!address->used_by_dhcp_server)
return -ENOENT;
if (!link_dhcp4_server_enabled(link))
return -ENOENT;
if (link->manager->persistent_storage_fd < 0)
return -EBUSY; /* The persistent storage is not ready, try later again. */
_cleanup_free_ char *lease_file = path_join("dhcp-server-lease", link->ifname);
if (!lease_file)
return -ENOMEM;
r = dhcp_server_leases_file_get_server_address(
link->manager->persistent_storage_fd,
lease_file,
&a,
&prefixlen);
if (r < 0)
return r;
if (prefixlen != address->prefixlen)
return -ENOENT;
ret->in = a;
return 0;
}
int link_start_dhcp4_server(Link *link) {
int r;