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networkd: Allow DHCP servers to be re-configured on carrier gain

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In normal operation this would trigger an assertion
when a DHCP server is configured every time the link goes up.

This change makes sd_dhcp_server_configure_pool idempotent
and stops the DHCP server when the link loses carrier.

In addition to this stopping the assertion being triggered,
this has the useful side-effect of allowing the link to be taken down
and then brought back up as a way to have it use DNS from an "upstream"
interface that got its DNS configuration via DHCP
after the downstream link was configured.
This commit is contained in:
Richard Maw 2017-06-09 16:18:25 +01:00
parent c1835a427f
commit 45a9eac9a0
3 changed files with 30 additions and 20 deletions
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46
src/libsystemd-network/sd-dhcp-server.c
View File

@ -34,6 +34,14 @@
#define DHCP_DEFAULT_LEASE_TIME_USEC USEC_PER_HOUR
#define DHCP_MAX_LEASE_TIME_USEC (USEC_PER_HOUR*12)
static void dhcp_lease_free(DHCPLease *lease) {
if (!lease)
return;
free(lease->client_id.data);
free(lease);
}
/* configures the server's address and subnet, and optionally the pool's size and offset into the subnet
* the whole pool must fit into the subnet, and may not contain the first (any) nor last (broadcast) address
* moreover, the server's own address may be in the pool, and is in that case reserved in order not to
@ -47,7 +55,6 @@ int sd_dhcp_server_configure_pool(sd_dhcp_server *server, struct in_addr *addres
assert_return(address, -EINVAL);
assert_return(address->s_addr != INADDR_ANY, -EINVAL);
assert_return(prefixlen <= 32, -ERANGE);
assert_return(server->address == INADDR_ANY, -EBUSY);
assert_se(in_addr_prefixlen_to_netmask(&netmask_addr, prefixlen));
netmask = netmask_addr.s_addr;
@ -78,19 +85,28 @@ int sd_dhcp_server_configure_pool(sd_dhcp_server *server, struct in_addr *addres
else
size = size_max;
server->bound_leases = new0(DHCPLease*, size);
if (!server->bound_leases)
return -ENOMEM;
if (server->address != address->s_addr || server->netmask != netmask || server->pool_size != size || server->pool_offset != offset) {
DHCPLease *lease;
server->pool_offset = offset;
server->pool_size = size;
free(server->bound_leases);
server->bound_leases = new0(DHCPLease*, size);
if (!server->bound_leases)
return -ENOMEM;
server->address = address->s_addr;
server->netmask = netmask;
server->subnet = address->s_addr & netmask;
server->pool_offset = offset;
server->pool_size = size;
if (server_off >= offset && server_off - offset < size)
server->bound_leases[server_off - offset] = &server->invalid_lease;
server->address = address->s_addr;
server->netmask = netmask;
server->subnet = address->s_addr & netmask;
if (server_off >= offset && server_off - offset < size)
server->bound_leases[server_off - offset] = &server->invalid_lease;
/* Drop any leases associated with the old address range */
while ((lease = hashmap_steal_first(server->leases_by_client_id)))
dhcp_lease_free(lease);
}
return 0;
}
@ -143,14 +159,6 @@ static const struct hash_ops client_id_hash_ops = {
.compare = client_id_compare_func
};
static void dhcp_lease_free(DHCPLease *lease) {
if (!lease)
return;
free(lease->client_id.data);
free(lease);
}
sd_dhcp_server *sd_dhcp_server_unref(sd_dhcp_server *server) {
DHCPLease *lease;

2
src/libsystemd-network/test-dhcp-server.c
View File

@ -63,7 +63,7 @@ static int test_basic(sd_event *event) {
assert_se(sd_dhcp_server_configure_pool(server, &address_any, 28, 0, 0) == -EINVAL);
assert_se(sd_dhcp_server_configure_pool(server, &address_lo, 38, 0, 0) == -ERANGE);
assert_se(sd_dhcp_server_configure_pool(server, &address_lo, 8, 0, 0) >= 0);
assert_se(sd_dhcp_server_configure_pool(server, &address_lo, 8, 0, 0) == -EBUSY);
assert_se(sd_dhcp_server_configure_pool(server, &address_lo, 8, 0, 0) >= 0);
test_pool(&address_any, 1, -EINVAL);
test_pool(&address_lo, 1, 0);

2
src/network/networkd-link.c
View File

@ -3060,6 +3060,8 @@ static int link_carrier_lost(Link *link) {
return r;
}
(void) sd_dhcp_server_stop(link->dhcp_server);
r = link_drop_config(link);
if (r < 0)
return r;