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network: enable DHCP broadcast flag if required by interface

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Some interfaces require that the DHCPOFFER message is sent via broadcast
if they can't receive unicast messages before they've been configured
with an IP address.

E.g., s390 ccwgroup network interfaces operating in layer3 mode face
this limitation. This can prevent the interfaces from receiving an
IP address via DHCP, if the have been configured for layer3.

To allow DHCP over such interfaces, we're introducing a new device
property ID_NET_DHCP_BROADCAST which can be set for those.
The networkd DHCP client will check whether this property is set
for an interface, and if so will set the broadcast flag, unless
the network configuration for the interface has an explicit
RequestBroadcast setting.

Besides that, we're adding a udev rule to set this device property
for ccwgroup devices operating in layer3 mode, which is the case
if the ID_NET_DRIVER property is qeth_l3.

Supercedes #18829
This commit is contained in:
Viktor Mihajlovski 2021-04-14 13:01:35 +02:00
parent 5c9f1c68f0
commit e70eca9b48
6 changed files with 44 additions and 4 deletions
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14
rules.d/81-net-dhcp.rules Normal file
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@ -0,0 +1,14 @@
# do not edit this file, it will be overwritten on update
ACTION=="remove", GOTO="net_dhcp_end"
SUBSYSTEM!="net", GOTO="net_dhcp_end"
# Network interfaces requiring DHCPOFFER messages to be broadcast
# must set ID_NET_DHCP_BROADCAST to "1". This property will be
# checked by the networkd DHCP4 client to set the DHCP option
# s390 ccwgroup interfaces in layer3 mode need broadcast DHCPOFFER
# using the link driver to detect this condition
ENV{ID_NET_DRIVER}=="qeth_l3", ENV{ID_NET_DHCP_BROADCAST}="1"
LABEL="net_dhcp_end"

1
rules.d/meson.build
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@ -26,6 +26,7 @@ rules = files('''
75-probe_mtd.rules
78-sound-card.rules
80-net-setup-link.rules
81-net-dhcp.rules
'''.split())
if conf.get('HAVE_KMOD') == 1

26
src/network/networkd-dhcp4.c
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@ -1283,6 +1283,30 @@ static int dhcp4_set_request_address(Link *link) {
return sd_dhcp_client_set_request_address(link->dhcp_client, &a->in_addr.in);
}
static bool link_needs_dhcp_broadcast(Link *link) {
const char *val;
int r;
assert(link);
assert(link->network);
/* Return the setting in DHCP[4].RequestBroadcast if specified. Otherwise return the device property
* ID_NET_DHCP_BROADCAST setting, which may be set for interfaces requiring that the DHCPOFFER message
* is being broadcast because they can't handle unicast messages while not fully configured.
* If neither is set or a failure occurs, return false, which is the default for this flag.
*/
r = link->network->dhcp_broadcast;
if (r < 0 && link->sd_device && sd_device_get_property_value(link->sd_device, "ID_NET_DHCP_BROADCAST", &val) >= 0) {
r = parse_boolean(val);
if (r < 0)
log_link_warning_errno(link, r, "DHCP4 CLIENT: Failed to parse ID_NET_DHCP_BROADCAST, ignoring: %m");
else
log_link_debug(link, "DHCP4 CLIENT: Detected ID_NET_DHCP_BROADCAST='%d'.", r);
}
return r == true;
}
int dhcp4_configure(Link *link) {
sd_dhcp_option *send_option;
void *request_options;
@ -1319,7 +1343,7 @@ int dhcp4_configure(Link *link) {
if (r < 0)
return log_link_warning_errno(link, r, "DHCP4 CLIENT: Failed to set callback: %m");
r = sd_dhcp_client_set_request_broadcast(link->dhcp_client, link->network->dhcp_broadcast);
r = sd_dhcp_client_set_request_broadcast(link->dhcp_client, link_needs_dhcp_broadcast(link));
if (r < 0)
return log_link_warning_errno(link, r, "DHCP4 CLIENT: Failed to set request flag for broadcast: %m");

4
src/network/networkd-network-gperf.gperf
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@ -207,7 +207,7 @@ DHCPv4.RequestOptions, config_parse_dhcp_request_options,
DHCPv4.Anonymize, config_parse_bool, 0, offsetof(Network, dhcp_anonymize)
DHCPv4.SendHostname, config_parse_bool, 0, offsetof(Network, dhcp_send_hostname)
DHCPv4.Hostname, config_parse_hostname, 0, offsetof(Network, dhcp_hostname)
DHCPv4.RequestBroadcast, config_parse_bool, 0, offsetof(Network, dhcp_broadcast)
DHCPv4.RequestBroadcast, config_parse_tristate, 0, offsetof(Network, dhcp_broadcast)
DHCPv4.VendorClassIdentifier, config_parse_string, 0, offsetof(Network, dhcp_vendor_class_identifier)
DHCPv4.MUDURL, config_parse_dhcp_mud_url, 0, 0
DHCPv4.MaxAttempts, config_parse_dhcp_max_attempts, 0, 0
@ -475,7 +475,7 @@ DHCP.UseRoutes, config_parse_bool,
DHCP.Anonymize, config_parse_bool, 0, offsetof(Network, dhcp_anonymize)
DHCP.SendHostname, config_parse_bool, 0, offsetof(Network, dhcp_send_hostname)
DHCP.Hostname, config_parse_hostname, 0, offsetof(Network, dhcp_hostname)
DHCP.RequestBroadcast, config_parse_bool, 0, offsetof(Network, dhcp_broadcast)
DHCP.RequestBroadcast, config_parse_tristate, 0, offsetof(Network, dhcp_broadcast)
DHCP.CriticalConnection, config_parse_tristate, 0, offsetof(Network, dhcp_critical)
DHCP.VendorClassIdentifier, config_parse_string, 0, offsetof(Network, dhcp_vendor_class_identifier)
DHCP.UserClass, config_parse_dhcp_user_or_vendor_class, AF_INET, offsetof(Network, dhcp_user_class)

1
src/network/networkd-network.c
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@ -368,6 +368,7 @@ int network_load_one(Manager *manager, OrderedHashmap **networks, const char *fi
/* NOTE: from man: UseTimezone=... Defaults to "no".*/
.dhcp_use_timezone = false,
.dhcp_ip_service_type = -1,
.dhcp_broadcast = -1,
.dhcp6_use_address = true,
.dhcp6_use_dns = true,

2
src/network/networkd-network.h
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@ -136,7 +136,7 @@ struct Network {
int dhcp_ip_service_type;
bool dhcp_anonymize;
bool dhcp_send_hostname;
bool dhcp_broadcast;
int dhcp_broadcast;
bool dhcp_use_dns;
bool dhcp_use_dns_set;
bool dhcp_routes_to_dns;