Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2025 insertions, 0 deletions

diff --git a/src/network/networkd-dhcp4.c b/src/network/networkd-dhcp4.c
new file mode 100644
index 0000000..49c452d
--- /dev/null
+++ b/src/network/networkd-dhcp4.c
@@ -0,0 +1,2025 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <linux/if.h>
+#include <linux/if_arp.h>
+
+#include "alloc-util.h"
+#include "dhcp-client-internal.h"
+#include "hostname-setup.h"
+#include "hostname-util.h"
+#include "parse-util.h"
+#include "network-internal.h"
+#include "networkd-address.h"
+#include "networkd-dhcp-prefix-delegation.h"
+#include "networkd-dhcp4-bus.h"
+#include "networkd-dhcp4.h"
+#include "networkd-ipv4acd.h"
+#include "networkd-link.h"
+#include "networkd-manager.h"
+#include "networkd-network.h"
+#include "networkd-nexthop.h"
+#include "networkd-queue.h"
+#include "networkd-route.h"
+#include "networkd-setlink.h"
+#include "networkd-state-file.h"
+#include "string-table.h"
+#include "strv.h"
+#include "sysctl-util.h"
+
+void network_adjust_dhcp4(Network *network) {
+        assert(network);
+
+        if (!FLAGS_SET(network->dhcp, ADDRESS_FAMILY_IPV4))
+                return;
+
+        if (network->dhcp_use_gateway < 0)
+                network->dhcp_use_gateway = network->dhcp_use_routes;
+
+        /* RFC7844 section 3.: MAY contain the Client Identifier option
+         * Section 3.5: clients MUST use client identifiers based solely on the link-layer address
+         * NOTE: Using MAC, as it does not reveal extra information, and some servers might not answer
+         * if this option is not sent */
+        if (network->dhcp_anonymize &&
+            network->dhcp_client_identifier >= 0 &&
+            network->dhcp_client_identifier != DHCP_CLIENT_ID_MAC) {
+                log_warning("%s: ClientIdentifier= is set, although Anonymize=yes. Using ClientIdentifier=mac.",
+                            network->filename);
+                network->dhcp_client_identifier = DHCP_CLIENT_ID_MAC;
+        }
+
+        if (network->dhcp_client_identifier < 0)
+                network->dhcp_client_identifier = network->dhcp_anonymize ? DHCP_CLIENT_ID_MAC : DHCP_CLIENT_ID_DUID;
+
+        /* By default, RapidCommit= is enabled when Anonymize=no and neither AllowList= nor DenyList= is specified. */
+        if (network->dhcp_use_rapid_commit < 0)
+                network->dhcp_use_rapid_commit =
+                        !network->dhcp_anonymize &&
+                        set_isempty(network->dhcp_allow_listed_ip) &&
+                        set_isempty(network->dhcp_deny_listed_ip);
+}
+
+static int dhcp4_prefix_covers(
+                Link *link,
+                const struct in_addr *in_prefix,
+                uint8_t in_prefixlen) {
+
+        struct in_addr prefix;
+        uint8_t prefixlen;
+        int r;
+
+        assert(link);
+        assert(link->dhcp_lease);
+        assert(in_prefix);
+
+        /* Return true if the input address or address range is in the assigned network.
+         * E.g. if the DHCP server provides 192.168.0.100/24, then this returns true for the address or
+         * address range in 192.168.0.0/24, and returns false otherwise. */
+
+        r = sd_dhcp_lease_get_prefix(link->dhcp_lease, &prefix, &prefixlen);
+        if (r < 0)
+                return r;
+
+        return in4_addr_prefix_covers_full(&prefix, prefixlen, in_prefix, in_prefixlen);
+}
+
+static int dhcp4_get_router(Link *link, struct in_addr *ret) {
+        const struct in_addr *routers;
+        int r;
+
+        assert(link);
+        assert(link->dhcp_lease);
+        assert(ret);
+
+        r = sd_dhcp_lease_get_router(link->dhcp_lease, &routers);
+        if (r < 0)
+                return r;
+
+        /* The router option may provide multiple routers, We only use the first non-null address. */
+
+        FOREACH_ARRAY(router, routers, r) {
+                if (in4_addr_is_null(router))
+                        continue;
+
+                *ret = *router;
+                return 0;
+        }
+
+        return -ENODATA;
+}
+
+static int dhcp4_get_classless_static_or_static_routes(Link *link, sd_dhcp_route ***ret_routes, size_t *ret_num) {
+        _cleanup_free_ sd_dhcp_route **routes = NULL;
+        int r;
+
+        assert(link);
+        assert(link->dhcp_lease);
+
+        /* If the DHCP server returns both a Classless Static Routes option and a Static Routes option,
+         * the DHCP client MUST ignore the Static Routes option. */
+
+        r = sd_dhcp_lease_get_classless_routes(link->dhcp_lease, &routes);
+        if (r >= 0) {
+                assert(r > 0);
+                if (ret_routes)
+                        *ret_routes = TAKE_PTR(routes);
+                if (ret_num)
+                        *ret_num = r;
+                return 1; /* classless */
+        } else if (r != -ENODATA)
+                return r;
+
+        r = sd_dhcp_lease_get_static_routes(link->dhcp_lease, &routes);
+        if (r < 0)
+                return r;
+
+        assert(r > 0);
+        if (ret_routes)
+                *ret_routes = TAKE_PTR(routes);
+        if (ret_num)
+                *ret_num = r;
+        return 0; /* static */
+}
+
+static int dhcp4_find_gateway_for_destination(
+                Link *link,
+                const struct in_addr *destination,
+                uint8_t prefixlength,
+                bool allow_null,
+                struct in_addr *ret) {
+
+        _cleanup_free_ sd_dhcp_route **routes = NULL;
+        size_t n_routes = 0;
+        bool is_classless, reachable;
+        uint8_t max_prefixlen = UINT8_MAX;
+        struct in_addr gw;
+        int r;
+
+        assert(link);
+        assert(link->dhcp_lease);
+        assert(destination);
+        assert(ret);
+
+        /* This tries to find the most suitable gateway for an address or address range.
+         * E.g. if the server provides the default gateway 192.168.0.1 and a classless static route for
+         * 8.0.0.0/8 with gateway 192.168.0.2, then this returns 192.168.0.2 for 8.8.8.8/32, and 192.168.0.1
+         * for 9.9.9.9/32. If 'allow_null' flag is set, and the input address or address range is in the
+         * assigned network, then the default gateway will be ignored and the null address will be returned
+         * unless a matching non-default gateway found. */
+
+        r = dhcp4_prefix_covers(link, destination, prefixlength);
+        if (r < 0)
+                return r;
+        reachable = r > 0;
+
+        r = dhcp4_get_classless_static_or_static_routes(link, &routes, &n_routes);
+        if (r < 0 && r != -ENODATA)
+                return r;
+        is_classless = r > 0;
+
+        /* First, find most suitable gateway. */
+        FOREACH_ARRAY(e, routes, n_routes) {
+                struct in_addr dst;
+                uint8_t len;
+
+                r = sd_dhcp_route_get_destination(*e, &dst);
+                if (r < 0)
+                        return r;
+
+                r = sd_dhcp_route_get_destination_prefix_length(*e, &len);
+                if (r < 0)
+                        return r;
+
+                r = in4_addr_prefix_covers_full(&dst, len, destination, prefixlength);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        continue;
+
+                if (max_prefixlen != UINT8_MAX && max_prefixlen > len)
+                        continue;
+
+                r = sd_dhcp_route_get_gateway(*e, &gw);
+                if (r < 0)
+                        return r;
+
+                max_prefixlen = len;
+        }
+
+        /* Found a suitable gateway in classless static routes or static routes. */
+        if (max_prefixlen != UINT8_MAX) {
+                if (max_prefixlen == 0 && reachable && allow_null)
+                        /* Do not return the default gateway, if the destination is in the assigned network. */
+                        *ret = (struct in_addr) {};
+                else
+                        *ret = gw;
+                return 0;
+        }
+
+        /* When the destination is in the assigned network, return the null address if allowed. */
+        if (reachable && allow_null) {
+                *ret = (struct in_addr) {};
+                return 0;
+        }
+
+        /* According to RFC 3442: If the DHCP server returns both a Classless Static Routes option and
+         * a Router option, the DHCP client MUST ignore the Router option. */
+        if (!is_classless) {
+                r = dhcp4_get_router(link, ret);
+                if (r >= 0)
+                        return 0;
+                if (r != -ENODATA)
+                        return r;
+        }
+
+        if (!reachable)
+                return -EHOSTUNREACH; /* Not in the same network, cannot reach the destination. */
+
+        assert(!allow_null);
+        return -ENODATA; /* No matching gateway found. */
+}
+
+static int dhcp4_remove_address_and_routes(Link *link, bool only_marked) {
+        Address *address;
+        Route *route;
+        int k, r = 0;
+
+        assert(link);
+
+        SET_FOREACH(route, link->routes) {
+                if (route->source != NETWORK_CONFIG_SOURCE_DHCP4)
+                        continue;
+                if (only_marked && !route_is_marked(route))
+                        continue;
+
+                k = route_remove(route);
+                if (k < 0)
+                        r = k;
+
+                route_cancel_request(route, link);
+        }
+
+        SET_FOREACH(address, link->addresses) {
+                if (address->source != NETWORK_CONFIG_SOURCE_DHCP4)
+                        continue;
+                if (only_marked && !address_is_marked(address))
+                        continue;
+
+                k = address_remove_and_drop(address);
+                if (k < 0)
+                        r = k;
+        }
+
+        return r;
+}
+
+static int dhcp4_address_get(Link *link, Address **ret) {
+        Address *address;
+
+        assert(link);
+
+        SET_FOREACH(address, link->addresses) {
+                if (address->source != NETWORK_CONFIG_SOURCE_DHCP4)
+                        continue;
+                if (address_is_marked(address))
+                        continue;
+
+                if (ret)
+                        *ret = address;
+                return 0;
+        }
+
+        return -ENOENT;
+}
+
+static int dhcp4_address_ready_callback(Address *address) {
+        assert(address);
+        assert(address->link);
+
+        /* Do not call this again. */
+        address->callback = NULL;
+
+        return dhcp4_check_ready(address->link);
+}
+
+int dhcp4_check_ready(Link *link) {
+        Address *address;
+        int r;
+
+        assert(link);
+
+        if (link->dhcp4_messages > 0) {
+                log_link_debug(link, "%s(): DHCPv4 address and routes are not set.", __func__);
+                return 0;
+        }
+
+        if (dhcp4_address_get(link, &address) < 0) {
+                log_link_debug(link, "%s(): DHCPv4 address is not set.", __func__);
+                return 0;
+        }
+
+        if (!address_is_ready(address)) {
+                log_link_debug(link, "%s(): DHCPv4 address is not ready.", __func__);
+                address->callback = dhcp4_address_ready_callback;
+                return 0;
+        }
+
+        link->dhcp4_configured = true;
+        log_link_debug(link, "DHCPv4 address and routes set.");
+
+        /* New address and routes are configured now. Let's release old lease. */
+        r = dhcp4_remove_address_and_routes(link, /* only_marked = */ true);
+        if (r < 0)
+                return r;
+
+        r = sd_ipv4ll_stop(link->ipv4ll);
+        if (r < 0)
+                return log_link_warning_errno(link, r, "Failed to drop IPv4 link-local address: %m");
+
+        link_check_ready(link);
+        return 0;
+}
+
+static int dhcp4_route_handler(sd_netlink *rtnl, sd_netlink_message *m, Request *req, Link *link, Route *route) {
+        int r;
+
+        assert(m);
+        assert(link);
+
+        r = sd_netlink_message_get_errno(m);
+        if (r < 0 && r != -EEXIST) {
+                log_link_message_warning_errno(link, m, r, "Could not set DHCPv4 route");
+                link_enter_failed(link);
+                return 1;
+        }
+
+        r = dhcp4_check_ready(link);
+        if (r < 0)
+                link_enter_failed(link);
+
+        return 1;
+}
+
+static int dhcp4_request_route(Route *in, Link *link) {
+        _cleanup_(route_freep) Route *route = in;
+        struct in_addr server;
+        Route *existing;
+        int r;
+
+        assert(route);
+        assert(link);
+        assert(link->network);
+        assert(link->dhcp_lease);
+
+        r = sd_dhcp_lease_get_server_identifier(link->dhcp_lease, &server);
+        if (r < 0)
+                return log_link_debug_errno(link, r, "Failed to get DHCP server IP address: %m");
+
+        route->source = NETWORK_CONFIG_SOURCE_DHCP4;
+        route->provider.in = server;
+        route->family = AF_INET;
+        if (!route->protocol_set)
+                route->protocol = RTPROT_DHCP;
+        if (!route->priority_set)
+                route->priority = link->network->dhcp_route_metric;
+        if (!route->table_set)
+                route->table = link_get_dhcp4_route_table(link);
+        if (route->mtu == 0)
+                route->mtu = link->network->dhcp_route_mtu;
+        if (route->quickack < 0)
+                route->quickack = link->network->dhcp_quickack;
+        if (route->initcwnd == 0)
+                route->initcwnd = link->network->dhcp_initial_congestion_window;
+        if (route->initrwnd == 0)
+                route->initrwnd = link->network->dhcp_advertised_receive_window;
+
+        if (route_get(NULL, link, route, &existing) < 0) /* This is a new route. */
+                link->dhcp4_configured = false;
+        else
+                route_unmark(existing);
+
+        return link_request_route(link, TAKE_PTR(route), true, &link->dhcp4_messages,
+                                  dhcp4_route_handler, NULL);
+}
+
+static bool link_prefixroute(Link *link) {
+        return !link->network->dhcp_route_table_set ||
+                link->network->dhcp_route_table == RT_TABLE_MAIN;
+}
+
+static int dhcp4_request_prefix_route(Link *link) {
+        _cleanup_(route_freep) Route *route = NULL;
+        int r;
+
+        assert(link);
+        assert(link->dhcp_lease);
+
+        if (link_prefixroute(link))
+                /* When true, the route will be created by kernel. See dhcp4_update_address(). */
+                return 0;
+
+        r = route_new(&route);
+        if (r < 0)
+                return r;
+
+        route->scope = RT_SCOPE_LINK;
+
+        r = sd_dhcp_lease_get_prefix(link->dhcp_lease, &route->dst.in, &route->dst_prefixlen);
+        if (r < 0)
+                return r;
+
+        r = sd_dhcp_lease_get_address(link->dhcp_lease, &route->prefsrc.in);
+        if (r < 0)
+                return r;
+
+        return dhcp4_request_route(TAKE_PTR(route), link);
+}
+
+static int dhcp4_request_route_to_gateway(Link *link, const struct in_addr *gw) {
+        _cleanup_(route_freep) Route *route = NULL;
+        struct in_addr address;
+        int r;
+
+        assert(link);
+        assert(link->dhcp_lease);
+        assert(gw);
+
+        r = sd_dhcp_lease_get_address(link->dhcp_lease, &address);
+        if (r < 0)
+                return r;
+
+        r = route_new(&route);
+        if (r < 0)
+                return r;
+
+        route->dst.in = *gw;
+        route->dst_prefixlen = 32;
+        route->prefsrc.in = address;
+        route->scope = RT_SCOPE_LINK;
+
+        return dhcp4_request_route(TAKE_PTR(route), link);
+}
+
+static int dhcp4_request_route_auto(
+                Route *in,
+                Link *link,
+                const struct in_addr *gw) {
+
+        _cleanup_(route_freep) Route *route = in;
+        struct in_addr address;
+        int r;
+
+        assert(route);
+        assert(link);
+        assert(link->dhcp_lease);
+        assert(gw);
+
+        r = sd_dhcp_lease_get_address(link->dhcp_lease, &address);
+        if (r < 0)
+                return r;
+
+        if (in4_addr_is_localhost(&route->dst.in)) {
+                if (in4_addr_is_set(gw))
+                        log_link_debug(link, "DHCP: requested route destination "IPV4_ADDRESS_FMT_STR"/%u is localhost, "
+                                       "ignoring gateway address "IPV4_ADDRESS_FMT_STR,
+                                       IPV4_ADDRESS_FMT_VAL(route->dst.in), route->dst_prefixlen, IPV4_ADDRESS_FMT_VAL(*gw));
+
+                route->scope = RT_SCOPE_HOST;
+                route->gw_family = AF_UNSPEC;
+                route->gw = IN_ADDR_NULL;
+                route->prefsrc = IN_ADDR_NULL;
+
+        } else if (in4_addr_equal(&route->dst.in, &address)) {
+                if (in4_addr_is_set(gw))
+                        log_link_debug(link, "DHCP: requested route destination "IPV4_ADDRESS_FMT_STR"/%u is equivalent to the acquired address, "
+                                       "ignoring gateway address "IPV4_ADDRESS_FMT_STR,
+                                       IPV4_ADDRESS_FMT_VAL(route->dst.in), route->dst_prefixlen, IPV4_ADDRESS_FMT_VAL(*gw));
+
+                route->scope = RT_SCOPE_HOST;
+                route->gw_family = AF_UNSPEC;
+                route->gw = IN_ADDR_NULL;
+                route->prefsrc.in = address;
+
+        } else if (in4_addr_is_null(gw)) {
+                r = dhcp4_prefix_covers(link, &route->dst.in, route->dst_prefixlen);
+                if (r < 0)
+                        return r;
+                if (r == 0 && DEBUG_LOGGING) {
+                        struct in_addr prefix;
+                        uint8_t prefixlen;
+
+                        r = sd_dhcp_lease_get_prefix(link->dhcp_lease, &prefix, &prefixlen);
+                        if (r < 0)
+                                return r;
+
+                        log_link_debug(link, "DHCP: requested route destination "IPV4_ADDRESS_FMT_STR"/%u is not in the assigned network "
+                                       IPV4_ADDRESS_FMT_STR"/%u, but no gateway is specified, using 'link' scope.",
+                                       IPV4_ADDRESS_FMT_VAL(route->dst.in), route->dst_prefixlen,
+                                       IPV4_ADDRESS_FMT_VAL(prefix), prefixlen);
+                }
+
+                route->scope = RT_SCOPE_LINK;
+                route->gw_family = AF_UNSPEC;
+                route->gw = IN_ADDR_NULL;
+                route->prefsrc.in = address;
+
+        } else {
+                r = dhcp4_request_route_to_gateway(link, gw);
+                if (r < 0)
+                        return r;
+
+                route->scope = RT_SCOPE_UNIVERSE;
+                route->gw_family = AF_INET;
+                route->gw.in = *gw;
+                route->prefsrc.in = address;
+        }
+
+        return dhcp4_request_route(TAKE_PTR(route), link);
+}
+
+static int dhcp4_request_classless_static_or_static_routes(Link *link) {
+        _cleanup_free_ sd_dhcp_route **routes = NULL;
+        size_t n_routes;
+        int r;
+
+        assert(link);
+        assert(link->dhcp_lease);
+
+        if (!link->network->dhcp_use_routes)
+                return 0;
+
+        r = dhcp4_get_classless_static_or_static_routes(link, &routes, &n_routes);
+        if (r == -ENODATA)
+                return 0;
+        if (r < 0)
+                return r;
+
+        FOREACH_ARRAY(e, routes, n_routes) {
+                _cleanup_(route_freep) Route *route = NULL;
+                struct in_addr gw;
+
+                r = route_new(&route);
+                if (r < 0)
+                        return r;
+
+                r = sd_dhcp_route_get_gateway(*e, &gw);
+                if (r < 0)
+                        return r;
+
+                r = sd_dhcp_route_get_destination(*e, &route->dst.in);
+                if (r < 0)
+                        return r;
+
+                r = sd_dhcp_route_get_destination_prefix_length(*e, &route->dst_prefixlen);
+                if (r < 0)
+                        return r;
+
+                r = dhcp4_request_route_auto(TAKE_PTR(route), link, &gw);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+static int dhcp4_request_default_gateway(Link *link) {
+        _cleanup_(route_freep) Route *route = NULL;
+        struct in_addr address, router;
+        int r;
+
+        assert(link);
+        assert(link->dhcp_lease);
+
+        if (!link->network->dhcp_use_gateway)
+                return 0;
+
+        /* According to RFC 3442: If the DHCP server returns both a Classless Static Routes option and
+         * a Router option, the DHCP client MUST ignore the Router option. */
+        if (link->network->dhcp_use_routes &&
+            dhcp4_get_classless_static_or_static_routes(link, NULL, NULL) > 0)
+                return 0;
+
+        r = sd_dhcp_lease_get_address(link->dhcp_lease, &address);
+        if (r < 0)
+                return r;
+
+        r = dhcp4_get_router(link, &router);
+        if (r == -ENODATA) {
+                log_link_debug(link, "DHCP: No valid router address received from DHCP server.");
+                return 0;
+        }
+        if (r < 0)
+                return r;
+
+        /* The dhcp netmask may mask out the gateway. First, add an explicit route for the gateway host
+         * so that we can route no matter the netmask or existing kernel route tables. */
+        r = dhcp4_request_route_to_gateway(link, &router);
+        if (r < 0)
+                return r;
+
+        r = route_new(&route);
+        if (r < 0)
+                return r;
+
+        /* Next, add a default gateway. */
+        route->gw_family = AF_INET;
+        route->gw.in = router;
+        route->prefsrc.in = address;
+
+        return dhcp4_request_route(TAKE_PTR(route), link);
+}
+
+static int dhcp4_request_semi_static_routes(Link *link) {
+        Route *rt;
+        int r;
+
+        assert(link);
+        assert(link->dhcp_lease);
+        assert(link->network);
+
+        HASHMAP_FOREACH(rt, link->network->routes_by_section) {
+                _cleanup_(route_freep) Route *route = NULL;
+                struct in_addr gw;
+
+                if (!rt->gateway_from_dhcp_or_ra)
+                        continue;
+
+                if (rt->gw_family != AF_INET)
+                        continue;
+
+                assert(rt->family == AF_INET);
+
+                r = dhcp4_find_gateway_for_destination(link, &rt->dst.in, rt->dst_prefixlen, /* allow_null = */ false, &gw);
+                if (IN_SET(r, -EHOSTUNREACH, -ENODATA)) {
+                        log_link_debug_errno(link, r, "DHCP: Cannot find suitable gateway for destination %s of semi-static route, ignoring: %m",
+                                             IN4_ADDR_PREFIX_TO_STRING(&rt->dst.in, rt->dst_prefixlen));
+                        continue;
+                }
+                if (r < 0)
+                        return r;
+
+                r = dhcp4_request_route_to_gateway(link, &gw);
+                if (r < 0)
+                        return r;
+
+                r = route_dup(rt, &route);
+                if (r < 0)
+                        return r;
+
+                route->gw.in = gw;
+
+                r = dhcp4_request_route(TAKE_PTR(route), link);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+static int dhcp4_request_routes_to_servers(
+                Link *link,
+                const struct in_addr *servers,
+                size_t n_servers) {
+
+        int r;
+
+        assert(link);
+        assert(link->dhcp_lease);
+        assert(link->network);
+        assert(servers || n_servers == 0);
+
+        FOREACH_ARRAY(dst, servers, n_servers) {
+                _cleanup_(route_freep) Route *route = NULL;
+                struct in_addr gw;
+
+                if (in4_addr_is_null(dst))
+                        continue;
+
+                r = dhcp4_find_gateway_for_destination(link, dst, 32, /* allow_null = */ true, &gw);
+                if (r == -EHOSTUNREACH) {
+                        log_link_debug_errno(link, r, "DHCP: Cannot find suitable gateway for destination %s, ignoring: %m",
+                                             IN4_ADDR_PREFIX_TO_STRING(dst, 32));
+                        continue;
+                }
+                if (r < 0)
+                        return r;
+
+                r = route_new(&route);
+                if (r < 0)
+                        return r;
+
+                route->dst.in = *dst;
+                route->dst_prefixlen = 32;
+
+                r = dhcp4_request_route_auto(TAKE_PTR(route), link, &gw);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+static int dhcp4_request_routes_to_dns(Link *link) {
+        const struct in_addr *dns;
+        int r;
+
+        assert(link);
+        assert(link->dhcp_lease);
+        assert(link->network);
+
+        if (!link->network->dhcp_use_dns ||
+            !link->network->dhcp_routes_to_dns)
+                return 0;
+
+        r = sd_dhcp_lease_get_dns(link->dhcp_lease, &dns);
+        if (IN_SET(r, 0, -ENODATA))
+                return 0;
+        if (r < 0)
+                return r;
+
+        return dhcp4_request_routes_to_servers(link, dns, r);
+}
+
+static int dhcp4_request_routes_to_ntp(Link *link) {
+        const struct in_addr *ntp;
+        int r;
+
+        assert(link);
+        assert(link->dhcp_lease);
+        assert(link->network);
+
+        if (!link->network->dhcp_use_ntp ||
+            !link->network->dhcp_routes_to_ntp)
+                return 0;
+
+        r = sd_dhcp_lease_get_ntp(link->dhcp_lease, &ntp);
+        if (IN_SET(r, 0, -ENODATA))
+                return 0;
+        if (r < 0)
+                return r;
+
+        return dhcp4_request_routes_to_servers(link, ntp, r);
+}
+
+static int dhcp4_request_routes(Link *link) {
+        int r;
+
+        assert(link);
+        assert(link->dhcp_lease);
+
+        r = dhcp4_request_prefix_route(link);
+        if (r < 0)
+                return log_link_error_errno(link, r, "DHCP error: Could not request prefix route: %m");
+
+        r = dhcp4_request_default_gateway(link);
+        if (r < 0)
+                return log_link_error_errno(link, r, "DHCP error: Could not request default gateway: %m");
+
+        r = dhcp4_request_classless_static_or_static_routes(link);
+        if (r < 0)
+                return log_link_error_errno(link, r, "DHCP error: Could not request static routes: %m");
+
+        r = dhcp4_request_semi_static_routes(link);
+        if (r < 0)
+                return log_link_error_errno(link, r, "DHCP error: Could not request routes with Gateway=_dhcp4 setting: %m");
+
+        r = dhcp4_request_routes_to_dns(link);
+        if (r < 0)
+                return log_link_error_errno(link, r, "DHCP error: Could not request routes to DNS servers: %m");
+
+        r = dhcp4_request_routes_to_ntp(link);
+        if (r < 0)
+                return log_link_error_errno(link, r, "DHCP error: Could not request routes to NTP servers: %m");
+
+        return 0;
+}
+
+static int dhcp_reset_mtu(Link *link) {
+        int r;
+
+        assert(link);
+
+        if (!link->network->dhcp_use_mtu)
+                return 0;
+
+        r = link_request_to_set_mtu(link, link->original_mtu);
+        if (r < 0)
+                return log_link_error_errno(link, r, "DHCP error: Could not queue request to reset MTU: %m");
+
+        return 0;
+}
+
+static int dhcp_reset_hostname(Link *link) {
+        const char *hostname;
+        int r;
+
+        assert(link);
+
+        if (!link->network->dhcp_use_hostname)
+                return 0;
+
+        hostname = link->network->dhcp_hostname;
+        if (!hostname)
+                (void) sd_dhcp_lease_get_hostname(link->dhcp_lease, &hostname);
+
+        if (!hostname)
+                return 0;
+
+        /* If a hostname was set due to the lease, then unset it now. */
+        r = manager_set_hostname(link->manager, NULL);
+        if (r < 0)
+                return log_link_error_errno(link, r, "DHCP error: Failed to reset transient hostname: %m");
+
+        return 0;
+}
+
+int dhcp4_lease_lost(Link *link) {
+        int k, r = 0;
+
+        assert(link);
+        assert(link->dhcp_lease);
+        assert(link->network);
+
+        log_link_info(link, "DHCP lease lost");
+
+        link->dhcp4_configured = false;
+
+        if (link->network->dhcp_use_6rd &&
+            sd_dhcp_lease_has_6rd(link->dhcp_lease))
+                dhcp4_pd_prefix_lost(link);
+
+        k = dhcp4_remove_address_and_routes(link, /* only_marked = */ false);
+        if (k < 0)
+                r = k;
+
+        k = dhcp_reset_mtu(link);
+        if (k < 0)
+                r = k;
+
+        k = dhcp_reset_hostname(link);
+        if (k < 0)
+                r = k;
+
+        link->dhcp_lease = sd_dhcp_lease_unref(link->dhcp_lease);
+        link_dirty(link);
+
+        /* If one of the above failed. Do not request nexthops and routes. */
+        if (r < 0)
+                return r;
+
+        r = link_request_static_nexthops(link, true);
+        if (r < 0)
+                return r;
+
+        return link_request_static_routes(link, true);
+}
+
+static int dhcp4_address_handler(sd_netlink *rtnl, sd_netlink_message *m, Request *req, Link *link, Address *address) {
+        int r;
+
+        assert(link);
+
+        r = address_configure_handler_internal(rtnl, m, link, "Could not set DHCPv4 address");
+        if (r <= 0)
+                return r;
+
+        r = dhcp4_check_ready(link);
+        if (r < 0)
+                link_enter_failed(link);
+
+        return 1;
+}
+
+static int dhcp4_request_address(Link *link, bool announce) {
+        _cleanup_(address_freep) Address *addr = NULL;
+        struct in_addr address, server;
+        uint8_t prefixlen;
+        Address *existing;
+        usec_t lifetime_usec;
+        int r;
+
+        assert(link);
+        assert(link->manager);
+        assert(link->network);
+        assert(link->dhcp_lease);
+
+        r = sd_dhcp_lease_get_address(link->dhcp_lease, &address);
+        if (r < 0)
+                return log_link_warning_errno(link, r, "DHCP error: no address: %m");
+
+        r = sd_dhcp_lease_get_prefix(link->dhcp_lease, NULL, &prefixlen);
+        if (r < 0)
+                return log_link_warning_errno(link, r, "DHCP error: no netmask: %m");
+
+        r = sd_dhcp_lease_get_server_identifier(link->dhcp_lease, &server);
+        if (r < 0)
+                return log_link_debug_errno(link, r, "DHCP error: failed to get DHCP server IP address: %m");
+
+        if (!FLAGS_SET(link->network->keep_configuration, KEEP_CONFIGURATION_DHCP)) {
+                r = sd_dhcp_lease_get_lifetime_timestamp(link->dhcp_lease, CLOCK_BOOTTIME, &lifetime_usec);
+                if (r < 0)
+                        return log_link_warning_errno(link, r, "DHCP error: failed to get lifetime: %m");
+        } else
+                lifetime_usec = USEC_INFINITY;
+
+        if (announce) {
+                const struct in_addr *router;
+
+                r = sd_dhcp_lease_get_router(link->dhcp_lease, &router);
+                if (r < 0 && r != -ENODATA)
+                        return log_link_error_errno(link, r, "DHCP error: Could not get gateway: %m");
+
+                if (r > 0 && in4_addr_is_set(&router[0]))
+                        log_struct(LOG_INFO,
+                                   LOG_LINK_INTERFACE(link),
+                                   LOG_LINK_MESSAGE(link, "DHCPv4 address "IPV4_ADDRESS_FMT_STR"/%u, gateway "IPV4_ADDRESS_FMT_STR" acquired from "IPV4_ADDRESS_FMT_STR,
+                                                    IPV4_ADDRESS_FMT_VAL(address),
+                                                    prefixlen,
+                                                    IPV4_ADDRESS_FMT_VAL(router[0]),
+                                                    IPV4_ADDRESS_FMT_VAL(server)),
+                                   "ADDRESS="IPV4_ADDRESS_FMT_STR, IPV4_ADDRESS_FMT_VAL(address),
+                                   "PREFIXLEN=%u", prefixlen,
+                                   "GATEWAY="IPV4_ADDRESS_FMT_STR, IPV4_ADDRESS_FMT_VAL(router[0]));
+                else
+                        log_struct(LOG_INFO,
+                                   LOG_LINK_INTERFACE(link),
+                                   LOG_LINK_MESSAGE(link, "DHCPv4 address "IPV4_ADDRESS_FMT_STR"/%u acquired from "IPV4_ADDRESS_FMT_STR,
+                                                    IPV4_ADDRESS_FMT_VAL(address),
+                                                    prefixlen,
+                                                    IPV4_ADDRESS_FMT_VAL(server)),
+                                   "ADDRESS="IPV4_ADDRESS_FMT_STR, IPV4_ADDRESS_FMT_VAL(address),
+                                   "PREFIXLEN=%u", prefixlen);
+        }
+
+        r = address_new(&addr);
+        if (r < 0)
+                return log_oom();
+
+        addr->source = NETWORK_CONFIG_SOURCE_DHCP4;
+        addr->provider.in = server;
+        addr->family = AF_INET;
+        addr->in_addr.in.s_addr = address.s_addr;
+        addr->lifetime_preferred_usec = lifetime_usec;
+        addr->lifetime_valid_usec = lifetime_usec;
+        addr->prefixlen = prefixlen;
+        r = sd_dhcp_lease_get_broadcast(link->dhcp_lease, &addr->broadcast);
+        if (r < 0 && r != -ENODATA)
+                return log_link_warning_errno(link, r, "DHCP: failed to get broadcast address: %m");
+        SET_FLAG(addr->flags, IFA_F_NOPREFIXROUTE, !link_prefixroute(link));
+        addr->route_metric = link->network->dhcp_route_metric;
+        addr->duplicate_address_detection = link->network->dhcp_send_decline ? ADDRESS_FAMILY_IPV4 : ADDRESS_FAMILY_NO;
+
+        r = free_and_strdup_warn(&addr->label, link->network->dhcp_label);
+        if (r < 0)
+                return r;
+
+        r = free_and_strdup_warn(&addr->netlabel, link->network->dhcp_netlabel);
+        if (r < 0)
+                return r;
+
+        if (address_get(link, addr, &existing) < 0) /* The address is new. */
+                link->dhcp4_configured = false;
+        else
+                address_unmark(existing);
+
+        r = link_request_address(link, addr, &link->dhcp4_messages,
+                                 dhcp4_address_handler, NULL);
+        if (r < 0)
+                return log_link_error_errno(link, r, "Failed to request DHCPv4 address: %m");
+
+        return 0;
+}
+
+static int dhcp4_request_address_and_routes(Link *link, bool announce) {
+        int r;
+
+        assert(link);
+
+        link_mark_addresses(link, NETWORK_CONFIG_SOURCE_DHCP4);
+        link_mark_routes(link, NETWORK_CONFIG_SOURCE_DHCP4);
+
+        r = dhcp4_request_address(link, announce);
+        if (r < 0)
+                return r;
+
+        r = dhcp4_request_routes(link);
+        if (r < 0)
+                return r;
+
+        if (!link->dhcp4_configured) {
+                link_set_state(link, LINK_STATE_CONFIGURING);
+                link_check_ready(link);
+        }
+
+        return 0;
+}
+
+static int dhcp_lease_renew(sd_dhcp_client *client, Link *link) {
+        _cleanup_(sd_dhcp_lease_unrefp) sd_dhcp_lease *old_lease = NULL;
+        sd_dhcp_lease *lease;
+        int r;
+
+        assert(link);
+        assert(link->network);
+        assert(client);
+
+        r = sd_dhcp_client_get_lease(client, &lease);
+        if (r < 0)
+                return log_link_warning_errno(link, r, "DHCP error: no lease: %m");
+
+        old_lease = TAKE_PTR(link->dhcp_lease);
+        link->dhcp_lease = sd_dhcp_lease_ref(lease);
+        link_dirty(link);
+
+        if (link->network->dhcp_use_6rd) {
+                if (sd_dhcp_lease_has_6rd(link->dhcp_lease)) {
+                        r = dhcp4_pd_prefix_acquired(link);
+                        if (r < 0)
+                                return log_link_warning_errno(link, r, "Failed to process 6rd option: %m");
+                } else if (sd_dhcp_lease_has_6rd(old_lease))
+                        dhcp4_pd_prefix_lost(link);
+        }
+
+        return dhcp4_request_address_and_routes(link, false);
+}
+
+static int dhcp_lease_acquired(sd_dhcp_client *client, Link *link) {
+        sd_dhcp_lease *lease;
+        int r;
+
+        assert(client);
+        assert(link);
+
+        r = sd_dhcp_client_get_lease(client, &lease);
+        if (r < 0)
+                return log_link_error_errno(link, r, "DHCP error: No lease: %m");
+
+        sd_dhcp_lease_unref(link->dhcp_lease);
+        link->dhcp_lease = sd_dhcp_lease_ref(lease);
+        link_dirty(link);
+
+        if (link->network->dhcp_use_mtu) {
+                uint16_t mtu;
+
+                r = sd_dhcp_lease_get_mtu(lease, &mtu);
+                if (r >= 0) {
+                        r = link_request_to_set_mtu(link, mtu);
+                        if (r < 0)
+                                log_link_error_errno(link, r, "Failed to set MTU to %" PRIu16 ": %m", mtu);
+                }
+        }
+
+        if (link->network->dhcp_use_hostname) {
+                const char *dhcpname = NULL;
+                _cleanup_free_ char *hostname = NULL;
+
+                if (link->network->dhcp_hostname)
+                        dhcpname = link->network->dhcp_hostname;
+                else
+                        (void) sd_dhcp_lease_get_hostname(lease, &dhcpname);
+
+                if (dhcpname) {
+                        r = shorten_overlong(dhcpname, &hostname);
+                        if (r < 0)
+                                log_link_warning_errno(link, r, "Unable to shorten overlong DHCP hostname '%s', ignoring: %m", dhcpname);
+                        if (r == 1)
+                                log_link_notice(link, "Overlong DHCP hostname received, shortened from '%s' to '%s'", dhcpname, hostname);
+                }
+
+                if (hostname) {
+                        r = manager_set_hostname(link->manager, hostname);
+                        if (r < 0)
+                                log_link_error_errno(link, r, "Failed to set transient hostname to '%s': %m", hostname);
+                }
+        }
+
+        if (link->network->dhcp_use_timezone) {
+                const char *tz = NULL;
+
+                (void) sd_dhcp_lease_get_timezone(link->dhcp_lease, &tz);
+
+                if (tz) {
+                        r = manager_set_timezone(link->manager, tz);
+                        if (r < 0)
+                                log_link_error_errno(link, r, "Failed to set timezone to '%s': %m", tz);
+                }
+        }
+
+        if (link->network->dhcp_use_6rd &&
+            sd_dhcp_lease_has_6rd(link->dhcp_lease)) {
+                r = dhcp4_pd_prefix_acquired(link);
+                if (r < 0)
+                        return log_link_warning_errno(link, r, "Failed to process 6rd option: %m");
+        }
+
+        return dhcp4_request_address_and_routes(link, true);
+}
+
+static int dhcp_lease_ip_change(sd_dhcp_client *client, Link *link) {
+        int r;
+
+        r = dhcp_lease_acquired(client, link);
+        if (r < 0)
+                (void) dhcp4_lease_lost(link);
+
+        return r;
+}
+
+static int dhcp_server_is_filtered(Link *link, sd_dhcp_client *client) {
+        sd_dhcp_lease *lease;
+        struct in_addr addr;
+        int r;
+
+        assert(link);
+        assert(link->network);
+        assert(client);
+
+        r = sd_dhcp_client_get_lease(client, &lease);
+        if (r < 0)
+                return log_link_error_errno(link, r, "Failed to get DHCP lease: %m");
+
+        r = sd_dhcp_lease_get_server_identifier(lease, &addr);
+        if (r < 0)
+                return log_link_debug_errno(link, r, "Failed to get DHCP server IP address: %m");
+
+        if (in4_address_is_filtered(&addr, link->network->dhcp_allow_listed_ip, link->network->dhcp_deny_listed_ip)) {
+                if (DEBUG_LOGGING) {
+                        if (link->network->dhcp_allow_listed_ip)
+                                log_link_debug(link, "DHCPv4 server IP address "IPV4_ADDRESS_FMT_STR" not found in allow-list, ignoring offer.",
+                                               IPV4_ADDRESS_FMT_VAL(addr));
+                        else
+                                log_link_debug(link, "DHCPv4 server IP address "IPV4_ADDRESS_FMT_STR" found in deny-list, ignoring offer.",
+                                               IPV4_ADDRESS_FMT_VAL(addr));
+                }
+
+                return true;
+        }
+
+        return false;
+}
+
+static int dhcp4_handler(sd_dhcp_client *client, int event, void *userdata) {
+        Link *link = ASSERT_PTR(userdata);
+        int r;
+
+        assert(link->network);
+        assert(link->manager);
+
+        if (IN_SET(link->state, LINK_STATE_FAILED, LINK_STATE_LINGER))
+                return 0;
+
+        switch (event) {
+                case SD_DHCP_CLIENT_EVENT_STOP:
+                        if (link->ipv4ll) {
+                                log_link_debug(link, "DHCP client is stopped. Acquiring IPv4 link-local address");
+
+                                if (in4_addr_is_set(&link->network->ipv4ll_start_address)) {
+                                        r = sd_ipv4ll_set_address(link->ipv4ll, &link->network->ipv4ll_start_address);
+                                        if (r < 0)
+                                                return log_link_warning_errno(link, r, "Could not set IPv4 link-local start address: %m");
+                                }
+
+                                r = sd_ipv4ll_start(link->ipv4ll);
+                                if (r < 0)
+                                        return log_link_warning_errno(link, r, "Could not acquire IPv4 link-local address: %m");
+                        }
+
+                        if (FLAGS_SET(link->network->keep_configuration, KEEP_CONFIGURATION_DHCP)) {
+                                log_link_notice(link, "DHCPv4 connection considered critical, ignoring request to reconfigure it.");
+                                return 0;
+                        }
+
+                        if (link->dhcp_lease) {
+                                if (link->network->dhcp_send_release) {
+                                        r = sd_dhcp_client_send_release(client);
+                                        if (r < 0)
+                                                log_link_full_errno(link,
+                                                                    ERRNO_IS_DISCONNECT(r) ? LOG_DEBUG : LOG_WARNING,
+                                                                    r, "Failed to send DHCP RELEASE, ignoring: %m");
+                                }
+
+                                r = dhcp4_lease_lost(link);
+                                if (r < 0) {
+                                        link_enter_failed(link);
+                                        return r;
+                                }
+                        }
+
+                        break;
+                case SD_DHCP_CLIENT_EVENT_EXPIRED:
+                        if (FLAGS_SET(link->network->keep_configuration, KEEP_CONFIGURATION_DHCP)) {
+                                log_link_notice(link, "DHCPv4 connection considered critical, ignoring request to reconfigure it.");
+                                return 0;
+                        }
+
+                        if (link->dhcp_lease) {
+                                r = dhcp4_lease_lost(link);
+                                if (r < 0) {
+                                        link_enter_failed(link);
+                                        return r;
+                                }
+                        }
+
+                        break;
+                case SD_DHCP_CLIENT_EVENT_IP_CHANGE:
+                        if (FLAGS_SET(link->network->keep_configuration, KEEP_CONFIGURATION_DHCP)) {
+                                log_link_notice(link, "DHCPv4 connection considered critical, ignoring request to reconfigure it.");
+                                return 0;
+                        }
+
+                        r = dhcp_lease_ip_change(client, link);
+                        if (r < 0) {
+                                link_enter_failed(link);
+                                return r;
+                        }
+
+                        break;
+                case SD_DHCP_CLIENT_EVENT_RENEW:
+                        r = dhcp_lease_renew(client, link);
+                        if (r < 0) {
+                                link_enter_failed(link);
+                                return r;
+                        }
+                        break;
+                case SD_DHCP_CLIENT_EVENT_IP_ACQUIRE:
+                        r = dhcp_lease_acquired(client, link);
+                        if (r < 0) {
+                                link_enter_failed(link);
+                                return r;
+                        }
+                        break;
+                case SD_DHCP_CLIENT_EVENT_SELECTING:
+                        r = dhcp_server_is_filtered(link, client);
+                        if (r < 0) {
+                                link_enter_failed(link);
+                                return r;
+                        }
+                        if (r > 0)
+                                return -ENOMSG;
+                        break;
+
+                case SD_DHCP_CLIENT_EVENT_TRANSIENT_FAILURE:
+                        if (link->ipv4ll && !sd_ipv4ll_is_running(link->ipv4ll)) {
+                                log_link_debug(link, "Problems acquiring DHCP lease, acquiring IPv4 link-local address");
+
+                                if (in4_addr_is_set(&link->network->ipv4ll_start_address)) {
+                                        r = sd_ipv4ll_set_address(link->ipv4ll, &link->network->ipv4ll_start_address);
+                                        if (r < 0)
+                                                return log_link_warning_errno(link, r, "Could not set IPv4 link-local start address: %m");
+                                }
+
+                                r = sd_ipv4ll_start(link->ipv4ll);
+                                if (r < 0)
+                                        return log_link_warning_errno(link, r, "Could not acquire IPv4 link-local address: %m");
+                        }
+                        break;
+
+                default:
+                        if (event < 0)
+                                log_link_warning_errno(link, event, "DHCP error: Client failed: %m");
+                        else
+                                log_link_warning(link, "DHCP unknown event: %i", event);
+                        break;
+        }
+
+        return 0;
+}
+
+static int dhcp4_set_hostname(Link *link) {
+        _cleanup_free_ char *hostname = NULL;
+        const char *hn;
+        int r;
+
+        assert(link);
+
+        if (!link->network->dhcp_send_hostname)
+                hn = NULL;
+        else if (link->network->dhcp_hostname)
+                hn = link->network->dhcp_hostname;
+        else {
+                r = gethostname_strict(&hostname);
+                if (r < 0 && r != -ENXIO) /* ENXIO: no hostname set or hostname is "localhost" */
+                        return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to get hostname: %m");
+
+                hn = hostname;
+        }
+
+        r = sd_dhcp_client_set_hostname(link->dhcp_client, hn);
+        if (r == -EINVAL && hostname)
+                /* Ignore error when the machine's hostname is not suitable to send in DHCP packet. */
+                log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set hostname from kernel hostname, ignoring: %m");
+        else if (r < 0)
+                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set hostname: %m");
+
+        return 0;
+}
+
+static int dhcp4_set_client_identifier(Link *link) {
+        int r;
+
+        assert(link);
+        assert(link->network);
+        assert(link->dhcp_client);
+
+        switch (link->network->dhcp_client_identifier) {
+        case DHCP_CLIENT_ID_DUID: {
+                /* If configured, apply user specified DUID and IAID */
+                const DUID *duid = link_get_dhcp4_duid(link);
+
+                if (duid->raw_data_len == 0)
+                        switch (duid->type) {
+                        case DUID_TYPE_LLT:
+                                r = sd_dhcp_client_set_iaid_duid_llt(link->dhcp_client,
+                                                                     link->network->dhcp_iaid_set,
+                                                                     link->network->dhcp_iaid,
+                                                                     duid->llt_time);
+                                break;
+                        case DUID_TYPE_LL:
+                                r = sd_dhcp_client_set_iaid_duid_ll(link->dhcp_client,
+                                                                    link->network->dhcp_iaid_set,
+                                                                    link->network->dhcp_iaid);
+                                break;
+                        case DUID_TYPE_EN:
+                                r = sd_dhcp_client_set_iaid_duid_en(link->dhcp_client,
+                                                                    link->network->dhcp_iaid_set,
+                                                                    link->network->dhcp_iaid);
+                                break;
+                        case DUID_TYPE_UUID:
+                                r = sd_dhcp_client_set_iaid_duid_uuid(link->dhcp_client,
+                                                                      link->network->dhcp_iaid_set,
+                                                                      link->network->dhcp_iaid);
+                                break;
+                        default:
+                                r = sd_dhcp_client_set_iaid_duid_raw(link->dhcp_client,
+                                                                     link->network->dhcp_iaid_set,
+                                                                     link->network->dhcp_iaid,
+                                                                     duid->type, NULL, 0);
+                        }
+                else
+                        r = sd_dhcp_client_set_iaid_duid_raw(link->dhcp_client,
+                                                             link->network->dhcp_iaid_set,
+                                                             link->network->dhcp_iaid,
+                                                             duid->type, duid->raw_data, duid->raw_data_len);
+                if (r < 0)
+                        return r;
+                break;
+        }
+        case DHCP_CLIENT_ID_MAC: {
+                const uint8_t *hw_addr = link->hw_addr.bytes;
+                size_t hw_addr_len = link->hw_addr.length;
+
+                if (link->iftype == ARPHRD_INFINIBAND && hw_addr_len == INFINIBAND_ALEN) {
+                        /* set_client_id expects only last 8 bytes of an IB address */
+                        hw_addr += INFINIBAND_ALEN - 8;
+                        hw_addr_len -= INFINIBAND_ALEN - 8;
+                }
+
+                r = sd_dhcp_client_set_client_id(link->dhcp_client,
+                                                 link->iftype,
+                                                 hw_addr,
+                                                 hw_addr_len);
+                if (r < 0)
+                        return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set client ID: %m");
+                break;
+        }
+        default:
+                assert_not_reached();
+        }
+
+        return 0;
+}
+
+static int dhcp4_find_dynamic_address(Link *link, struct in_addr *ret) {
+        Address *a;
+
+        assert(link);
+        assert(link->network);
+        assert(ret);
+
+        if (!FLAGS_SET(link->network->keep_configuration, KEEP_CONFIGURATION_DHCP))
+                return false;
+
+        SET_FOREACH(a, link->addresses) {
+                if (a->source != NETWORK_CONFIG_SOURCE_FOREIGN)
+                        continue;
+                if (a->family != AF_INET)
+                        continue;
+                if (link_address_is_dynamic(link, a))
+                        break;
+        }
+
+        if (!a)
+                return false;
+
+        *ret = a->in_addr.in;
+        return true;
+}
+
+static int dhcp4_set_request_address(Link *link) {
+        struct in_addr a;
+
+        assert(link);
+        assert(link->network);
+        assert(link->dhcp_client);
+
+        a = link->network->dhcp_request_address;
+
+        if (in4_addr_is_null(&a))
+                (void) dhcp4_find_dynamic_address(link, &a);
+
+        if (in4_addr_is_null(&a))
+                return 0;
+
+        log_link_debug(link, "DHCPv4 CLIENT: requesting %s.", IN4_ADDR_TO_STRING(&a));
+        return sd_dhcp_client_set_request_address(link->dhcp_client, &a);
+}
+
+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->dev && sd_device_get_property_value(link->dev, "ID_NET_DHCP_BROADCAST", &val) >= 0) {
+                r = parse_boolean(val);
+                if (r < 0)
+                        log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to parse ID_NET_DHCP_BROADCAST, ignoring: %m");
+                else
+                        log_link_debug(link, "DHCPv4 CLIENT: Detected ID_NET_DHCP_BROADCAST='%d'.", r);
+
+        }
+        return r == true;
+}
+
+static bool link_dhcp4_ipv6_only_mode(Link *link) {
+        assert(link);
+        assert(link->network);
+
+        /* If it is explicitly specified, then honor the setting. */
+        if (link->network->dhcp_ipv6_only_mode >= 0)
+                return link->network->dhcp_ipv6_only_mode;
+
+        /* Defaults to false, until we support 464XLAT. See issue #30891. */
+        return false;
+}
+
+static int dhcp4_configure(Link *link) {
+        sd_dhcp_option *send_option;
+        void *request_options;
+        int r;
+
+        assert(link);
+        assert(link->network);
+
+        if (link->dhcp_client)
+                return log_link_debug_errno(link, SYNTHETIC_ERRNO(EBUSY), "DHCPv4 client is already configured.");
+
+        r = sd_dhcp_client_new(&link->dhcp_client, link->network->dhcp_anonymize);
+        if (r < 0)
+                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to allocate DHCPv4 client: %m");
+
+        r = sd_dhcp_client_attach_event(link->dhcp_client, link->manager->event, 0);
+        if (r < 0)
+                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to attach event to DHCPv4 client: %m");
+
+        r = sd_dhcp_client_attach_device(link->dhcp_client, link->dev);
+        if (r < 0)
+                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to attach device: %m");
+
+        r = sd_dhcp_client_set_rapid_commit(link->dhcp_client, link->network->dhcp_use_rapid_commit);
+        if (r < 0)
+                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set rapid commit: %m");
+
+        r = sd_dhcp_client_set_mac(link->dhcp_client,
+                                   link->hw_addr.bytes,
+                                   link->bcast_addr.length > 0 ? link->bcast_addr.bytes : NULL,
+                                   link->hw_addr.length, link->iftype);
+        if (r < 0)
+                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set MAC address: %m");
+
+        r = sd_dhcp_client_set_ifindex(link->dhcp_client, link->ifindex);
+        if (r < 0)
+                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set ifindex: %m");
+
+        r = sd_dhcp_client_set_callback(link->dhcp_client, dhcp4_handler, link);
+        if (r < 0)
+                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set callback: %m");
+
+        r = sd_dhcp_client_set_request_broadcast(link->dhcp_client, link_needs_dhcp_broadcast(link));
+        if (r < 0)
+                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set request flag for broadcast: %m");
+
+        r = dhcp_client_set_state_callback(link->dhcp_client, dhcp_client_callback_bus, link);
+        if (r < 0)
+                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set state change callback: %m");
+
+        if (link->mtu > 0) {
+                r = sd_dhcp_client_set_mtu(link->dhcp_client, link->mtu);
+                if (r < 0)
+                        return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set MTU: %m");
+        }
+
+        if (!link->network->dhcp_anonymize) {
+                r = dhcp4_set_request_address(link);
+                if (r < 0)
+                        return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set initial DHCPv4 address: %m");
+
+                if (link->network->dhcp_use_mtu) {
+                        r = sd_dhcp_client_set_request_option(link->dhcp_client, SD_DHCP_OPTION_MTU_INTERFACE);
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set request flag for MTU: %m");
+                }
+
+                if (link->network->dhcp_use_routes) {
+                        r = sd_dhcp_client_set_request_option(link->dhcp_client, SD_DHCP_OPTION_STATIC_ROUTE);
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set request flag for static route: %m");
+
+                        r = sd_dhcp_client_set_request_option(link->dhcp_client, SD_DHCP_OPTION_CLASSLESS_STATIC_ROUTE);
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set request flag for classless static route: %m");
+                }
+
+                if (link->network->dhcp_use_domains != DHCP_USE_DOMAINS_NO) {
+                        r = sd_dhcp_client_set_request_option(link->dhcp_client, SD_DHCP_OPTION_DOMAIN_SEARCH);
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set request flag for domain search list: %m");
+                }
+
+                if (link->network->dhcp_use_ntp) {
+                        r = sd_dhcp_client_set_request_option(link->dhcp_client, SD_DHCP_OPTION_NTP_SERVER);
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set request flag for NTP server: %m");
+                }
+
+                if (link->network->dhcp_use_sip) {
+                        r = sd_dhcp_client_set_request_option(link->dhcp_client, SD_DHCP_OPTION_SIP_SERVER);
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set request flag for SIP server: %m");
+                }
+                if (link->network->dhcp_use_captive_portal) {
+                        r = sd_dhcp_client_set_request_option(link->dhcp_client, SD_DHCP_OPTION_DHCP_CAPTIVE_PORTAL);
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set request flag for captive portal: %m");
+                }
+
+                if (link->network->dhcp_use_timezone) {
+                        r = sd_dhcp_client_set_request_option(link->dhcp_client, SD_DHCP_OPTION_TZDB_TIMEZONE);
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set request flag for timezone: %m");
+                }
+
+                if (link->network->dhcp_use_6rd) {
+                        r = sd_dhcp_client_set_request_option(link->dhcp_client, SD_DHCP_OPTION_6RD);
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set request flag for 6rd: %m");
+                }
+
+                if (link_dhcp4_ipv6_only_mode(link)) {
+                        r = sd_dhcp_client_set_request_option(link->dhcp_client, SD_DHCP_OPTION_IPV6_ONLY_PREFERRED);
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set request flag for IPv6-only preferred option: %m");
+                }
+
+                SET_FOREACH(request_options, link->network->dhcp_request_options) {
+                        uint32_t option = PTR_TO_UINT32(request_options);
+
+                        r = sd_dhcp_client_set_request_option(link->dhcp_client, option);
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set request flag for '%u': %m", option);
+                }
+
+                ORDERED_HASHMAP_FOREACH(send_option, link->network->dhcp_client_send_options) {
+                        r = sd_dhcp_client_add_option(link->dhcp_client, send_option);
+                        if (r == -EEXIST)
+                                continue;
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set send option: %m");
+                }
+
+                ORDERED_HASHMAP_FOREACH(send_option, link->network->dhcp_client_send_vendor_options) {
+                        r = sd_dhcp_client_add_vendor_option(link->dhcp_client, send_option);
+                        if (r == -EEXIST)
+                                continue;
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set send option: %m");
+                }
+
+                r = dhcp4_set_hostname(link);
+                if (r < 0)
+                        return r;
+
+                if (link->network->dhcp_vendor_class_identifier) {
+                        r = sd_dhcp_client_set_vendor_class_identifier(link->dhcp_client,
+                                                                       link->network->dhcp_vendor_class_identifier);
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set vendor class identifier: %m");
+                }
+
+                if (link->network->dhcp_mudurl) {
+                        r = sd_dhcp_client_set_mud_url(link->dhcp_client, link->network->dhcp_mudurl);
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set MUD URL: %m");
+                }
+
+                if (link->network->dhcp_user_class) {
+                        r = sd_dhcp_client_set_user_class(link->dhcp_client, link->network->dhcp_user_class);
+                        if (r < 0)
+                                return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set user class: %m");
+                }
+        }
+
+        if (link->network->dhcp_client_port > 0) {
+                r = sd_dhcp_client_set_client_port(link->dhcp_client, link->network->dhcp_client_port);
+                if (r < 0)
+                        return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set listen port: %m");
+        }
+
+        if (link->network->dhcp_max_attempts > 0) {
+                r = sd_dhcp_client_set_max_attempts(link->dhcp_client, link->network->dhcp_max_attempts);
+                if (r < 0)
+                        return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set max attempts: %m");
+        }
+
+        if (link->network->dhcp_ip_service_type >= 0) {
+                r = sd_dhcp_client_set_service_type(link->dhcp_client, link->network->dhcp_ip_service_type);
+                if (r < 0)
+                        return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set IP service type: %m");
+        }
+
+        if (link->network->dhcp_socket_priority_set) {
+                r = sd_dhcp_client_set_socket_priority(link->dhcp_client, link->network->dhcp_socket_priority);
+                if (r < 0)
+                        return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed to set socket priority: %m");
+        }
+
+        if (link->network->dhcp_fallback_lease_lifetime_usec > 0) {
+                r = sd_dhcp_client_set_fallback_lease_lifetime(link->dhcp_client, link->network->dhcp_fallback_lease_lifetime_usec);
+                if (r < 0)
+                        return log_link_debug_errno(link, r, "DHCPv4 CLIENT: Failed set to lease lifetime: %m");
+        }
+
+        return dhcp4_set_client_identifier(link);
+}
+
+int dhcp4_update_mac(Link *link) {
+        bool restart;
+        int r;
+
+        assert(link);
+
+        if (!link->dhcp_client)
+                return 0;
+
+        restart = sd_dhcp_client_is_running(link->dhcp_client);
+
+        r = sd_dhcp_client_stop(link->dhcp_client);
+        if (r < 0)
+                return r;
+
+        r = sd_dhcp_client_set_mac(link->dhcp_client,
+                                   link->hw_addr.bytes,
+                                   link->bcast_addr.length > 0 ? link->bcast_addr.bytes : NULL,
+                                   link->hw_addr.length, link->iftype);
+        if (r < 0)
+                return r;
+
+        r = dhcp4_set_client_identifier(link);
+        if (r < 0)
+                return r;
+
+        if (restart) {
+                r = dhcp4_start(link);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+int dhcp4_update_ipv6_connectivity(Link *link) {
+        assert(link);
+
+        if (!link->network)
+                return 0;
+
+        if (!link->network->dhcp_ipv6_only_mode)
+                return 0;
+
+        if (!link->dhcp_client)
+                return 0;
+
+        /* If the client is running, set the current connectivity. */
+        if (sd_dhcp_client_is_running(link->dhcp_client))
+                return sd_dhcp_client_set_ipv6_connectivity(link->dhcp_client, link_has_ipv6_connectivity(link));
+
+        /* If the client has been already stopped or not started yet, let's check the current connectivity
+         * and start the client if necessary. */
+        if (link_has_ipv6_connectivity(link))
+                return 0;
+
+        return dhcp4_start_full(link, /* set_ipv6_connectivity = */ false);
+}
+
+int dhcp4_start_full(Link *link, bool set_ipv6_connectivity) {
+        int r;
+
+        assert(link);
+        assert(link->network);
+
+        if (!link->dhcp_client)
+                return 0;
+
+        if (!link_has_carrier(link))
+                return 0;
+
+        if (sd_dhcp_client_is_running(link->dhcp_client) > 0)
+                return 0;
+
+        r = sd_dhcp_client_start(link->dhcp_client);
+        if (r < 0)
+                return r;
+
+        if (set_ipv6_connectivity) {
+                r = dhcp4_update_ipv6_connectivity(link);
+                if (r < 0)
+                        return r;
+        }
+
+        return 1;
+}
+
+int dhcp4_renew(Link *link) {
+        assert(link);
+
+        if (!link->dhcp_client)
+                return 0;
+
+        /* The DHCPv4 client may have been stopped by the IPv6 only mode. Let's unconditionally restart the
+         * client if it is not running. */
+        if (!sd_dhcp_client_is_running(link->dhcp_client))
+                return dhcp4_start(link);
+
+        /* The client may be waiting for IPv6 connectivity. Let's restart the client in that case. */
+        if (dhcp_client_get_state(link->dhcp_client) != DHCP_STATE_BOUND)
+                return sd_dhcp_client_interrupt_ipv6_only_mode(link->dhcp_client);
+
+        /* Otherwise, send a RENEW command. */
+        return sd_dhcp_client_send_renew(link->dhcp_client);
+}
+
+static int dhcp4_configure_duid(Link *link) {
+        assert(link);
+        assert(link->network);
+
+        if (link->network->dhcp_client_identifier != DHCP_CLIENT_ID_DUID)
+                return 1;
+
+        return dhcp_configure_duid(link, link_get_dhcp4_duid(link));
+}
+
+static int dhcp4_process_request(Request *req, Link *link, void *userdata) {
+        int r;
+
+        assert(link);
+
+        if (!link_is_ready_to_configure(link, /* allow_unmanaged = */ false))
+                return 0;
+
+        r = dhcp4_configure_duid(link);
+        if (r <= 0)
+                return r;
+
+        r = dhcp4_configure(link);
+        if (r < 0)
+                return log_link_warning_errno(link, r, "Failed to configure DHCPv4 client: %m");
+
+        r = dhcp4_start(link);
+        if (r < 0)
+                return log_link_warning_errno(link, r, "Failed to start DHCPv4 client: %m");
+
+        log_link_debug(link, "DHCPv4 client is configured%s.",
+                       r > 0 ? ", acquiring DHCPv4 lease" : "");
+        return 1;
+}
+
+int link_request_dhcp4_client(Link *link) {
+        int r;
+
+        assert(link);
+
+        if (!link_dhcp4_enabled(link))
+                return 0;
+
+        if (link->dhcp_client)
+                return 0;
+
+        r = link_queue_request(link, REQUEST_TYPE_DHCP4_CLIENT, dhcp4_process_request, NULL);
+        if (r < 0)
+                return log_link_warning_errno(link, r, "Failed to request configuring of the DHCPv4 client: %m");
+
+        log_link_debug(link, "Requested configuring of the DHCPv4 client.");
+        return 0;
+}
+
+int config_parse_dhcp_max_attempts(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        Network *network = ASSERT_PTR(data);
+        uint64_t a;
+        int r;
+
+        assert(lvalue);
+        assert(rvalue);
+
+        if (isempty(rvalue)) {
+                network->dhcp_max_attempts = 0;
+                return 0;
+        }
+
+        if (streq(rvalue, "infinity")) {
+                network->dhcp_max_attempts = UINT64_MAX;
+                return 0;
+        }
+
+        r = safe_atou64(rvalue, &a);
+        if (r < 0) {
+                log_syntax(unit, LOG_WARNING, filename, line, r,
+                           "Failed to parse DHCP maximum attempts, ignoring: %s", rvalue);
+                return 0;
+        }
+
+        if (a == 0) {
+                log_syntax(unit, LOG_WARNING, filename, line, 0,
+                           "%s= must be positive integer or 'infinity', ignoring: %s", lvalue, rvalue);
+                return 0;
+        }
+
+        network->dhcp_max_attempts = a;
+
+        return 0;
+}
+
+int config_parse_dhcp_ip_service_type(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        int *tos = ASSERT_PTR(data);
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+
+        if (isempty(rvalue))
+                *tos = -1; /* use sd_dhcp_client's default (currently, CS6). */
+        else if (streq(rvalue, "none"))
+                *tos = 0;
+        else if (streq(rvalue, "CS4"))
+                *tos = IPTOS_CLASS_CS4;
+        else if (streq(rvalue, "CS6"))
+                *tos = IPTOS_CLASS_CS6;
+        else
+                log_syntax(unit, LOG_WARNING, filename, line, 0,
+                           "Failed to parse %s=, ignoring assignment: %s", lvalue, rvalue);
+
+        return 0;
+}
+
+int config_parse_dhcp_socket_priority(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        Network *network = ASSERT_PTR(data);
+        int a, r;
+
+        assert(lvalue);
+        assert(rvalue);
+
+        if (isempty(rvalue)) {
+                network->dhcp_socket_priority_set = false;
+                return 0;
+        }
+
+        r = safe_atoi(rvalue, &a);
+        if (r < 0) {
+                log_syntax(unit, LOG_WARNING, filename, line, r,
+                           "Failed to parse socket priority, ignoring: %s", rvalue);
+                return 0;
+        }
+
+        network->dhcp_socket_priority_set = true;
+        network->dhcp_socket_priority = a;
+
+        return 0;
+}
+
+int config_parse_dhcp_fallback_lease_lifetime(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        Network *network = userdata;
+
+        assert(filename);
+        assert(section);
+        assert(lvalue);
+        assert(rvalue);
+        assert(data);
+
+        if (isempty(rvalue)) {
+                network->dhcp_fallback_lease_lifetime_usec = 0;
+                return 0;
+        }
+
+        /* We accept only "forever" or "infinity". */
+        if (!STR_IN_SET(rvalue, "forever", "infinity")) {
+                log_syntax(unit, LOG_WARNING, filename, line, 0,
+                           "Invalid LeaseLifetime= value, ignoring: %s", rvalue);
+                return 0;
+        }
+
+        network->dhcp_fallback_lease_lifetime_usec = USEC_INFINITY;
+
+        return 0;
+}
+
+int config_parse_dhcp_label(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        char **label = ASSERT_PTR(data);
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+
+        if (isempty(rvalue)) {
+                *label = mfree(*label);
+                return 0;
+        }
+
+        if (!address_label_valid(rvalue)) {
+                log_syntax(unit, LOG_WARNING, filename, line, 0,
+                           "Address label is too long or invalid, ignoring assignment: %s", rvalue);
+                return 0;
+        }
+
+        return free_and_strdup_warn(label, rvalue);
+}
+
+static const char* const dhcp_client_identifier_table[_DHCP_CLIENT_ID_MAX] = {
+        [DHCP_CLIENT_ID_MAC]  = "mac",
+        [DHCP_CLIENT_ID_DUID] = "duid",
+};
+
+DEFINE_PRIVATE_STRING_TABLE_LOOKUP_FROM_STRING(dhcp_client_identifier, DHCPClientIdentifier);
+DEFINE_CONFIG_PARSE_ENUM(config_parse_dhcp_client_identifier, dhcp_client_identifier, DHCPClientIdentifier,
+                         "Failed to parse client identifier type");