network: split networkd-dhcp6.c

This moves DHCPv6 prefix delegation related functions to
networkd-dhcp-prefix-delegation.c.

1 files changed, 1046 insertions, 0 deletions

diff --git a/src/network/networkd-dhcp-prefix-delegation.c b/src/network/networkd-dhcp-prefix-delegation.c
new file mode 100644
index 0000000000..dc4868300a
--- /dev/null
+++ b/src/network/networkd-dhcp-prefix-delegation.c
@@ -0,0 +1,1046 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "sd-dhcp6-client.h"
+
+#include "hashmap.h"
+#include "in-addr-prefix-util.h"
+#include "networkd-address-generation.h"
+#include "networkd-address.h"
+#include "networkd-dhcp-prefix-delegation.h"
+#include "networkd-dhcp6.h"
+#include "networkd-link.h"
+#include "networkd-manager.h"
+#include "networkd-queue.h"
+#include "networkd-radv.h"
+#include "networkd-route.h"
+#include "parse-util.h"
+#include "string-util.h"
+#include "strv.h"
+
+bool link_dhcp6_pd_is_enabled(Link *link) {
+        assert(link);
+
+        if (!link->network)
+                return false;
+
+        return link->network->dhcp6_pd;
+}
+
+bool dhcp6_pd_is_uplink(Link *link, Link *target, bool accept_auto) {
+        assert(link);
+        assert(target);
+
+        if (!link_dhcp6_pd_is_enabled(link))
+                return false;
+
+        if (link->network->dhcp6_pd_uplink_name)
+                return streq_ptr(target->ifname, link->network->dhcp6_pd_uplink_name) ||
+                        strv_contains(target->alternative_names, link->network->dhcp6_pd_uplink_name);
+
+        if (link->network->dhcp6_pd_uplink_index > 0)
+                return target->ifindex == link->network->dhcp6_pd_uplink_index;
+
+        if (link->network->dhcp6_pd_uplink_index == UPLINK_INDEX_SELF)
+                return link == target;
+
+        assert(link->network->dhcp6_pd_uplink_index == UPLINK_INDEX_AUTO);
+        return accept_auto;
+}
+
+bool dhcp6_lease_has_pd_prefix(sd_dhcp6_lease *lease) {
+        uint32_t lifetime_preferred_sec, lifetime_valid_sec;
+        struct in6_addr pd_prefix;
+        uint8_t pd_prefix_len;
+
+        if (!lease)
+                return false;
+
+        sd_dhcp6_lease_reset_pd_prefix_iter(lease);
+
+        return sd_dhcp6_lease_get_pd(lease, &pd_prefix, &pd_prefix_len, &lifetime_preferred_sec, &lifetime_valid_sec) >= 0;
+}
+
+static void link_remove_dhcp6_pd_prefix(Link *link, const struct in6_addr *prefix) {
+        void *key;
+
+        assert(link);
+        assert(link->manager);
+        assert(prefix);
+
+        if (hashmap_get(link->manager->links_by_dhcp6_pd_prefix, prefix) != link)
+                return;
+
+        hashmap_remove2(link->manager->links_by_dhcp6_pd_prefix, prefix, &key);
+        free(key);
+}
+
+static int link_add_dhcp6_pd_prefix(Link *link, const struct in6_addr *prefix) {
+        _cleanup_free_ struct in6_addr *copy = NULL;
+        int r;
+
+        assert(link);
+        assert(prefix);
+
+        copy = newdup(struct in6_addr, prefix, 1);
+        if (!copy)
+                return -ENOMEM;
+
+        r = hashmap_ensure_put(&link->manager->links_by_dhcp6_pd_prefix, &in6_addr_hash_ops_free, copy, link);
+        if (r < 0)
+                return r;
+        if (r > 0)
+                TAKE_PTR(copy);
+
+        return 0;
+}
+
+static int link_get_by_dhcp6_pd_prefix(Manager *manager, const struct in6_addr *prefix, Link **ret) {
+        Link *link;
+
+        assert(manager);
+        assert(prefix);
+
+        link = hashmap_get(manager->links_by_dhcp6_pd_prefix, prefix);
+        if (!link)
+                return -ENODEV;
+
+        if (ret)
+                *ret = link;
+        return 0;
+}
+
+static int dhcp6_pd_get_assigned_prefix(Link *link, const struct in6_addr *pd_prefix, uint8_t pd_prefix_len, struct in6_addr *ret) {
+        assert(link);
+        assert(pd_prefix);
+
+        if (!link_dhcp6_pd_is_enabled(link))
+                return -ENOENT;
+
+        if (link->network->dhcp6_pd_assign) {
+                Address *address;
+
+                SET_FOREACH(address, link->addresses) {
+                        if (address->source != NETWORK_CONFIG_SOURCE_DHCP6PD)
+                                continue;
+                        assert(address->family == AF_INET6);
+
+                        if (in6_addr_prefix_covers(pd_prefix, pd_prefix_len, &address->in_addr.in6) <= 0)
+                                continue;
+
+                        if (ret) {
+                                struct in6_addr prefix = address->in_addr.in6;
+
+                                in6_addr_mask(&prefix, 64);
+                                *ret = prefix;
+                        }
+                        return 0;
+                }
+        } else {
+                Route *route;
+
+                SET_FOREACH(route, link->routes) {
+                        if (route->source != NETWORK_CONFIG_SOURCE_DHCP6PD)
+                                continue;
+                        assert(route->family == AF_INET6);
+
+                        if (in6_addr_prefix_covers(pd_prefix, pd_prefix_len, &route->dst.in6) > 0) {
+                                if (ret)
+                                        *ret = route->dst.in6;
+                                return 0;
+                        }
+                }
+        }
+
+        return -ENOENT;
+}
+
+int dhcp6_pd_remove(Link *link, bool only_marked) {
+        int k, r = 0;
+
+        assert(link);
+        assert(link->manager);
+
+        if (!link_dhcp6_pd_is_enabled(link))
+                return 0;
+
+        if (!only_marked)
+                link->dhcp6_pd_configured = false;
+
+        if (!link->network->dhcp6_pd_assign) {
+                Route *route;
+
+                SET_FOREACH(route, link->routes) {
+                        if (route->source != NETWORK_CONFIG_SOURCE_DHCP6PD)
+                                continue;
+                        if (only_marked && !route_is_marked(route))
+                                continue;
+
+                        if (link->radv)
+                                (void) sd_radv_remove_prefix(link->radv, &route->dst.in6, 64);
+
+                        link_remove_dhcp6_pd_prefix(link, &route->dst.in6);
+
+                        k = route_remove(route);
+                        if (k < 0)
+                                r = k;
+
+                        route_cancel_request(route);
+                }
+        } else {
+                Address *address;
+
+                SET_FOREACH(address, link->addresses) {
+                        struct in6_addr prefix;
+
+                        if (address->source != NETWORK_CONFIG_SOURCE_DHCP6PD)
+                                continue;
+                        if (only_marked && !address_is_marked(address))
+                                continue;
+
+                        prefix = address->in_addr.in6;
+                        in6_addr_mask(&prefix, 64);
+
+                        if (link->radv)
+                                (void) sd_radv_remove_prefix(link->radv, &prefix, 64);
+
+                        link_remove_dhcp6_pd_prefix(link, &prefix);
+
+                        k = address_remove(address);
+                        if (k < 0)
+                                r = k;
+
+                        address_cancel_request(address);
+                }
+        }
+
+        return r;
+}
+
+static int dhcp6_pd_check_ready(Link *link);
+
+static int dhcp6_pd_address_ready_callback(Address *address) {
+        Address *a;
+
+        assert(address);
+        assert(address->link);
+
+        SET_FOREACH(a, address->link->addresses)
+                if (a->source == NETWORK_CONFIG_SOURCE_DHCP6PD)
+                        a->callback = NULL;
+
+        return dhcp6_pd_check_ready(address->link);
+}
+
+static int dhcp6_pd_check_ready(Link *link) {
+        int r;
+
+        assert(link);
+        assert(link->network);
+
+        if (link->dhcp6_pd_messages > 0) {
+                log_link_debug(link, "%s(): DHCPv6PD addresses and routes are not set.", __func__);
+                return 0;
+        }
+
+        if (link->network->dhcp6_pd_assign) {
+                bool has_ready = false;
+                Address *address;
+
+                SET_FOREACH(address, link->addresses) {
+                        if (address->source != NETWORK_CONFIG_SOURCE_DHCP6PD)
+                                continue;
+                        if (address_is_ready(address)) {
+                                has_ready = true;
+                                break;
+                        }
+                }
+
+                if (!has_ready) {
+                        SET_FOREACH(address, link->addresses)
+                                if (address->source == NETWORK_CONFIG_SOURCE_DHCP6PD)
+                                        address->callback = dhcp6_pd_address_ready_callback;
+
+                        log_link_debug(link, "%s(): no DHCPv6PD address is ready.", __func__);
+                        return 0;
+                }
+        }
+
+        link->dhcp6_pd_configured = true;
+
+        log_link_debug(link, "DHCPv6 PD addresses and routes set.");
+
+        r = dhcp6_pd_remove(link, /* only_marked = */ true);
+        if (r < 0)
+                return r;
+
+        link_check_ready(link);
+        return 1;
+}
+
+static int dhcp6_pd_route_handler(sd_netlink *rtnl, sd_netlink_message *m, Link *link) {
+        int r;
+
+        assert(link);
+        assert(link->dhcp6_pd_messages > 0);
+
+        link->dhcp6_pd_messages--;
+
+        r = route_configure_handler_internal(rtnl, m, link, "Failed to add DHCPv6 Prefix Delegation route");
+        if (r <= 0)
+                return r;
+
+        r = dhcp6_pd_check_ready(link);
+        if (r < 0)
+                link_enter_failed(link);
+
+        return 1;
+}
+
+static int dhcp6_pd_request_route(Link *link, const struct in6_addr *prefix, usec_t lifetime_usec) {
+        _cleanup_(route_freep) Route *route = NULL;
+        Route *existing;
+        int r;
+
+        assert(link);
+        assert(link->network);
+        assert(prefix);
+
+        if (link->network->dhcp6_pd_assign)
+                return 0;
+
+        r = route_new(&route);
+        if (r < 0)
+                return r;
+
+        route->source = NETWORK_CONFIG_SOURCE_DHCP6PD;
+        route->family = AF_INET6;
+        route->dst.in6 = *prefix;
+        route->dst_prefixlen = 64;
+        route->protocol = RTPROT_DHCP;
+        route->priority = link->network->dhcp6_pd_route_metric;
+        route->lifetime_usec = lifetime_usec;
+
+        if (route_get(NULL, link, route, &existing) < 0)
+                link->dhcp6_pd_configured = false;
+        else
+                route_unmark(existing);
+
+        r = link_request_route(link, TAKE_PTR(route), true, &link->dhcp6_pd_messages,
+                               dhcp6_pd_route_handler, NULL);
+        if (r < 0)
+                return log_link_error_errno(link, r, "Failed to request DHCPv6 prefix route: %m");
+
+        return 0;
+}
+
+static int dhcp6_pd_address_handler(sd_netlink *rtnl, sd_netlink_message *m, Link *link) {
+        int r;
+
+        assert(link);
+        assert(link->dhcp6_pd_messages > 0);
+
+        link->dhcp6_pd_messages--;
+
+        r = address_configure_handler_internal(rtnl, m, link, "Could not set DHCPv6 delegated prefix address");
+        if (r <= 0)
+                return r;
+
+        r = dhcp6_pd_check_ready(link);
+        if (r < 0)
+                link_enter_failed(link);
+
+        return 1;
+}
+
+static void log_dhcp6_pd_address(Link *link, const Address *address) {
+        _cleanup_free_ char *buffer = NULL;
+        int log_level;
+
+        assert(address);
+        assert(address->family == AF_INET6);
+
+        log_level = address_get(link, address, NULL) >= 0 ? LOG_DEBUG : LOG_INFO;
+
+        if (log_level < log_get_max_level())
+                return;
+
+        (void) in6_addr_prefix_to_string(&address->in_addr.in6, address->prefixlen, &buffer);
+
+        log_link_full(link, log_level, "DHCPv6-PD address %s (valid %s, preferred %s)",
+                      strna(buffer),
+                      FORMAT_LIFETIME(address->lifetime_valid_usec),
+                      FORMAT_LIFETIME(address->lifetime_preferred_usec));
+}
+
+static int dhcp6_pd_request_address(
+                Link *link,
+                const struct in6_addr *prefix,
+                usec_t lifetime_preferred_usec,
+                usec_t lifetime_valid_usec) {
+
+        _cleanup_set_free_ Set *addresses = NULL;
+        struct in6_addr *a;
+        int r;
+
+        assert(link);
+        assert(link->network);
+        assert(prefix);
+
+        if (!link->network->dhcp6_pd_assign)
+                return 0;
+
+        r = dhcp6_pd_generate_addresses(link, prefix, &addresses);
+        if (r < 0)
+                return log_link_warning_errno(link, r, "Failed to generate addresses for acquired DHCPv6 delegated prefix: %m");
+
+        SET_FOREACH(a, addresses) {
+                _cleanup_(address_freep) Address *address = NULL;
+                Address *existing;
+
+                r = address_new(&address);
+                if (r < 0)
+                        return log_link_error_errno(link, r, "Failed to allocate address for DHCPv6 delegated prefix: %m");
+
+                address->source = NETWORK_CONFIG_SOURCE_DHCP6PD;
+                address->family = AF_INET6;
+                address->in_addr.in6 = *a;
+                address->prefixlen = 64;
+                address->lifetime_preferred_usec = lifetime_preferred_usec;
+                address->lifetime_valid_usec = lifetime_valid_usec;
+                SET_FLAG(address->flags, IFA_F_MANAGETEMPADDR, link->network->dhcp6_pd_manage_temporary_address);
+                address->route_metric = link->network->dhcp6_pd_route_metric;
+
+                log_dhcp6_pd_address(link, address);
+
+                if (address_get(link, address, &existing) < 0)
+                        link->dhcp6_pd_configured = false;
+                else
+                        address_unmark(existing);
+
+                r = link_request_address(link, TAKE_PTR(address), true, &link->dhcp6_pd_messages,
+                                         dhcp6_pd_address_handler, NULL);
+                if (r < 0)
+                        return log_link_error_errno(link, r, "Failed to request DHCPv6 delegated prefix address: %m");
+        }
+
+        return 0;
+}
+
+static bool link_has_preferred_subnet_id(Link *link) {
+        if (!link->network)
+                return false;
+
+        return link->network->dhcp6_pd_subnet_id >= 0;
+}
+
+static int dhcp6_pd_calculate_prefix(
+                const struct in6_addr *pd_prefix,
+                uint8_t pd_prefix_len,
+                uint64_t subnet_id,
+                struct in6_addr *ret) {
+
+        struct in6_addr prefix;
+
+        assert(pd_prefix);
+        assert(pd_prefix_len <= 64);
+        assert(ret);
+
+        if (subnet_id >= UINT64_C(1) << (64 - pd_prefix_len))
+                return -ERANGE;
+
+        prefix = *pd_prefix;
+
+        if (pd_prefix_len < 32)
+                prefix.s6_addr32[0] |= htobe32(subnet_id >> 32);
+
+        prefix.s6_addr32[1] |= htobe32(subnet_id & 0xffffffff);
+
+        *ret = prefix;
+        return 0;
+}
+
+static int dhcp6_pd_get_preferred_prefix(
+                Link *link,
+                const struct in6_addr *pd_prefix,
+                uint8_t pd_prefix_len,
+                struct in6_addr *ret) {
+
+        struct in6_addr prefix;
+        Link *assigned_link;
+        int r;
+
+        assert(link);
+        assert(link->manager);
+        assert(pd_prefix);
+
+        if (link_has_preferred_subnet_id(link)) {
+                /* If the link has a preference for a particular subnet id try to allocate that */
+
+                r = dhcp6_pd_calculate_prefix(pd_prefix, pd_prefix_len, link->network->dhcp6_pd_subnet_id, &prefix);
+                if (r < 0)
+                        return log_link_warning_errno(link, r,
+                                                      "subnet id %" PRIu64 " is out of range. Only have %" PRIu64 " subnets.",
+                                                      link->network->dhcp6_pd_subnet_id, UINT64_C(1) << (64 - pd_prefix_len));
+
+                if (link_get_by_dhcp6_pd_prefix(link->manager, &prefix, &assigned_link) >= 0 &&
+                    assigned_link != link) {
+                        _cleanup_free_ char *assigned_buf = NULL;
+
+                        (void) in6_addr_to_string(&prefix, &assigned_buf);
+                        return log_link_warning_errno(link, SYNTHETIC_ERRNO(EAGAIN),
+                                                      "The requested prefix %s is already assigned to another link.",
+                                                      strna(assigned_buf));
+                }
+
+                *ret = prefix;
+                return 0;
+        }
+
+        for (uint64_t n = 0; ; n++) {
+                /* If we do not have an allocation preference just iterate
+                 * through the address space and return the first free prefix. */
+
+                r = dhcp6_pd_calculate_prefix(pd_prefix, pd_prefix_len, n, &prefix);
+                if (r < 0)
+                        return log_link_warning_errno(link, r,
+                                                      "Couldn't find a suitable prefix. Ran out of address space.");
+
+                /* Do not use explicitly requested subnet IDs. Note that the corresponding link may not
+                 * appear yet. So, we need to check the ID is not used in any .network files. */
+                if (set_contains(link->manager->dhcp6_pd_subnet_ids, &n))
+                        continue;
+
+                /* Check that the prefix is not assigned to another link. */
+                if (link_get_by_dhcp6_pd_prefix(link->manager, &prefix, &assigned_link) < 0 ||
+                    assigned_link == link) {
+                        *ret = prefix;
+                        return 0;
+                }
+        }
+}
+
+static int dhcp6_pd_assign_prefix(
+                Link *link,
+                const struct in6_addr *pd_prefix,
+                uint8_t pd_prefix_len,
+                usec_t lifetime_preferred_usec,
+                usec_t lifetime_valid_usec) {
+
+        _cleanup_free_ char *buf = NULL;
+        struct in6_addr prefix;
+        int r;
+
+        assert(link);
+        assert(link->network);
+        assert(pd_prefix);
+
+        if (dhcp6_pd_get_assigned_prefix(link, pd_prefix, pd_prefix_len, &prefix) < 0 &&
+            dhcp6_pd_get_preferred_prefix(link, pd_prefix, pd_prefix_len, &prefix) < 0)
+                return 0;
+
+        (void) in6_addr_prefix_to_string(&prefix, 64, &buf);
+
+        if (link->network->dhcp6_pd_announce) {
+                r = radv_add_prefix(link, &prefix, 64, lifetime_preferred_usec, lifetime_valid_usec);
+                if (r < 0)
+                        return log_link_warning_errno(link, r,
+                                                      "Failed to assign/update prefix %s to IPv6 Router Advertisement: %m",
+                                                      strna(buf));
+        }
+
+        r = dhcp6_pd_request_route(link, &prefix, lifetime_valid_usec);
+        if (r < 0)
+                return log_link_warning_errno(link, r,
+                                              "Failed to assign/update route for prefix %s: %m",
+                                              strna(buf));
+
+        r = dhcp6_pd_request_address(link, &prefix, lifetime_preferred_usec, lifetime_valid_usec);
+        if (r < 0)
+                return log_link_warning_errno(link, r,
+                                              "Failed to assign/update address for prefix %s: %m",
+                                              strna(buf));
+
+        r = link_add_dhcp6_pd_prefix(link, &prefix);
+        if (r < 0)
+                return log_link_warning_errno(link, r,
+                                              "Failed to save assigned prefix %s: %m",
+                                              strna(buf));
+
+        log_link_debug(link, "Assigned prefix %s", strna(buf));
+        return 1;
+}
+
+static int dhcp6_pd_distribute_prefix(
+                Link *dhcp6_link,
+                const struct in6_addr *pd_prefix,
+                uint8_t pd_prefix_len,
+                usec_t lifetime_preferred_usec,
+                usec_t lifetime_valid_usec) {
+
+        Link *link;
+        int r;
+
+        assert(dhcp6_link);
+        assert(dhcp6_link->manager);
+        assert(pd_prefix);
+        assert(pd_prefix_len <= 64);
+
+        HASHMAP_FOREACH(link, dhcp6_link->manager->links_by_index) {
+                if (!IN_SET(link->state, LINK_STATE_CONFIGURING, LINK_STATE_CONFIGURED))
+                        continue;
+
+                if (!dhcp6_pd_is_uplink(link, dhcp6_link, /* accept_auto = */ true))
+                        continue;
+
+                if (link->network->dhcp6_pd_announce && !link->radv)
+                        continue;
+
+                if (link == dhcp6_link && !link->network->dhcp6_pd_assign)
+                        continue;
+
+                r = dhcp6_pd_assign_prefix(link, pd_prefix, pd_prefix_len, lifetime_preferred_usec, lifetime_valid_usec);
+                if (r < 0) {
+                        if (link == dhcp6_link)
+                                return r;
+
+                        link_enter_failed(link);
+                        continue;
+                }
+        }
+
+        return 0;
+}
+
+static int dhcp6_pd_prepare(Link *link) {
+        if (!IN_SET(link->state, LINK_STATE_CONFIGURING, LINK_STATE_CONFIGURED))
+                return 0;
+
+        if (!link_dhcp6_pd_is_enabled(link))
+                return 0;
+
+        if (link->network->dhcp6_pd_announce && !link->radv)
+                return 0;
+
+        link_mark_addresses(link, NETWORK_CONFIG_SOURCE_DHCP6PD, NULL);
+        link_mark_routes(link, NETWORK_CONFIG_SOURCE_DHCP6PD, NULL);
+
+        return 0;
+}
+
+static int dhcp6_pd_finalize(Link *link) {
+        int r;
+
+        if (!IN_SET(link->state, LINK_STATE_CONFIGURING, LINK_STATE_CONFIGURED))
+                return 0;
+
+        if (!link_dhcp6_pd_is_enabled(link))
+                return 0;
+
+        if (link->network->dhcp6_pd_announce && !link->radv)
+                return 0;
+
+        if (link->dhcp6_pd_messages == 0) {
+                link->dhcp6_pd_configured = false;
+
+                r = dhcp6_pd_remove(link, /* only_marked = */ true);
+                if (r < 0)
+                        return r;
+        }
+
+        if (!link->dhcp6_pd_configured)
+                link_set_state(link, LINK_STATE_CONFIGURING);
+
+        link_check_ready(link);
+        return 0;
+}
+
+void dhcp6_pd_prefix_lost(Link *dhcp6_link) {
+        Link *link;
+        int r;
+
+        assert(dhcp6_link);
+        assert(dhcp6_link->manager);
+
+        HASHMAP_FOREACH(link, dhcp6_link->manager->links_by_index) {
+                if (link == dhcp6_link)
+                        continue;
+
+                r = dhcp6_pd_remove(link, /* only_marked = */ false);
+                if (r < 0)
+                        link_enter_failed(link);
+        }
+
+        set_clear(dhcp6_link->dhcp6_pd_prefixes);
+}
+
+static int dhcp6_route_handler(sd_netlink *rtnl, sd_netlink_message *m, Link *link) {
+        int r;
+
+        assert(link);
+        assert(link->dhcp6_messages > 0);
+
+        link->dhcp6_messages--;
+
+        r = route_configure_handler_internal(rtnl, m, link, "Failed to set unreachable route for DHCPv6 delegated subnet");
+        if (r <= 0)
+                return r;
+
+        r = dhcp6_check_ready(link);
+        if (r < 0)
+                link_enter_failed(link);
+
+        return 1;
+}
+
+static int dhcp6_request_unreachable_route(Link *link, const struct in6_addr *addr, uint8_t prefixlen, usec_t lifetime_usec) {
+        _cleanup_(route_freep) Route *route = NULL;
+        _cleanup_free_ char *buf = NULL;
+        Route *existing;
+        int r;
+
+        assert(link);
+        assert(addr);
+
+        (void) in6_addr_prefix_to_string(addr, prefixlen, &buf);
+
+        if (prefixlen == 64) {
+                log_link_debug(link, "Not adding a blocking route for DHCPv6 delegated subnet %s since distributed prefix is 64",
+                               strna(buf));
+                return 0;
+        }
+
+        r = route_new(&route);
+        if (r < 0)
+                return log_oom();
+
+        route->source = NETWORK_CONFIG_SOURCE_DHCP6;
+        route->family = AF_INET6;
+        route->dst.in6 = *addr;
+        route->dst_prefixlen = prefixlen;
+        route->table = link_get_dhcp6_route_table(link);
+        route->type = RTN_UNREACHABLE;
+        route->protocol = RTPROT_DHCP;
+        route->priority = DHCP_ROUTE_METRIC;
+        route->lifetime_usec = lifetime_usec;
+
+        if (route_get(link->manager, NULL, route, &existing) < 0)
+                link->dhcp6_configured = false;
+        else
+                route_unmark(existing);
+
+        r = link_request_route(link, TAKE_PTR(route), true, &link->dhcp6_messages,
+                               dhcp6_route_handler, NULL);
+        if (r < 0)
+                return log_link_error_errno(link, r, "Failed to request unreachable route for DHCPv6 delegated subnet %s: %m",
+                                            strna(buf));
+
+        return 0;
+}
+
+static int dhcp6_pd_prefix_add(Link *link, const struct in6_addr *prefix, uint8_t prefixlen) {
+        _cleanup_free_ char *buf = NULL;
+        struct in_addr_prefix *p;
+        int r;
+
+        assert(link);
+        assert(prefix);
+
+        p = new(struct in_addr_prefix, 1);
+        if (!p)
+                return log_oom();
+
+        *p = (struct in_addr_prefix) {
+                .family = AF_INET6,
+                .prefixlen = prefixlen,
+                .address.in6 = *prefix,
+        };
+
+        (void) in6_addr_prefix_to_string(prefix, prefixlen, &buf);
+
+        log_link_full(link,
+                      set_contains(link->dhcp6_pd_prefixes, p) ? LOG_DEBUG :
+                      prefixlen > 64 || prefixlen < 48 ? LOG_WARNING : LOG_INFO,
+                      "DHCPv6: received PD Prefix %s%s",
+                      strna(buf),
+                      prefixlen > 64 ? " with prefix length > 64, ignoring." :
+                      prefixlen < 48 ? " with prefix length < 48, looks unusual.": "");
+
+        /* Store PD prefix even if prefixlen > 64, not to make logged at warning level so frequently. */
+        r = set_ensure_consume(&link->dhcp6_pd_prefixes, &in_addr_prefix_hash_ops_free, p);
+        if (r < 0)
+                return log_link_error_errno(link, r, "Failed to store DHCPv6 PD prefix %s: %m", strna(buf));
+
+        return prefixlen <= 64;
+}
+
+int dhcp6_pd_prefix_acquired(Link *dhcp6_link) {
+        usec_t timestamp_usec;
+        Link *link;
+        int r;
+
+        assert(dhcp6_link);
+        assert(dhcp6_link->dhcp6_lease);
+
+        r = sd_dhcp6_lease_get_timestamp(dhcp6_link->dhcp6_lease, clock_boottime_or_monotonic(), &timestamp_usec);
+        if (r < 0)
+                return log_link_warning_errno(dhcp6_link, r, "Failed to get timestamp of DHCPv6 lease: %m");
+
+        HASHMAP_FOREACH(link, dhcp6_link->manager->links_by_index) {
+                r = dhcp6_pd_prepare(link);
+                if (r < 0) {
+                        /* When failed on the upstream interface (i.e., the case link == dhcp6_link),
+                         * immediately abort the assignment of the prefixes. As, the all assigned
+                         * prefixes will be dropped soon in link_enter_failed(), and it is meaningless
+                         * to continue the assignment. */
+                        if (link == dhcp6_link)
+                                return r;
+
+                        link_enter_failed(link);
+                }
+        }
+
+        for (sd_dhcp6_lease_reset_pd_prefix_iter(dhcp6_link->dhcp6_lease);;) {
+                uint32_t lifetime_preferred_sec, lifetime_valid_sec;
+                usec_t lifetime_preferred_usec, lifetime_valid_usec;
+                struct in6_addr pd_prefix;
+                uint8_t pd_prefix_len;
+
+                r = sd_dhcp6_lease_get_pd(dhcp6_link->dhcp6_lease, &pd_prefix, &pd_prefix_len,
+                                          &lifetime_preferred_sec, &lifetime_valid_sec);
+                if (r < 0)
+                        break;
+
+                lifetime_preferred_usec = usec_add(lifetime_preferred_sec * USEC_PER_SEC, timestamp_usec);
+                lifetime_valid_usec = usec_add(lifetime_valid_sec * USEC_PER_SEC, timestamp_usec);
+
+                r = dhcp6_pd_prefix_add(dhcp6_link, &pd_prefix, pd_prefix_len);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        continue;
+
+                r = dhcp6_request_unreachable_route(dhcp6_link, &pd_prefix, pd_prefix_len, lifetime_valid_usec);
+                if (r < 0)
+                        return r;
+
+                /* We are doing prefix allocation in two steps:
+                 * 1. all those links that have a preferred subnet id will be assigned their subnet
+                 * 2. all those links that remain will receive prefixes in sequential order. Prefixes
+                 *    that were previously already allocated to another link will be skipped.
+                 * The assignment has to be split in two phases since subnet id
+                 * preferences should be honored. Meaning that any subnet id should be
+                 * handed out to the requesting link and not to some link that didn't
+                 * specify any preference. */
+
+                assert(pd_prefix_len <= 64);
+
+                /* Mask prefix for safety. */
+                r = in6_addr_mask(&pd_prefix, pd_prefix_len);
+                if (r < 0)
+                        return log_link_error_errno(dhcp6_link, r, "Failed to mask DHCPv6 PD prefix: %m");
+
+                if (DEBUG_LOGGING) {
+                        uint64_t n_prefixes = UINT64_C(1) << (64 - pd_prefix_len);
+                        _cleanup_free_ char *buf = NULL;
+
+                        (void) in6_addr_prefix_to_string(&pd_prefix, pd_prefix_len, &buf);
+                        log_link_debug(dhcp6_link, "Assigning up to %" PRIu64 " prefixes from %s",
+                                       n_prefixes, strna(buf));
+                }
+
+                r = dhcp6_pd_distribute_prefix(dhcp6_link,
+                                               &pd_prefix,
+                                               pd_prefix_len,
+                                               lifetime_preferred_usec,
+                                               lifetime_valid_usec);
+                if (r < 0)
+                        return r;
+        }
+
+        HASHMAP_FOREACH(link, dhcp6_link->manager->links_by_index) {
+                r = dhcp6_pd_finalize(link);
+                if (r < 0) {
+                        if (link == dhcp6_link)
+                                return r;
+
+                        link_enter_failed(link);
+                }
+        }
+
+        return 0;
+}
+
+static int dhcp6_pd_assign_prefixes(Link *link, Link *uplink) {
+        usec_t timestamp_usec;
+        int r;
+
+        assert(link);
+        assert(uplink);
+        assert(uplink->dhcp6_lease);
+
+        /* This is similar to dhcp6_pd_prefix_acquired(), but called when a downstream interface
+         * appears later or reconfiguring the interface. */
+
+        r = sd_dhcp6_lease_get_timestamp(uplink->dhcp6_lease, clock_boottime_or_monotonic(), &timestamp_usec);
+        if (r < 0)
+                return r;
+
+        r = dhcp6_pd_prepare(link);
+        if (r < 0)
+                return r;
+
+        for (sd_dhcp6_lease_reset_pd_prefix_iter(uplink->dhcp6_lease);;) {
+                uint32_t lifetime_preferred_sec, lifetime_valid_sec;
+                usec_t lifetime_preferred_usec, lifetime_valid_usec;
+                struct in6_addr pd_prefix;
+                uint8_t pd_prefix_len;
+
+                r = sd_dhcp6_lease_get_pd(uplink->dhcp6_lease, &pd_prefix, &pd_prefix_len,
+                                          &lifetime_preferred_sec, &lifetime_valid_sec);
+                if (r < 0)
+                        break;
+
+                lifetime_preferred_usec = usec_add(lifetime_preferred_sec * USEC_PER_SEC, timestamp_usec);
+                lifetime_valid_usec = usec_add(lifetime_valid_sec * USEC_PER_SEC, timestamp_usec);
+
+                if (pd_prefix_len > 64)
+                        continue;
+
+                /* Mask prefix for safety. */
+                r = in6_addr_mask(&pd_prefix, pd_prefix_len);
+                if (r < 0)
+                        return r;
+
+                r = dhcp6_pd_assign_prefix(link, &pd_prefix, pd_prefix_len, lifetime_preferred_usec, lifetime_valid_usec);
+                if (r < 0)
+                        return r;
+        }
+
+        r = dhcp6_pd_finalize(link);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static bool dhcp6_pd_uplink_is_ready(Link *link) {
+        assert(link);
+
+        if (!link->network)
+                return false;
+
+        if (!link->network->dhcp6_use_pd_prefix)
+                return false;
+
+        if (!IN_SET(link->state, LINK_STATE_CONFIGURING, LINK_STATE_CONFIGURED))
+                return false;
+
+        if (!link->dhcp6_client)
+                return false;
+
+        if (sd_dhcp6_client_is_running(link->dhcp6_client) <= 0)
+                return false;
+
+        if (!link->dhcp6_lease)
+                return false;
+
+        return dhcp6_lease_has_pd_prefix(link->dhcp6_lease);
+}
+
+int dhcp6_pd_find_uplink(Link *link, Link **ret) {
+        Link *uplink = NULL;
+        int r = 0;
+
+        assert(link);
+        assert(link->manager);
+        assert(link_dhcp6_pd_is_enabled(link));
+        assert(ret);
+
+        if (link->network->dhcp6_pd_uplink_name)
+                r = link_get_by_name(link->manager, link->network->dhcp6_pd_uplink_name, &uplink);
+        else if (link->network->dhcp6_pd_uplink_index > 0)
+                r = link_get_by_index(link->manager, link->network->dhcp6_pd_uplink_index, &uplink);
+        else if (link->network->dhcp6_pd_uplink_index == UPLINK_INDEX_SELF)
+                uplink = link;
+        if (r < 0)
+                return r;
+
+        if (uplink) {
+                if (!dhcp6_pd_uplink_is_ready(uplink))
+                        return -EBUSY;
+
+                *ret = uplink;
+                return 0;
+        }
+
+        HASHMAP_FOREACH(uplink, link->manager->links_by_index) {
+                if (!dhcp6_pd_uplink_is_ready(uplink))
+                        continue;
+
+                /* Assume that there exists at most one link which acquired delegated prefixes. */
+                *ret = uplink;
+                return 0;
+        }
+
+        return -ENODEV;
+}
+
+int dhcp6_request_prefix_delegation(Link *link) {
+        Link *uplink;
+
+        assert(link);
+
+        if (!link_dhcp6_pd_is_enabled(link))
+                return 0;
+
+        if (dhcp6_pd_find_uplink(link, &uplink) < 0)
+                return 0;
+
+        log_link_debug(link, "Requesting subnets of delegated prefixes acquired by %s", uplink->ifname);
+        return dhcp6_pd_assign_prefixes(link, uplink);
+}
+
+int config_parse_dhcp6_pd_subnet_id(
+                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) {
+
+        int64_t *p = data;
+        uint64_t t;
+        int r;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(data);
+
+        if (isempty(rvalue) || streq(rvalue, "auto")) {
+                *p = -1;
+                return 0;
+        }
+
+        r = safe_atoux64(rvalue, &t);
+        if (r < 0) {
+                log_syntax(unit, LOG_WARNING, filename, line, r,
+                           "Failed to parse %s=, ignoring assignment: %s",
+                           lvalue, rvalue);
+                return 0;
+        }
+        if (t > INT64_MAX) {
+                log_syntax(unit, LOG_WARNING, filename, line, 0,
+                           "Invalid subnet id '%s', ignoring assignment.",
+                           rvalue);
+                return 0;
+        }
+
+        *p = (int64_t) t;
+
+        return 0;
+}