Merge pull request #29633 from yuwata/dhcp-ipv6-only-mode-follow-ups

dhcp: several follow-ups for IPv6 only mode

src/libsystemd-network/sd-dhcp-client.c

@@ -709,7 +709,7 @@ int sd_dhcp_client_add_vendor_option(sd_dhcp_client *client, sd_dhcp_option *v)
 int sd_dhcp_client_get_lease(sd_dhcp_client *client, sd_dhcp_lease **ret) {
         assert_return(client, -EINVAL);
 
-        if (!IN_SET(client->state, DHCP_STATE_SELECTING, DHCP_STATE_BOUND, DHCP_STATE_RENEWING, DHCP_STATE_REBINDING))
+        if (!client->lease)
                 return -EADDRNOTAVAIL;
 
         if (ret)
@@ -1661,10 +1661,37 @@ static int client_handle_offer(sd_dhcp_client *client, DHCPMessage *message, siz
         return 0;
 }
 
+static int client_enter_requesting_now(sd_dhcp_client *client) {
+        assert(client);
+
+        client_set_state(client, DHCP_STATE_REQUESTING);
+        client->attempt = 0;
+
+        return event_reset_time(client->event, &client->timeout_resend,
+                                CLOCK_BOOTTIME, 0, 0,
+                                client_timeout_resend, client,
+                                client->event_priority, "dhcp4-resend-timer",
+                                /* force_reset = */ true);
+}
+
+static int client_enter_requesting_delayed(sd_event_source *s, uint64_t usec, void *userdata) {
+        sd_dhcp_client *client = ASSERT_PTR(userdata);
+        DHCP_CLIENT_DONT_DESTROY(client);
+        int r;
+
+        r = client_enter_requesting_now(client);
+        if (r < 0)
+                client_stop(client, r);
+
+        return 0;
+}
+
 static int client_enter_requesting(sd_dhcp_client *client) {
         assert(client);
         assert(client->lease);
 
+        (void) event_source_disable(client->timeout_resend);
+
         if (client->lease->ipv6_only_preferred_usec > 0) {
                 if (client->ipv6_acquired) {
                         log_dhcp_client(client,
@@ -1675,17 +1702,16 @@ static int client_enter_requesting(sd_dhcp_client *client) {
                 log_dhcp_client(client,
                                 "Received an OFFER with IPv6-only preferred option, delaying to send REQUEST with %s.",
                                 FORMAT_TIMESPAN(client->lease->ipv6_only_preferred_usec, USEC_PER_SEC));
+
+                return event_reset_time_relative(client->event, &client->timeout_ipv6_only_mode,
+                                                 CLOCK_BOOTTIME,
+                                                 client->lease->ipv6_only_preferred_usec, 0,
+                                                 client_enter_requesting_delayed, client,
+                                                 client->event_priority, "dhcp4-ipv6-only-mode-timer",
+                                                 /* force_reset = */ true);
         }
 
-        client_set_state(client, DHCP_STATE_REQUESTING);
-        client->attempt = 0;
-
-        return event_reset_time_relative(client->event, &client->timeout_resend,
-                                         CLOCK_BOOTTIME,
-                                         client->lease->ipv6_only_preferred_usec, 0,
-                                         client_timeout_resend, client,
-                                         client->event_priority, "dhcp4-resend-timer",
-                                         /* force_reset = */ true);
+        return client_enter_requesting_now(client);
 }
 
 static int client_handle_forcerenew(sd_dhcp_client *client, DHCPMessage *force, size_t len) {
@@ -1887,7 +1913,7 @@ static int client_enter_bound_now(sd_dhcp_client *client, int notify_event) {
         return 0;
 }
 
-static int client_timeout_ipv6_only_mode(sd_event_source *s, uint64_t usec, void *userdata) {
+static int client_enter_bound_delayed(sd_event_source *s, uint64_t usec, void *userdata) {
         sd_dhcp_client *client = ASSERT_PTR(userdata);
         DHCP_CLIENT_DONT_DESTROY(client);
         int r;
@@ -1906,6 +1932,13 @@ static int client_enter_bound(sd_dhcp_client *client, int notify_event) {
         client->start_delay = 0;
         (void) event_source_disable(client->timeout_resend);
 
+        /* RFC 8925 section 3.2
+         * If the client is in the INIT-REBOOT state, it SHOULD stop the DHCPv4 configuration process or
+         * disable the IPv4 stack completely for V6ONLY_WAIT seconds or until the network attachment event,
+         * whichever happens first.
+         *
+         * In the below, the condition uses REBOOTING, instead of INIT-REBOOT, as the client state has
+         * already transitioned from INIT-REBOOT to REBOOTING after sending a DHCPREQUEST message. */
         if (client->state == DHCP_STATE_REBOOTING && client->lease->ipv6_only_preferred_usec > 0) {
                 if (client->ipv6_acquired) {
                         log_dhcp_client(client,
@@ -1920,7 +1953,7 @@ static int client_enter_bound(sd_dhcp_client *client, int notify_event) {
                 return event_reset_time_relative(client->event, &client->timeout_ipv6_only_mode,
                                                  CLOCK_BOOTTIME,
                                                  client->lease->ipv6_only_preferred_usec, 0,
-                                                 client_timeout_ipv6_only_mode, client,
+                                                 client_enter_bound_delayed, client,
                                                  client->event_priority, "dhcp4-ipv6-only-mode",
                                                  /* force_reset = */ true);
         }
@@ -2161,9 +2194,11 @@ int sd_dhcp_client_send_renew(sd_dhcp_client *client) {
         assert_return(sd_dhcp_client_is_running(client), -ESTALE);
         assert_return(client->fd >= 0, -EINVAL);
 
-        if (!client->lease)
+        if (client->state != DHCP_STATE_BOUND)
                 return 0;
 
+        assert(client->lease);
+
         client->start_delay = 0;
         client->attempt = 1;
         client_set_state(client, DHCP_STATE_RENEWING);
@@ -2316,6 +2351,18 @@ int sd_dhcp_client_set_ipv6_connectivity(sd_dhcp_client *client, int have) {
         return 0;
 }
 
+int sd_dhcp_client_interrupt_ipv6_only_mode(sd_dhcp_client *client) {
+        assert_return(client, -EINVAL);
+        assert_return(sd_dhcp_client_is_running(client), -ESTALE);
+        assert_return(client->fd >= 0, -EINVAL);
+
+        if (sd_event_source_get_enabled(client->timeout_ipv6_only_mode, NULL) <= 0)
+                return 0;
+
+        client_initialize(client);
+        return client_start(client);
+}
+
 int sd_dhcp_client_attach_event(sd_dhcp_client *client, sd_event *event, int64_t priority) {
         int r;
 

src/network/networkd-dhcp4.c

@@ -1744,6 +1744,25 @@ int dhcp4_start_full(Link *link, bool set_ipv6_connectivity) {
         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);

src/network/networkd-dhcp4.h

@@ -20,6 +20,7 @@ int dhcp4_start_full(Link *link, bool set_ipv6_connectivity);
 static inline int dhcp4_start(Link *link) {
         return dhcp4_start_full(link, true);
 }
+int dhcp4_renew(Link *link);
 int dhcp4_lease_lost(Link *link);
 int dhcp4_check_ready(Link *link);
 

src/network/networkd-link-bus.c

@@ -10,6 +10,7 @@
 #include "bus-message-util.h"
 #include "bus-polkit.h"
 #include "dns-domain.h"
+#include "networkd-dhcp4.h"
 #include "networkd-json.h"
 #include "networkd-link-bus.h"
 #include "networkd-link.h"
@@ -626,13 +627,7 @@ int bus_link_method_renew(sd_bus_message *message, void *userdata, sd_bus_error
         if (r == 0)
                 return 1; /* Polkit will call us back */
 
-        if (sd_dhcp_client_is_running(l->dhcp_client))
-                r = sd_dhcp_client_send_renew(l->dhcp_client);
-        else
-                /* The DHCPv4 client may have been stopped by the IPv6 only mode. Let's unconditionally
-                 * restart the client here. Note, if the DHCPv4 client is disabled, then dhcp4_start() does
-                 * nothing and returns 0. */
-                r = dhcp4_start(l);
+        r = dhcp4_renew(l);
         if (r < 0)
                 return r;
 

src/systemd/sd-dhcp-client.h

@@ -153,6 +153,7 @@ int sd_dhcp_client_send_release(sd_dhcp_client *client);
 int sd_dhcp_client_send_decline(sd_dhcp_client *client);
 int sd_dhcp_client_send_renew(sd_dhcp_client *client);
 int sd_dhcp_client_set_ipv6_connectivity(sd_dhcp_client *client, int have);
+int sd_dhcp_client_interrupt_ipv6_only_mode(sd_dhcp_client *client);
 
 sd_dhcp_client *sd_dhcp_client_ref(sd_dhcp_client *client);
 sd_dhcp_client *sd_dhcp_client_unref(sd_dhcp_client *client);