network/ndisc: check if there exists a conflicting address

Follow-up for 0a0c2672dbd22dc85d660e5baa7e1bef701beb88.

Before the commit, if a conflicting address exists or already requested,
then the configuration of newly requested address (especially, prefix
length) is mostly ignored silently.

However, after the commit, even if there exists a conflicting address,
networkd anyway tries to configure the newly requested address, and
enter failed state. Such situation can be triggered, e.g. when the DHCPv6
client is started earlier than NDisc, by WithoutRA=solicit.

Fixes #31263.

diff --git a/src/network/networkd-ndisc.c b/src/network/networkd-ndisc.c
index 7e6758714b369ed3b6be360b675192b1b3cc4975..030b4a43394116023ecffbe6c851f74db8499f14 100644 (file)
--- a/src/network/networkd-ndisc.c
+++ b/src/network/networkd-ndisc.c
@@ -269,7 +269,26 @@ static int ndisc_request_address(Address *address, Link *link, sd_ndisc_router *
         if (r < 0)
                 return r;
 
-        is_new = address_get(link, address, NULL) < 0;
+        Address *existing;
+        if (address_get_harder(link, address, &existing) < 0)
+                is_new = true;
+        else if (address_can_update(existing, address))
+                is_new = false;
+        else if (existing->source == NETWORK_CONFIG_SOURCE_DHCP6) {
+                /* SLAAC address is preferred over DHCPv6 address. */
+                log_link_debug(link, "Conflicting DHCPv6 address %s exists, removing.",
+                               IN_ADDR_PREFIX_TO_STRING(existing->family, &existing->in_addr, existing->prefixlen));
+                r = address_remove(existing, link);
+                if (r < 0)
+                        return r;
+
+                is_new = true;
+        } else {
+                /* Conflicting static address is configured?? */
+                log_link_debug(link, "Conflicting address %s exists, ignoring request.",
+                               IN_ADDR_PREFIX_TO_STRING(existing->family, &existing->in_addr, existing->prefixlen));
+                return 0;
+        }
 
         r = link_request_address(link, address, &link->ndisc_messages,
                                  ndisc_address_handler, NULL);