From 39a1f55447f3eec0cf089d8bec29b3303f3e7f99 Mon Sep 17 00:00:00 2001
From: Jonathan Hui <jonhui@google.com>
Date: Mon, 8 Nov 2021 21:33:21 -0800
Subject: [PATCH] [routing-manager] require on-link prefix to support SLAAC
 (#7142)

Existing IPv6 implementations may not implement DHCPv6 to acquire an
IPv6 address. As a result, a Thread Border Router must advertise a ULA
if there is no existing prefix that supports SLAAC (i.e. has A flag
set).
---
 src/core/border_router/routing_manager.cpp | 11 +++++------
 src/core/border_router/routing_manager.hpp |  4 ++--
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/src/core/border_router/routing_manager.cpp b/src/core/border_router/routing_manager.cpp
index 85ba1e804..693832a97 100644
--- a/src/core/border_router/routing_manager.cpp
+++ b/src/core/border_router/routing_manager.cpp
@@ -795,10 +795,9 @@ bool RoutingManager::IsValidOmrPrefix(const Ip6::Prefix &aOmrPrefix)
            (aOmrPrefix.mLength >= 3 && (aOmrPrefix.GetBytes()[0] & 0xE0) == 0x20);
 }
 
-bool RoutingManager::IsValidOnLinkPrefix(const RouterAdv::PrefixInfoOption &aPio, bool aManagedAddrConfig)
+bool RoutingManager::IsValidOnLinkPrefix(const RouterAdv::PrefixInfoOption &aPio)
 {
-    return IsValidOnLinkPrefix(aPio.GetPrefix()) && aPio.GetOnLink() &&
-           (aPio.GetAutoAddrConfig() || aManagedAddrConfig);
+    return IsValidOnLinkPrefix(aPio.GetPrefix()) && aPio.GetOnLink() && aPio.GetAutoAddrConfig();
 }
 
 bool RoutingManager::IsValidOnLinkPrefix(const Ip6::Prefix &aOnLinkPrefix)
@@ -1015,7 +1014,7 @@ void RoutingManager::HandleRouterAdvertisement(const Ip6::Address &aSrcAddress,
 
             if (pio->IsValid())
             {
-                needReevaluate |= UpdateDiscoveredPrefixes(*pio, routerAdvMessage->GetManagedAddrConfig());
+                needReevaluate |= UpdateDiscoveredPrefixes(*pio);
             }
         }
         break;
@@ -1052,7 +1051,7 @@ exit:
     return;
 }
 
-bool RoutingManager::UpdateDiscoveredPrefixes(const RouterAdv::PrefixInfoOption &aPio, bool aManagedAddrConfig)
+bool RoutingManager::UpdateDiscoveredPrefixes(const RouterAdv::PrefixInfoOption &aPio)
 {
     Ip6::Prefix     prefix         = aPio.GetPrefix();
     bool            needReevaluate = false;
@@ -1060,7 +1059,7 @@ bool RoutingManager::UpdateDiscoveredPrefixes(const RouterAdv::PrefixInfoOption
     ExternalPrefix  onLinkPrefix;
     ExternalPrefix *existingPrefix = nullptr;
 
-    if (!IsValidOnLinkPrefix(aPio, aManagedAddrConfig))
+    if (!IsValidOnLinkPrefix(aPio))
     {
         otLogInfoBr("Ignore invalid on-link prefix in PIO: %s", prefix.ToString().AsCString());
         ExitNow();
diff --git a/src/core/border_router/routing_manager.hpp b/src/core/border_router/routing_manager.hpp
index 4d26d2628..bdf86c2b2 100644
--- a/src/core/border_router/routing_manager.hpp
+++ b/src/core/border_router/routing_manager.hpp
@@ -306,7 +306,7 @@ private:
     void DeprecateOnLinkPrefix(void);
     void HandleRouterSolicit(const Ip6::Address &aSrcAddress, const uint8_t *aBuffer, uint16_t aBufferLength);
     void HandleRouterAdvertisement(const Ip6::Address &aSrcAddress, const uint8_t *aBuffer, uint16_t aBufferLength);
-    bool UpdateDiscoveredPrefixes(const RouterAdv::PrefixInfoOption &aPio, bool aManagedAddrConfig);
+    bool UpdateDiscoveredPrefixes(const RouterAdv::PrefixInfoOption &aPio);
     bool UpdateDiscoveredPrefixes(const RouterAdv::RouteInfoOption &aRio);
     bool InvalidateDiscoveredPrefixes(const Ip6::Prefix *aPrefix = nullptr, bool aIsOnLinkPrefix = true);
     void InvalidateAllDiscoveredPrefixes(void);
@@ -315,7 +315,7 @@ private:
 
     static bool IsValidOmrPrefix(const NetworkData::OnMeshPrefixConfig &aOnMeshPrefixConfig);
     static bool IsValidOmrPrefix(const Ip6::Prefix &aOmrPrefix);
-    static bool IsValidOnLinkPrefix(const RouterAdv::PrefixInfoOption &aPio, bool aManagedAddrConfig);
+    static bool IsValidOnLinkPrefix(const RouterAdv::PrefixInfoOption &aPio);
     static bool IsValidOnLinkPrefix(const Ip6::Prefix &aOnLinkPrefix);
 
     // Indicates whether the Routing Manager is running (started).