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[nat64] withdraw greater NAT64 prefix in network data (#7337)

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This commit enables BR to withdraw its local NAT64 prefix if a smaller
one is found in network data.

It might happen when two BRs join the Thread network at merely the
same time and thus both advertise its local NAT64 prefix. The BR with
numerically greater prefix will withdraw its NAT64 prefix.
This commit is contained in:
Yi
2022-01-26 21:27:08 -08:00
committed by GitHub
parent 137c40136c
commit 5896eefc21
1 changed files with 26 additions and 6 deletions
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src/core/border_router/routing_manager.cpp
+26 -6
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@@ -641,26 +641,46 @@ void RoutingManager::EvaluateNat64Prefix(void)
NetworkData::Iterator iterator = NetworkData::kIteratorInit;
NetworkData::ExternalRouteConfig config;
bool hasAdvertisedNat64Prefix = false;
Ip6::Prefix smallestNat64Prefix;
otLogInfoBr("Evaluating NAT64 prefix");
smallestNat64Prefix.Clear();
while (Get<NetworkData::Leader>().GetNextExternalRoute(iterator, config) == kErrorNone)
{
if (config.mNat64 && config.GetPrefix().IsValidNat64())
const Ip6::Prefix &prefix = config.GetPrefix();
if (config.mNat64 && prefix.IsValidNat64())
{
hasAdvertisedNat64Prefix = true;
if (smallestNat64Prefix.GetLength() == 0 || prefix < smallestNat64Prefix)
{
smallestNat64Prefix = prefix;
}
}
}
if (!hasAdvertisedNat64Prefix && !mIsAdvertisingLocalNat64Prefix)
if (smallestNat64Prefix.GetLength() == 0 || smallestNat64Prefix == mLocalNat64Prefix)
{
// TODO: when multiple prefixes exits, remove the ones with lower preference or numerically larger.
if (AddExternalRoute(mLocalNat64Prefix, NetworkData::kRoutePreferenceLow, /* aNat64= */ true) == kErrorNone)
otLogInfoBr("No NAT64 prefix in Network Data is smaller than the local NAT64 prefix %s",
mLocalNat64Prefix.ToString().AsCString());
// Advertise local NAT64 prefix.
if (!mIsAdvertisingLocalNat64Prefix &&
AddExternalRoute(mLocalNat64Prefix, NetworkData::kRoutePreferenceLow, /* aNat64= */ true) == kErrorNone)
{
mIsAdvertisingLocalNat64Prefix = true;
}
}
else if (mIsAdvertisingLocalNat64Prefix && smallestNat64Prefix < mLocalNat64Prefix)
{
// Withdraw local NAT64 prefix if it's not the smallest one in Network Data.
// TODO: remove the prefix with lower preference after discovering upstream NAT64 prefix is supported
otLogNoteBr("Withdrawing local NAT64 prefix since a smaller one %s exists.",
smallestNat64Prefix.ToString().AsCString());
RemoveExternalRoute(mLocalNat64Prefix);
mIsAdvertisingLocalNat64Prefix = false;
}
}
#endif