From 388f734b6499d39818912da3a1bbeb4402ba5f48 Mon Sep 17 00:00:00 2001
From: Abtin Keshavarzian <abtink@google.com>
Date: Tue, 26 Aug 2025 21:08:30 -0700
Subject: [PATCH] [nat64] simplify mapping lookup and `Touch()` method (#11864)

This change streamlines NAT64 mapping management by removing the
`FindMapping()` and `FindOrAllocateMapping()` helper methods.

Following recent simplifications, such as adding new `Matches()`
flavors, the logic within these `Find` methods became much
simpler. Their functionality is now incorporated directly into
`TranslateToIp6()` and `TranslateFromIp6()`, respectively.

Additionally, the `Mapping::Touch()` method is simplified to no longer
require the current time as an argument. It now retrieves the time
internally.
---
 src/core/net/nat64_translator.cpp | 46 +++++++++++--------------------
 src/core/net/nat64_translator.hpp |  4 +--
 2 files changed, 17 insertions(+), 33 deletions(-)

diff --git a/src/core/net/nat64_translator.cpp b/src/core/net/nat64_translator.cpp
index 8c366e434..fa5baf594 100644
--- a/src/core/net/nat64_translator.cpp
+++ b/src/core/net/nat64_translator.cpp
@@ -148,7 +148,12 @@ Translator::Result Translator::TranslateFromIp6(Message &aMessage)
         ExitNow(result = kNotTranslated);
     }
 
-    mapping = FindOrAllocateMapping(ip6Headers);
+    mapping = mActiveMappings.FindMatching(ip6Headers);
+
+    if (mapping == nullptr)
+    {
+        mapping = AllocateMapping(ip6Headers);
+    }
 
     if (mapping == nullptr)
     {
@@ -261,7 +266,7 @@ Translator::Result Translator::TranslateToIp6(Message &aMessage)
         ExitNow(result = kDrop);
     }
 
-    mapping = FindMapping(ip4Headers);
+    mapping = mActiveMappings.FindMatching(ip4Headers);
 
     if (mapping == nullptr)
     {
@@ -270,6 +275,8 @@ Translator::Result Translator::TranslateToIp6(Message &aMessage)
         ExitNow(result = kDrop);
     }
 
+    mapping->Touch(ip4Headers.GetIpProto());
+
 #if OPENTHREAD_CONFIG_NAT64_PORT_TRANSLATION_ENABLE
     dstPortOrId = mapping->mSrcPortOrId;
 #else
@@ -485,7 +492,7 @@ Translator::Mapping *Translator::AllocateMapping(const Ip6::Headers &aIp6Headers
     mapping->mSrcPortOrId        = 0;
     mapping->mTranslatedPortOrId = 0;
 #endif
-    mapping->Touch(TimerMilli::GetNow(), aIp6Headers.GetIpProto());
+    mapping->Touch(aIp6Headers.GetIpProto());
 
     LogInfo("Mapping created: %s", mapping->ToString().AsCString());
 
@@ -493,41 +500,20 @@ exit:
     return mapping;
 }
 
-Translator::Mapping *Translator::FindOrAllocateMapping(const Ip6::Headers &aIp6Headers)
+void Translator::Mapping::Touch(uint8_t aProtocol)
 {
-    Mapping *mapping = mActiveMappings.FindMatching(aIp6Headers);
+    uint32_t timeout;
 
-    // Exit if we found a valid mapping.
-    VerifyOrExit(mapping == nullptr);
-
-    mapping = AllocateMapping(aIp6Headers);
-
-exit:
-    return mapping;
-}
-
-Translator::Mapping *Translator::FindMapping(const Ip4::Headers &aIp4Headers)
-{
-    Mapping *mapping = mActiveMappings.FindMatching(aIp4Headers);
-
-    if (mapping != nullptr)
-    {
-        mapping->Touch(TimerMilli::GetNow(), aIp4Headers.GetIpProto());
-    }
-
-    return mapping;
-}
-
-void Translator::Mapping::Touch(TimeMilli aNow, uint8_t aProtocol)
-{
     if ((aProtocol == Ip6::kProtoIcmp6) || (aProtocol == Ip4::kProtoIcmp))
     {
-        mExpiry = aNow + kIcmpTimeout;
+        timeout = kIcmpTimeout;
     }
     else
     {
-        mExpiry = aNow + kIdleTimeout;
+        timeout = kIdleTimeout;
     }
+
+    mExpiry = TimerMilli::GetNow() + timeout;
 }
 
 bool Translator::Mapping::Matches(const Ip6::Headers &aIp6Headers) const
diff --git a/src/core/net/nat64_translator.hpp b/src/core/net/nat64_translator.hpp
index 1e7b1ac40..5f1809ca8 100644
--- a/src/core/net/nat64_translator.hpp
+++ b/src/core/net/nat64_translator.hpp
@@ -304,7 +304,7 @@ private:
 
         typedef String<kInfoStringSize> InfoString;
 
-        void       Touch(TimeMilli aNow, uint8_t aProtocol);
+        void       Touch(uint8_t aProtocol);
         InfoString ToString(void) const;
         void       CopyTo(AddressMapping &aMapping, TimeMilli aNow) const;
         bool       Matches(const Ip6::Headers &aIp6Headers) const;
@@ -328,8 +328,6 @@ private:
     void     ReleaseMapping(Mapping &aMapping);
     uint16_t ReleaseExpiredMappings(void);
     Mapping *AllocateMapping(const Ip6::Headers &aIp6Headers);
-    Mapping *FindOrAllocateMapping(const Ip6::Headers &aIp6Headers);
-    Mapping *FindMapping(const Ip4::Headers &aIp4Headers);
     void     HandleTimer(void);
     void     UpdateState(void);
 #if OPENTHREAD_CONFIG_NAT64_PORT_TRANSLATION_ENABLE