[cli] refactor IPv6 address parsing and synthesis helper (openthread#13205)

This commit renames the static helper `Utils::ParseToIp6Address()` to
`Utils::ParseOrSynthesizeIp6Address()` to better reflect its behavior
of parsing an IPv6 address or synthesizing one from an IPv4 address
via NAT64.

Additionally, the method is refactored into a non-static member of the
`Utils` class. This eliminates the need to manually pass the `otInstance`
pointer, as the `Utils` class already maintains it. The internal
implementation is also simplified to reduce nesting by exiting early
upon successful IPv6 address parsing.

All callers in the CLI module (TCP, UDP, Ping, DNS) have been updated
to use the new member method.

Author: abtink

src/cli/cli_dns.cpp

@@ -452,7 +452,8 @@ otError Dns::GetDnsConfig(Arg aArgs[], otDnsQueryConfig *&aConfig)
 
     VerifyOrExit(!aArgs[0].IsEmpty(), aConfig = nullptr);
 
-    SuccessOrExit(error = ParseToIp6Address(GetInstancePtr(), aArgs[0], aConfig->mServerSockAddr.mAddress, nat64Synth));
+    SuccessOrExit(error = ParseOrSynthesizeIp6Address(aArgs[0], aConfig->mServerSockAddr.mAddress, nat64Synth));
+
     if (nat64Synth)
     {
         OutputFormat("Synthesized IPv6 DNS server address: ");

src/cli/cli_ping.cpp

@@ -96,7 +96,7 @@ otError PingSender::Process(Arg aArgs[])
         aArgs++;
     }
 
-    SuccessOrExit(error = ParseToIp6Address(GetInstancePtr(), aArgs[0], config.mDestination, nat64Synth));
+    SuccessOrExit(error = ParseOrSynthesizeIp6Address(aArgs[0], config.mDestination, nat64Synth));
 
     if (nat64Synth)
     {

src/cli/cli_tcp.cpp

@@ -400,7 +400,7 @@ template <> otError TcpExample::Process<Cmd("connect")>(Arg aArgs[])
 
     VerifyOrExit(mInitialized, error = OT_ERROR_INVALID_STATE);
 
-    SuccessOrExit(error = ParseToIp6Address(GetInstancePtr(), aArgs[0], sockaddr.mAddress, nat64Synth));
+    SuccessOrExit(error = ParseOrSynthesizeIp6Address(aArgs[0], sockaddr.mAddress, nat64Synth));
 
     if (nat64Synth)
     {

src/cli/cli_udp.cpp

@@ -144,7 +144,7 @@ template <> otError UdpExample::Process<Cmd("connect")>(Arg aArgs[])
     otSockAddr sockaddr;
     bool       nat64Synth;
 
-    SuccessOrExit(error = ParseToIp6Address(GetInstancePtr(), aArgs[0], sockaddr.mAddress, nat64Synth));
+    SuccessOrExit(error = ParseOrSynthesizeIp6Address(aArgs[0], sockaddr.mAddress, nat64Synth));
 
     if (nat64Synth)
     {
@@ -281,7 +281,7 @@ template <> otError UdpExample::Process<Cmd("send")>(Arg aArgs[])
     {
         bool nat64Synth;
 
-        SuccessOrExit(error = ParseToIp6Address(GetInstancePtr(), aArgs[0], messageInfo.mPeerAddr, nat64Synth));
+        SuccessOrExit(error = ParseOrSynthesizeIp6Address(aArgs[0], messageInfo.mPeerAddr, nat64Synth));
 
         if (nat64Synth)
         {

src/cli/cli_utils.cpp

@@ -629,25 +629,27 @@ const char *Utils::PreferenceToString(signed int aPreference)
 }
 
 #if OPENTHREAD_FTD || OPENTHREAD_MTD
-otError Utils::ParseToIp6Address(otInstance *aInstance, const Arg &aArg, otIp6Address &aAddress, bool &aSynthesized)
+
+otError Utils::ParseOrSynthesizeIp6Address(const Arg &aArg, otIp6Address &aAddress, bool &aSynthesized)
 {
-    Error error = OT_ERROR_NONE;
+    Error        error;
+    otIp4Address ip4Address;
 
-    VerifyOrExit(!aArg.IsEmpty(), error = OT_ERROR_INVALID_ARGS);
-    error        = aArg.ParseAsIp6Address(aAddress);
     aSynthesized = false;
 
-    if (error != OT_ERROR_NONE)
-    {
-        // It might be an IPv4 address, let's have a try.
-        otIp4Address ip4Address;
+    error = aArg.ParseAsIp6Address(aAddress);
 
-        // Do not touch the error value if we failed to parse it as an IPv4 address.
-        SuccessOrExit(aArg.ParseAsIp4Address(ip4Address));
-        SuccessOrExit(error = otNat64SynthesizeIp6Address(aInstance, &ip4Address, &aAddress));
-        aSynthesized = true;
+    if (error == OT_ERROR_NONE)
+    {
+        ExitNow();
     }
 
+    // Try to parse it as an IPv4 address and synthesize.
+
+    SuccessOrExit(error = aArg.ParseAsIp4Address(ip4Address));
+    SuccessOrExit(error = otNat64SynthesizeIp6Address(GetInstancePtr(), &ip4Address, &aAddress));
+    aSynthesized = true;
+
 exit:
     return error;
 }

src/cli/cli_utils.hpp

@@ -674,24 +674,20 @@ class Utils
     static const char *PreferenceToString(signed int aPreference);
 
     /**
-     * Parses the argument as an IP address.
+     * Parses the argument as an IPv6 address or synthesizes it from an IPv4 address.
      *
      * If the argument string is an IPv4 address, this method will try to synthesize an IPv6 address using preferred
      * NAT64 prefix in the network data.
      *
-     * @param[in]  aInstance       A pointer to OpenThread instance.
      * @param[in]  aArg            The argument string to parse.
-     * @param[out] aAddress        A reference to an `otIp6Address` to output the parsed IPv6 address.
+     * @param[out] aAddress        A reference to an `otIp6Address` to output the parsed/synthesized IPv6 address.
      * @param[out] aSynthesized    Whether @p aAddress is synthesized from an IPv4 address.
      *
-     * @retval OT_ERROR_NONE           The argument was parsed successfully.
+     * @retval OT_ERROR_NONE           The argument was parsed/synthesized successfully.
      * @retval OT_ERROR_INVALID_ARGS   The argument is empty or does not contain a valid IP address.
      * @retval OT_ERROR_INVALID_STATE  No valid NAT64 prefix in the network data.
      */
-    static otError ParseToIp6Address(otInstance   *aInstance,
-                                     const Arg    &aArg,
-                                     otIp6Address &aAddress,
-                                     bool         &aSynthesized);
+    otError ParseOrSynthesizeIp6Address(const Arg &aArg, otIp6Address &aAddress, bool &aSynthesized);
 
     /**
      * Parses the argument as a Joiner Discerner.