[llvm-branch-commits] [libc] [libc] Add `IN6_IS_ADDR_LOOPBACK` (PR #172312)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libc

Author: Connector Switch (c8ef)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/172312.diff


2 Files Affected:

- (modified) libc/include/llvm-libc-macros/netinet-in-macros.h (+9) 
- (modified) libc/test/include/netinet_in_test.cpp (+5) 


``````````diff
diff --git a/libc/include/llvm-libc-macros/netinet-in-macros.h b/libc/include/llvm-libc-macros/netinet-in-macros.h
index f97a2dd0c3fda..3148aed6bb112 100644
--- a/libc/include/llvm-libc-macros/netinet-in-macros.h
+++ b/libc/include/llvm-libc-macros/netinet-in-macros.h
@@ -44,6 +44,15 @@
    (__LLVM_LIBC_CAST(reinterpret_cast, uint32_t *, a)[2]) == 0 &&              \
    (__LLVM_LIBC_CAST(reinterpret_cast, uint32_t *, a)[3]) == 0)
 
+#define IN6_IS_ADDR_LOOPBACK(a)                                                \
+  ((__LLVM_LIBC_CAST(reinterpret_cast, uint32_t *, a)[0]) == 0 &&              \
+   (__LLVM_LIBC_CAST(reinterpret_cast, uint32_t *, a)[1]) == 0 &&              \
+   (__LLVM_LIBC_CAST(reinterpret_cast, uint32_t *, a)[2]) == 0 &&              \
+   (__LLVM_LIBC_CAST(reinterpret_cast, uint8_t *, a)[12]) == 0 &&              \
+   (__LLVM_LIBC_CAST(reinterpret_cast, uint8_t *, a)[13]) == 0 &&              \
+   (__LLVM_LIBC_CAST(reinterpret_cast, uint8_t *, a)[14]) == 0 &&              \
+   (__LLVM_LIBC_CAST(reinterpret_cast, uint8_t *, a)[15]) == 1)
+
 #define IN6_IS_ADDR_LINKLOCAL(a)                                               \
   ((__LLVM_LIBC_CAST(reinterpret_cast, uint8_t *, a)[0]) == 0xfe &&            \
    (__LLVM_LIBC_CAST(reinterpret_cast, uint8_t *, a)[1] & 0xc0) == 0x80)
diff --git a/libc/test/include/netinet_in_test.cpp b/libc/test/include/netinet_in_test.cpp
index d70c780800858..15e57ccef7ac5 100644
--- a/libc/test/include/netinet_in_test.cpp
+++ b/libc/test/include/netinet_in_test.cpp
@@ -19,6 +19,11 @@ TEST(LlvmLibcNetinetInTest, IN6Macro) {
     buff[i] = 0;
   }
 
+  EXPECT_FALSE(IN6_IS_ADDR_LOOPBACK(buff));
+  buff[15] = 1;
+  EXPECT_TRUE(IN6_IS_ADDR_LOOPBACK(buff));
+  buff[15] = 0;
+
   buff[0] = 0xfe;
   buff[1] = 0x80;
   EXPECT_TRUE(IN6_IS_ADDR_LINKLOCAL(buff));

``````````

</details>


https://github.com/llvm/llvm-project/pull/172312