[libc-commits] [libc] 3f79d13 - [libc] Add `IN6_IS_ADDR_MULTICAST` (#172498)

[via libc-commits]

Author: Connector Switch
Date: 2025-12-18T23:10:33+08:00
New Revision: 3f79d13aff69219aa1cbafc4b59a0369d11d83b0

URL: https://github.com/llvm/llvm-project/commit/3f79d13aff69219aa1cbafc4b59a0369d11d83b0
DIFF: https://github.com/llvm/llvm-project/commit/3f79d13aff69219aa1cbafc4b59a0369d11d83b0.diff

LOG: [libc] Add `IN6_IS_ADDR_MULTICAST` (#172498)

This patch adds the `IN6_IS_ADDR_MULTICAST` macro, which checks whether
an address is multicast address.

Added: 
    

Modified: 
    libc/include/llvm-libc-macros/netinet-in-macros.h
    libc/test/include/netinet_in_test.cpp

Removed: 
    


################################################################################
diff  --git a/libc/include/llvm-libc-macros/netinet-in-macros.h b/libc/include/llvm-libc-macros/netinet-in-macros.h
index 3148aed6bb112..863ff8759e446 100644
--- a/libc/include/llvm-libc-macros/netinet-in-macros.h
+++ b/libc/include/llvm-libc-macros/netinet-in-macros.h
@@ -53,6 +53,9 @@
    (__LLVM_LIBC_CAST(reinterpret_cast, uint8_t *, a)[14]) == 0 &&              \
    (__LLVM_LIBC_CAST(reinterpret_cast, uint8_t *, a)[15]) == 1)
 
+#define IN6_IS_ADDR_MULTICAST(a)                                               \
+  (__LLVM_LIBC_CAST(reinterpret_cast, uint8_t *, a)[0]) == 0xff
+
 #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 15e57ccef7ac5..e8cb8e48ff4b4 100644
--- a/libc/test/include/netinet_in_test.cpp
+++ b/libc/test/include/netinet_in_test.cpp
@@ -24,6 +24,11 @@ TEST(LlvmLibcNetinetInTest, IN6Macro) {
   EXPECT_TRUE(IN6_IS_ADDR_LOOPBACK(buff));
   buff[15] = 0;
 
+  EXPECT_FALSE(IN6_IS_ADDR_MULTICAST(buff));
+  buff[0] = 0xff;
+  EXPECT_TRUE(IN6_IS_ADDR_MULTICAST(buff));
+  buff[0] = 0;
+
   buff[0] = 0xfe;
   buff[1] = 0x80;
   EXPECT_TRUE(IN6_IS_ADDR_LINKLOCAL(buff));