[libc] Add IN6_IS_ADDR_MULTICAST

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[c8ef]

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• [libc] Add IN6_IS_ADDR_V4COMPAT #172646
• [libc] Add IN6_IS_ADDR_V4MAPPED #172645
• [libc] Add IN6_IS_ADDR_MC* #172643
• [libc] Add IN6_IS_ADDR_MULTICAST #172498 👈 (View in Graphite)
• [libc] Add IN6_IS_ADDR_LOOPBACK #172312
• [libc] Add IN6_IS_ADDR_UNSPECIFIED #172311
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[llvmbot]

@llvm/pr-subscribers-libc

Author: Connector Switch (c8ef)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/172498.diff

2 Files Affected:

• (modified) libc/include/llvm-libc-macros/netinet-in-macros.h (+3)
• (modified) libc/test/include/netinet_in_test.cpp (+5)

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));