diff --git a/libc/bionic/ifaddrs.cpp b/libc/bionic/ifaddrs.cpp
index d03d76f..1fb16d4 100644
--- a/libc/bionic/ifaddrs.cpp
+++ b/libc/bionic/ifaddrs.cpp
@@ -67,20 +67,12 @@
     *list = reinterpret_cast<ifaddrs*>(this);
   }
 
-  // Netlink gives us the address family in the header, and the
-  // sockaddr_in or sockaddr_in6 bytes as the payload. We need to
-  // stitch the two bits together into the sockaddr that's part of
-  // our portable interface.
   void SetAddress(int family, const void* data, size_t byteCount) {
-      addr.ss_family = family;
-      memcpy(SockaddrBytes(family, &addr), data, byteCount);
-      ifa.ifa_addr = reinterpret_cast<sockaddr*>(&addr);
+      ifa.ifa_addr = CopyAddress(family, data, byteCount, &addr);
   }
 
   void SetBroadcastAddress(int family, const void* data, size_t byteCount) {
-      ifa_ifu.ss_family = family;
-      memcpy(SockaddrBytes(family, &ifa_ifu), data, byteCount);
-      ifa.ifa_dstaddr = reinterpret_cast<sockaddr*>(&ifa_ifu);
+      ifa.ifa_dstaddr = CopyAddress(family, data, byteCount, &ifa_ifu);
   }
 
   // Netlink gives us the prefix length as a bit count. We need to turn
@@ -104,6 +96,22 @@
   }
 
  private:
+  sockaddr* CopyAddress(int family, const void* data, size_t byteCount, sockaddr_storage* ss) {
+      // Netlink gives us the address family in the header, and the
+      // sockaddr_in or sockaddr_in6 bytes as the payload. We need to
+      // stitch the two bits together into the sockaddr that's part of
+      // our portable interface.
+      ss->ss_family = family;
+      memcpy(SockaddrBytes(family, ss), data, byteCount);
+
+      // For IPv6 we might also have to set the scope id.
+      if (family == AF_INET6 && (IN6_IS_ADDR_LINKLOCAL(data) || IN6_IS_ADDR_MC_LINKLOCAL(data))) {
+          reinterpret_cast<sockaddr_in6*>(ss)->sin6_scope_id = interface_index;
+      }
+
+      return reinterpret_cast<sockaddr*>(ss);
+  }
+
   // Returns a pointer to the first byte in the address data (which is
   // stored in network byte order).
   uint8_t* SockaddrBytes(int family, sockaddr_storage* ss) {
diff --git a/libc/include/netinet/in6.h b/libc/include/netinet/in6.h
index 7f3286a..879ac75 100644
--- a/libc/include/netinet/in6.h
+++ b/libc/include/netinet/in6.h
@@ -25,48 +25,47 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
+
 #ifndef _NETINET_IN6_H
 #define _NETINET_IN6_H
 
 #include <linux/in6.h>
 
-#define IN6_IS_ADDR_UNSPECIFIED(a)	\
-	((*(const uint32_t *)(const void *)(&(a)->s6_addr[0]) == 0) &&	\
-	 (*(const uint32_t *)(const void *)(&(a)->s6_addr[4]) == 0) &&	\
-	 (*(const uint32_t *)(const void *)(&(a)->s6_addr[8]) == 0) &&	\
-	 (*(const uint32_t *)(const void *)(&(a)->s6_addr[12]) == 0))
+#define IN6_IS_ADDR_UNSPECIFIED(a) \
+  ((*(const uint32_t*)(&(a)->s6_addr[0]) == 0) && \
+   (*(const uint32_t*)(&(a)->s6_addr[4]) == 0) && \
+   (*(const uint32_t*)(&(a)->s6_addr[8]) == 0) && \
+   (*(const uint32_t*)(&(a)->s6_addr[12]) == 0))
 
-#define IN6_IS_ADDR_LOOPBACK(a)		\
-	((*(const uint32_t *)(const void *)(&(a)->s6_addr[0]) == 0) &&	\
-	 (*(const uint32_t *)(const void *)(&(a)->s6_addr[4]) == 0) &&	\
-	 (*(const uint32_t *)(const void *)(&(a)->s6_addr[8]) == 0) &&	\
-	 (*(const uint32_t *)(const void *)(&(a)->s6_addr[12]) == ntohl(1)))
+#define IN6_IS_ADDR_LOOPBACK(a) \
+  ((*(const uint32_t*)(&(a)->s6_addr[0]) == 0) && \
+   (*(const uint32_t*)(&(a)->s6_addr[4]) == 0) && \
+   (*(const uint32_t*)(&(a)->s6_addr[8]) == 0) && \
+   (*(const uint32_t*)(&(a)->s6_addr[12]) == ntohl(1)))
 
-#define IN6_IS_ADDR_V4COMPAT(a)		\
-	((*(const uint32_t *)(const void *)(&(a)->s6_addr[0]) == 0) &&	\
-	 (*(const uint32_t *)(const void *)(&(a)->s6_addr[4]) == 0) &&	\
-	 (*(const uint32_t *)(const void *)(&(a)->s6_addr[8]) == 0) &&	\
-	 (*(const uint32_t *)(const void *)(&(a)->s6_addr[12]) != 0) &&	\
-	 (*(const uint32_t *)(const void *)(&(a)->s6_addr[12]) != ntohl(1)))
+#define IN6_IS_ADDR_V4COMPAT(a) \
+  ((*(const uint32_t*)(&(a)->s6_addr[0]) == 0) && \
+   (*(const uint32_t*)(&(a)->s6_addr[4]) == 0) && \
+   (*(const uint32_t*)(&(a)->s6_addr[8]) == 0) && \
+   (*(const uint32_t*)(&(a)->s6_addr[12]) != 0) && \
+   (*(const uint32_t*)(&(a)->s6_addr[12]) != ntohl(1)))
 
-#define IN6_IS_ADDR_V4MAPPED(a)		      \
-	((*(const uint32_t *)(const void *)(&(a)->s6_addr[0]) == 0) &&	\
-	 (*(const uint32_t *)(const void *)(&(a)->s6_addr[4]) == 0) &&	\
-	 (*(const uint32_t *)(const void *)(&(a)->s6_addr[8]) == ntohl(0x0000ffff)))
+#define IN6_IS_ADDR_V4MAPPED(a) \
+  ((*(const uint32_t*)(&(a)->s6_addr[0]) == 0) && \
+   (*(const uint32_t*)(&(a)->s6_addr[4]) == 0) && \
+   (*(const uint32_t*)(&(a)->s6_addr[8]) == ntohl(0x0000ffff)))
 
-#define IN6_IS_ADDR_LINKLOCAL(a)	\
-	(((a)->s6_addr[0] == 0xfe) && (((a)->s6_addr[1] & 0xc0) == 0x80))
+#define __bionic_s6_addr(a) ((const uint8_t*)(a))
 
-#define IN6_IS_ADDR_SITELOCAL(a)	\
-	(((a)->s6_addr[0] == 0xfe) && (((a)->s6_addr[1] & 0xc0) == 0xc0))
+#define IN6_IS_ADDR_LINKLOCAL(a) \
+  ((__bionic_s6_addr(a)[0] == 0xfe) && ((__bionic_s6_addr(a)[1] & 0xc0) == 0x80))
 
-/* RFC 4193. */
-#define IN6_IS_ADDR_ULA(a)	\
-	(((a)->s6_addr[0] & 0xfe) == 0xfc)
+#define IN6_IS_ADDR_SITELOCAL(a) \
+  ((__bionic_s6_addr(a)[0] == 0xfe) && ((__bionic_s6_addr(a)[1] & 0xc0) == 0xc0))
 
-#define IN6_IS_ADDR_MULTICAST(a)	\
-	(((__const uint8_t *) (a))[0] == 0xff)
+#define IN6_IS_ADDR_MULTICAST(a) (__bionic_s6_addr(a)[0] == 0xff)
 
+#define IN6_IS_ADDR_ULA(a) ((__bionic_s6_addr(a)[0] & 0xfe) == 0xfc)
 
 #define IPV6_ADDR_SCOPE_NODELOCAL       0x01
 #define IPV6_ADDR_SCOPE_INTFACELOCAL    0x01
@@ -75,27 +74,21 @@
 #define IPV6_ADDR_SCOPE_ORGLOCAL        0x08
 #define IPV6_ADDR_SCOPE_GLOBAL          0x0e
 
-#define IPV6_ADDR_MC_SCOPE(a)	\
-	((a)->s6_addr[1] & 0x0f)
+#define IPV6_ADDR_MC_SCOPE(a) (__bionic_s6_addr(a)[1] & 0x0f)
 
-#define IN6_IS_ADDR_MC_NODELOCAL(a)     \
-	(IN6_IS_ADDR_MULTICAST(a) &&  \
-	 (IPV6_ADDR_MC_SCOPE(a) == IPV6_ADDR_SCOPE_NODELOCAL))
-#define IN6_IS_ADDR_MC_LINKLOCAL(a)	\
-	(IN6_IS_ADDR_MULTICAST(a) &&  \
-	 (IPV6_ADDR_MC_SCOPE(a) == IPV6_ADDR_SCOPE_LINKLOCAL))
-#define IN6_IS_ADDR_MC_SITELOCAL(a)     \
-	(IN6_IS_ADDR_MULTICAST(a) &&  \
-	 (IPV6_ADDR_MC_SCOPE(a) == IPV6_ADDR_SCOPE_SITELOCAL))
-#define IN6_IS_ADDR_MC_ORGLOCAL(a)     \
-	(IN6_IS_ADDR_MULTICAST(a) &&  \
-	 (IPV6_ADDR_MC_SCOPE(a) == IPV6_ADDR_SCOPE_ORGLOCAL))
-#define IN6_IS_ADDR_MC_GLOBAL(a)       \
-	(IN6_IS_ADDR_MULTICAST(a) &&  \
-	 (IPV6_ADDR_MC_SCOPE(a) == IPV6_ADDR_SCOPE_GLOBAL))
+#define IN6_IS_ADDR_MC_NODELOCAL(a) \
+  (IN6_IS_ADDR_MULTICAST(a) && (IPV6_ADDR_MC_SCOPE(a) == IPV6_ADDR_SCOPE_NODELOCAL))
+#define IN6_IS_ADDR_MC_LINKLOCAL(a) \
+  (IN6_IS_ADDR_MULTICAST(a) && (IPV6_ADDR_MC_SCOPE(a) == IPV6_ADDR_SCOPE_LINKLOCAL))
+#define IN6_IS_ADDR_MC_SITELOCAL(a) \
+  (IN6_IS_ADDR_MULTICAST(a) && (IPV6_ADDR_MC_SCOPE(a) == IPV6_ADDR_SCOPE_SITELOCAL))
+#define IN6_IS_ADDR_MC_ORGLOCAL(a) \
+  (IN6_IS_ADDR_MULTICAST(a) && (IPV6_ADDR_MC_SCOPE(a) == IPV6_ADDR_SCOPE_ORGLOCAL))
+#define IN6_IS_ADDR_MC_GLOBAL(a) \
+  (IN6_IS_ADDR_MULTICAST(a) && (IPV6_ADDR_MC_SCOPE(a) == IPV6_ADDR_SCOPE_GLOBAL))
 
-#define IN6_ARE_ADDR_EQUAL(a, b)			\
-    (memcmp(&(a)->s6_addr[0], &(b)->s6_addr[0], sizeof(struct in6_addr)) == 0)
+#define IN6_ARE_ADDR_EQUAL(a, b) \
+  (memcmp(&(a)->s6_addr[0], &(b)->s6_addr[0], sizeof(struct in6_addr)) == 0)
 
 #define INET6_ADDRSTRLEN 46
 
@@ -107,5 +100,4 @@
 
 #define ipv6mr_interface ipv6mr_ifindex
 
-
 #endif /* _NETINET_IN6_H */
diff --git a/tests/ifaddrs_test.cpp b/tests/ifaddrs_test.cpp
index 2c34633..c3f0273 100644
--- a/tests/ifaddrs_test.cpp
+++ b/tests/ifaddrs_test.cpp
@@ -93,8 +93,7 @@
 
   std::vector<std::string> sys_class_net;
   {
-    auto dir_deleter = [](DIR* handle) { if (handle) closedir(handle); };
-    std::unique_ptr<DIR, decltype(dir_deleter)> d(opendir("/sys/class/net"), dir_deleter);
+    std::unique_ptr<DIR, decltype(&closedir)> d(opendir("/sys/class/net"), closedir);
     ASSERT_TRUE(d != nullptr);
     dirent* dir;
     while ((dir = readdir(d.get())) != nullptr) {
@@ -150,6 +149,7 @@
       for (auto ub = addrs.upper_bound(it->first); it != ub; ++it) {
         if (it->second == addr) {
           found = true;
+          break;
         }
       }
       EXPECT_TRUE(found) << if_name;
@@ -220,3 +220,21 @@
 
   freeifaddrs(addrs);
 }
+
+TEST(ifaddrs, inet6_scope_ids) {
+  ifaddrs* addrs;
+  ASSERT_EQ(0, getifaddrs(&addrs));
+
+  for (ifaddrs* ifa = addrs; ifa != nullptr; ifa = ifa->ifa_next) {
+    if (ifa->ifa_addr && ifa->ifa_addr->sa_family == AF_INET6) {
+      sockaddr_in6* sa6 = reinterpret_cast<sockaddr_in6*>(ifa->ifa_addr);
+      // Any link-local IPv6 address should have a scope id. (http://b/27219454.)
+      // 0 isn't a valid interface index, so that would mean the scope id wasn't set.
+      if (IN6_IS_ADDR_LINKLOCAL(&sa6->sin6_addr) || IN6_IS_ADDR_MC_LINKLOCAL(&sa6->sin6_addr)) {
+        ASSERT_NE(sa6->sin6_scope_id, 0U);
+      }
+    }
+  }
+
+  freeifaddrs(addrs);
+}