Use the canonical idiom for sockaddr_storage.

This works out a bit silly/ugly because the bits/ header file has the
wrong name, so I've also changed the map from kernel struct to boolean
to be a map from kernel struct to filename. That not only fixes this,
it's a bit more readable too. (Just yesterday, when I had no real reason
to change it, I was asking myself "why is this a boolean?"!)

Bug: http://b/236042740
Test: treehugger
Change-Id: I3eee25b493ea97d46cc5dc5fde07f7c5e77d2a46
diff --git a/libc/include/bits/sockaddr_storage.h b/libc/include/bits/sockaddr_storage.h
new file mode 100644
index 0000000..effafab
--- /dev/null
+++ b/libc/include/bits/sockaddr_storage.h
@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#pragma once
+
+/**
+ * @file bits/sockaddr_storage.h
+ * @brief The `sockaddr_storage` struct.
+ */
+
+#include <sys/cdefs.h>
+
+#include <bits/sa_family_t.h>
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnullability-completeness"
+/**
+ * [sockaddr_storage](https://man7.org/linux/man-pages/man3/sockaddr.3type.html)
+ * is a structure large enough to contain any other `sockaddr_*` type, used to
+ * pass socket addresses without needing to know what kind of socket address
+ * you're passing.
+ */
+struct sockaddr_storage {
+  union {
+    struct {
+      sa_family_t ss_family;
+      char __data[128 - sizeof(sa_family_t)];
+    };
+    void* __align;
+  };
+};
+#pragma clang diagnostic pop
diff --git a/libc/include/netinet/in.h b/libc/include/netinet/in.h
index b235e6e..163e614 100644
--- a/libc/include/netinet/in.h
+++ b/libc/include/netinet/in.h
@@ -33,20 +33,10 @@
 #include <sys/cdefs.h>
 #include <sys/socket.h>
 
-// Include linux/socket.h first to trigger the header guard without
-// the__kernel_sockaddr_storage define, so its definition uses the
-// kernel name.
-#include <linux/socket.h>
-
-// Redefine __kernel_sockaddr_storage to sockaddr_storage so that
-// the structs defined in linux/in.h use the sockaddr_storage defined
-// in sys/sockets.h.
-#define __kernel_sockaddr_storage sockaddr_storage
 #include <linux/in.h>
-#undef __kernel_sockaddr_storage
-
 #include <linux/in6.h>
 #include <linux/ipv6.h>
+#include <linux/socket.h>
 
 __BEGIN_DECLS
 
diff --git a/libc/include/sys/socket.h b/libc/include/sys/socket.h
index 22b88cb..9402e70 100644
--- a/libc/include/sys/socket.h
+++ b/libc/include/sys/socket.h
@@ -39,6 +39,7 @@
 #include <linux/types.h>
 #include <linux/compiler.h>
 
+#include <bits/sockaddr_storage.h>
 #include <bits/sa_family_t.h>
 
 __BEGIN_DECLS
@@ -72,15 +73,6 @@
 
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wnullability-completeness"
-struct sockaddr_storage {
-  union {
-    struct {
-      sa_family_t ss_family;
-      char __data[128 - sizeof(sa_family_t)];
-    };
-    void* __align;
-  };
-};
 
 struct linger {
   int l_onoff;