Avoid multiple definitions of `struct tcphdr`.

No-one's hit this in practice, that I know of, but there are very few
instances of this old workaround for kernel/userspace mismatches still
present, and (as part of the much harder and less effective `struct
sigaction` cleanup), we should just remove them.

Bug: http://b/236042740
Test: treehugger
Change-Id: I6c71d4353044cf57cfa8a9796a4c3d6a4d51cd86
diff --git a/libc/include/bits/tcphdr.h b/libc/include/bits/tcphdr.h
new file mode 100644
index 0000000..a9b6fe0
--- /dev/null
+++ b/libc/include/bits/tcphdr.h
@@ -0,0 +1,71 @@
+/*
+ * Copyright (C) 2008 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
+
+#include <sys/cdefs.h>
+#include <stdint.h>
+
+__BEGIN_DECLS
+
+struct tcphdr {
+  __extension__ union {
+    struct {
+      uint16_t th_sport;
+      uint16_t th_dport;
+      uint32_t th_seq;
+      uint32_t th_ack;
+      uint8_t th_x2:4;
+      uint8_t th_off:4;
+      uint8_t th_flags;
+      uint16_t th_win;
+      uint16_t th_sum;
+      uint16_t th_urp;
+    };
+    struct {
+      uint16_t source;
+      uint16_t dest;
+      uint32_t seq;
+      uint32_t ack_seq;
+      uint16_t res1:4;
+      uint16_t doff:4;
+      uint16_t fin:1;
+      uint16_t syn:1;
+      uint16_t rst:1;
+      uint16_t psh:1;
+      uint16_t ack:1;
+      uint16_t urg:1;
+      uint16_t res2:2;
+      uint16_t window;
+      uint16_t check;
+      uint16_t urg_ptr;
+    };
+  };
+};
+
+__END_DECLS
diff --git a/libc/include/netinet/tcp.h b/libc/include/netinet/tcp.h
index 147f6f7..d1c657b 100644
--- a/libc/include/netinet/tcp.h
+++ b/libc/include/netinet/tcp.h
@@ -32,47 +32,10 @@
 #include <sys/cdefs.h>
 #include <stdint.h>
 
-#define tcphdr __kernel_tcphdr
 #include <linux/tcp.h>
-#undef tcphdr
 
 __BEGIN_DECLS
 
-struct tcphdr {
-  __extension__ union {
-    struct {
-      uint16_t th_sport;
-      uint16_t th_dport;
-      uint32_t th_seq;
-      uint32_t th_ack;
-      uint8_t th_x2:4;
-      uint8_t th_off:4;
-      uint8_t th_flags;
-      uint16_t th_win;
-      uint16_t th_sum;
-      uint16_t th_urp;
-    };
-    struct {
-      uint16_t source;
-      uint16_t dest;
-      uint32_t seq;
-      uint32_t ack_seq;
-      uint16_t res1:4;
-      uint16_t doff:4;
-      uint16_t fin:1;
-      uint16_t syn:1;
-      uint16_t rst:1;
-      uint16_t psh:1;
-      uint16_t ack:1;
-      uint16_t urg:1;
-      uint16_t res2:2;
-      uint16_t window;
-      uint16_t check;
-      uint16_t urg_ptr;
-    };
-  };
-};
-
 #define TH_FIN 0x01
 #define TH_SYN 0x02
 #define TH_RST 0x04
diff --git a/libc/kernel/tools/defaults.py b/libc/kernel/tools/defaults.py
index ac12fc7..e2426c6 100644
--- a/libc/kernel/tools/defaults.py
+++ b/libc/kernel/tools/defaults.py
@@ -43,6 +43,7 @@
     "in_addr": False,
     "ip_mreq_source": False,
     "ip_msfilter": False,
+    "tcphdr": False,
     "timespec": False,
     }
 
diff --git a/libc/kernel/uapi/linux/tcp.h b/libc/kernel/uapi/linux/tcp.h
index 843b6ef..20fbcec 100644
--- a/libc/kernel/uapi/linux/tcp.h
+++ b/libc/kernel/uapi/linux/tcp.h
@@ -6,25 +6,10 @@
  */
 #ifndef _UAPI_LINUX_TCP_H
 #define _UAPI_LINUX_TCP_H
+#include <bits/tcphdr.h>
 #include <linux/types.h>
 #include <asm/byteorder.h>
 #include <linux/socket.h>
-struct tcphdr {
-  __be16 source;
-  __be16 dest;
-  __be32 seq;
-  __be32 ack_seq;
-#ifdef __LITTLE_ENDIAN_BITFIELD
-  __u16 res1 : 4, doff : 4, fin : 1, syn : 1, rst : 1, psh : 1, ack : 1, urg : 1, ece : 1, cwr : 1;
-#elif defined(__BIG_ENDIAN_BITFIELD)
-  __u16 doff : 4, res1 : 4, cwr : 1, ece : 1, urg : 1, ack : 1, psh : 1, rst : 1, syn : 1, fin : 1;
-#else
-#error "Adjust your <asm/byteorder.h> defines"
-#endif
-  __be16 window;
-  __sum16 check;
-  __be16 urg_ptr;
-};
 union tcp_word_hdr {
   struct tcphdr hdr;
   __be32 words[5];