Update netinet/tcp.h from Linux 4.18.

This patch adds constants from netinet/tcp.h in Linux 4.18, and an
associated struct tcp_zerocopy_receive, to sysdeps/gnu/netinet/tcp.h.
The new TCP_REPAIR_* constants seemed sufficiently related to those
already present to include them.

Note that this patch does not include additions to struct tcp_info;
there are many other elements in this structure in the Linux kernel
that are not included in the glibc version (which was last extended in
2007, it seems).  Such additions to the end of the structure may be OK
with the expected way it is used (size passed explicitly to the kernel
with getsockopt), but in principle any change to the size of a type
provided by glibc is an ABI change for external applications /
libraries using that type in their ABIs, and has the associated risks
of such a change.

Tested for x86_64.

	* sysdeps/gnu/netinet/tcp.h (TCP_ZEROCOPY_RECEIVE): New macro.
	(TCP_INQ): Likewise.
	(TCP_CM_INQ): Likewise.
	(TCP_REPAIR_ON): Likewise.
	(TCP_REPAIR_OFF): Likewise.
	(TCP_REPAIR_OFF_NO_WP): Likewise.
	(struct tcp_zerocopy_receive): New type.

ChangeLog

@@ -1,3 +1,13 @@
+2018-08-21  Joseph Myers  <[email protected]>
+
+	* sysdeps/gnu/netinet/tcp.h (TCP_ZEROCOPY_RECEIVE): New macro.
+	(TCP_INQ): Likewise.
+	(TCP_CM_INQ): Likewise.
+	(TCP_REPAIR_ON): Likewise.
+	(TCP_REPAIR_OFF): Likewise.
+	(TCP_REPAIR_OFF_NO_WP): Likewise.
+	(struct tcp_zerocopy_receive): New type.
+
 2018-08-21  Florian Weimer  <[email protected]>
 
 	* support/support.h (support_descriptor_supports_holes): Declare.

sysdeps/gnu/netinet/tcp.h

@@ -75,6 +75,14 @@
 #define TCP_MD5SIG_EXT		 32 /* TCP MD5 Signature with extensions.  */
 #define TCP_FASTOPEN_KEY	 33 /* Set the key for Fast Open (cookie).  */
 #define TCP_FASTOPEN_NO_COOKIE	 34 /* Enable TFO without a TFO cookie.  */
+#define TCP_ZEROCOPY_RECEIVE	 35
+#define TCP_INQ			 36 /* Notify bytes available to read
+				       as a cmsg on read.  */
+#define TCP_CM_INQ		 TCP_INQ
+
+#define TCP_REPAIR_ON		 1
+#define TCP_REPAIR_OFF		 0
+#define TCP_REPAIR_OFF_NO_WP	 -1
 
 #ifdef __USE_MISC
 # include <sys/types.h>
@@ -327,6 +335,14 @@ struct tcp_repair_window
   uint32_t rcv_wup;
 };
 
+/* For use with TCP_ZEROCOPY_RECEIVE.  */
+struct tcp_zerocopy_receive
+{
+  uint64_t address; /* In: address of mapping.  */
+  uint32_t length; /* In/out: number of bytes to map/mapped.  */
+  uint32_t recv_skip_hint; /* Out: amount of bytes to skip.  */
+};
+
 #endif /* Misc.  */
 
 #endif /* netinet/tcp.h */