[PATCH 36/44] Load balance sockets with new SO_REUSEPORT_LB option.

[Sebastian Huber <sebastian dot huber at embedded-brains dot de>]

From: sbruno <sbruno@FreeBSD.org>

This patch adds a new socket option, SO_REUSEPORT_LB, which allow multiple
programs or threads to bind to the same port and incoming connections will be
load balanced using a hash function.

Most of the code was copied from a similar patch for DragonflyBSD.

However, in DragonflyBSD, load balancing is a global on/off setting and can not
be set per socket. This patch allows for simultaneous use of both the current
SO_REUSEPORT and the new SO_REUSEPORT_LB options on the same system.

Required changes to structures:
Globally change so_options from 16 to 32 bit value to allow for more options.
Add hashtable in pcbinfo to hold all SO_REUSEPORT_LB sockets.

Limitations:
As DragonflyBSD, a load balance group is limited to 256 pcbs (256 programs or
threads sharing the same socket).

This is a substantially different contribution as compared to its original
incarnation at svn r332894 and reverted at svn r332967.  Thanks to rwatson@
for the substantive feedback that is included in this commit.

Submitted by:	Johannes Lundberg <johalun0@gmail.com>
Obtained from:	DragonflyBSD
Relnotes:	Yes
Sponsored by:	Limelight Networks
Differential Revision:	https://reviews.freebsd.org/D11003
---
 newlib/libc/sys/rtems/include/sys/socket.h | 35 +++++++++++++++---------------
 1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/newlib/libc/sys/rtems/include/sys/socket.h b/newlib/libc/sys/rtems/include/sys/socket.h
index 345eaa83f..a1ffbbdcb 100644
--- a/newlib/libc/sys/rtems/include/sys/socket.h
+++ b/newlib/libc/sys/rtems/include/sys/socket.h
@@ -126,26 +126,27 @@ typedef	__uintptr_t	uintptr_t;
 /*
  * Option flags per-socket.
  */
-#define	SO_DEBUG	0x0001		/* turn on debugging info recording */
-#define	SO_ACCEPTCONN	0x0002		/* socket has had listen() */
-#define	SO_REUSEADDR	0x0004		/* allow local address reuse */
-#define	SO_KEEPALIVE	0x0008		/* keep connections alive */
-#define	SO_DONTROUTE	0x0010		/* just use interface addresses */
-#define	SO_BROADCAST	0x0020		/* permit sending of broadcast msgs */
+#define	SO_DEBUG	0x00000001	/* turn on debugging info recording */
+#define	SO_ACCEPTCONN	0x00000002	/* socket has had listen() */
+#define	SO_REUSEADDR	0x00000004	/* allow local address reuse */
+#define	SO_KEEPALIVE	0x00000008	/* keep connections alive */
+#define	SO_DONTROUTE	0x00000010	/* just use interface addresses */
+#define	SO_BROADCAST	0x00000020	/* permit sending of broadcast msgs */
 #if __BSD_VISIBLE
-#define	SO_USELOOPBACK	0x0040		/* bypass hardware when possible */
+#define	SO_USELOOPBACK	0x00000040	/* bypass hardware when possible */
 #endif
-#define	SO_LINGER	0x0080		/* linger on close if data present */
-#define	SO_OOBINLINE	0x0100		/* leave received OOB data in line */
+#define	SO_LINGER	0x00000080	/* linger on close if data present */
+#define	SO_OOBINLINE	0x00000100	/* leave received OOB data in line */
 #if __BSD_VISIBLE
-#define	SO_REUSEPORT	0x0200		/* allow local address & port reuse */
-#define	SO_TIMESTAMP	0x0400		/* timestamp received dgram traffic */
-#define	SO_NOSIGPIPE	0x0800		/* no SIGPIPE from EPIPE */
-#define	SO_ACCEPTFILTER	0x1000		/* there is an accept filter */
-#define	SO_BINTIME	0x2000		/* timestamp received dgram traffic */
-#endif
-#define	SO_NO_OFFLOAD	0x4000		/* socket cannot be offloaded */
-#define	SO_NO_DDP	0x8000		/* disable direct data placement */
+#define	SO_REUSEPORT	0x00000200	/* allow local address & port reuse */
+#define	SO_TIMESTAMP	0x00000400	/* timestamp received dgram traffic */
+#define	SO_NOSIGPIPE	0x00000800	/* no SIGPIPE from EPIPE */
+#define	SO_ACCEPTFILTER	0x00001000	/* there is an accept filter */
+#define	SO_BINTIME	0x00002000	/* timestamp received dgram traffic */
+#endif
+#define	SO_NO_OFFLOAD	0x00004000	/* socket cannot be offloaded */
+#define	SO_NO_DDP	0x00008000	/* disable direct data placement */
+#define	SO_REUSEPORT_LB	0x00010000	/* reuse with load balancing */
 
 /*
  * Additional options, not kept in so_options.
-- 
2.13.7