[newlib-cygwin] Introduce scalable route multipath.

[Sebastian Huber <sh@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=48ba673ce9180335ff324d94e41221a3a61dc959

commit 48ba673ce9180335ff324d94e41221a3a61dc959
Author: Alexander V. Chernikov <melifaro@FreeBSD.org>
Date:   Sat Oct 3 10:47:17 2020 +0000

    Introduce scalable route multipath.
    
    This change is based on the nexthop objects landed in D24232.
    
    The change introduces the concept of nexthop groups.
    Each group contains the collection of nexthops with their
     relative weights and a dataplane-optimized structure to enable
     efficient nexthop selection.
    
    Simular to the nexthops, nexthop groups are immutable. Dataplane part
     gets compiled during group creation and is basically an array of
     nexthop pointers, compiled w.r.t their weights.
    
    With this change, `rt_nhop` field of `struct rtentry` contains either
     nexthop or nexthop group. They are distinguished by the presense of
     NHF_MULTIPATH flag.
    All dataplane lookup functions returns pointer to the nexthop object,
    leaving nexhop groups details inside routing subsystem.
    
    User-visible changes:
    
    The change is intended to be backward-compatible: all non-mpath operations
     should work as before with ROUTE_MPATH and net.route.multipath=1.
    
    All routes now comes with weight, default weight is 1, maximum is 2^24-1.
    
    Current maximum multipath group width is statically set to 64.
     This will become sysctl-tunable in the followup changes.
    
    Using functionality:
    * Recompile kernel with ROUTE_MPATH
    * set net.route.multipath to 1
    
    route add -6 2001:db8::/32 2001:db8::2 -weight 10
    route add -6 2001:db8::/32 2001:db8::3 -weight 20
    
    netstat -6On
    
    Nexthop groups data
    
    Internet6:
    GrpIdx  NhIdx     Weight   Slots                                 Gateway     Netif  Refcnt
    1         ------- ------- ------- --------------------------------------- ---------       1
                  13      10       1                             2001:db8::2     vlan2
                  14      20       2                             2001:db8::3     vlan2
    
    Next steps:
    * Land outbound hashing for locally-originated routes ( D26523 ).
    * Fix net/bird multipath (net/frr seems to work fine)
    * Add ROUTE_MPATH to GENERIC
    * Set net.route.multipath=1 by default
    
    Tested by:      olivier
    Reviewed by:    glebius
    Relnotes:       yes
    Differential Revision:  https://reviews.freebsd.org/D26449

Diff:
---
 newlib/libc/sys/rtems/include/sys/socket.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/newlib/libc/sys/rtems/include/sys/socket.h b/newlib/libc/sys/rtems/include/sys/socket.h
index 78831a54f..0be6879de 100644
--- a/newlib/libc/sys/rtems/include/sys/socket.h
+++ b/newlib/libc/sys/rtems/include/sys/socket.h
@@ -409,6 +409,7 @@ struct sockproto {
 #define	NET_RT_IFLISTL	5		/* Survey interface list, using 'l'en
 					 * versions of msghdr structs. */
 #define NET_RT_NHOP	6		/* dump routing nexthops */
+#define NET_RT_NHGRP	7		/* dump routing nexthop groups */
 #endif /* __BSD_VISIBLE */
 
 /*