From 59d3a3611f05c05040cec4bf09f31c26ade0fa0a Mon Sep 17 00:00:00 2001
From: "Ondrej Zajicek (work)" <santiago@crfreenet.org>
Date: Tue, 2 Jul 2019 18:23:06 +0200
Subject: [PATCH] Netlink: Handle alien routes with unsorted nexthops

Nest requires that nexthops are sorted, the kernel protocol have to
ensure that for alien routes.
---
 nest/route.h           |  1 +
 nest/rt-attr.c         | 20 +++++++++++++++++++-
 sysdep/linux/netlink.c |  4 ++++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/nest/route.h b/nest/route.h
index 15aac8f6..e356f686 100644
--- a/nest/route.h
+++ b/nest/route.h
@@ -628,6 +628,7 @@ int nexthop__same(struct nexthop *x, struct nexthop *y); /* Compare multipath ne
 static inline int nexthop_same(struct nexthop *x, struct nexthop *y)
 { return (x == y) || nexthop__same(x, y); }
 struct nexthop *nexthop_merge(struct nexthop *x, struct nexthop *y, int rx, int ry, int max, linpool *lp);
+struct nexthop *nexthop_sort(struct nexthop *x);
 static inline void nexthop_link(struct rta *a, struct nexthop *from)
 { memcpy(&a->nh, from, nexthop_size(from)); }
 void nexthop_insert(struct nexthop **n, struct nexthop *y);
diff --git a/nest/rt-attr.c b/nest/rt-attr.c
index cc362cab..1803db92 100644
--- a/nest/rt-attr.c
+++ b/nest/rt-attr.c
@@ -200,7 +200,7 @@ nexthop__same(struct nexthop *x, struct nexthop *y)
 }
 
 static int
-nexthop_compare_node(struct nexthop *x, struct nexthop *y)
+nexthop_compare_node(const struct nexthop *x, const  struct nexthop *y)
 {
   int r;
 
@@ -318,6 +318,24 @@ nexthop_insert(struct nexthop **n, struct nexthop *x)
   *n = x;
 }
 
+struct nexthop *
+nexthop_sort(struct nexthop *x)
+{
+  struct nexthop *s = NULL;
+
+  /* Simple insert-sort */
+  while (x)
+  {
+    struct nexthop *n = x;
+    x = n->next;
+    n->next = NULL;
+
+    nexthop_insert(&s, n);
+  }
+
+  return s;
+}
+
 int
 nexthop_is_sorted(struct nexthop *x)
 {
diff --git a/sysdep/linux/netlink.c b/sysdep/linux/netlink.c
index 5a0b4d0c..6e3fe488 100644
--- a/sysdep/linux/netlink.c
+++ b/sysdep/linux/netlink.c
@@ -725,6 +725,10 @@ nl_parse_multipath(struct nl_parse_state *s, struct krt_proto *p, struct rtattr
       nh = RTNH_NEXT(nh);
     }
 
+  /* Ensure nexthops are sorted to satisfy nest invariant */
+  if (!nexthop_is_sorted(first))
+    first = nexthop_sort(first);
+
   return first;
 }