Re: [PATCH v4 net-next] net: ipv4: Consider failed nexthops in multipath routes

[David Ahern]

On 4/3/16 3:57 PM, Julian Anastasov wrote:

        Hello,

On Sun, 3 Apr 2016, David Ahern wrote:

--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -63,6 +63,16 @@ fwmark_reflect - BOOLEAN
        fwmark of the packet they are replying to.
        Default: 0

+fib_multipath_use_neigh - BOOLEAN
+       Use status of existing neighbor entry when determining nexthop for
+       multipath routes. If disabled neighbor information is not used and

        Comma from v3 is removed?

+       packets could be directed to a failed nexthop. Only valid for kernels

--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
  void fib_select_multipath(struct fib_result *res, int hash)
  {
        struct fib_info *fi = res->fi;
+       struct net *net = fi->fib_net;
+       bool first = false;

        for_nexthops(fi) {
                if (hash > atomic_read(&nh->nh_upper_bound))
                        continue;

-               res->nh_sel = nhsel;
-               return;
+               if (!net->ipv4.sysctl_fib_multipath_use_neigh ||
+                   fib_good_nh(nh)) {
+                       res->nh_sel = nhsel;
+                       return;
+               }
+               if (!first) {
+                       res->nh_sel = nhsel;
+                       first = true;
+               }
        } endfor_nexthops(fi);

        /* Race condition: route has just become dead. */

        The 'res->nh_sel = 0;' that is here should be
removed because it invalidates the above assignment.

right. will send a v5