Thread (46 messages) 46 messages, 6 authors, 2017-07-31

Re: [PATCH net] ipv6: no need to return rt->dst.error if it is not null entry.

From: Roopa Prabhu <hidden>
Date: 2017-07-26 19:38:26

On Wed, Jul 26, 2017 at 12:00 PM, David Ahern [off-list ref] wrote:
quoted hunk ↗ jump to hunk
On 7/26/17 12:55 PM, Roopa Prabhu wrote:
quoted
On Wed, Jul 26, 2017 at 11:49 AM, David Ahern [off-list ref] wrote:
quoted
On 7/26/17 12:27 PM, Roopa Prabhu wrote:
quoted
agreed...so looks like the check in v3 should be


+       if ( rt == net->ipv6.ip6_null_entry ||
+            (rt->dst.error &&
+ #ifdef CONFIG_IPV6_MULTIPLE_TABLES
+              rt != net->ipv6.ip6_prohibit_entry &&
+              rt != net->ipv6.ip6_blk_hole_entry &&
+#endif
+             )) {
                err = rt->dst.error;
                ip6_rt_put(rt);
                goto errout;
I don't think so. If I add a prohibit route and use the fibmatch
attribute, I want to see the route from the FIB that was matched.

yes, exactly. wouldn't  'rt != net->ipv6.ip6_prohibit_entry' above let
it fall through to the route fill code ?

ah...but i guess you are saying that they will have rt6_info's of
their own and will not match. got it. ack.
This:
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 4d30c96a819d..24de81c804c2 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3637,11 +3637,6 @@ static int inet6_rtm_getroute(struct sk_buff
*in_skb, struct nlmsghdr *nlh,
                dst = ip6_route_lookup(net, &fl6, 0);

        rt = container_of(dst, struct rt6_info, dst);
-       if (rt->dst.error) {
-               err = rt->dst.error;
-               ip6_rt_put(rt);
-               goto errout;
-       }

        if (rt == net->ipv6.ip6_null_entry) {
                err = rt->dst.error;

Puts back the original behavior. In that case, only rt == null_entry
drops to the error path which is correct. All other rt values will drop
to rt6_fill_node and return rt data.
yes, i thought so too and hence acked v1. But, following congs
comment, realized that it may mask some real errors for fibmatch ?

I just tested a case of unreachable route with just the above patch
you posted, and I do get the error correctly.

so, I guess you are saying all real errors for fibmatch will have "rt
== net->ipv6.ip6_null_entry" and we should be ok.
sounds good to me.
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