IPv4 ABI has the table hardcoded as RT_TABLE_MAIN regardless of the table
hit for the route lookup. Add the table using a new attribute,
RTA_TABLE_LOOKUP, to maintain the ABI yet return the right table id.

Signed-off-by: David Ahern <d...@cumulusnetworks.com>
---

Thomas: Something like this?

The current ABI is returning wrong data in some cases; that seems worse
to me than breaking the ABI.

 include/uapi/linux/rtnetlink.h | 1 +
 net/ipv4/route.c               | 5 +++++
 net/ipv6/route.c               | 4 ++++
 3 files changed, 10 insertions(+)

diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index 702024769c74..5add1468350a 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -310,6 +310,7 @@ enum rtattr_type_t {
        RTA_PREF,
        RTA_ENCAP_TYPE,
        RTA_ENCAP,
+       RTA_TABLE_LOOKUP,  /* table hit for fib lookup */
        __RTA_MAX
 };
 
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 92acc95b7578..95454c368e66 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2328,6 +2328,11 @@ static int rt_fill_info(struct net *net,  __be32 dst, 
__be32 src,
        r->rtm_table    = RT_TABLE_MAIN;
        if (nla_put_u32(skb, RTA_TABLE, RT_TABLE_MAIN))
                goto nla_put_failure;
+
+       if (rt->rt_table_id && rt->rt_table_id != RT_TABLE_MAIN &&
+           nla_put_u32(skb, RTA_TABLE_LOOKUP, rt->rt_table_id))
+               goto nla_put_failure;
+
        r->rtm_type     = rt->rt_type;
        r->rtm_scope    = RT_SCOPE_UNIVERSE;
        r->rtm_protocol = RTPROT_UNSPEC;
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index f45cac6f8356..3c5d3a50bb7b 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2922,6 +2922,10 @@ static int rt6_fill_node(struct net *net,
        rtm->rtm_table = table;
        if (nla_put_u32(skb, RTA_TABLE, table))
                goto nla_put_failure;
+
+       if (table && nla_put_u32(skb, RTA_TABLE_LOOKUP, table))
+               goto nla_put_failure;
+
        if (rt->rt6i_flags & RTF_REJECT) {
                switch (rt->dst.error) {
                case -EINVAL:
-- 
1.9.1

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