The problem seen is that when adding a route with a nexthop with no
via address specified, iproute2 generates bogus output:
# ip -f mpls route add 100 dev lo
# ip -f mpls route list
100 via inet 0.0.8.0 dev lo
The reason for this is that the kernel generates an RTA_VIA attribute
with the family set to AF_INET, but the via address data having zero
length. The cause of family being AF_INET is that on route insert
cfg->rc_via_table is left set to 0, which just happens to be
NEIGH_ARP_TABLE which is then translated into AF_INET.
iproute2 doesn't validate the length prior to printing and so prints
garbage. Although it could be fixed to do the validation, I would
argue that AF_INET addresses should always be exactly 4 bytes so the
kernel is really giving userspace bogus data.
Therefore, avoid generating the RTA_VIA attribute when dumping the
route if the via address wasn't specified on add/modify. This is
indicated by NEIGH_ARP_TABLE and a zero via address length - if the
user specified a via address the address length would have been
validated such that it was 4 bytes. Although this is a change in
behaviour that is visible to userspace, I believe that what was
generated before was invalid and as such userspace wouldn't be
expecting it.
Signed-off-by: Robert Shearman <rshea...@brocade.com>
---
net/mpls/af_mpls.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index 3be29cb1f658..ac1c116abaac 100644
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -1235,7 +1235,9 @@ static int mpls_dump_route(struct sk_buff *skb, u32
portid, u32 seq, int event,
nla_put_labels(skb, RTA_NEWDST, nh->nh_labels,
nh->nh_label))
goto nla_put_failure;
- if (nla_put_via(skb, nh->nh_via_table, mpls_nh_via(rt, nh),
+ if ((nh->nh_via_table != NEIGH_ARP_TABLE ||
+ nh->nh_via_alen != 0) &&
+ nla_put_via(skb, nh->nh_via_table, mpls_nh_via(rt, nh),
nh->nh_via_alen))
goto nla_put_failure;
dev = rtnl_dereference(nh->nh_dev);
@@ -1323,7 +1325,9 @@ static inline size_t lfib_nlmsg_size(struct mpls_route
*rt)
if (nh->nh_dev)
payload += nla_total_size(4); /* RTA_OIF */
- payload += nla_total_size(2 + nh->nh_via_alen); /* RTA_VIA */
+ if (nh->nh_via_table != NEIGH_ARP_TABLE ||
+ nh->nh_via_alen != 0) /* RTA_VIA */
+ payload += nla_total_size(2 + nh->nh_via_alen);
if (nh->nh_labels) /* RTA_NEWDST */
payload += nla_total_size(nh->nh_labels * 4);
} else {
--
2.1.4
--
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