[PATCH net] ipv4: fib: Fix metrics match when deleting a route

[Phil Sutter]

The recently added fib_metrics_match() causes a regression for routes
with both RTAX_FEATURES and RTAX_CC_ALGO if the latter has
TCP_CONG_NEEDS_ECN flag set:

| # ip link add d0 type dummy
| # ip link set d0 up
| # ip route add 172.29.29.0/24 dev d0 features ecn congctl dctcp
| # ip route del 172.29.29.0/24 dev d0 features ecn congctl dctcp
| RTNETLINK answers: No such process

During route insertion, fib_convert_metrics() detects that the given CC
algo requires ECN and hence sets DST_FEATURE_ECN_CA bit in
RTAX_FEATURES.

During route deletion though, fib_metrics_match() compares stored
RTAX_FEATURES value with that from userspace (which obviously has no
knowledge about DST_FEATURE_ECN_CA) and fails.

Fixes: 5f9ae3d9e7e4a ("ipv4: do metrics match when looking up and deleting a 
route")
Signed-off-by: Phil Sutter <p...@nwl.cc>
---
 net/ipv4/fib_semantics.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index f04d944f8abe0..c586597da20db 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -698,7 +698,7 @@ bool fib_metrics_match(struct fib_config *cfg, struct 
fib_info *fi)
 
        nla_for_each_attr(nla, cfg->fc_mx, cfg->fc_mx_len, remaining) {
                int type = nla_type(nla);
-               u32 val;
+               u32 fi_val, val;
 
                if (!type)
                        continue;
@@ -715,7 +715,11 @@ bool fib_metrics_match(struct fib_config *cfg, struct 
fib_info *fi)
                        val = nla_get_u32(nla);
                }
 
-               if (fi->fib_metrics->metrics[type - 1] != val)
+               fi_val = fi->fib_metrics->metrics[type - 1];
+               if (type == RTAX_FEATURES)
+                       fi_val &= ~DST_FEATURE_ECN_CA;
+
+               if (fi_val != val)
                        return false;
        }
 
-- 
2.13.1