Patch "ipv4: fib: Fix metrics match when deleting a route" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

ipv4: fib: Fix metrics match when deleting a route

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ipv4-fib-fix-metrics-match-when-deleting-a-route.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Phil Sutter <[email protected]>
Date: Tue, 19 Dec 2017 15:17:13 +0100
Subject: ipv4: fib: Fix metrics match when deleting a route

From: Phil Sutter <[email protected]>

[ Upstream commit d03a45572efa068fa64db211d6d45222660e76c5 ]

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.

---
 net/ipv4/fib_semantics.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

@@ -706,7 +706,7 @@ bool fib_metrics_match(struct fib_config
 
 	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;

@@ -723,7 +723,11 @@ bool fib_metrics_match(struct fib_config
 			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;
 	}
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/ipv4-fib-fix-metrics-match-when-deleting-a-route.patch