netdev - [PATCH v2] neighbour: confirm neigh entries when ARP packet is received

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Message-Id: <20180911180406.31283-1-vasilykh@arista.com>
Date:   Tue, 11 Sep 2018 11:04:06 -0700
From:   Vasily Khoruzhick <vasilykh@...sta.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Roopa Prabhu <roopa@...ulusnetworks.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Jim Westfall <jwestfall@...realistic.net>,
        Wolfgang Bumiller <w.bumiller@...xmox.com>,
        Vasily Khoruzhick <anarsoul@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Ihar Hrachyshka <ihrachys@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Vasily Khoruzhick <vasilykh@...sta.com>
Subject: [PATCH v2] neighbour: confirm neigh entries when ARP packet is received

Update 'confirmed' timestamp when ARP packet is received. It shouldn't
affect locktime logic and anyway entry can be confirmed by any higher-layer
protocol. Thus it makes to sense not to confirm it when ARP packet is
received.

Fixes: 77d7123342 ("neighbour: update neigh timestamps iff update is
effective")

Signed-off-by: Vasily Khoruzhick <vasilykh@...sta.com>
---
v2: - update comment to match new code.

 net/core/neighbour.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index aa19d86937af..56a554597db5 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1180,6 +1180,12 @@ int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new,
 		lladdr = neigh->ha;
 	}
 
+	/* Update confirmed timestamp for neighbour entry after we
+	 * received ARP packet even if it doesn't change IP to MAC binding.
+	 */
+	if (new & NUD_CONNECTED)
+		neigh->confirmed = jiffies;
+
 	/* If entry was valid and address is not changed,
 	   do not change entry state, if new one is STALE.
 	 */
@@ -1201,15 +1207,12 @@ int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new,
 		}
 	}
 
-	/* Update timestamps only once we know we will make a change to the
+	/* Update timestamp only once we know we will make a change to the
 	 * neighbour entry. Otherwise we risk to move the locktime window with
 	 * noop updates and ignore relevant ARP updates.
 	 */
-	if (new != old || lladdr != neigh->ha) {
-		if (new & NUD_CONNECTED)
-			neigh->confirmed = jiffies;
+	if (new != old || lladdr != neigh->ha)
 		neigh->updated = jiffies;
-	}
 
 	if (new != old) {
 		neigh_del_timer(neigh);
-- 
2.18.0