netdev - [PATCH iproute2 1/5] iplink: Fix setting of -1 as ifindex

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Message-Id: <1412351718-22921-2-git-send-email-therbert@google.com>
Date:	Fri,  3 Oct 2014 08:55:14 -0700
From:	Tom Herbert <therbert@...gle.com>
To:	davem@...emloft.net, stephen@...workplumber.org,
	netdev@...r.kernel.org
Subject: [PATCH iproute2 1/5] iplink: Fix setting of -1 as ifindex

Commit 3c682146aeff157ec3540 ("iplink: forbid negative ifindex and
modifying ifindex") initializes index to -1 in iplink_modify. When
creating a link, req.i.ifi_index is then set to -1 if the link option is
not used. In the kernel this is then used to set dev->ifindex. For
dev->ifindex, zero is considered to be unset and -1 is treated as
a set index, so when a second tunnel is create the new device conflicts
with the old one (both have ifindex of -1) so -EBUSY is returned.

This patch set zero in req.i.ifi_index is index is unset (still -1).

Signed-off-by: Tom Herbert <therbert@...gle.com>
---
 ip/iplink.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ip/iplink.c b/ip/iplink.c
index cb9c870..1b6ffc6 100644
--- a/ip/iplink.c
+++ b/ip/iplink.c
@@ -689,7 +689,7 @@ static int iplink_modify(int cmd, unsigned int flags, int argc, char **argv)
 			addattr_l(&req.n, sizeof(req), IFLA_LINK, &ifindex, 4);
 		}

-		req.i.ifi_index = index;
+		req.i.ifi_index = (index > 0) ? : 0;
 	}

 	if (name) {
-- 
2.1.0.rc2.206.gedb03e5

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