On Thu, Jul 30, 2020 at 04:20:30PM -0700, Jakub Kicinski wrote:

On Thu, 30 Jul 2020 22:33:51 +0530 Martin Varghese wrote:

quoted

From: Martin Varghese <redacted>

Kernel does not support udp destination port 0 on wire. Hence
bareudp device with udp destination port 0 must be disallowed.

Fixes: 571912c69f0e ("net: UDP tunnel encapsulation module for tunnelling different protocols like MPLS, IP, NSH etc.")
Signed-off-by: Martin Varghese <redacted>
---
 drivers/net/bareudp.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/bareudp.c b/drivers/net/bareudp.c
index 88e7900853db..08b195d32cbe 100644
--- a/drivers/net/bareudp.c
+++ b/drivers/net/bareudp.c

@@ -578,8 +578,13 @@ static int bareudp2info(struct nlattr *data[], struct bareudp_conf *conf,
 		return -EINVAL;
 	}
 
-	if (data[IFLA_BAREUDP_PORT])
+	if (data[IFLA_BAREUDP_PORT]) {
 		conf->port =  nla_get_u16(data[IFLA_BAREUDP_PORT]);
+		if (!conf->port) {
+			NL_SET_ERR_MSG(extack, "udp port 0 not supported");
+			return -EINVAL;
+		}
+	}

Please use one of the NLA_POLICY_**-ies, probably NLA_POLICY_MIN() ? 
That's better for documenting, exporting for user space, and will also
point the user space to the attribute in exack automatically.

Ok, I will check how to do this way. Thanks for the feedback.

Regards,
Martin