From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alexis Bauvin <abauvin@scaleway.com>
Subject: Re: [PATCH v6 1/4] udp_tunnel: add config option to bind to a device
Date: Mon, 3 Dec 2018 10:14:00 +0100
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Cc: netdev <netdev@vger.kernel.org>, akherbouche@scaleway.com,
        Alexis Bauvin <abauvin@scaleway.com>
To: Sabrina Dubroca <sd@queasysnail.net>,
        David Ahern <dsa@cumulusnetworks.com>,
        Roopa Prabhu <roopa@cumulusnetworks.com>,
        Stephen Hemminger <stephen@networkplumber.org>
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Le 30 nov. 2018 à 15:31, Sabrina Dubroca <sd@queasysnail.net> a écrit :
> 2018-11-27, 14:05:42 +0100, Alexis Bauvin wrote:
>> diff --git a/net/ipv4/udp_tunnel.c b/net/ipv4/udp_tunnel.c
>> index 6539ff15e9a3..dc68e15a4f72 100644
>> --- a/net/ipv4/udp_tunnel.c
>> +++ b/net/ipv4/udp_tunnel.c
>> @@ -20,6 +20,16 @@ int udp_sock_create4(struct net *net, struct udp_port_cfg *cfg,
>> 	if (err < 0)
>> 		goto error;
>> 
>> +	if (cfg->bind_ifindex) {
>> +		struct net_device *dev;
>> +
>> +		dev = __dev_get_by_index(net, cfg->bind_ifindex);
> 
> Quoting from net/core/dev.c:
> 
> *	[...]                                    The device has not
> *	had its reference counter increased so the caller must be careful
> *	about locking. The caller must hold either the RTNL semaphore
> *	or @dev_base_lock.
> */
> 
> which is the case for VXLAN (and GENEVE) during ndo_open, but I don't
> think other UDP tunnels (FOU, L2TP) are holding RTNL when they call
> udp_sock_create(). dev_get_by_index() + dev_put() should be safe.
> 
> Also, I don't think it's a problem with vxlan, but this could handle
> the case where __dev_get_by_index returns NULL.

First, sorry for the (late) response, thanks for the feedback!

That’s a real issue I did not take into account when writing the patch; still
too new to kernel dev.

Fixing and spinning up v7.

>> +		err = kernel_setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
>> +					dev->name, strlen(dev->name) + 1);
>> +		if (err < 0)
>> +			goto error;
>> +	}
>> +
>> 	udp_addr.sin_family = AF_INET;
>> 	udp_addr.sin_addr = cfg->local_ip;
>> 	udp_addr.sin_port = cfg->local_udp_port;
> 
> -- 
> Sabrina