netdev - Re: [PATCH net-next v7 02/11] net: tunnel: convert iptunnel

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Message-ID: <60baa2a5-806e-4d8b-8601-976fb62fa203@yahoo.com>
Date: Wed, 4 Feb 2026 17:52:17 +0100
From: Marek Mietus <mmietus97@...oo.com>
To: Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
 sd@...asysnail.net, kuba@...nel.org
Cc: Jason@...c4.com
Subject: Re: [PATCH net-next v7 02/11] net: tunnel: convert iptunnel_xmit to
 noref

W dniu 2/3/26 o 09:21, Paolo Abeni pisze:
> On 1/27/26 8:04 AM, Marek Mietus wrote:
>> diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
>> index cf37ad9686e6..a0d699082747 100644
>> --- a/net/ipv6/sit.c
>> +++ b/net/ipv6/sit.c
>> @@ -1028,6 +1028,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
>>  
>>  	iptunnel_xmit(NULL, rt, skb, fl4.saddr, fl4.daddr, protocol, tos, ttl,
>>  		      df, !net_eq(tunnel->net, dev_net(dev)), 0);
>> +	ip_rt_put(rt);
>>  	return NETDEV_TX_OK;
>>  
>>  tx_error_icmp:
> 
> Could you please double check that all ndo_start_xmit caller are under
> RCU protection?
> 

The docs in Documentation/networking/netdevices.rst mention that ndo_start_xmit
is called from a BH context or from a process context with BHs disabled.

Ever since the consolidation of the different RCU flavors, running with BHs
disabled implies an RCU read-side critical section. This is mentioned in the docs
for rcu_read_lock_bh.

> Specifically I don't see it in the
> xsk_generic_xmit()/__dev_direct_xmit() path.
> 

As for this, __dev_direct_xmit() calls local_bh_disable() before calling
netdev_start_xmit(), which eventually calls ops->ndo_start_xmit().

> /P
> 
>