netdev - Re: [PATCH v4 net] net, ip6_tunnel: enhance tunnel locate with link check

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Date:   Thu, 13 Feb 2020 17:33:01 +0100
From:   Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:     William Dauchy <w.dauchy@...teo.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v4 net] net, ip6_tunnel: enhance tunnel locate with link
 check

Le 13/02/2020 à 16:35, William Dauchy a écrit :
[snip]
> @@ -1420,9 +1441,11 @@ ip6_tnl_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  static void ip6_tnl_link_config(struct ip6_tnl *t)
>  {
>  	struct net_device *dev = t->dev;
> +	struct net_device *tdev = NULL;
>  	struct __ip6_tnl_parm *p = &t->parms;
>  	struct flowi6 *fl6 = &t->fl.u.ip6;
>  	int t_hlen;
> +	int mtu;
>  
>  	memcpy(dev->dev_addr, &p->laddr, sizeof(struct in6_addr));
>  	memcpy(dev->broadcast, &p->raddr, sizeof(struct in6_addr));
> @@ -1457,22 +1480,24 @@ static void ip6_tnl_link_config(struct ip6_tnl *t)
>  		struct rt6_info *rt = rt6_lookup(t->net,
>  						 &p->raddr, &p->laddr,
>  						 p->link, NULL, strict);
> +		if (!IS_ERR(rt)) {
Why IS_ERR()? rt6_lookup() returns a valid pointer or NULL.

> +			tdev = rt->dst.dev;
> +			ip6_rt_put(rt);
> +		} else if (t->parms.link) {
> +			tdev = __dev_get_by_index(t->net, t->parms.link);
p->link to be consistent with the rest of the function.

> +		}
>  
> -		if (!rt)
> -			return;
> -
> -		if (rt->dst.dev) {
But rt->dst.dev can be NULL.

> -			dev->hard_header_len = rt->dst.dev->hard_header_len +
> -				t_hlen;
> +		if (tdev) {
> +			dev->hard_header_len = tdev->hard_header_len + t_hlen;
> +			mtu = min(tdev->mtu, IP_MAX_MTU);
IP6_MAX_MTU?

>  
> -			dev->mtu = rt->dst.dev->mtu - t_hlen;
> +			dev->mtu = mtu - t_hlen;
>  			if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
>  				dev->mtu -= 8;
>  
>  			if (dev->mtu < IPV6_MIN_MTU)
>  				dev->mtu = IPV6_MIN_MTU;
>  		}
> -		ip6_rt_put(rt);
>  	}
>  }
>  
>