netdev - Re: [PATCH net-next v2 2/2] mpls: allow TTL propagation from IP packets to be configured

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Message-ID: <3a3b0cfe-106c-88ee-e225-0df1458aab4b@cumulusnetworks.com>
Date:   Thu, 9 Mar 2017 19:54:23 -0700
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Robert Shearman <rshearma@...cade.com>, davem@...emloft.net
Cc:     netdev@...r.kernel.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        roopa <roopa@...ulusnetworks.com>
Subject: Re: [PATCH net-next v2 2/2] mpls: allow TTL propagation from IP
 packets to be configured

On 3/7/17 5:46 PM, Robert Shearman wrote:
> @@ -78,6 +70,29 @@ static int mpls_xmit(struct sk_buff *skb)
>  
>  	tun_encap_info = mpls_lwtunnel_encap(dst->lwtstate);
>  
> +	/* Obtain the ttl */
> +	if (dst->ops->family == AF_INET) {
> +		if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DISABLED)
> +			ttl = tun_encap_info->default_ttl;
> +		else if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DEFAULT &&
> +			 !net->mpls.ip_ttl_propagate)
> +			ttl = net->mpls.default_ttl;
> +		else
> +			ttl = ip_hdr(skb)->ttl;

After staring at that for a while, an explanation above this if {} else
{} section on the ttl selection will be very helpful.