netdev - Re: [PATCH] NET: SRv6: seg6_local: Fixed SRH processing when segments left is 0

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Date:   Sun, 31 Jan 2021 10:33:14 -0700
From:   David Ahern <dsahern@...il.com>
To:     Suprit Japagal <suprit.japagal@...il.com>, davem@...emloft.net,
        yoshfuji@...ux-ipv6.org, dsahern@...nel.org,
        David Lebrun <david.lebrun@...ouvain.be>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH] NET: SRv6: seg6_local: Fixed SRH processing when segments
 left is 0

[ cc David Lebrun, author of the original code ]

On 1/31/21 6:08 AM, Suprit Japagal wrote:
> From: "Suprit.Japagal" <suprit.japagal@...il.com>
> 
> According to the standard IETF RFC 8754, section 4.3.1.1
> (https://tools.ietf.org/html/rfc8754#section-4.3.1.1)
> When the segments left in SRH equals to 0, proceed to process the
> next header in the packet, whose type is identified by the
> Next header field of the routing header.
> 
> Signed-off-by: Suprit.Japagal <suprit.japagal@...il.com>
> ---
>  net/ipv6/seg6_local.c | 54 +++++++++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 48 insertions(+), 6 deletions(-)
> 
> diff --git a/net/ipv6/seg6_local.c b/net/ipv6/seg6_local.c
> index b07f7c1..b17f9dc 100644
> --- a/net/ipv6/seg6_local.c
> +++ b/net/ipv6/seg6_local.c
> @@ -273,11 +273,25 @@ static int input_action_end(struct sk_buff *skb, struct seg6_local_lwt *slwt)
>  {
>  	struct ipv6_sr_hdr *srh;
>  
> -	srh = get_and_validate_srh(skb);
> +	srh = get_srh(skb);
>  	if (!srh)
>  		goto drop;
>  
> -	advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
> +#ifdef CONFIG_IPV6_SEG6_HMAC
> +	if (srh->segments_left > 0)
> +		if (!seg6_hmac_validate_skb(skb))
> +			goto drop;
> +#endif
> +
> +	if (srh->segments_left == 0) {
> +		if (!decap_and_validate(skb, srh->nexthdr))
> +			goto drop;
> +
> +		if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
> +			goto drop;
> +	} else {
> +		advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
> +	}
>  
>  	seg6_lookup_nexthop(skb, NULL, 0);
>  
> @@ -293,11 +307,25 @@ static int input_action_end_x(struct sk_buff *skb, struct seg6_local_lwt *slwt)
>  {
>  	struct ipv6_sr_hdr *srh;
>  
> -	srh = get_and_validate_srh(skb);
> +	srh = get_srh(skb);
>  	if (!srh)
>  		goto drop;
>  
> -	advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
> +#ifdef CONFIG_IPV6_SEG6_HMAC
> +	if (srh->segments_left > 0)
> +		if (!seg6_hmac_validate_skb(skb))
> +			goto drop;
> +#endif
> +
> +	if (srh->segments_left == 0) {
> +		if (!decap_and_validate(skb, srh->nexthdr))
> +			goto drop;
> +
> +		if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
> +			goto drop;
> +	} else {
> +		advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
> +	}
>  
>  	seg6_lookup_nexthop(skb, &slwt->nh6, 0);
>  
> @@ -312,11 +340,25 @@ static int input_action_end_t(struct sk_buff *skb, struct seg6_local_lwt *slwt)
>  {
>  	struct ipv6_sr_hdr *srh;
>  
> -	srh = get_and_validate_srh(skb);
> +	srh = get_srh(skb);
>  	if (!srh)
>  		goto drop;
>  
> -	advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
> +#ifdef CONFIG_IPV6_SEG6_HMAC
> +	if (srh->segments_left > 0)
> +		if (!seg6_hmac_validate_skb(skb))
> +			goto drop;
> +#endif
> +
> +	if (srh->segments_left == 0) {
> +		if (!decap_and_validate(skb, srh->nexthdr))
> +			goto drop;
> +
> +		if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
> +			goto drop;
> +	} else {
> +		advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
> +	}
>  
>  	seg6_lookup_nexthop(skb, NULL, slwt->table);
>  
>