From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH 4/4] net/l2tp: add support for L2TP over IPv6 UDP encap
Date: Wed, 18 Apr 2012 14:30:57 -0400 (EDT)
Message-ID: <20120418.143057.38880609278817544.davem@davemloft.net>
References: <20120418134438.GA5162@kvack.org>
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Cc: netdev@vger.kernel.org, jchapman@katalix.com
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From: Benjamin LaHaise <bcrl@kvack.org>
Date: Wed, 18 Apr 2012 09:44:38 -0400

> +#if IS_ENABLED(CONFIG_IPV6)
> +	if (sk->sk_family == PF_INET6) {
> +		if (!uh->check) {
> +			LIMIT_NETDEBUG(KERN_INFO "L2TP: IPv6: checksum is 0\n");
> +			return 1;
> +		}
> +		if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
> +		    !csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
> +				     &ipv6_hdr(skb)->daddr, ulen,
> +				     IPPROTO_UDP, skb->csum)) {
> +			skb->ip_summed = CHECKSUM_UNNECESSARY;
> +			return 0;
> +		}
> +		skb->csum = ~csum_unfold(csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
> +							 &ipv6_hdr(skb)->daddr,
> +							 skb->len, IPPROTO_UDP,
> +							 0));

Both the csum_ipv6_magic() calls should either use "ulen" or both
should use "skb->len".