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SubjectRe: [PATCH] vti4: Fix a ipip packet processing bug in 'IPCOMP' virtual tunnel
On Thu, Jan 03, 2019 at 07:48:41AM -0500, Su Yanjun wrote:
> Recently we run a network test over ipcomp virtual tunnel.We find that
> if a ipv4 packet needs fragment, then the peer can't receive
> it.
>
> We deep into the code and find that when packet need fragment the smaller
> fragment will be encapsulated by ipip not ipcomp. So when the ipip packet
> goes into xfrm, it's skb->dev is not properly set. The ipv4 reassembly code
> always set skb'dev to the last fragment's dev. After ipv4 defrag processing,
> when the kernel rp_filter parameter is set, the skb will be drop by -EXDEV
> error.

Why not just leaving rp_filter disabled or in 'loose mode' if you use ipcomp?

>
> This patch adds compatible support for the ipip process in ipcomp virtual tunnel.
>
> Signed-off-by: Su Yanjun <suyj.fnst@cn.fujitsu.com>
> ---
> net/ipv4/ip_vti.c | 25 ++++++++++++++++++++++++-
> 1 file changed, 24 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv4/ip_vti.c b/net/ipv4/ip_vti.c
> index de31b30..63de2f6 100644
> --- a/net/ipv4/ip_vti.c
> +++ b/net/ipv4/ip_vti.c
> @@ -65,6 +65,9 @@ static int vti_input(struct sk_buff *skb, int nexthdr, __be32 spi,
>
> XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4 = tunnel;
>
> + if (iph->protocol == IPPROTO_IPIP)
> + skb->dev = tunnel->dev;
> +
> return xfrm_input(skb, nexthdr, spi, encap_type);
> }
>
> @@ -76,10 +79,15 @@ static int vti_input(struct sk_buff *skb, int nexthdr, __be32 spi,
>
> static int vti_rcv(struct sk_buff *skb)
> {
> + __be32 spi = 0;
> +
> XFRM_SPI_SKB_CB(skb)->family = AF_INET;
> XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct iphdr, daddr);
> +
> + if (ip_hdr(skb)->protocol == IPPROTO_IPIP)
> + spi = ip_hdr(skb)->saddr;
>
> - return vti_input(skb, ip_hdr(skb)->protocol, 0, 0);
> + return vti_input(skb, ip_hdr(skb)->protocol, spi, 0);

You use the src address as spi, how is this supposed to work?

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