Re: [PATCH] vti4: Fix a ipip packet processing bug in 'IPCOMP' virtual tunnel

[Su Yanjun <suyj.fnst@xxxxxxxxxxxxxx>]

On 1/4/2019 3:43 PM, Steffen Klassert wrote:

> 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?
In my option rp_filter should not affect the ip_vti functionality.
The root cause is the origin tunnel code doesn't update skb->dev.
vti only cares about ipcomp, esp, ah packets.
> > This patch adds compatible support for the ipip process in ipcomp virtual tunnel.
> >
> > Signed-off-by: Su Yanjun <suyj.fnst@xxxxxxxxxxxxxx>
> > ---
> >   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?
This code derives from xfrm4_tunnel and i just want the vti can handle 
ipip packet as xfrm4 tunnel does.


Thanks,
Su