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bpf: Fix bpf_redirect to an ipip/ip6tnl dev

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If the bpf program calls bpf_redirect(dev, 0) and dev is
an ipip/ip6tnl, it currently includes the mac header.
e.g. If dev is ipip, the end result is IP-EthHdr-IP instead
of IP-IP.

The fix is to pull the mac header.  At ingress, skb_postpull_rcsum()
is not needed because the ethhdr should have been pulled once already
and then got pushed back just before calling the bpf_prog.
At egress, this patch calls skb_postpull_rcsum().

If bpf_redirect(dev, BPF_F_INGRESS) is called,
it also fails now because it calls dev_forward_skb() which
eventually calls eth_type_trans(skb, dev).  The eth_type_trans()
will set skb->type = PACKET_OTHERHOST because the mac address
does not match the redirecting dev->dev_addr.  The PACKET_OTHERHOST
will eventually cause the ip_rcv() errors out.  To fix this,
____dev_forward_skb() is added.

Joint work with Daniel Borkmann.

Fixes: cfc7381b30 ("ip_tunnel: add collect_md mode to IPIP tunnel")
Fixes: 8d79266bc4 ("ip6_tunnel: add collect_md mode to IPv6 tunnels")
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Martin KaFai Lau 2016-11-09 15:36:33 -08:00 • committed by David S. Miller
parent 23dd831548
commit 4e3264d21b
3 changed files with 81 additions and 19 deletions
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15
include/linux/netdevice.h
View file

@ -3354,6 +3354,21 @@ int dev_forward_skb(struct net_device *dev, struct sk_buff *skb);
bool is_skb_forwardable(const struct net_device *dev,
const struct sk_buff *skb);
static __always_inline int ____dev_forward_skb(struct net_device *dev,
struct sk_buff *skb)
{
if (skb_orphan_frags(skb, GFP_ATOMIC) ||
unlikely(!is_skb_forwardable(dev, skb))) {
atomic_long_inc(&dev->rx_dropped);
kfree_skb(skb);
return NET_RX_DROP;
}
skb_scrub_packet(skb, true);
skb->priority = 0;
return 0;
}
void dev_queue_xmit_nit(struct sk_buff *skb, struct net_device *dev);
extern int netdev_budget;