XDP can modify (and resize) the Ethernet header in the packet.
There is a bug in generic-XDP, because skb->protocol and skb->pkt_type
are setup before reaching (netif_receive_)generic_xdp.
This bug was hit when XDP were popping VLAN headers (changing
eth->h_proto), as skb->protocol still contains VLAN-indication
(ETH_P_8021Q) causing invocation of skb_vlan_untag(skb), which corrupt
the packet (basically popping the VLAN again).
This patch catch if XDP changed eth header in such a way, that SKB
fields needs to be updated.
Fixes: d445516966dc ("net: xdp: support xdp generic on virtual devices")
Signed-off-by: Jesper Dangaard Brouer <bro...@redhat.com>
---
net/core/dev.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/net/core/dev.c b/net/core/dev.c
index ca78dc5a79a3..db6d89f536cb 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4258,6 +4258,9 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
struct netdev_rx_queue *rxqueue;
void *orig_data, *orig_data_end;
u32 metalen, act = XDP_DROP;
+ __be16 orig_eth_type;
+ struct ethhdr *eth;
+ bool orig_bcast;
int hlen, off;
u32 mac_len;
@@ -4298,6 +4301,9 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
xdp->data_hard_start = skb->data - skb_headroom(skb);
orig_data_end = xdp->data_end;
orig_data = xdp->data;
+ eth = (struct ethhdr *)xdp->data;
+ orig_bcast = is_multicast_ether_addr_64bits(eth->h_dest);
+ orig_eth_type = eth->h_proto;
rxqueue = netif_get_rxqueue(skb);
xdp->rxq = &rxqueue->xdp_rxq;
@@ -4321,6 +4327,14 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
}
+ /* check if XDP changed eth hdr such SKB needs update */
+ eth = (struct ethhdr *)xdp->data;
+ if ((orig_eth_type != eth->h_proto) ||
+ (orig_bcast != is_multicast_ether_addr_64bits(eth->h_dest))) {
+ __skb_push(skb, mac_len);
+ skb->protocol = eth_type_trans(skb, skb->dev);
+ }
+
switch (act) {
case XDP_REDIRECT:
case XDP_TX:
