net: fix generic XDP to handle if eth header was mangled (29724956) · Commits · 戴 / test

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. V2: on request from Song Liu, use ETH_HLEN instead of mac_len, in __skb_push() as eth_type_trans() use ETH_HLEN in paired skb_pull_inline(). Fixes: ("net: xdp: support xdp generic on virtual devices") Signed-off-by:

Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by:

Alexei Starovoitov <ast@kernel.org>

net/core/dev.c

+14 −0

Original line number	Original line	Diff line number	Diff line
	@@ -4258,6 +4258,9 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
	struct netdev_rx_queue *rxqueue;		struct netdev_rx_queue *rxqueue;
	void orig_data, orig_data_end;		void orig_data, orig_data_end;
	u32 metalen, act = XDP_DROP;		u32 metalen, act = XDP_DROP;
			__be16 orig_eth_type;
			struct ethhdr *eth;
			bool orig_bcast;
	int hlen, off;		int hlen, off;
	u32 mac_len;		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);		xdp->data_hard_start = skb->data - skb_headroom(skb);
	orig_data_end = xdp->data_end;		orig_data_end = xdp->data_end;
	orig_data = xdp->data;		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);		rxqueue = netif_get_rxqueue(skb);
	xdp->rxq = &rxqueue->xdp_rxq;		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, ETH_HLEN);
			skb->protocol = eth_type_trans(skb, skb->dev);
			}

	switch (act) {		switch (act) {
	case XDP_REDIRECT:		case XDP_REDIRECT:
	case XDP_TX:		case XDP_TX:

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