bpf: allow BPF programs access skb->skb_iif and skb->dev->ifindex fields (37e82c2f) · Commits · 戴 / test

classic BPF already exposes skb->dev->ifindex via SKF_AD_IFINDEX extension. Allow eBPF program to access it as well. Note that classic aborts execution of the program if 'skb->dev == NULL' (which is inconvenient for program writers), whereas eBPF returns zero in such case. Also expose the 'skb_iif' field, since programs triggered by redirected packet need to known the original interface index. Summary: __skb->ifindex -> skb->dev->ifindex __skb->ingress_ifindex -> skb->skb_iif Signed-off-by:

Alexei Starovoitov <ast@plumgrid.com> Acked-by:

Daniel Borkmann <daniel@iogearbox.net> Signed-off-by:

David S. Miller <davem@davemloft.net>

include/uapi/linux/bpf.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -236,6 +236,8 @@ struct __sk_buff {
		__u32 vlan_tci;
		__u32 vlan_proto;
		__u32 priority;
		__u32 ingress_ifindex;
		__u32 ifindex;
		};

		#endif /* _UAPI__LINUX_BPF_H__ */

net/core/filter.c

+18 −0

Original line number	Diff line number	Diff line
		@@ -1499,6 +1499,24 @@ static u32 sk_filter_convert_ctx_access(int dst_reg, int src_reg, int ctx_off,
		offsetof(struct sk_buff, priority));
		break;

		case offsetof(struct __sk_buff, ingress_ifindex):
		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, skb_iif) != 4);

		*insn++ = BPF_LDX_MEM(BPF_W, dst_reg, src_reg,
		offsetof(struct sk_buff, skb_iif));
		break;

		case offsetof(struct __sk_buff, ifindex):
		BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4);

		*insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct sk_buff, dev)),
		dst_reg, src_reg,
		offsetof(struct sk_buff, dev));
		*insn++ = BPF_JMP_IMM(BPF_JEQ, dst_reg, 0, 1);
		*insn++ = BPF_LDX_MEM(BPF_W, dst_reg, dst_reg,
		offsetof(struct net_device, ifindex));
		break;

		case offsetof(struct __sk_buff, mark):
		return convert_skb_access(SKF_AD_MARK, dst_reg, src_reg, insn);

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